Colloid-facilitated Transport Of Steroid Estrogens In Subsurface Environment

Steroid estrogens(SEs)usually have stronger endocrine disruptive and biological activity.They cause human or animal reproductive disorders,behavioral abnormalities and larval variation even at very low concentrations(ng/L).Although people have gradually begun to realize the seriousness of SEs pollution problem,the detected SEs in groundwater is still almost ignored.These SEs are introduced into the farmland with faeces,which can migrate into groundwater and surface water via rainfall,surface runoff,infiltration,which then pose risk to the aquatic environment.SEs as weakly hydrophobic organic compounds,it is still a question that how SEs migrate from top soil to unsaturated zone and aquifer,and which factors effect these processes.The mobile colloids in soil and subsurface aquifers not only adsorb contaminants like solid phase matrices,but also can migrate in subsurface environment under suitable conditions,resulting in accelerated migration of some radionuclides,trace metals and organic pollutants.Silica as a main component of quartz sand and silicate minerals,is one of the important inorganic colloidal sources in the subsurface environment.The illite colloid is also a kind of clay mineral prevalently in soil and aquifer systems.Humic acid colloid is a kind of organic colloid widely present in soil and groundwater.These colloids can migrate and effect the migration of contaminants in subsurface environment.It is unclear how do these colloids affect the migration of SEs in the aquifer,and what is the co-migration mechanism.This paper developed and optimized solid phase extraction-derivatization-gas chromatography-mass spectrometry technology to achieve the separation,enrichment and content determination of SEs.This method has been successfully applied to the actual water sample detection.Estrone(E1)and estradiol(E2)were used as the target contaminants,and silica,illite,and humic acid as three colloids to study SEs migration in the aquifer including isothermal adsorption of estrone and estradiol in three colloids.It was found that three colloids all had certain adsorption effect on SEs,and the adsorbed amount of SEs by humic acid was ten times higher than that of silica colloids and illite colloids under the same initial concentration.In the migration experiments of three colloids in two simulated aquifer sand columns,it was found that the silica colloids have a penetration rate of about 10% higher in the river sand column than that in the quartz sand column whilst the penetration rate of illite colloids and the humic acid colloids in the quartz sand column was 15% and 30% higher respectively than that in the river sand column.From the study of estrone and estradiol migration in the river sand column with the three colloids it was found that the colloids promoted the migration of estrone relatively weakly and strongly promoted the migration of estradiol.The penetration rate of estradiol was enhanced by humic acid colloid about 30% in river sand column;the penetration rate of estradiol was enhanced by illite colloid about 20% in river sand column;and the penetration rate of estradiol was enhanced about 10% by silica colloid in river sand column.Therefore this study provides scientific basis for the actual treatment and remediation of contaminated sites and regional protection and safety of drinking water.