The Study Of Sorption/Desorption, Vertical Migration And Evaporation Of Organchlorine Pesticides In Simulated Aquatic Environment

Organchlorine pesticides is an important pollutant in the environment. Although they had been banned, they could be remain in the environment such as soil and aquatic enviroment. The impact of organchlorine pesticides on the environment could not be ignored. Organchlorine pesticides in soil could be washed into the aquatic environment. The organchlorine pesticides in water could transfer between atmospheric phase and solid phase. As organochlorine pesticides are hydrophobic contaminants, one part of organchlorine pesticides in water transferred into the atmosphere through volatilization. Another part of organchlorine pesticides in the aquatic environment of organochlorine pesticides in water environment had reaction with the solid materials, such as biofilm, suspended particles and sediments. Adsorption/desorption played significant role in the transportation of organchlorine pesticides which determined whether the organochlorine pesticides transport to the aquatic environment again. The content of sediment is the largest in three solid phases. The role of sediment in the migration of contaminants could not be ignored.In this study, HCHs and DDTs were selected as a representative material of organochlorine pesticides. The study used laboratory simulation method to study the sorption and desorption of HCHs and DDTs to three solid phases which collected from Songhua River. The effects of pH and the addition of heavy metals (Cu,Pb) were also considered in this study. The volatilization of HCHs and DDTs were studied to know the rate of volatilization. Meanwhile the migrations of HCHs and DDTs in sediment were also studied.The results showed that the the mount of HCHs to three solid phases is lower than DDTs. The adsorptions of HCHs to solid phases were not shown significant difference. HCHs which were adsorbed by solid phase were not desorbed easily. The desorptions of HCHs from solid phases existed desorption hysteresis. The DDTs can be adsorbed by solid phases easily. The mount of DDTs which were adsorbed by surface coating were the highest in three solid phases, followed by suspended particulate materials and surface sediments. The desorption hysteresis indexs of DDTs were small that meaned the hysteresis of desorption existed, but it was not obvious. The effects of pH on sorption/desorption of DDTs to solid phases were insignificant. The adsorption of DDTs to solid phases decreased with the increasing pH values, while desorption of DDTs from solid phases increased. The addition of heavy metals did not have great impact on sorption/desorption of DDTs. The addition of Cu and Pb inhibited the adsorption of DDTs to surface coatings, while promote the desorption of DDTs from surface coatings. The adsorption of DDTs to suspended particulate materials and sediments increased with the addition of Cu and Pb. The desorption of DDTs from suspended particulate materials and sediments inhibited with the hysteresis index decreased. To further understand the migration of DDTs, the vertical migrations of HCHs and DDTs on sediments were studied. The results showed that the rate of HCHs was faster than DDTs. The addition of sand increased the rate of migrations of HCHs and DDTs. The rate of evaporation of HCHs and DDTs increased with the increased temperature and wind speed.