Study On The Remediation Of Different Ameliorants In Heavy Mental Cr Contaminated Soil

The Pollution of heavy metal chromium in soil has been becoming more serious at Present. It has already become one of the pollution elements in soil. In situ remediation technology by ameliorant is one of the effective approaches to decrease the amount of heavy mental existed in soils. This study makes use of pakchoi as the materials, and uses pot-testing to research on the effect of the application of lime, activated carbon and the co-application of lime and activated carbon on pakchoi's growth, physical and biochemical conditions, Cr absorption amount, pH of Cr contaminated soil and the morphological distribution of Cr. This study aims at explaining the mechanism of ameliorants in preventing Cr poison to the pakchoi. The main results are as follows:(1) Cr contaminated soil has certain effect on Pakchoi's growth. Proper concentration of Cr is beneficial to pakchoi's growth, while excessive concentration of Cr can prevent pakchoi's growth and the more serious the Cr contamination, the more serious growth suppression the pakchoi suffers. The application of soil conditioner can effectively mitigate Cr's supression influence on pakchoi, and can increase pskchoi's biological production. The increase of plant height and the dry weight of parts above the ground and the roots as well as the amount of chlorophyll can explain the phenomena. In the study, groups treated with activated carbon has the best production effect, followed by groups with the combination of activated carbon and lime, with groups treated with limes the worst. Treatment with high concentration of lime (L3, 2g/kg) and Cr shows obvious suppression effect on pakchoi's growth.(2) Cr can prevent the compound of chlorophyll. Proper concentrations of lime (L1, L2; 1.0, 1.5g/kg) can decrease Cr's toxins on chlorophyll. When it comes to high-concentration lime treatment, the effect is not obvious. The co-application of lime and activated carbon and the mere application of lime share nearly the same effect, worse than activated carbon treatment.(3) Cr contamination influences pakchoi's physical and biochemical activities. With the increase of adding Cr, the activity of pakchoi's SOD increases, then decreases and then increases; POD increases and next decreases; CAT enzymes firstly decreases and then increases; the amount of MDA gradually increases, which indicates that Cr causes membrane-lipid peroxidation. Treatments with proper amount of ameliorants can remiss membrane-lipid peroxidation. Excessive lime treatment (L3 Concentration) can cause another stress, which influences pakchoi together with Cr stress, exacerbating damage on pakchoi's cell membranes. With different Cr treatments and different concentrations of activated carbon, the effects of Antioxidant System are different, the reasons of which need to be further studied.(4) Cr contaminated soil can clearly increase pakchoi's absorption of Cr. When planting pakchoi in Cr contaminated soil, Cr amount in pakchoi increase largely, and the more serious the pollution, the larger amount pakchoi contains. Different parts share different Cr amount, with roots the most, followed by leaves and then stems. After adding ameliorants like lime, activated carbon, etc. to Cr contaminated soil, the amount of Cr contained by pakchoi decreases to certain extent compared with the control group. The larger amount of ameliorants added, the less Cr contained in pakchoi. This showed that ameliorants like lime and activated carbon can effectively suppress pakchoi's absorption of Cr. Different soil conditioners share different suppression effect with different Cr treatment.(5) The adding Cr can create an increasing tendency of pH. With low-concentration Cr treatment, the add of lime obviously increase soils pH, while with high-concentration Cr treatment, lime has little influence on soil pH. Activated carbon displayed little influence on soil pH. Under the circumstances of the co-application of lime and activated carbon, soil pH still increases, but not as obvious as that of lime. Then we can see that the add of activated carbon can in a sense mitigate soil pH changes.(6) The amount of Cr absorbed by pakchoi is not only related with the amount of soil, but also importantly with the amount of exchangeable Cr in soil. The more exchangeable Cr in soils, the easier the plant absorbed. The add of lime for one thing can enhance soil pH, increase the amount of settling Cr and decrease Cr activity; for another Ca can cause antagonistic effect on Cr, and then prevent pakchoi's absorption from Cr. Activated carbon for one thing can directly absorb heavy mental in soil and decrease the amount of exchangeable Cr; for another the add of activated carbon can enhance the amount of organic carbon in soil and the amount of organic coated Cr, and then fix Cr.