| Influenced by seasonal inundation,erosion and sedimentation,soils in the water-fluctuating zone of the Three Gorges Reservoir would become both source and sink of various pollutants in the near future.At the same time,the long-term alternate drying-wetting of the water-fluctuating zone will have a series of effects on the nature of the water body.EDCs,a kind of emerging pollutant,has been widely detected in the water and soils of Three Gorges Reservoir and had a greater security risk to the water environment of reservoir.Accordingly,this study has simulated the regular pattern of the migration and release processes of EE2 and BPA in the soil of fluctuating zone using the soil collected from Chongqing fuling in Three Gorges Reservoir as studying object and examined the impacts on the migration and release processes of EE2 and BPA in different environmental condition(temperature?ion concentration).The results are as follows:(1)The soils are purple soil and weak alkaline.Due to different flooding durations,soils at elevations of 155m,160m,165m and 170m have significant differences in soil organic matter content and soil granules.(2)The adsorption and desorption kinetics of EE2 and BPA in soil included two stages:one was quik release,another was slow release.Adsorption and desorption could reach equilibrium within 24h and 48h,respectively.The kinetic data could achieve the best fitting effect with the quasi-second-order kinetic equation.The soils sorption of EE2 and BPA was an exothermic and entropy decrease process,mainly attribute to the physical sorption driven by spontaneous enthalpy.(3)The adsorption and desorption equilibrium isotherms were nonlinear and were well fitted by the Freundlich model in single solute systems.The adsorption affinity coefficient K_F of EE2 and BPA in four soil samples ranked as follows:155m>160m>165m>170m,which was positively correlated with the accumulation of organic matter in soil and negatively correlated with sand content.However,there was a certain irreversibility in the adsorption process.The desorption curves of EE2 and BPA did not completely coincide with the adsorption curves,and t here was a hysteresis effect in desorption.The desorption hysteresis coefficient H I follows the order of 155m<160m<165m<170m,that was,the soil with a longer flooding time had a stronger desorption hysteresis.(4)When EE2 and BPA coexist,there was a significant competitive effect in the adsorption and desorption processes.Under the double solute condition,the degree of nonlinearity of EE2 adsorption and desorption was reduced,while the degree of nonlinearity of BPA adsorption was reduced,and the degree of nonlinea rity of release was increased.The presence of competing substances sould inhibit the adsorption of target substances,and the lagging competitive adsorption could cause stronger competition than competitive adsorption.At the same time,the competitive effect of BPA on EE2 adsorption was stronger than that of EE2 on B PA adsorption,which was opposite to that of delayed competitive adsorption.Du ring simulated flooding periods,when EE2 and BPA adsorbed in the soil desorbe d in the upward water,the desorption rate and desorption hysteresis of EE2 incr eased,and the desorption rate and desorption hysteresis of BPA decreased.(5)Changes in environmental conditions also had an important impact on the adsorption and release processes of EE2 and BPA.When the pH value of the so lution increased from 3 to 10,the adsorption amount of EE2 and BPA in the soil at each water level decreased,and the desorption rate of EE2 and BPA in different elevation soils increased.When the temperature was increased from 15?to 35?,the adsorption capacity of EE2 and BPA in the soil is reduced,while the desorption hysteresis coefficient HI of EE2 and BPA in the soil followed the order of 15?>25?>35?,that is,the temperature rise was favorable to desorption. |
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