Study On Transport And Transformation Rules Of Organophosphor In Aquitard

In recent years, with the further understanding of the clay layers as impermeablelayers in the groundwater system,especially of its faint water permeability has begunto raise concerns gradually.The over exploitation of groundwater at present has led toa sharp decline of the underground water level,because of the large permeatepressure,the pollutants in the table water aquifer will penetrate the confined Aquifersand cause the groundwater pollution with the ground water penetrated through theaquitard to supply the deeper confined water.So,the penetrability of aquitard andtransport and transformation rules of pollutant in aquitard have become a importantresearch problem at the world of groundwater pollution control and remediation.Based on investigating a large amount of documents,the paper designed thesimulative seepage instrument indoor and simulated the permeation and migrationprocess of omethoate through the permeable clay layers with the combined methodsof theoretical research and simulation indoor. This test discussed the migration forms、the attenuation law of concentration and rules of migration and conversion on the baseof analysis for the influence of leachate pH、initial concentration of organophosphorand clay pH to the process of seepage flow, and the test analysed and summarized theretardation of clay layer to organophosphor also,for the research of effect of claygeologic-hydrogeological conditions on the degradation of organophosphor, andprovide the theoretical basis for prevent the permeation of organophosphor in theaquitard and caused the pollution of groundwater.The research show that the leachate pH、initial concentration of organophosphorand clay pH are all has significant effect on the permeation process when theorganophosphor penetrate clay layer under the pressurized condition.①Under theexperimental condition,the abilities of translocation of organophosphor fell into adecline with the increases of leachate pH,and the hydrochemistry mobility oforganophosphor reduced gradually also; as the leachate pH value reached to8.5,themigration rate was less than0.05%, the translocation abilities of organophospho reduced greatly; On the contrary,the lower leachate pH condition not conducive to thedegradation and conversion of organophospho.②When leachate pH was lower thanclay pH, the adsorptive power of clay will strengthen but at a modest rate with theincrease of leachate concentration;the lower pH condition expressed definiteinhibition on adsorption of organophospho,and weighted against the adsorbed on thesurface of particle of clay. The adsorption capacity will improve obviously with theincrease of leachate pH. When the initial concentration of organophosphor different,the mineralization rate of organophosphor was identical or similar;the remanentconcentration were also relatively high with the increase of initial concentration oforganophosphor, the clay got a successful removal relatively with the lower initialorganophosphor concentration.③The mineralization rate of organophosphorincreased and translocation abilities declined obviously in clay layer with the increaseof clay pH:the mineralization rate was98.75%when clay pH was7.5,andmineralization rate will be more higher when clay pH reaches over8.5,the retardationof clay on organophosphor was obvious when pH≥8.5and organophosphor will cannot permeate the clay layer.Under the conditions of leachate pH was from5.5to8.5and clay pH was about6.3, the activities of acid phosphate was positively correlated with leachate pH:theactivity of acid phosphatase going up with leachate pH value increases,while theability of degradation and conversion becomes stronger,the increase of leachate pH isgood for the degradation and conversion of clay layer on the organophosphor, theaction of microorganisms plays an important role in the degradation oforganophosphor,the retardation effect is obviously.The plenty of chemical precipitatec formed by PO₄^3-and Ca²⁺accumulated andstopped up the migration passageway of leachate, as a result the transport and flowvelocity of leachate declined obviously,the hydraulic retention time of leachatebecame longer and the control level of clay layer on environment（oxidation orreduction） of leachate became stronger,this tendency seems to be more obvious withthe increase of clay pH. When contaminated fluid alkaline became stronger, theaquatic environment of leachate will be change from oxidation to reductiveenvironment more prominently. When25℃,the adsorption of clay for organophosphor is consistent withLangmuir and Freundlich adsorption isotherms,it shall be the monolayeradsorption,the adsorption relies mainly on molecular attraction and the ionic bondstrength. The saturated adsorptive capacity of organophosphor is0.71mg/g,whichrepresents the adsorption potential of Aquitard for organophosphor when flowvelocity of leachate approach zero.The concentration of PO₄^3-ion that frommineralization reduced slightly with increase of clay pH and increased significantlywith time,the migration chemical kinetics equation of PO₄^3-ion is:log c=0.1367pH+0.0038337t+0.9136.A one-dimensional model for migration and conversion of organophosphor inAquitard was got and analyzed.The parameters of it was calculated based on theexperimental data,and to simulate the migration and conversion of organophosphor inAquitard.The simulation result fits the experimental result well,it can predict theconcentration change of organophosphor during migration process in the clay layer toa certain extent.