Fate And Trasport Of Steriod Estrogens In Soil

Endogenous steroidal estrogens are endocrine disruptors of secretion in manand mammals. They have strong growth and developmental toxicity to aquaticanimals even in ng/L level of concentration. Lots of steroidal estrogens migratedinto soil with manure fertilizer and sewage irrigation. It is of great inportance tolearn about the fate and transport of estrogens in soil. In this paper, several factorsthat affeceted the adsorption, migration and degradation of estrone (E1) and17β-estradiol (17β-E2) in soil were studied. The main conclusions are as follows:Soil adsorption of estrogen is a fast process, it can be completed within1h.Pseudo-second-kinetic equation and the Freundlich isotherm model were used tosimulate the adsorption estrogens to soil. The thermodynamic analysis showed thatthe soil adsorption of estrogen was spontaneous and exothermic. The adsorptioncapacity was increased with the adding of K ion and humic acid into the soil. Instrong acidic condition, the absorption of estrogens was enhanced. While in strongalkali condition, the opposite results was obtained.17β-E2showed stronger mobility in sandy soil than in clay during soil columnleaching experiments, with the residual17β-E2concentration of0.06and0.18mg/kg respectively in sandy soil and clay column after leaching experiment(200min) at filtration rate of0.1mL/s and estradiol dosage of2.50mg. Migration of17β-E2was accelerated when humic acid was added into soil due to competitiveadsorption of organic compands in soil. While K ion added into soil, the mobilityof17β-E2was inhibited. The migration of17β-E2was enhanced slightly in weakacidic leaching condition. While in weak alkali condition, the opposite results wasobtained.The degradation rate of17β-E2was increased with the increasing of themoisture content or activation soil proportion. The degradation of17β-E2fittedfirst-order kinetic model well when activation soil proportion was10%and20%.While when activation soil proportion was40%and100%. modified first-orderkinetic model was used. The biodegradation of17β-E2was inhibited whenantibiotics and antibacterial agents added into soil. The type and composition ofsoil affect the biodegradation of17β-E2. When oxytetracycline(2mg/kg) coexist,degradation rate of17β-E2in soil was91.66%in100%clay,85.00%in50%sand ＋50%clay and67.30%in100%sand after6days.