RESEARCH ON THE MIGRATION LAW OF CONSERVATIVE ION IN LAYERED SOIL UNDER UNSATURATED ZONE

For studying solute migration law in layered soil under the unsaturated zone，this paper picked five kinds of soils from different particles ratio and then filled them into two group soil columns: From coarse to fine and the opposite，of which the hierarchical order was inverse． Via the laboratory experiment，the basic migration law of conservative Br － was uncovered under two types of layered soil． When the soil surface was polluted in the rainfall intensity of 15 mm/12 h，the Br － concentration of 1st and 2nd layers experienced three stages in the two sorts of soil structures: rising period rapidly，peak period and declining period． The soil concentration of 3rd，4th，and 5th layers had been through rising period and declining period stably． At the end of the test，Br － concentration was well-distributed in the columns from the coarse to fine，while it concentrated on the soil surface in the other one． Meanwhile，the time when the solute penetrated the entire soil column was about 96 h in advance composed of the structure from coarse to fine than the inverse． The structure from coarse to fine was better in the sewage entrapment performance and the solute delay to recharge the groundwater．