| In recent years, heavy use of road deicing salt has brought gteat environmentalissues and drawn great interest. Sodium chloride and CMA deicing salt are two typesof currently using deicing salt. When deicing salt enter into the environment, one partcan directly into soil and be enriched and migrated; another part can be washed intosurface water and have an impact on surface water environment. Heavy metals areimportant class of pollutants in soil environment, deicing salt in soil willconsequentially change the physical and chemical properties, structure conditions ofsoil, and all these factors will play their role in the fate, speciation and bioavailabilityof soil. CMA is a class of organic deicing salt that can be biodegradable in naturalwater. Different lighting conditions may influence the degradation rate of CMA andduring the process of degradation pH and dissolved oxygen of natural water might beinfluenced.In order to quantify the direct and indirect effects on Cd, Zn, Pb,Cu and Nitransfer from contaminated soil which sampled from the surface soil next to the roadof high-tech development zone in Changchun China, we set up an experimentalapproach based on indoor microcosms. Soil column and immersion tests were used toinvestigate the impact of sodium chloride and CMA deicing salt on transportation andspeciation transformation of Cu, Pb, Cd, Ni and Zn. We also study the degradationprocesses of CMA deicing salt in natural water under different light conditions bylaboratory simulation.As the results shown, the concentrations of Cd, Zn, Pb, Ni and Cu in soil areeffected by column of deicing salt to some extent. The effects of sodium chloride onthe transportation of heavy metals are much greater than CMA. The transportations ofheavy metals also are affected by the concentration of deicing salt. The deicing saltswith high concentration have much greater effect on transportation of heavy metalsthan that with low concentration. In this study, there are five formations of heavy metals existed in the soil, which are exchangeable fraction, carbonates fraction,Fe-Mn oxides fraction, organic/sulfide matters fraction and residuals fraction. For Cd,Zn and Ni, the exchangeable fraction, carbonates fraction and Fe-Mn oxides fractionwith higher activity and mobility take larger proportions which are good for therelease and transportation. Soil column of deicing salt could advance releasing andtransporting of Cd, Zn and Ni through effects of ion exchange. While thetransportation of Cu and Pb are little affected by deicing salts, because theorganic/sulfide matters fraction and residuals fraction are exited steadily in soil.The formation of Cu、Pb、Cd、Ni and Zn in soil are affected by the immersion ofsodium chloride and CMA deicing salt. The sodium chloride and CMA influencedproportion of exchangeable fraction, carbonates fraction and Fe-Mn oxides fractionmore greatly than the proportion of organic/sulfide matters fraction and residualsfraction. The percentage of metal exchangeable fraction increased by the immersionof sodium chloride deicing salt, while the amount of carbonates fraction significantlydecreased and the amount of Fe-Mn oxides fraction also reduced. The heavy metals inthe soil are also influenced by the immersion of CMA deicing salt. The percentage ofmetal exchangeable fraction and carbonates fraction increased, while the amount ofFe-Mn oxides fraction decreased greatly.The degradation of CMA deicing salt in natural water are significantly influencedby the condition of light. The degradable rates of CMA and organic materials arequick, while the dissolved oxygen and pH have little change under the irradiation ofthe light. The degradable rate of CMA deicing salt became slower without theirradiation of the light. The pH values became lower and the dissolved oxygen innatural water reduced much more quickly when there is no irradiation of the light. |
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