Eco-toxicity and metal contamination of paddy soil in an e-wastes recycling area.

Paddy soil samples taken from different sites in an old primitive electronic-waste (e-waste) processing region were examined for eco-toxicity and metal contamination. Using the environmental quality standard for soils (China, Grade II) as reference, soil samples of two sites were weakly contaminated with trace metal, but site G was heavily contaminated with Cd (6.37 mg kg(-1)), and weakly contaminated with Cu (256.36 mg kg(-1)) and Zn (209.85 mg kg(-1)). Zn appeared to be strongly bound in the residual fraction (72.24-77.86%), no matter the soil was metal contaminated or not. However, more than 9% Cd and 16% Cu was present in the non-residual fraction in the metal contaminated soils than in the uncontaminated soil, especially for site G and site F. Compared with that of the control soil, the micronucleus rates of site G and site F soil treatments increased by 2.7-fold and 1.7-fold, respectively. Low germination rates were observed in site C (50%) and site G (50%) soil extraction treated rice seeds. The shortest root length (0.2377 cm) was observed in site G soil treated groups, which is only 37.57% of that of the control soil treated groups. All of the micronucleus ratio of Vicia faba root cells, rice germination rate and root length after treatment of soil extraction indicate the eco-toxicity in site F and G soils although the three indexes are different in sensitivity to soil metal contamination.