Study On Different Soil Texture On The Migration And Transformation And Remediation Of Chrome

Treatment and remediation of soil chrome pollution is increasing concern inChina. Currently a sound system of chromium contaminated soil remediation is notestablished. Transformation and exchange of chromium in soil is the key and isfluenced by several factors to remediation technology. In this paper, chromiumcontaminated sites of Qingdao Hongxing Chemical Plant as a case, made governanceidea of "detoxification chrome pollution soil+interdiction chrome pollutiongroundwater", integrated consider more factors, used "pollution soil characteristicsregulation+chemical leaching+chemical restore/stable" of integrated repairtechnology. A series of studies were conducted, such as soil repair conditions research,Cr (VI) static adsorption experiment, different fill materials preventing groundwaterchrome pollution, dynamic leaching experiment inquiride different soil texture affecton chrome transpotation and remediation, and risk evaluation of remediated soil torepair chrome pollution soil. As the same time, blocked the migration of chromiumcontamination of groundwat effectively, revealed different texture soil on chromemigration into of effects law, analyzed feasibility of repair technology,This paper willgive a guid for other pollution sites management. The main results were summarizedas follows.(1)The study area survey found that the vast majority of contaminated sites isheavily polluted. The highest total chromium content is27254.50mg/kg, the averageis80~90times the environmental background values of national and Shandong.Chrome in soil has enormous migration risks, because of Cr (VI) accounting for39.1%percent of total chromium.(2)Selected the highest concentrations of chromium contaminated sites soil forsampling points, and then identified the remediated conditions. It found that changingthe pH of the soil solution and adjusting the soil organic matter were contributed to Cr(VI) migration and transformation. They also could reduce the direct or indirect biological use risks of chromium in soil. pH through the effects of chromium in soilby dissolution, chelation, oxidation-reduction effects of Cr (VI) migration andtransformation. And organic matter will by dosing of different weight and groupdifferences caused the surface to be restored, eventual impact of Cr (VI) migrationand transformation. Lower the pH value, stronger reductive of organic matter, themore favourable Cr (VI) migration and transformation. Certain concentration in soilof sodium carbonate solution in favour of Cr (VI) leaching, but excessiveconcentrations also inhibits Cr (VI) leaching.(3) Cr (VI) adsorption experiments showed that with "activated carbon/acidifi-cation activated carbon+ferrous sulfate" or "artificial zeolite/acidification of artificialzeolite+ferrous sulfate" composed of activity reaction media can removal Cr (VI)effectively.Removal efficiency depends on adsorbent itself of adsorptioncharacteristics, acid used by acidification processing provides H+and interactionbetween capacity and adsorbent with reducing agents. Activated carbon/acidificationActivated carbon as adsorbent of reaction medium on the Cr (VI) removal efficiencyreached85%~99%, well above artificial zeolite/acid-ification artificial zeolite.Besides,acidification in favour of artificial zeolite and activated carbon for Cr (VI) removed.Bentonite, kaolin or attapulgite clay mineral composition of chitosan supported threecomposite adsorbent, whose Cr (VI) adsorption capacity is proportional to thechitosan theoretical load.The different lattice structures, composite adsorbent for Cr(VI) adsorption capacity is different. Carrier for bentonite composite adsorbent for Cr(VI) adsorption capacity is significantly higher than the other two clay compositeadsorbent.(4) Dynamic leaching experiments indicated that chrome effects of migration andtransformation laws were different, so were levels of risk. Different layer structure isrealized through the change soil retention capabilities of the system chrome. Indifferent layers, packed layer more removal of chromium contributes greaterinterception capability is stronger. Macro pore influence migration and transformationof chromium by increasing soil seepage flow, reducing migration resistance to shortenthe leaching agents contact time, reducing leaching agent efficiency, filler fixed capacity and retention capabilities. Changes in soil texture affect the unstable statechromium is higher than the relatively stable state. But the small overall impact onvarious forms of chromium, and not a regular. Soil repaired after the end of multilayerstructure, migration risk and the biological risks of total chromium and Cr (VI) wereboth decreased. However, soil under large pore structure reduced the migration risk oftotal chromium and Cr (VI), but increased risk of biological.(5) Used "pollution soil characteristics regulation+chemical leaching+chemi-cal restore/stable" of joint repair technology, after the repair end of contaminated soilCr (VI) levels decreased by92%, blocking more than60%of chromium leachingvacate.Whatmore effectively delaying the flow of fluid out of Cr (VI) peakconcentration occurs, reducing the peak concentration and equilibrium concentration.It indicated that the remediation technology is feasible.