Study On Chemical Stabilization Technology Of Soil Arsenic

The Pre-experiment and pot experiment, Chinese cabbage-pakchoi (Brassica campestris L.) as the tested plant, were conducted to study effects of different Fe2O3, Fe2(SO4)3, CeCl3, LaCl3concentrations on arsenic bioavailability of mining area arsenic contaminated soil, forms change of soil arsenic, arsenic content of pakchoi leaves and roots, chlorophyll content, fresh weght and microorganism index. At the same time, the relationships between adding materials and soil pH, exchangeable arsenic and aviarable iron, arsenic content of pakchoi leaves and roots, chlorophyll content and total iron content of pakchoi leaves were stuied. The main conclusions of the experiments were as follows:(1) Both of the two kinds of meterials can effectively reduce the arsenic migrating from soil to pakchoi. Fe2(SO4)3is the most effective, followed by LaCl3and CeCl3, and Fe2O3has poor effect.(2) Either iron materials or rare-earth materials could notably decrease available arsenic contents in soils. Exchangeable arsenic, calcium combined arsenic and aluminum combined arsenic, which were of higher bioavailability to plants, were significantly reduced; but in contrast, iron combined arsenic was remarkably increased. There was a highly significant positive correlation between increasing contents of iron combined arsenic and decreasing amounts of the other three kinds of arsenic forms.(3) Two mechanisms could be used to explain soil arsenic stabilization due to addition of these two kinds of materials to soil. One was co-precipitation of soil arsenic with the added materials in soil, and the other was adsorption of soil arsenic on clays, which could be improved by acidifying soil.(4) Among the four materials, Fe2(SO4)3, CeCl3, and LaCl3showed acidification effects on soils, but not for Fe2O3.(5) The chlorophyll contents and fresh weights of pakchoi increased when lower concentrations of the materials used and decreased when higher concentrations of the materials used both for Fe-containing materials and rare-containing materials. When Fe2O3or CeCl3concentration was lower than0.25g·kg-1, or/and Fe2(SO4)3or LaCl3concentration was lower than2.00g·kg-1, the chlorophyll contents and fresh weights increased.(6) Both soil basal respiration intensity and soil metabolic quotient were promoted in every addition level of the materials. Lower amount of LaCl3could also increase soil microbial biomass carbon, but higher amount decrease it.(7) The relationship between adding amounts of rare-earth materials and soil pH, and the relationship between exchangeable arsenic and available iron in soils were significant or highly significant negative correlation in a certain range of the materials addition to soil. In contrast, the relationships between As contents in pakchoi leaves and in pakchoi roots, and the relationship between chlorophyll contents and total iron contents in pakchoi leaves were significant or very significant positive correlation in a certain range.