Remediation Of DDTs Contaminated Soil By Medicago Sativa

The residual concentrations of Dichloro-diphenyl-trichloroethane (DDT), one kind of Organochlorine pesticides, in the soil of different sites in Nanjing were investigated; the accumulation mechanism and capacity in Medicago sativa to DDTs in contaminated soil were preliminary studied through the experiment cultivated in pot. Effects of adding surfactant and changing pH value on accumulating capacity of Medicago sativa was researched; the antioxidant enzymes activities and MDA contents in the leaves of Medicago sativa in different develop stage were tested, indicating that Medicago sativa exhibited a higher endurance abilities to DDTs and could be used for remediation of DDTs contaminated soil. The results were as follows:(1) Organochlorine pesticides DDTs was found in soils of all the selected sites in Nanjing city, and the residue amount was range from 0.148 to 0.26mg/kg. May be there was newly added DDTs in the soil of selected sites.(2) The concentrations of DDTs in Medicago sativa exhibited a trend of increase— decrease—increase when 0.5mg/kg DDTs was supplied in the soil, the maxim concentration 2.06μg was reached after 105 days treatment; when 2.4mg/kg DDTs was supplied in the soil, the absorption and accumulation of DDTs in Medicago sativa increased at the beginning stage and decreased later, the maxim concentration of 10.30μg was achieved after 90 days treatment. at the same time, 0.57-0.68 percent of total amount of DDTs was transported from soil to Medicago sativa respectively.The absorptive abilities to DDTs varied in different parts of Medicago sativa and the roots played a predominant role. The Roots/Shoots (dry weight) DDTs quality reached the maxim 1.61 when 0.5mg/kg DDTs were supplied in the soil, but it reached the maxim 10.81 when 2.4mg/kg DDTs were supplied in the soil.(3) Both the surfactant Sodium laurylsuifonate (SLS) and Cetyltrimethyl Ammonium Bromide (CTAB) at different dose could promote the DDTs accumulation by Medicago sativa, and SLS was more efficient than CTAB. The accumulation ability of Medicago sativa to DDTs was increased at 1.5mg/kg concentration of NaHCO₃ in the soil, but decreased at 0.5mg/kg level, with 3.0mg/kg NaHCO₃ added in the soil, could improve the DDTs accumulation in shoots but inhibit its accumulation in roots.(4) No significant changes were observed for the biomass of Medicago sativa when treated with various concentrations of DDTs, but some physiological index had been changed. The SOD and POD activities were first increased and later decreased,...