| Polychlorinated biphenyls (PCBs) have been recognized as a potential health risk due to their intrinsic chemical stability, high recalcitrance to different types of degradation and high toxicity to living organisms. They are ubiquitous in modern environment due to their persistence and hydrophobicity. These omnipresent compounds accumulate in soil where they are likely to be retained for many years. Consequently, soil is an important reservoir for these compounds. In this paper, PCBs contamination statuses were investigated in agricultural soils from heavily metal typical contaminated area and PCBs typical contaminated area in Yangzte River Delta. Soil microbial properties in soils long-term contaminated with PCBs were analyzed using Biolog system and others. And the effect of straw ash in soils on adsorption behavior of PCBs was studied by POM-SPE. At last, a series of soil incubation and pot experiments were conducted to examine bioremediation of PCBs- contaminated soils. In soil incubation experiments, pig manure and rice straw were put into contaminated soils, and then treated under anaerobic/ aerobic or anaerobic-aerobic conditions. The diversity of microbial structure was analysed by the PLFA method in soils. In pot experiments, alfalfa, AM fungi and rhizobium were differently combined in a completely randomized design with three replicates. The main results of this study are presented:1. In heavily metal typical contaminated area, PCBs were detected in 71.0% of soil samples, with average concentrations of 13.8 ng g~-1, of which tetra- to hexa-chlorinated congeners were dominant. Among OCPs, DDTs were most abundant compounds in soils, found in 81% of soil samples and with average concentrations of 13.4 ng g~-1, followed by HCHs in 72.5% of soil samples and with 5.01 ng g~-1. p,p'-DDT and α-HCH were dominant in DDTs and HCHs, respectively. The contents of PCBs and OCPs were related to copper contents in soils, which were higher in soils with elevated copper contents than those values in soils with depressed copper contents. The elevated copper contents inhibit bioremediation of organic chlorines in soils. The soils have been mixed contaminated with heavy metal and organic chlorines.2. In PCBs typical contaminated area, average contents of PCBs were 30.6 ng g~-1 in soil, with maxi. 484.5 ng g~-1. Tetra- to hexa-chlorinated congeners were accounted for 65% above. 88.6% of total PCBs detected accumulated in top soils (0-15 cm). Not only in soils, PCBs can be detected in some vegetables, poultries and fishes growing in the locality and it has threatened the health of local residents. Among poultries detected, the contents of PCBs in fat tissues were higher than those inother tissues owing to PCBs lipophilic property, of which the highest values of 2.5 ug g"1 wt was found in chicken fat tissue. Analysis for contamination resources indicated that improper treatments of PCB-containing old transformers and capacitors and combustions of chlorine-containing plastic waster were both responsible for it.3. The analyses on soil microbial properties indicated that bacterial populations were not different (p > 0.05) in soils long-term polluted differently by PCBs, while the change of fungal populations was subjected to PCBs pollution levels in soils and which decreased in heavily polluted soils. Furthermore, biomass C and N declined in heavily polluted soils compared to weakly polluted soils, which were similar to the soil respiration. Measured with Biolog GN, the composition and function of microbial community were influenced by contents of PCBs in soils, of which the abundance of community and the populations of common microbes both decreased with the increases of PCBs contents in soils. 4.The ashes from combustion of straw influenced the distribution of PCBs in soil-water system, in which the distribution coefficients (concentration in soil/concentration in water) of PCB congeners increased with the increase of amount of ash in soils. And lightly chlorinated congeners were more influenced than heavily chlorinated congeners. N...
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