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2021 Vol. 39, No. 5
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2021, 39(5): 1-8.
doi: 10.13205/j.hjgc.202105001
Abstract:
In order to improve the lake sediment-water interface habitat, a slow-release oxygen material that can supply oxygen in situ and reduce the release of endogenous nitrogen was developed. The slow-release oxygen material prepared with CaO2:white clay:cement=2:1:1 (mass ratio) had good oxygen release and pH buffering capability. The simulation experiment compared the effects of different dosing methods of slow-release oxygen materials (surface dosing and in-mud dosing) on the release of oxygen and the release of pollutants in the sediments. The results showed that:1) the DO concentration and pH value of the overlying water were significantly increased by surface dosing, and in-mud dosing could maintain the pH value within 7.5, while the DO concentration increased slowly, prolonging the oxygen release period; 2) slow-release oxygen materials had a significant inhibitory effect on release of NH4+-N in the sediment, and surface dosing was significantly effective than in-mud dosing. Taking the blank group as the reference, after 31 days of static culture, the inhibition rate of NH4+-N by adding slow-release oxygen material into the mud was 53.4%, and that of the surface dosing was 81.1%. Adding oxygen-releasing materials increased the level of DO in the overlying water and promoted the growth of nitrifying bacteria, thereby inhibiting the release of NH4+-N; 3) slow-release oxygen materials were beneficial to microorganisms growth which promoted the humification of microorganisms, thereby slightly promoted the release of terrestrial-like humic acids in the sediments, while slightly inhibited the release of tyrosine-like proteins; 4) slow-release oxygen materials could promote the conversion of Fe/Al-P to Ca-P in the sediment which slightly inhibited the release of DIP, but the release of DOC and arsenic and chromium in the sediment increased slightly, due to the increase of pH.
In order to improve the lake sediment-water interface habitat, a slow-release oxygen material that can supply oxygen in situ and reduce the release of endogenous nitrogen was developed. The slow-release oxygen material prepared with CaO2:white clay:cement=2:1:1 (mass ratio) had good oxygen release and pH buffering capability. The simulation experiment compared the effects of different dosing methods of slow-release oxygen materials (surface dosing and in-mud dosing) on the release of oxygen and the release of pollutants in the sediments. The results showed that:1) the DO concentration and pH value of the overlying water were significantly increased by surface dosing, and in-mud dosing could maintain the pH value within 7.5, while the DO concentration increased slowly, prolonging the oxygen release period; 2) slow-release oxygen materials had a significant inhibitory effect on release of NH4+-N in the sediment, and surface dosing was significantly effective than in-mud dosing. Taking the blank group as the reference, after 31 days of static culture, the inhibition rate of NH4+-N by adding slow-release oxygen material into the mud was 53.4%, and that of the surface dosing was 81.1%. Adding oxygen-releasing materials increased the level of DO in the overlying water and promoted the growth of nitrifying bacteria, thereby inhibiting the release of NH4+-N; 3) slow-release oxygen materials were beneficial to microorganisms growth which promoted the humification of microorganisms, thereby slightly promoted the release of terrestrial-like humic acids in the sediments, while slightly inhibited the release of tyrosine-like proteins; 4) slow-release oxygen materials could promote the conversion of Fe/Al-P to Ca-P in the sediment which slightly inhibited the release of DIP, but the release of DOC and arsenic and chromium in the sediment increased slightly, due to the increase of pH.
2021, 39(5): 9-15.
doi: 10.13205/j.hjgc.202105002
Abstract:
The problems of low influent flow and concentration generally existed in sewage treatment plants in villages and towns in China, which led to the poor operation stability of sewage treatment plants in villages and towns. In order to prevent the low load operation from affecting treatment performance, taking the inverted AAO process of multiple points in the sewage treatment plant in villages and towns near Taihu Lake as the research object, based on mathematical model, a dynamic response model of sewage treatment plant was established. With mathematical simulation as the main research method and experiment as the supplementary method, the simulation results showed that aeration was excessive in summer, and then MLVSS/MLSS was 0.37. The results of the experiment showed that the influent ISS concentration was 57~92 mg/L, ISS/SS was 0.71~0.82 and ISS/COD was 0.50~0.84. The ISS particle size entered AAO system ranged from 36 μm to 52 μm. Small particle sized ISS was the main reason for low MLVSS/MLSS in the activated sludge. By optimizing influent ISS/COD, sludge retention age, returned sludge ratio and aeration velocity, the effluent quality reached grade A in standard GB 18918-2002 stably, sludge activity was increased to 0.7, and aeration cost was reduced by about 10%.
The problems of low influent flow and concentration generally existed in sewage treatment plants in villages and towns in China, which led to the poor operation stability of sewage treatment plants in villages and towns. In order to prevent the low load operation from affecting treatment performance, taking the inverted AAO process of multiple points in the sewage treatment plant in villages and towns near Taihu Lake as the research object, based on mathematical model, a dynamic response model of sewage treatment plant was established. With mathematical simulation as the main research method and experiment as the supplementary method, the simulation results showed that aeration was excessive in summer, and then MLVSS/MLSS was 0.37. The results of the experiment showed that the influent ISS concentration was 57~92 mg/L, ISS/SS was 0.71~0.82 and ISS/COD was 0.50~0.84. The ISS particle size entered AAO system ranged from 36 μm to 52 μm. Small particle sized ISS was the main reason for low MLVSS/MLSS in the activated sludge. By optimizing influent ISS/COD, sludge retention age, returned sludge ratio and aeration velocity, the effluent quality reached grade A in standard GB 18918-2002 stably, sludge activity was increased to 0.7, and aeration cost was reduced by about 10%.
2021, 39(5): 16-24,30.
doi: 10.13205/j.hjgc.202105003
Abstract:
Based on the web of Science (WoS) and CNKI scientific literature, using bibliometric statistics and visualization methods, research indicators of rural domestic sewage treatment in the past 25 years were analyzed, induding the amount of papers, main countries, research institutions, source publications, main authors and key words. From 1995 to 2019, 883 and 584 literatures from WoS and CNKI database were collected respectively in this field. The documents in WoS involve 64 countries in the world, and the amount of Chinese publications accounted for 22.2% of the total number of publications, leading the developed countries in Europe and America. In terms of major contributors, Lü Xiwu, a Chinese researches, had published 22 articles in the WoS and CNKI databases, ranking first in the world. Wastewater Treatment, Rural Domestic Sewage and Constructed Wetlands were the high-frequency key words in the literature, indicating that the core content of this field was rural domestic sewage treatment, and commonly used treatment process of constructed wetland. In the past 25 years, the research field of rural domestic sewage treatment had gradually developed from the aspects of early sewage treatment process selection and application, target pollutant removal effect and operation cost of treatment facilities to the aspects of microbial community to reveal the removal mechanism, GIS analysis in sourcing and the interaction relationship with rural residential environment improvement.
Based on the web of Science (WoS) and CNKI scientific literature, using bibliometric statistics and visualization methods, research indicators of rural domestic sewage treatment in the past 25 years were analyzed, induding the amount of papers, main countries, research institutions, source publications, main authors and key words. From 1995 to 2019, 883 and 584 literatures from WoS and CNKI database were collected respectively in this field. The documents in WoS involve 64 countries in the world, and the amount of Chinese publications accounted for 22.2% of the total number of publications, leading the developed countries in Europe and America. In terms of major contributors, Lü Xiwu, a Chinese researches, had published 22 articles in the WoS and CNKI databases, ranking first in the world. Wastewater Treatment, Rural Domestic Sewage and Constructed Wetlands were the high-frequency key words in the literature, indicating that the core content of this field was rural domestic sewage treatment, and commonly used treatment process of constructed wetland. In the past 25 years, the research field of rural domestic sewage treatment had gradually developed from the aspects of early sewage treatment process selection and application, target pollutant removal effect and operation cost of treatment facilities to the aspects of microbial community to reveal the removal mechanism, GIS analysis in sourcing and the interaction relationship with rural residential environment improvement.
2021, 39(5): 25-30.
doi: 10.13205/j.hjgc.202105004
Abstract:
The water-purifying constructed wetland for the Qiangwei Lake protection was monitored, and the water quality data from March 2017 to October 2018 was analyzed and discussed. The results showed that the overall performance of the wetland was in good condition, and the effluent of CODMn, NH3-N, TN, and TP was stable and met the class Ⅲ in Environment Quality Standard for Surface Water (GB 3838-2002), which realized the effective protection of drinking water sources. The average total nitrogen removal efficiency was more than 60% during the operation period, from spring to winter. Even the change of temperature did not influence the nitrogen removal. The synergistic effect of plant/animal and microorganism in the Qiangwei Lake constructed wetland made the TN removal rate reach the standard stably.
The water-purifying constructed wetland for the Qiangwei Lake protection was monitored, and the water quality data from March 2017 to October 2018 was analyzed and discussed. The results showed that the overall performance of the wetland was in good condition, and the effluent of CODMn, NH3-N, TN, and TP was stable and met the class Ⅲ in Environment Quality Standard for Surface Water (GB 3838-2002), which realized the effective protection of drinking water sources. The average total nitrogen removal efficiency was more than 60% during the operation period, from spring to winter. Even the change of temperature did not influence the nitrogen removal. The synergistic effect of plant/animal and microorganism in the Qiangwei Lake constructed wetland made the TN removal rate reach the standard stably.
2021, 39(5): 31-37,54.
doi: 10.13205/j.hjgc.202105005
Abstract:
In order to investigate the effects of nano-valent zero iron (NZVI) dosage on the reactor performance and microbial community diversity of mesophilic sludge anaerobic digester with low organic load, a series of lab-scale tests were carried out with four NZVI dosage of 0, 0.1, 0.3 and 0.5 g/g VS. Results showed that NZVI could promote methanogenesis in the early period, while with the accumulation of NZVI in the reactor, the methane production was gradually inhibited; and the higher the concentration of zero-valent iron, the stronger the inhibition. The addition of NZVI did not cause acidification or ammonia suppression. Noticeably, the anaerobic digestors had great stability and the removal rate of phosphate in supernatant could reach 97.78%. The addition of NZVI promoted the growth of hydrolytic acid-producing bacteria, such as Firmicutes, Proteobacteria, and the growth of hydrogenotrophic methanogens such as Methanosarcina, while it had inhibitory effect on the growth of Methanosaeta.
In order to investigate the effects of nano-valent zero iron (NZVI) dosage on the reactor performance and microbial community diversity of mesophilic sludge anaerobic digester with low organic load, a series of lab-scale tests were carried out with four NZVI dosage of 0, 0.1, 0.3 and 0.5 g/g VS. Results showed that NZVI could promote methanogenesis in the early period, while with the accumulation of NZVI in the reactor, the methane production was gradually inhibited; and the higher the concentration of zero-valent iron, the stronger the inhibition. The addition of NZVI did not cause acidification or ammonia suppression. Noticeably, the anaerobic digestors had great stability and the removal rate of phosphate in supernatant could reach 97.78%. The addition of NZVI promoted the growth of hydrolytic acid-producing bacteria, such as Firmicutes, Proteobacteria, and the growth of hydrogenotrophic methanogens such as Methanosarcina, while it had inhibitory effect on the growth of Methanosaeta.
2021, 39(5): 38-44.
doi: 10.13205/j.hjgc.202105006
Abstract:
The Partial Denitrification (PD) process can not only provide the substrate for the anaerobic ammonium oxidation (ANAMMOX) reaction, but also consume nitrate that is produced by ANAMMOX. Due to the advantages of low demand of organic carbon source, high reaction rate, low sludge yield and stable operation, PD has important scientific and engineering significance and become a research hotspot in recent years. In this review, the development process of PD technology was summarized in detail, together with the principle of PD which was expounded from the aspects of environmental factors on nitrite accumulation and microbial community structure, the existing problems and application prospects of PD. Finally, some suggestions on realizing the transition from traditional process to emerging and efficient PD process in China were put forward.
The Partial Denitrification (PD) process can not only provide the substrate for the anaerobic ammonium oxidation (ANAMMOX) reaction, but also consume nitrate that is produced by ANAMMOX. Due to the advantages of low demand of organic carbon source, high reaction rate, low sludge yield and stable operation, PD has important scientific and engineering significance and become a research hotspot in recent years. In this review, the development process of PD technology was summarized in detail, together with the principle of PD which was expounded from the aspects of environmental factors on nitrite accumulation and microbial community structure, the existing problems and application prospects of PD. Finally, some suggestions on realizing the transition from traditional process to emerging and efficient PD process in China were put forward.
2021, 39(5): 45-54.
doi: 10.13205/j.hjgc.202105007
Abstract:
The distributed hydrological and pollution load model for the Minjiang River Basin was constructed based on SWAT. The Nash-Sutcliffe of simulated hydrological transformation processes exceeded 0.6 and Nash-Sutcliffe of simulated pollutant concentrations exceeded 0.5, which could effectively simulate the hydrological, concentration and flux transformation processes of the Minjiang River Basin from 2015 to 2018. The changes of the main pollutant discharge, the different emission reduction measures of Water Pollution Prevention Action Plan and the meteorological driving conditions contributed to the improvement of the water environment in the Minjiang River Basin were calculated. The results showed that CODMn, NH3, and total TP emissions of 11 national examination sections of the Minjiang River Basin decreased by 8%, 13%, and 12% in 2018, the discharge of wastewater in 8 national examination sections increased, and the discharge of major pollutants decreased simultaneously. The intensity of point sources decreased, but the density increased. The emission intensity in the middle of the Minjiang River Basin was high, and the amount of emission reduction was also prominent. The emission and reduction of pollutants of Chengdu were higher than Meishan at Liangjianggou section. Among the emission reduction measures, urban pollution control played a leading role in reducing pollutant emissions, contributing 53%, 71% and 81% of total emission reduction to CODMn, NH3 and TP, namely. The contribution of emission reduction from domestic sources was greater than that from industrial sources, and the contribution rate of the point sources emission reduction was greater than that of the non-point sources. The contribution rate of pollution reduction measures to the CODMn, NH3 and TP in Liangjianggou section were 20.7%, 26.8% and 34.4%, respectively.
The distributed hydrological and pollution load model for the Minjiang River Basin was constructed based on SWAT. The Nash-Sutcliffe of simulated hydrological transformation processes exceeded 0.6 and Nash-Sutcliffe of simulated pollutant concentrations exceeded 0.5, which could effectively simulate the hydrological, concentration and flux transformation processes of the Minjiang River Basin from 2015 to 2018. The changes of the main pollutant discharge, the different emission reduction measures of Water Pollution Prevention Action Plan and the meteorological driving conditions contributed to the improvement of the water environment in the Minjiang River Basin were calculated. The results showed that CODMn, NH3, and total TP emissions of 11 national examination sections of the Minjiang River Basin decreased by 8%, 13%, and 12% in 2018, the discharge of wastewater in 8 national examination sections increased, and the discharge of major pollutants decreased simultaneously. The intensity of point sources decreased, but the density increased. The emission intensity in the middle of the Minjiang River Basin was high, and the amount of emission reduction was also prominent. The emission and reduction of pollutants of Chengdu were higher than Meishan at Liangjianggou section. Among the emission reduction measures, urban pollution control played a leading role in reducing pollutant emissions, contributing 53%, 71% and 81% of total emission reduction to CODMn, NH3 and TP, namely. The contribution of emission reduction from domestic sources was greater than that from industrial sources, and the contribution rate of the point sources emission reduction was greater than that of the non-point sources. The contribution rate of pollution reduction measures to the CODMn, NH3 and TP in Liangjianggou section were 20.7%, 26.8% and 34.4%, respectively.
2021, 39(5): 55-60,70.
doi: 10.13205/j.hjgc.202105008
Abstract:
In this paper, graphite phase carbon nitride was prepared by thermal polymerization process using melamine and dilute nitric acid as raw materials. Effects of calcination temperature on the photocatalytic activity to degradation of Rhodamine B (RhB) of the graphite phase carbon nitride were researched. Their morphologies, crystal structure, chemical composition of as prepared graphite phase carbon nitride were characterized by means of SEM, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS),Fourier transform infrared spectroscopy(FT-IR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and photoluminescence spectra (PL). The photocatalytic performance of g-C3N4 was tested by photo-decomposition of RhB and the experiment result manifested that the prepared graphite phase carbon nitride samples showed best photocatalyst property when the calcination temperature was 550℃. The degradation rate of RhB in 50 min was about 91.7% after 50 min irradiation under visible light with the dosage of photocatalyst at 0.04 g. Appropriate calcination temperature would be beneficial to enhance light absorption capacity and promote the separation of photogenerated electrons (e-) and holes (h+).
In this paper, graphite phase carbon nitride was prepared by thermal polymerization process using melamine and dilute nitric acid as raw materials. Effects of calcination temperature on the photocatalytic activity to degradation of Rhodamine B (RhB) of the graphite phase carbon nitride were researched. Their morphologies, crystal structure, chemical composition of as prepared graphite phase carbon nitride were characterized by means of SEM, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS),Fourier transform infrared spectroscopy(FT-IR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and photoluminescence spectra (PL). The photocatalytic performance of g-C3N4 was tested by photo-decomposition of RhB and the experiment result manifested that the prepared graphite phase carbon nitride samples showed best photocatalyst property when the calcination temperature was 550℃. The degradation rate of RhB in 50 min was about 91.7% after 50 min irradiation under visible light with the dosage of photocatalyst at 0.04 g. Appropriate calcination temperature would be beneficial to enhance light absorption capacity and promote the separation of photogenerated electrons (e-) and holes (h+).
2021, 39(5): 61-70.
doi: 10.13205/j.hjgc.202105009
Abstract:
Some organisms in nature can produce minerals, which could form mineralized protective shells. The protective shells perform well in improving the resistance of the organisms to adverse external environments and life functions. In order to make better use of the advantages of protective shells, researchers have begun to study the biomineralization mechanism, and developed various biomimetic mineralization methods to make artificial protective shells for organisms that cannot produce mineral shells by themselves. These organisms with protective shells show broad application prospects in the fields of diseases treatment, environmental protection and new energies. This article mainly focuses on the preparation methods and application values of protective shells of microbial cells. Main methods of preparing protective shells were outlined from the aspects of the preparation mechanism, the specific procedure and the application scope. The value of the application of protective shells in both protecting cells from outside attack and saving cells at room temperature were then discussed. Finally, the application of microorganisms with protective shells in environmental pollution control was prospected.
Some organisms in nature can produce minerals, which could form mineralized protective shells. The protective shells perform well in improving the resistance of the organisms to adverse external environments and life functions. In order to make better use of the advantages of protective shells, researchers have begun to study the biomineralization mechanism, and developed various biomimetic mineralization methods to make artificial protective shells for organisms that cannot produce mineral shells by themselves. These organisms with protective shells show broad application prospects in the fields of diseases treatment, environmental protection and new energies. This article mainly focuses on the preparation methods and application values of protective shells of microbial cells. Main methods of preparing protective shells were outlined from the aspects of the preparation mechanism, the specific procedure and the application scope. The value of the application of protective shells in both protecting cells from outside attack and saving cells at room temperature were then discussed. Finally, the application of microorganisms with protective shells in environmental pollution control was prospected.
2021, 39(5): 71-79.
doi: 10.13205/j.hjgc.202105010
Abstract:
The statistical method, Pearson correlation coefficient method and linear regression method were adopted to analyse the variation characteristics of the concentrations of SO2, NO2, PM10, PM2.5, CO and O3, the correlation between pollutants concentrations, as well as the relationship between pollutants and meteorological factors in Jilin city in 2018. The results showed that:1) the exceeding standard rate of daily average value of O3, PM10 and PM2.5 concentrations in Jilin city account for 1.06%, 3.27% and 7.14%, respectively; consequently, air pollution control should focus on particles, O3 and their precursors; the pollution of CO, SO2, NO2, PM10 and PM2.5 were more serious in spring and winter, and the less in summer; the concentration of pollutants varied periodically with seasons, hour and human activities. 2) The concentrations of PM10 and PM2.5, PM2.5 and CO, as well as NO2 and CO, were highly correlated with each other (correlation coefficients r were all above 0.8), and the prediction linear model was established in this research. 3) The concentration of pollutants (except O3) was negatively correlated with temperature, wind speed and mixed layer height, but positively correlated with air pressure; precipitation had a certain reduction effect on SO2, PM10 and PM2.5 concentration, the percentage of pollutant concentration reduced after precipitation were 68.75%, 84.38% and 78.13%, respectively; the particles, the most seriously pollutant in Jilin city, were greatly affected by mixed height, wind speed and precipitation. This study could provide references for air pollution control, calculation of regional atmospheric environmental capacity and prediction of air pollution potential and elated researches in Jilin city.
The statistical method, Pearson correlation coefficient method and linear regression method were adopted to analyse the variation characteristics of the concentrations of SO2, NO2, PM10, PM2.5, CO and O3, the correlation between pollutants concentrations, as well as the relationship between pollutants and meteorological factors in Jilin city in 2018. The results showed that:1) the exceeding standard rate of daily average value of O3, PM10 and PM2.5 concentrations in Jilin city account for 1.06%, 3.27% and 7.14%, respectively; consequently, air pollution control should focus on particles, O3 and their precursors; the pollution of CO, SO2, NO2, PM10 and PM2.5 were more serious in spring and winter, and the less in summer; the concentration of pollutants varied periodically with seasons, hour and human activities. 2) The concentrations of PM10 and PM2.5, PM2.5 and CO, as well as NO2 and CO, were highly correlated with each other (correlation coefficients r were all above 0.8), and the prediction linear model was established in this research. 3) The concentration of pollutants (except O3) was negatively correlated with temperature, wind speed and mixed layer height, but positively correlated with air pressure; precipitation had a certain reduction effect on SO2, PM10 and PM2.5 concentration, the percentage of pollutant concentration reduced after precipitation were 68.75%, 84.38% and 78.13%, respectively; the particles, the most seriously pollutant in Jilin city, were greatly affected by mixed height, wind speed and precipitation. This study could provide references for air pollution control, calculation of regional atmospheric environmental capacity and prediction of air pollution potential and elated researches in Jilin city.
2021, 39(5): 80-88.
doi: 10.13205/j.hjgc.202105011
Abstract:
Fine particulate matter (PM2.5) samples from four kinds of open-sources (soil dust, construction dust, road dust and yard dust) in Wuhan were obtained by re-suspension sampling method, then the content of inorganic elements, water-soluble ions and carbon fractions of samples were analyzed. On this basis, the source profiles of PM2.5 for four kinds of open-sources in Wuhan were established. The results showed that crustal elements were the primary components in PM2.5 source profiles of open-sources and accounted for 62.69%~80.14% of the total chemical compositions, which was obviously a natural background feature. The results revealed that Si and Al were the relatively high constituents in soil dust, and the contents of Ca and OC in PM2.5 of construction dust were significantly higher than other three kinds of sources. Ca, Si and OC were the main composition in PM2.5 of road dust, and the main composition in PM2.5 of yard dust were Si and Ca. Ca, Cu and Zn were strongly enriched in construction dust, road dust and yard dust, respectively, and each of the enrichment facts(EF) was all greater than 20, which suggested that the influence of man-made sources was significant. OC was the dominating part of carbon fractions of source profiles, and all the values of OC/EC were greater than 2, indicating that open-sources had a certain influence on the formation of secondary aerosols. The divergence coefficient among four kinds of source profiles was between 0.29 and 0.47, and the correlation coefficient was between 0.19 and 0.97. The similarity between soil dust and the other three kinds of source profiles was not high. Relatively high similarity were observed among yard dust, construction dust and road dust, and these three kinds of sources had extremely strong collinearity. The establishment of refined PM2.5 source profiles of open-source in Wuhan could provide scientific support for PM2.5 source apportionment, and also provide important references for the prevention and control of open-sources in Wuhan.
Fine particulate matter (PM2.5) samples from four kinds of open-sources (soil dust, construction dust, road dust and yard dust) in Wuhan were obtained by re-suspension sampling method, then the content of inorganic elements, water-soluble ions and carbon fractions of samples were analyzed. On this basis, the source profiles of PM2.5 for four kinds of open-sources in Wuhan were established. The results showed that crustal elements were the primary components in PM2.5 source profiles of open-sources and accounted for 62.69%~80.14% of the total chemical compositions, which was obviously a natural background feature. The results revealed that Si and Al were the relatively high constituents in soil dust, and the contents of Ca and OC in PM2.5 of construction dust were significantly higher than other three kinds of sources. Ca, Si and OC were the main composition in PM2.5 of road dust, and the main composition in PM2.5 of yard dust were Si and Ca. Ca, Cu and Zn were strongly enriched in construction dust, road dust and yard dust, respectively, and each of the enrichment facts(EF) was all greater than 20, which suggested that the influence of man-made sources was significant. OC was the dominating part of carbon fractions of source profiles, and all the values of OC/EC were greater than 2, indicating that open-sources had a certain influence on the formation of secondary aerosols. The divergence coefficient among four kinds of source profiles was between 0.29 and 0.47, and the correlation coefficient was between 0.19 and 0.97. The similarity between soil dust and the other three kinds of source profiles was not high. Relatively high similarity were observed among yard dust, construction dust and road dust, and these three kinds of sources had extremely strong collinearity. The establishment of refined PM2.5 source profiles of open-source in Wuhan could provide scientific support for PM2.5 source apportionment, and also provide important references for the prevention and control of open-sources in Wuhan.
2021, 39(5): 89-95.
doi: 10.13205/j.hjgc.202105012
Abstract:
In order to solve the problem of non-uniformity in the traditional pulse cleaning, the upper open scatter had been proposed to improve the internal flow field characteristics of the filter cartridge, so as to improve the cleaning efficiency. By numerical simulation method, the dynamic changes of pulse flow field and the dust cleaning pressure in the filter cartridge under different conditions were investigated, and the formation mechanism of the peak pressure of ash cleaning was explored. The results showed that the pulse-jet flow entered the filter cartridge in the form of pressure wave and transferred to the sidewall, and the pressure and radial velocity of the sidewall changed synchronously with time, and there was a direct connection between them. As a result of the diverting and guiding effect of the scatter on the jet flow, compared with no scatter case, the radial velocity of the upper part of the filter cartridge increased, thus dust cleaning pressure increased correspondingly, which the dust cleaning pressure increased from 484 Pa to 744 Pa, by 53.7%. On the contrary, the flow rate and axial velocity of the impulse injection in the middle and lower part of the filter cartridge would be reduced, the compression effect of the impulse airflow on the gas inside the filter cartridge would be reduced as well. The pressure in the middle and lower parts would be reduced respectively, and the pressure peak in the lower part decreased from 2175 Pa to 1468 Pa, by 32.5%. Therefore, adding a scatterer could obviously improve the uniformity of pulse ash cleaning and meet the requirements of ash cleaning.
In order to solve the problem of non-uniformity in the traditional pulse cleaning, the upper open scatter had been proposed to improve the internal flow field characteristics of the filter cartridge, so as to improve the cleaning efficiency. By numerical simulation method, the dynamic changes of pulse flow field and the dust cleaning pressure in the filter cartridge under different conditions were investigated, and the formation mechanism of the peak pressure of ash cleaning was explored. The results showed that the pulse-jet flow entered the filter cartridge in the form of pressure wave and transferred to the sidewall, and the pressure and radial velocity of the sidewall changed synchronously with time, and there was a direct connection between them. As a result of the diverting and guiding effect of the scatter on the jet flow, compared with no scatter case, the radial velocity of the upper part of the filter cartridge increased, thus dust cleaning pressure increased correspondingly, which the dust cleaning pressure increased from 484 Pa to 744 Pa, by 53.7%. On the contrary, the flow rate and axial velocity of the impulse injection in the middle and lower part of the filter cartridge would be reduced, the compression effect of the impulse airflow on the gas inside the filter cartridge would be reduced as well. The pressure in the middle and lower parts would be reduced respectively, and the pressure peak in the lower part decreased from 2175 Pa to 1468 Pa, by 32.5%. Therefore, adding a scatterer could obviously improve the uniformity of pulse ash cleaning and meet the requirements of ash cleaning.
2021, 39(5): 96-103.
doi: 10.13205/j.hjgc.202105013
Abstract:
To understand the characteristics and differences of PM2.5 concentration in the northwest inland and east coast, this paper used wavelet analysis and Spearman correlation analysis to compare the distribution characteristics and differences of PM2.5 concentration values in 12 major cities in winter and spring. The results showed that, affected by differences in geographic location and topography, the concentration of PM2.5 was significantly different in the northwest inland and east coastal cities. The results mainly manifested in:1) the distribution of PM2.5 in the northwest inland and the eastern coastal areas was significantly different in winter and spring. The east Coastal areas were better than the northwest inland areas, while the east coastal areas had relatively low excess rates. Urumqi and Xi'an accounted for a relatively high percentage of excesses; 2) Wavelet analysis showed that the northwest inland and the east coast possessed obvious differences in cycle, but the overall appearance occurred in winter (before 80 d); 3) The Spearman correlation coefficient had obvious distance attenuation, and the correlation coefficient weakened from the northwest inland to the coastal cities in the east; 4) The abrupt changes of PM2.5 concentration values in the east and northwest were significantly different on time scales. The overall abrupt changes in the northwestern inland areas appeared on the 2nd, 11th, 24th, 49th, and 70th day, and the eastern coastal areas appear on 2nd, 17th, 42th, 53th, 70th day.
To understand the characteristics and differences of PM2.5 concentration in the northwest inland and east coast, this paper used wavelet analysis and Spearman correlation analysis to compare the distribution characteristics and differences of PM2.5 concentration values in 12 major cities in winter and spring. The results showed that, affected by differences in geographic location and topography, the concentration of PM2.5 was significantly different in the northwest inland and east coastal cities. The results mainly manifested in:1) the distribution of PM2.5 in the northwest inland and the eastern coastal areas was significantly different in winter and spring. The east Coastal areas were better than the northwest inland areas, while the east coastal areas had relatively low excess rates. Urumqi and Xi'an accounted for a relatively high percentage of excesses; 2) Wavelet analysis showed that the northwest inland and the east coast possessed obvious differences in cycle, but the overall appearance occurred in winter (before 80 d); 3) The Spearman correlation coefficient had obvious distance attenuation, and the correlation coefficient weakened from the northwest inland to the coastal cities in the east; 4) The abrupt changes of PM2.5 concentration values in the east and northwest were significantly different on time scales. The overall abrupt changes in the northwestern inland areas appeared on the 2nd, 11th, 24th, 49th, and 70th day, and the eastern coastal areas appear on 2nd, 17th, 42th, 53th, 70th day.
2021, 39(5): 104-110.
doi: 10.13205/j.hjgc.202105014
Abstract:
To study the effect of ambient temperature on the changes of antibiotic resistance gene variation in sludge composting process, municipal sewage treatment plant sludge dewatering, peanut shells and compost backmixing material were selected as composting materials. The effects of the three external environment temperature on changes of antibiotic resistances genes in sludge composting process were analyzed and compared by measuring the physical and chemical properties of composted materials and resistance genes(tetA、tetQ、sul2、sul3) and class integron(IntI1) abundance in the composting process at 30℃, 50℃ and 55℃ by the indoor static composting and turning method. The results showed that the abundance of tetA, tetQ, sul2 and sul3 resistance genes in the process of sludge composting at ambient temperatures outside 50℃ and 55℃ could be effectively reduced, and the degradation rate of total ARGs reached 66%~83% at the end of composting, while the degradation rate of total ARGs was about 30% at the end of composting at external temperature of 30℃. The degradation rate of mobile genetic elements IntI1 at the end of the composting at 50℃ and 55℃ was 92% above, higher than that of at 30℃ (71.9%). The reason may be that proper high ambient temperature inhibited the growth and metabolism of some microbial in the pile and reduced the spread of IntI1, and then affected the spread of the ARGs. The compost at ambient temperature of 30℃ reached maturity on the 36th day, and the germination index was 59.80%. The compost at 50℃ and 55℃ reached maturity on the 28th day, the germination index reached 60%, and the maturity rate was significantly higher than that at 30℃. The study showed that composting conditions at ambient temperatures of 50℃ and 55℃ could shorten the time required for composting compared with that of 30℃, and had a good degradation effect on tetA, tetQ, sul2, sul3 resistance genes and IntI1 abundance. Therefore, appropriately increasing the ambient temperature during the composting process had certain effect on sludge fermentation and ARGs.
To study the effect of ambient temperature on the changes of antibiotic resistance gene variation in sludge composting process, municipal sewage treatment plant sludge dewatering, peanut shells and compost backmixing material were selected as composting materials. The effects of the three external environment temperature on changes of antibiotic resistances genes in sludge composting process were analyzed and compared by measuring the physical and chemical properties of composted materials and resistance genes(tetA、tetQ、sul2、sul3) and class integron(IntI1) abundance in the composting process at 30℃, 50℃ and 55℃ by the indoor static composting and turning method. The results showed that the abundance of tetA, tetQ, sul2 and sul3 resistance genes in the process of sludge composting at ambient temperatures outside 50℃ and 55℃ could be effectively reduced, and the degradation rate of total ARGs reached 66%~83% at the end of composting, while the degradation rate of total ARGs was about 30% at the end of composting at external temperature of 30℃. The degradation rate of mobile genetic elements IntI1 at the end of the composting at 50℃ and 55℃ was 92% above, higher than that of at 30℃ (71.9%). The reason may be that proper high ambient temperature inhibited the growth and metabolism of some microbial in the pile and reduced the spread of IntI1, and then affected the spread of the ARGs. The compost at ambient temperature of 30℃ reached maturity on the 36th day, and the germination index was 59.80%. The compost at 50℃ and 55℃ reached maturity on the 28th day, the germination index reached 60%, and the maturity rate was significantly higher than that at 30℃. The study showed that composting conditions at ambient temperatures of 50℃ and 55℃ could shorten the time required for composting compared with that of 30℃, and had a good degradation effect on tetA, tetQ, sul2, sul3 resistance genes and IntI1 abundance. Therefore, appropriately increasing the ambient temperature during the composting process had certain effect on sludge fermentation and ARGs.
2021, 39(5): 111-117,130.
doi: 10.13205/j.hjgc.202105015
Abstract:
In order to further improve the disposing efficiency of continuous high-temperature composting disposing food waste, we obtained thermophilic microbial consortium (TMC) degrading organic matter efficiently, by screening and high-temperature domestication. Three treatments, including continuous high-temperature composting with (T1) and without TMC inoculation (T2) and natural composting (T3) were set. The influence of TMC inoculation on continuous high-temperature composting process was revealed by comparison of physical and chemical indexes, crude fat and protein content and GI index and analysis of dominant bacterial succession law. Results showed that the decreased levels of organic matter content, C/N, crude fat and protein content were all in order of T1>T2>T3 after composting. The above indicators were significantly different among T1, T2 and T3 (P<0.05). These results confirmed that inoculation of TMC could accelerate the continuous high-temperature composting process and improve composting efficiency. On the 14th day of composting, the GI was 110% and 99% in T1 and T2 treatment respectively, but that of T3 treatment was only 80%, indicating that the continuous high-temperature composting could accelerate the degradation of phytotoxic substances and significantly improve compost quality. TMC inoculation could further promote harm-free compost. PCR-DGGE results showed that the diversities of thermophilic or heat-resistant bacteria and heat-resistant lignocellulose-degrading bacteria increased remarkably in T1 and T2 treatment. At the same time, mesophilic lignocellulose-degrading bacterial diversity did not decrease. Two kinds of bacteria cooperated to achieve faster degradation of lignocellulose, which was helpful in shortening food waste composting process. In conclusion, TMC inoculation could significantly improve the efficiency of continuous high-temperature composting and food waste compost quality.
In order to further improve the disposing efficiency of continuous high-temperature composting disposing food waste, we obtained thermophilic microbial consortium (TMC) degrading organic matter efficiently, by screening and high-temperature domestication. Three treatments, including continuous high-temperature composting with (T1) and without TMC inoculation (T2) and natural composting (T3) were set. The influence of TMC inoculation on continuous high-temperature composting process was revealed by comparison of physical and chemical indexes, crude fat and protein content and GI index and analysis of dominant bacterial succession law. Results showed that the decreased levels of organic matter content, C/N, crude fat and protein content were all in order of T1>T2>T3 after composting. The above indicators were significantly different among T1, T2 and T3 (P<0.05). These results confirmed that inoculation of TMC could accelerate the continuous high-temperature composting process and improve composting efficiency. On the 14th day of composting, the GI was 110% and 99% in T1 and T2 treatment respectively, but that of T3 treatment was only 80%, indicating that the continuous high-temperature composting could accelerate the degradation of phytotoxic substances and significantly improve compost quality. TMC inoculation could further promote harm-free compost. PCR-DGGE results showed that the diversities of thermophilic or heat-resistant bacteria and heat-resistant lignocellulose-degrading bacteria increased remarkably in T1 and T2 treatment. At the same time, mesophilic lignocellulose-degrading bacterial diversity did not decrease. Two kinds of bacteria cooperated to achieve faster degradation of lignocellulose, which was helpful in shortening food waste composting process. In conclusion, TMC inoculation could significantly improve the efficiency of continuous high-temperature composting and food waste compost quality.
2021, 39(5): 118-123.
doi: 10.13205/j.hjgc.202105016
Abstract:
To investigate the dewatering performance of sewage sludge and the relationship between dewaterability with protein (PN) and polysaccharide (PS) of extracellular polymers (EPS) in bioleaching process, in which ferrous ammonium sulfate (FAS) and sulfur powder (S0) were supplied as substrates, raw sludge was bioleached with 10% inoculum+(0, 2 g/L, 4 g/L, 6 g/L) FAS+(0 g/L, 2 g/L, 4 g/L, 6 g/L) S0. Meanwhile, the raw sludge and raw sludge with 10% inoculum were designed as control groups. Results showed that the best bioleaching process condition was 4 g/L FAS+2g/L S0 for 6 days, and then SRF and viscosity decreased by 83.11% and 65.74%, respectively. Both dissolved and bound PN and PS content in EPS changed with the bioleaching progress, which influenced the SRF and viscosity of sludge. It was determined that dissolved PS was negatively correlate with SRF and viscosity(R=-0.813、-0.813,P<0.05),suggesting that the content of dissolved PS was the main factor affecting the dewaterability of sludge. Subsequent experiments showed that more hydrophobic PS was produced together with the dissolved PS with the bioleaching progress, contributing to the improvement of dewatering performance of sludge.
To investigate the dewatering performance of sewage sludge and the relationship between dewaterability with protein (PN) and polysaccharide (PS) of extracellular polymers (EPS) in bioleaching process, in which ferrous ammonium sulfate (FAS) and sulfur powder (S0) were supplied as substrates, raw sludge was bioleached with 10% inoculum+(0, 2 g/L, 4 g/L, 6 g/L) FAS+(0 g/L, 2 g/L, 4 g/L, 6 g/L) S0. Meanwhile, the raw sludge and raw sludge with 10% inoculum were designed as control groups. Results showed that the best bioleaching process condition was 4 g/L FAS+2g/L S0 for 6 days, and then SRF and viscosity decreased by 83.11% and 65.74%, respectively. Both dissolved and bound PN and PS content in EPS changed with the bioleaching progress, which influenced the SRF and viscosity of sludge. It was determined that dissolved PS was negatively correlate with SRF and viscosity(R=-0.813、-0.813,P<0.05),suggesting that the content of dissolved PS was the main factor affecting the dewaterability of sludge. Subsequent experiments showed that more hydrophobic PS was produced together with the dissolved PS with the bioleaching progress, contributing to the improvement of dewatering performance of sludge.
2021, 39(5): 124-130.
doi: 10.13205/j.hjgc.202105017
Abstract:
Aiming at the problems of long treatment cycle and low dehydration efficiency of kitchen waste bio-drying, the effects of different aeration modes (groups with aeration controlled by temperature:TFWD 45-50, TFWD 50-55, TFWD 55-60, TFWD 60-65; groups with aeration controlled by time:TFSJ 20, TFSJ 60) on energy consumption, dehydration efficiency and nitrogen loss of kitchen waste biol-drying, on the bio-drying machine with external auxiliary heating, were evaluated. The results showed that:1) compared with the four treatments of aeration controlled by temperature, the two treatments of aeration controlled by time were with less total nitrogen (TN) and ammonium nitrogen losses, and higher germination index (GI); 2) continuous aeration, TFSJ 60, was with the lowest dehydration efficiency (66.78%), lowest TN and ammonium nitrogen losses (8.14% and 12.96%, respectively), highest maturity (EC was 2.72 mS/cm and GI was 75.00%), and the lowest energy consumption per unit of mass dehydration (1.10 kW·h/kg); 3) TFWD 50-55 was with the highest dehydration efficiency (more than 99%), TN and ammonium nitrogen losses (16.95% and 57.83%, respectively), lower maturity (EC was 4.28 mS/cm and GI was 19.58%), and higher energy consumption per unit of mass dehydration (1.74 kW·h/kg). Pearson correlation analysis results showed that TN and ammonium nitrogen were positively correlated with moisture content (P<0.05), and negatively correlated with temperature, EC and energy consumption (P<0.05). Therefore, continuous aeration (TFSJ 60) was recommended for kitchen waste, if the bio-dried materials were treated by aerobic composting to return to the soil; aeration controlled by temperature (TFWD 50-55) was recommended, if the bio-dried materials were to be incinerated or landfilled. This study could provide references for the selection of aeration mode for the treatment of kitchen waste by external auxiliary heating bio-drying machine.
Aiming at the problems of long treatment cycle and low dehydration efficiency of kitchen waste bio-drying, the effects of different aeration modes (groups with aeration controlled by temperature:TFWD 45-50, TFWD 50-55, TFWD 55-60, TFWD 60-65; groups with aeration controlled by time:TFSJ 20, TFSJ 60) on energy consumption, dehydration efficiency and nitrogen loss of kitchen waste biol-drying, on the bio-drying machine with external auxiliary heating, were evaluated. The results showed that:1) compared with the four treatments of aeration controlled by temperature, the two treatments of aeration controlled by time were with less total nitrogen (TN) and ammonium nitrogen losses, and higher germination index (GI); 2) continuous aeration, TFSJ 60, was with the lowest dehydration efficiency (66.78%), lowest TN and ammonium nitrogen losses (8.14% and 12.96%, respectively), highest maturity (EC was 2.72 mS/cm and GI was 75.00%), and the lowest energy consumption per unit of mass dehydration (1.10 kW·h/kg); 3) TFWD 50-55 was with the highest dehydration efficiency (more than 99%), TN and ammonium nitrogen losses (16.95% and 57.83%, respectively), lower maturity (EC was 4.28 mS/cm and GI was 19.58%), and higher energy consumption per unit of mass dehydration (1.74 kW·h/kg). Pearson correlation analysis results showed that TN and ammonium nitrogen were positively correlated with moisture content (P<0.05), and negatively correlated with temperature, EC and energy consumption (P<0.05). Therefore, continuous aeration (TFSJ 60) was recommended for kitchen waste, if the bio-dried materials were treated by aerobic composting to return to the soil; aeration controlled by temperature (TFWD 50-55) was recommended, if the bio-dried materials were to be incinerated or landfilled. This study could provide references for the selection of aeration mode for the treatment of kitchen waste by external auxiliary heating bio-drying machine.
2021, 39(5): 131-134.
doi: 10.13205/j.hjgc.202105018
Abstract:
Drying is a process in which the moisture in the material absorbs enough sensible heat and latent heat. Moisture evaporation consumes a lot of heat, and produces a large quantity of secondary steam. According to the principle of high efficiency and energy saving of MVR heat pump,if the secondary steam whose enthalpy is increased by mechanical steam recompression technology, is used as the heat source in the drying process, all latent heat of the secondary steam can be recovered. The exchange of latent heat of evaporation and vaporization with latent heat of condensation was realized in the system, and the energy saving effect was remarkable. This paper summarized the application of MVR heat pump drying, and expounded the advantages of superheated steam as MVR heat pump drying medium, as well as the problems to be considered in the design of MVR heat pump dryer and the selection of compressor. It was pointed out that the inlet and outlet should minimize the non-condensable gas entering into the drying system, avoiding the influence of non-condensable gas on condensation heat transfer in the drying process.
Drying is a process in which the moisture in the material absorbs enough sensible heat and latent heat. Moisture evaporation consumes a lot of heat, and produces a large quantity of secondary steam. According to the principle of high efficiency and energy saving of MVR heat pump,if the secondary steam whose enthalpy is increased by mechanical steam recompression technology, is used as the heat source in the drying process, all latent heat of the secondary steam can be recovered. The exchange of latent heat of evaporation and vaporization with latent heat of condensation was realized in the system, and the energy saving effect was remarkable. This paper summarized the application of MVR heat pump drying, and expounded the advantages of superheated steam as MVR heat pump drying medium, as well as the problems to be considered in the design of MVR heat pump dryer and the selection of compressor. It was pointed out that the inlet and outlet should minimize the non-condensable gas entering into the drying system, avoiding the influence of non-condensable gas on condensation heat transfer in the drying process.
2021, 39(5): 135-141,149.
doi: 10.13205/j.hjgc.202105019
Abstract:
In order to alleviate the risk caused by China's high dependence on oil import, the development of a coal-to-liquid process that converts coal into oil through scientific means is a practical mean. This article reviewed the four most common coal-to-liquid technologies in China, analyzed the advantages and disadvantages of the four coal-to-liquid technologies, and provided a basis for the research of coal-to-liquid technology. The coal-to-liquid residue was the main pollution product of the coal-to-liquid industry. This article also classified the residues produced by different coal-to-liquid processes, summarized their composition and physical and chemical properties, and selected the direct coal liquefaction residue system to explain the current utilization technology of coal direct liquefaction residues. The research progress mainly included four parts:combustion, pyrolysis, preparation of asphalt products and the other. It was suggested that the development trend of coal-to-liquid technology was to study the structure conversion process of coal, cheaper and more efficient catalysts and their catalytic principles, high-throughput reactors for catalyst separation, and product separation technology. Among the high-value utilization methods of coal-to-liquid residue, asphalt products and high-performance carbon materials had good economic prospects and research value.
In order to alleviate the risk caused by China's high dependence on oil import, the development of a coal-to-liquid process that converts coal into oil through scientific means is a practical mean. This article reviewed the four most common coal-to-liquid technologies in China, analyzed the advantages and disadvantages of the four coal-to-liquid technologies, and provided a basis for the research of coal-to-liquid technology. The coal-to-liquid residue was the main pollution product of the coal-to-liquid industry. This article also classified the residues produced by different coal-to-liquid processes, summarized their composition and physical and chemical properties, and selected the direct coal liquefaction residue system to explain the current utilization technology of coal direct liquefaction residues. The research progress mainly included four parts:combustion, pyrolysis, preparation of asphalt products and the other. It was suggested that the development trend of coal-to-liquid technology was to study the structure conversion process of coal, cheaper and more efficient catalysts and their catalytic principles, high-throughput reactors for catalyst separation, and product separation technology. Among the high-value utilization methods of coal-to-liquid residue, asphalt products and high-performance carbon materials had good economic prospects and research value.
2021, 39(5): 142-149.
doi: 10.13205/j.hjgc.202105020
Abstract:
Indium is a rare and dispersed metal, which has been widely used in military, national defense, energy, electronic industry, medical and other fields. The reserved content of indium on earth is one sixth of that of gold. With the development of science and technology, the application field of indium is expanding and the demand of indium is increasing. The rarity and importance of indium promoted the development of research on the recovery of secondary-indium from e-waste. This paper reviewed the processes and principles of secondary-indium recovery from different kinds of indium-containing e-wastes, and the technological development bottlenecks and prospects of different recovery procedures were also proposed.
Indium is a rare and dispersed metal, which has been widely used in military, national defense, energy, electronic industry, medical and other fields. The reserved content of indium on earth is one sixth of that of gold. With the development of science and technology, the application field of indium is expanding and the demand of indium is increasing. The rarity and importance of indium promoted the development of research on the recovery of secondary-indium from e-waste. This paper reviewed the processes and principles of secondary-indium recovery from different kinds of indium-containing e-wastes, and the technological development bottlenecks and prospects of different recovery procedures were also proposed.
2021, 39(5): 150-155.
doi: 10.13205/j.hjgc.202105021
Abstract:
As a kind of hazardous solid waste, oily scum does not only pose a huge threat to the ecosystem, but also cause of non-renewable resources. Aiming at the problems of high oil content, high organic matter of oily scum, based on the modification of oil content residue phase and TOC removal rate in water phase, the conditions of ultrasonic-Fenton oxidation process assisted by demulsifier were optimized by single factor experiment. The results showed that the optimal conditions were as follows:the concentration of SP-142 was 20 mg/L, ultrasonic time was 10 min, solid-to-liquid ratio was 1:4, temperature was 60℃, pH value was 3, the concentration of Fe2+ was 0.4 g/L, and the dosage of H2O2 was 2 mL. As a result, the oil content in the residue phase was 20.65%, and the removal rate of TOC in water phase was 45.98%, which provided a reference for the resource utilization of oily scum.
As a kind of hazardous solid waste, oily scum does not only pose a huge threat to the ecosystem, but also cause of non-renewable resources. Aiming at the problems of high oil content, high organic matter of oily scum, based on the modification of oil content residue phase and TOC removal rate in water phase, the conditions of ultrasonic-Fenton oxidation process assisted by demulsifier were optimized by single factor experiment. The results showed that the optimal conditions were as follows:the concentration of SP-142 was 20 mg/L, ultrasonic time was 10 min, solid-to-liquid ratio was 1:4, temperature was 60℃, pH value was 3, the concentration of Fe2+ was 0.4 g/L, and the dosage of H2O2 was 2 mL. As a result, the oil content in the residue phase was 20.65%, and the removal rate of TOC in water phase was 45.98%, which provided a reference for the resource utilization of oily scum.
2021, 39(5): 156-164,15.
doi: 10.13205/j.hjgc.202105022
Abstract:
Micro plastic is a new kind of soil pollutant, which has a serious impact on soil environment and health, and has become a hot research topic. In this paper, the pollution status and distribution characteristics of farmland soil microplastics were systematically analyzed, and the effects of different agricultural production modes on the pollution abundance of soil microplastics and their distribution and migration characteristics in soil were summarized. This paper expounds the pollution sources of different micro plastics and their harm to the soil environment, and points out that plastic film mulching will become an important source of farmland soil micro plastics pollution. Different particle size, concentration and type of micro plastics will have different degrees of impact on farmland soil physical and chemical properties and soil biology. At the same time, the detection and analysis methods and means of soil micro plastics are also compared and analyzed. Future scientific problems and research directions of soil microplastics are prospected from four aspects:traceability, migration and transformation, pollution hazards and analysis methods, so as to provide a comprehensive scientific reference for the research of farmland soil microplastics and control of microplastics pollution.
Micro plastic is a new kind of soil pollutant, which has a serious impact on soil environment and health, and has become a hot research topic. In this paper, the pollution status and distribution characteristics of farmland soil microplastics were systematically analyzed, and the effects of different agricultural production modes on the pollution abundance of soil microplastics and their distribution and migration characteristics in soil were summarized. This paper expounds the pollution sources of different micro plastics and their harm to the soil environment, and points out that plastic film mulching will become an important source of farmland soil micro plastics pollution. Different particle size, concentration and type of micro plastics will have different degrees of impact on farmland soil physical and chemical properties and soil biology. At the same time, the detection and analysis methods and means of soil micro plastics are also compared and analyzed. Future scientific problems and research directions of soil microplastics are prospected from four aspects:traceability, migration and transformation, pollution hazards and analysis methods, so as to provide a comprehensive scientific reference for the research of farmland soil microplastics and control of microplastics pollution.
2021, 39(5): 165-170,79.
doi: 10.13205/j.hjgc.202105023
Abstract:
The chelating agent could enhance the absorption of plants for heavy metal in soil. To explore the effect of chelating agent L-glutamic acid N, N-diacetic acid (GLDA) enhanced phytoextraction for cadmium-contaminated soil, a pot experiment was conducted to investigate the influence on applying GLDA for the growth, antioxidant enzyme activities and cadmium accumulation characteristic of Humulus scandens and soil physical, chemical properties. The results showed that when the chelating agent GLDA was applied to 50 mg/kg cadmium-contaminated soil, the biomass, root length and stem length of Humulus scandens significantly decreased by 13.1%~59.1%, 6.6%~26.0% and 6.8%~10.6%, compared with the control group; the activity of the antioxidant enzyme system of Humulus scandens increased first and then decreased, and the content of available cadmium in soil significantly increased by 10.4%~53.8%, compared with the control group. GLDA also significantly increased the accumulation of cadmium in various parts of Humulus scandens, and the best accumulation effect of Humulus scandens, which was 1.29~1.32 times higher than the control group, was achieved at the GLDA concentration of 2.50~3.75 mmol/kg. In general, the best results were obtained at 2.5 mmol/kg. In this case, the cadmium content of underground and ground part were 1.07 and 1.67 times higher than the control group, respectively. Further, the translocation factor, underground bioconcentration factor and aboveground bioconcentration factor of Humulus scandens were 1.00, 1.61 and 1.60, respectively. The above results indicated that the application of GLDA of the appropriate concentration could improve the remediation efficiency of humulus scandens in cadmium-contaminated soil.
The chelating agent could enhance the absorption of plants for heavy metal in soil. To explore the effect of chelating agent L-glutamic acid N, N-diacetic acid (GLDA) enhanced phytoextraction for cadmium-contaminated soil, a pot experiment was conducted to investigate the influence on applying GLDA for the growth, antioxidant enzyme activities and cadmium accumulation characteristic of Humulus scandens and soil physical, chemical properties. The results showed that when the chelating agent GLDA was applied to 50 mg/kg cadmium-contaminated soil, the biomass, root length and stem length of Humulus scandens significantly decreased by 13.1%~59.1%, 6.6%~26.0% and 6.8%~10.6%, compared with the control group; the activity of the antioxidant enzyme system of Humulus scandens increased first and then decreased, and the content of available cadmium in soil significantly increased by 10.4%~53.8%, compared with the control group. GLDA also significantly increased the accumulation of cadmium in various parts of Humulus scandens, and the best accumulation effect of Humulus scandens, which was 1.29~1.32 times higher than the control group, was achieved at the GLDA concentration of 2.50~3.75 mmol/kg. In general, the best results were obtained at 2.5 mmol/kg. In this case, the cadmium content of underground and ground part were 1.07 and 1.67 times higher than the control group, respectively. Further, the translocation factor, underground bioconcentration factor and aboveground bioconcentration factor of Humulus scandens were 1.00, 1.61 and 1.60, respectively. The above results indicated that the application of GLDA of the appropriate concentration could improve the remediation efficiency of humulus scandens in cadmium-contaminated soil.
2021, 39(5): 171-177,183.
doi: 10.13205/j.hjgc.202105024
Abstract:
Passivation remediation technology has good advantages in remediation of low-concentration soil pollution due to its low investment, quick effect, and simple operation. The microbial extracellular polymeric substances (EPS) have excellent heavy metal adsorption capacity. The EPS solution was used to synergize bentonite to passivate the lead-contaminated soil. The effects of EPS dosage, acid rain treatment, and passivation treatment time on the passivation effect were investigated. The results showed that the adsorption capacity of EPS for lead (Ⅱ) was 241 mg/g. In the passivation experiment, as the amount of EPS increased, the passivation effect was firstly enhanced and then weakened. After adding bentonite, it could produce a synergistic passivation effect with EPS, which could increase the residue lead content by up to 59%. Both acid rain treatment and extended treatment time could increase the passivation effect. Various evaluation results for different pollution pathways showed that EPS and bentonite could effectively reduce the proportion of extractable lead in the soil.
Passivation remediation technology has good advantages in remediation of low-concentration soil pollution due to its low investment, quick effect, and simple operation. The microbial extracellular polymeric substances (EPS) have excellent heavy metal adsorption capacity. The EPS solution was used to synergize bentonite to passivate the lead-contaminated soil. The effects of EPS dosage, acid rain treatment, and passivation treatment time on the passivation effect were investigated. The results showed that the adsorption capacity of EPS for lead (Ⅱ) was 241 mg/g. In the passivation experiment, as the amount of EPS increased, the passivation effect was firstly enhanced and then weakened. After adding bentonite, it could produce a synergistic passivation effect with EPS, which could increase the residue lead content by up to 59%. Both acid rain treatment and extended treatment time could increase the passivation effect. Various evaluation results for different pollution pathways showed that EPS and bentonite could effectively reduce the proportion of extractable lead in the soil.
2021, 39(5): 178-183.
doi: 10.13205/j.hjgc.202105025
Abstract:
Biochar derived from sewage sludge is widely used for the treatment of various environmental contaminants. However, little is known about the effects of the biochar on remediation of Cr contaminated soil. In this study, the effects and mechanisms of the biochar prepared via co-pyrolysis of sewage sludge and cotton stalks on the immobilization of Cr in a sandy loam soil (Cr, 33.9 mg/kg) were investigated. The Cr content increased from 34.0 mg/kg to 38.5 mg/kg with the addition ratio increasing from 1% to 15%. The contents of Cr in all treatments were lower than the thresholds of China National Standard (GB 15618-2018). The results of BCR sequential extraction procedure showed that the biochar amendment promoted the transformation of Cr from the acid soluble and reducible fractions to the oxidizable and residua fractions, reducing Cr bioavailability in the soil. Meanwhile, biochar amendment effectively reduced the leaching ability of Cr. In addition, biochar amendment increased soil pH, CEC, organic matter, and available phosphorus in the soil, which were conducive to the immobilization of Cr. The possible immobilization mechanisms includes ion exchange, precipitation/co-precipitation, complexation, but the influence of the biochar on the valence of Cr in soil needs further study.
Biochar derived from sewage sludge is widely used for the treatment of various environmental contaminants. However, little is known about the effects of the biochar on remediation of Cr contaminated soil. In this study, the effects and mechanisms of the biochar prepared via co-pyrolysis of sewage sludge and cotton stalks on the immobilization of Cr in a sandy loam soil (Cr, 33.9 mg/kg) were investigated. The Cr content increased from 34.0 mg/kg to 38.5 mg/kg with the addition ratio increasing from 1% to 15%. The contents of Cr in all treatments were lower than the thresholds of China National Standard (GB 15618-2018). The results of BCR sequential extraction procedure showed that the biochar amendment promoted the transformation of Cr from the acid soluble and reducible fractions to the oxidizable and residua fractions, reducing Cr bioavailability in the soil. Meanwhile, biochar amendment effectively reduced the leaching ability of Cr. In addition, biochar amendment increased soil pH, CEC, organic matter, and available phosphorus in the soil, which were conducive to the immobilization of Cr. The possible immobilization mechanisms includes ion exchange, precipitation/co-precipitation, complexation, but the influence of the biochar on the valence of Cr in soil needs further study.
2021, 39(5): 184-189,195.
doi: 10.13205/j.hjgc.202105026
Abstract:
The research mainly studied whether the use of different concentrations of nano-titanium dioxide (TiO2-NPs) (0, 25, 50, 100 and 200 mg/L) in hydroponic environment could alleviate the physiological toxicity of Cd to wheat seedlings. The oxidative stress on wheat caused by Cd was alleviated by TiO2-NPs application in the hydroponic environment. The toxicity of Cd to wheat seedlings was alleviated, the biomass, root length and plant height of wheat were significantly increased, and the photosynthesis of wheat was improved. The net photosynthetic rate of wheat seedlings was increased significantly at medium concentrations (50, 100 mg/L) of TiO2-NPs. For all concentrations of TiO2-NPs, the POD enzyme activity was significantly lower than the Cd treatment group; the SOD enzyme activity was significantly lower than Cd treatment group at lower concentrations (<200 mg/L). Results showed that the use of TiO2-NPs effectively alleviated the toxicity of Cd to wheat seedlings and improved the photosynthesis of wheat seedlings by reducing the oxidative stress caused by Cd.
The research mainly studied whether the use of different concentrations of nano-titanium dioxide (TiO2-NPs) (0, 25, 50, 100 and 200 mg/L) in hydroponic environment could alleviate the physiological toxicity of Cd to wheat seedlings. The oxidative stress on wheat caused by Cd was alleviated by TiO2-NPs application in the hydroponic environment. The toxicity of Cd to wheat seedlings was alleviated, the biomass, root length and plant height of wheat were significantly increased, and the photosynthesis of wheat was improved. The net photosynthetic rate of wheat seedlings was increased significantly at medium concentrations (50, 100 mg/L) of TiO2-NPs. For all concentrations of TiO2-NPs, the POD enzyme activity was significantly lower than the Cd treatment group; the SOD enzyme activity was significantly lower than Cd treatment group at lower concentrations (<200 mg/L). Results showed that the use of TiO2-NPs effectively alleviated the toxicity of Cd to wheat seedlings and improved the photosynthesis of wheat seedlings by reducing the oxidative stress caused by Cd.
2021, 39(5): 190-195.
doi: 10.13205/j.hjgc.202105027
Abstract:
In view of the lack of monitoring of the effectiveness of various sponge facilities, complex means and low accuracy in the construction of sponge cities, by applying fiber-optic sensing technology to sponge urban permeable paving, the optical fiber grating temperature sensors were used as the monitoring method and the basic principle was the change in the output signal of the sensor on the water-permeable surface layer caused by changes in external quantity. With the rainwater penetration rate obtained and used as the core index, based on rainstorm data of Hubei, the simulation of different permeable pavements on rainwater runoff reduction was conducted under different recurring periods (1a, 5a, 10a, 50a, 100a). Based on the experimental data, the linear fitting relationships between the permeability of rainwater in the permeable surface layer and the permeable pavement to runoff reduction indicators were established. The results showed that there was a good correlation between the infiltration speed and the runoff reduction rate and the time of the runoff (R2>0.93、R2>0.92).The application of the system in high-speed railway stations in western Hubei area successfully proved the feasibility of using infiltration rate to monitor the time of runoff and runoff reduction rate.
In view of the lack of monitoring of the effectiveness of various sponge facilities, complex means and low accuracy in the construction of sponge cities, by applying fiber-optic sensing technology to sponge urban permeable paving, the optical fiber grating temperature sensors were used as the monitoring method and the basic principle was the change in the output signal of the sensor on the water-permeable surface layer caused by changes in external quantity. With the rainwater penetration rate obtained and used as the core index, based on rainstorm data of Hubei, the simulation of different permeable pavements on rainwater runoff reduction was conducted under different recurring periods (1a, 5a, 10a, 50a, 100a). Based on the experimental data, the linear fitting relationships between the permeability of rainwater in the permeable surface layer and the permeable pavement to runoff reduction indicators were established. The results showed that there was a good correlation between the infiltration speed and the runoff reduction rate and the time of the runoff (R2>0.93、R2>0.92).The application of the system in high-speed railway stations in western Hubei area successfully proved the feasibility of using infiltration rate to monitor the time of runoff and runoff reduction rate.
2021, 39(5): 196-203.
doi: 10.13205/j.hjgc.202105028
Abstract:
In order to preliminarily find out the health risk of heavy metals in groundwater of the Qingjiang River, here the springs (with discharge>50 L/s, and applied as the regional water supply source) in the Qingjiang River were sampled and analyzed for Pb, As, Mn, Cr, Ni, Fe, Cu, Zn and Cd concentration. Health risk for adults and children from these heavy metals was evaluate by a water environmental health risk assessment model of the USEPA and AHP model was also combined. It found that concentration of As and Pb exceeded the national standard limit, and their distribution sequence was downstream>upstream>middle, which mainly originated from human input. As, Cr and Cd were the chemical carcinogens and the reginal health risk prevention elements of groundwater. The health risk assessment result was in the sequence of downstream>upstream>middle. Children were the main concerning group of health risk prevention in the study area.
In order to preliminarily find out the health risk of heavy metals in groundwater of the Qingjiang River, here the springs (with discharge>50 L/s, and applied as the regional water supply source) in the Qingjiang River were sampled and analyzed for Pb, As, Mn, Cr, Ni, Fe, Cu, Zn and Cd concentration. Health risk for adults and children from these heavy metals was evaluate by a water environmental health risk assessment model of the USEPA and AHP model was also combined. It found that concentration of As and Pb exceeded the national standard limit, and their distribution sequence was downstream>upstream>middle, which mainly originated from human input. As, Cr and Cd were the chemical carcinogens and the reginal health risk prevention elements of groundwater. The health risk assessment result was in the sequence of downstream>upstream>middle. Children were the main concerning group of health risk prevention in the study area.
2021, 39(5): 204-216,224.
doi: 10.13205/j.hjgc.202105029
Abstract:
As a passive sampling technique, the polar organic chemical integrative sampler (POCIS) has the advantages of safety, simple operation, low concentration monitoring, high recovery, and anti-biological pollution. Due to the determination of time-weighted average concentration (TWA) for polar organic chemicals, reflecting the long-term effects of pollutants, POCIS has been widely applied in the separation and enrichment of pesticides, drugs, endocrine disruptors and other organic pollutants in water environment, as well as the assessment of the environmental behaviors and ecological risks for emerging trace organic pollutants. This paper introduced the structure, principle and calibration method of POCIS, and summarized its application in monitoring of different types of organic pollutants in water environment. Based upon the characteristics and practical application of the device, the problems faced in the actual environment were suggested and the research direction for further improvement of the device was proposed.
As a passive sampling technique, the polar organic chemical integrative sampler (POCIS) has the advantages of safety, simple operation, low concentration monitoring, high recovery, and anti-biological pollution. Due to the determination of time-weighted average concentration (TWA) for polar organic chemicals, reflecting the long-term effects of pollutants, POCIS has been widely applied in the separation and enrichment of pesticides, drugs, endocrine disruptors and other organic pollutants in water environment, as well as the assessment of the environmental behaviors and ecological risks for emerging trace organic pollutants. This paper introduced the structure, principle and calibration method of POCIS, and summarized its application in monitoring of different types of organic pollutants in water environment. Based upon the characteristics and practical application of the device, the problems faced in the actual environment were suggested and the research direction for further improvement of the device was proposed.
2021, 39(5): 217-224.
doi: 10.13205/j.hjgc.202105030
Abstract:
By collecting the routine monitoring data of the centralized drinking water sources in Suzhou from 2015 to 2019 and adopting the health risk assessment model recommended by the US EPA, a comprehensive health risk assessment was carried out on 12 water sources in use. The results showed that the average risk of carcinogens, non-carcinogens were 4.07×10-5/a, 3.61×10-9/a and 4.07×10-5/a for total health risk respectively. The rank of total health risk by water sources was Changjiang Xinhaiba water source (5.33×10-5)>Changshu Changjiang Rive water source (4.68×10-5)>Yangcheng Lake water source (4.49×10-5)>Zhenhu Tai Lake water source (4.30×10-5)>Gonghu jinshuwan Tai Lake water source (4.14×10-5)>Liuhekou Changjiang Rive water source (3.96×10-5)>Siqian Tai Lake water source (3.95×10-5)>Puppet Lake water source (3.79×10-5)>ShangLake water source (3.77×10-5)>Yuyangshan Taihu Lake water source (3.69×10-5)>Miaogang Taihu Lake water source (3.46×10-5)>North tingzi Taihu Lake water source (3.39×10-5); by region, they were in the sequence of Zhangjiagang City>Industrial Park>Changshu City>Xiangcheng District>High tech Zone>Taicang City>Wuzhong District>Gusu District>Kunshan City>Wujiang District; the carcinogenic risk was higher than that of non-carcinogenic. More attention should be paid to Cr(Ⅵ) and Cd for carcinogens and fluoride for non-carcinogens. In general, water sources in Suzhou were relatively safe and their risk rank were within the maximum acceptable risk threshold recommended by USEPA.
By collecting the routine monitoring data of the centralized drinking water sources in Suzhou from 2015 to 2019 and adopting the health risk assessment model recommended by the US EPA, a comprehensive health risk assessment was carried out on 12 water sources in use. The results showed that the average risk of carcinogens, non-carcinogens were 4.07×10-5/a, 3.61×10-9/a and 4.07×10-5/a for total health risk respectively. The rank of total health risk by water sources was Changjiang Xinhaiba water source (5.33×10-5)>Changshu Changjiang Rive water source (4.68×10-5)>Yangcheng Lake water source (4.49×10-5)>Zhenhu Tai Lake water source (4.30×10-5)>Gonghu jinshuwan Tai Lake water source (4.14×10-5)>Liuhekou Changjiang Rive water source (3.96×10-5)>Siqian Tai Lake water source (3.95×10-5)>Puppet Lake water source (3.79×10-5)>ShangLake water source (3.77×10-5)>Yuyangshan Taihu Lake water source (3.69×10-5)>Miaogang Taihu Lake water source (3.46×10-5)>North tingzi Taihu Lake water source (3.39×10-5); by region, they were in the sequence of Zhangjiagang City>Industrial Park>Changshu City>Xiangcheng District>High tech Zone>Taicang City>Wuzhong District>Gusu District>Kunshan City>Wujiang District; the carcinogenic risk was higher than that of non-carcinogenic. More attention should be paid to Cr(Ⅵ) and Cd for carcinogens and fluoride for non-carcinogens. In general, water sources in Suzhou were relatively safe and their risk rank were within the maximum acceptable risk threshold recommended by USEPA.
2021, 39(5): 225-230.
doi: 10.13205/j.hjgc.202105031
Abstract:
Characteristics of thermodynamic parameters of supercritical CO2, and analysis of dynamic physical parameters during non-pure CO2 leakage, as well as computational fluid dynamics method were conducted to study the diffusion law of CO2 under different conditions. Wind speed v, distance x, leakage aperture type, probability distribution characteristics of logical functions lv and relevant results of numerical simulation were applied to the QRA quantitative risk assessment model. Combined with mild injury, irreversible injury and death, three types of health risks (HR1, HR2 and HR3) in supercritical non-pure CO2 pipeline area were quantitatively evaluated. The results showed that under large aperture leakage scenario, the individual mortality risk within the distance of 200 m from the leakage point was higher than the tolerable level (10-5); and the individual mortality health risk within 200~350 m was higher than the acceptable level (10-6), and the individual slight health risk couldn't be reduced to the acceptable level until a distance of 1850 m from the leakage point. The research results could be applied to the route and early design stage of CCUS supercritical pipeline, and provided quantitative data support for exploring alternatives to reduce population health risk.
Characteristics of thermodynamic parameters of supercritical CO2, and analysis of dynamic physical parameters during non-pure CO2 leakage, as well as computational fluid dynamics method were conducted to study the diffusion law of CO2 under different conditions. Wind speed v, distance x, leakage aperture type, probability distribution characteristics of logical functions lv and relevant results of numerical simulation were applied to the QRA quantitative risk assessment model. Combined with mild injury, irreversible injury and death, three types of health risks (HR1, HR2 and HR3) in supercritical non-pure CO2 pipeline area were quantitatively evaluated. The results showed that under large aperture leakage scenario, the individual mortality risk within the distance of 200 m from the leakage point was higher than the tolerable level (10-5); and the individual mortality health risk within 200~350 m was higher than the acceptable level (10-6), and the individual slight health risk couldn't be reduced to the acceptable level until a distance of 1850 m from the leakage point. The research results could be applied to the route and early design stage of CCUS supercritical pipeline, and provided quantitative data support for exploring alternatives to reduce population health risk.
2021, 39(5): 231-237,245.
doi: 10.13205/j.hjgc.202105032
Abstract:
Based on the PSR model, 14 evaluation indexes, including sewage treatment rate, water quality status, biodiversity and environmental investment index were selected to establish the water environment health evaluation system of Pan'an Lake wetland, and their weights of indexes were determined by analytic hierarchy process. The health status of wetland water environment was classified into 5 levels from very healthy to morbid, and then the fuzzy comprehensive evaluation method was used to evaluate the health status of Pan'an Lake wetland water environment. The evaluation results showed that the water environmental health index of Pan'an Lake wetland was 2.8166, belonging to sub-health state. The stress index score was 1.7405, which was in disease status. The status index score was 3.2563, belonging to the sub-health state. The response index score was 2.4483, which was between sub-health state and disease state.
Based on the PSR model, 14 evaluation indexes, including sewage treatment rate, water quality status, biodiversity and environmental investment index were selected to establish the water environment health evaluation system of Pan'an Lake wetland, and their weights of indexes were determined by analytic hierarchy process. The health status of wetland water environment was classified into 5 levels from very healthy to morbid, and then the fuzzy comprehensive evaluation method was used to evaluate the health status of Pan'an Lake wetland water environment. The evaluation results showed that the water environmental health index of Pan'an Lake wetland was 2.8166, belonging to sub-health state. The stress index score was 1.7405, which was in disease status. The status index score was 3.2563, belonging to the sub-health state. The response index score was 2.4483, which was between sub-health state and disease state.
2021, 39(5): 238-245.
doi: 10.13205/j.hjgc.202105033
Abstract:
In order to understand the distribution characteristics and potential risks of heavy metals in farmland soil around an abandoned smelter in Hechi, the pollution status of five heavy metals (Cd, Pb, Cr, Cu, Zn) and main crops in different depths in the region were studied. The soil pollution investigation and ecological risk assessment were carried out by using multivariate statistical analysis, improved Nemerow index method, latent hazard index method and GIS interpolation. The results showed that the average contents of Cd, Pb, Cr, Cu, Zn in soil were higher than the background values of soil environment in Guangxi. The accumulation of Cd and Pb were more obvious, and their contents were 11.5 and 3.3 times higher than the limiting values listed in Soil Environmental Quality Risk Control Standard for Agricultural Land (GB 15618-2018), respectively. The spatial distribution of soil heavy metal content in the study area showed a trend of centered by the adjacent to the smelter, and radiated to the surrounding area. The content of heavy metals in the northwest and southeast of the smelter was higher. According to the analysis of heavy metal content in the soil profile of the study area, only Pb in the surface soil exceeded the screening value of soil pollution risk, the content of Zn, Cr and Cu in different depths of soil was lower than the risk screening value, while the content of Cd in each soil layer exceeded the risk control value of agricultural land, indicating that Cd pollution was serious in this area. Therefore, we should pay more attention to the ecological risk of soil pollution to crops and groundwater. The average contents of Pb, Cd and Cr in corn and sugarcane in the study area were 21.87, 18.48, 7.34 times and 7.97, 3.73 and 6.25 times of the standard limits in the Food Safety National Standard:Contaminants Limits in Food (GB 2762-2017), respectively, with the exceeding rate of 100%.
In order to understand the distribution characteristics and potential risks of heavy metals in farmland soil around an abandoned smelter in Hechi, the pollution status of five heavy metals (Cd, Pb, Cr, Cu, Zn) and main crops in different depths in the region were studied. The soil pollution investigation and ecological risk assessment were carried out by using multivariate statistical analysis, improved Nemerow index method, latent hazard index method and GIS interpolation. The results showed that the average contents of Cd, Pb, Cr, Cu, Zn in soil were higher than the background values of soil environment in Guangxi. The accumulation of Cd and Pb were more obvious, and their contents were 11.5 and 3.3 times higher than the limiting values listed in Soil Environmental Quality Risk Control Standard for Agricultural Land (GB 15618-2018), respectively. The spatial distribution of soil heavy metal content in the study area showed a trend of centered by the adjacent to the smelter, and radiated to the surrounding area. The content of heavy metals in the northwest and southeast of the smelter was higher. According to the analysis of heavy metal content in the soil profile of the study area, only Pb in the surface soil exceeded the screening value of soil pollution risk, the content of Zn, Cr and Cu in different depths of soil was lower than the risk screening value, while the content of Cd in each soil layer exceeded the risk control value of agricultural land, indicating that Cd pollution was serious in this area. Therefore, we should pay more attention to the ecological risk of soil pollution to crops and groundwater. The average contents of Pb, Cd and Cr in corn and sugarcane in the study area were 21.87, 18.48, 7.34 times and 7.97, 3.73 and 6.25 times of the standard limits in the Food Safety National Standard:Contaminants Limits in Food (GB 2762-2017), respectively, with the exceeding rate of 100%.
