Eco-toxicological Diagnosis Of Contaminated Soil From An E-waste Recycling Area

Developing countries such as China face a rapidly increasing amount of imported Waste Electrical and Electronic Equipment (WEEE) or electronic and electric waste (e-waste), which is from developed countries for recycling. Unregulated salvaging operations have resulted in severe contamination of toxic metals and organic chemicals for soil in these areas, which turned to be a great study case on soil complex pollution. However, instrumental analysis can provide little information on the biological effects and can not evaluate the complex contamination and the soil quality very well. This dissertation aimed to develop methods of ecological toxicological diagnosis of contaminated soil from a typical e-waste recycling center in Zhejiang province in China. The main results are summarized as follows.The concentrations of toxic metals including Cu, Zn, Pb, Cr, Cd, As, Hg, and organic pollutants including PCDD/Fs, PCBs and PAHs were determined in about 300 soil samples from the e-waste recycling center, which covers 278 km~2. It was indicated that Cd, Cu, Hg, Zn, PCBs, PCDD/Fs and PAHs were the contaminants which should be preferentially controlled. The sources of these pollutants were identified as rude dismantling of e-waste. And spatial distributions of the contaminants were geo-statistically analyzed, which indicated the wide spread of pollution in this area.The acute toxicities of the soil samples were determined by using seed germination assay, root elongation test, earthworm lethal assay, earthworm weight inhibition test and luminescent bacterium bioassay. The results indicated that the soils in the study area have acute toxicities to plant, earthworm and microorganism. These toxicities had correlations with the contaminations of Cu. The luminescent assay using fresh water microorganism based on different solvents mild extraction is valuable to assess the acute toxicities of soluble and hydrophobic contaminants in soil, and the risk to groundwater. The eco-toxicological diagnosis system for acute toxicity evaluation is helpful to valuate the soil pollution and soil quality.The significant AhR effect of soil from the e-waste recycling area was detected using in vitro EROD bioassay. The prevalent contributor of effect was identified as PCBs near e-waste recycling sites by combining of chemical analysis and bioassay. However, in the cropland soil which was not polluted directly in the recycling area, the main contributors were PCDD/Fs, PCBs and PAHs. The combination of bioassay and chemical analysis is useful to identify the contamination of dioxin-like compounds.Finally, the comet assay, micronucleus test and SOS/umu test were performed to evaluate the genotoxicity of soil by using organisms from multiple trophic levels. It was indicated that the soil was genotoxic to microorganism, soil invertebrate, and plant. The contributors of genotoxicities were considered as PCBs and Cd. The genotoxicity of soil could be better evaluated when using a battery of bioassays.The methodologies of ecological toxicological diagnosis were proved to be valuable to access the soil complex contamination and soil quality.