The Ya-Er Lake is a seriously polychlorinated dibenzo-p-dioxins/dibenzo-furans (PCDD/Fs) and mercury (Hg)-contaminated lake by pesticide and chlor-alkali plants in China. The oxidation pond method has been conducted to control pollution, moreover, the contaminated sediment was dredged and stacked, becoming a sediment stack yard for vegetable cultivation. To assess effects of oxidation pond method and dredging programme on pollution management and long-term risks of PCDD/Fs and Hg, the concentrations of PCDD/Fs, total Hg (THg), and methylmercury (MeHg) in soil and vegetable sampled from the sediment stack yard were measured and analyzed. Significantly positive relationships between concentrations of PCDD/Fs (p < 0.01), THg, and MeHg (p < 0.05) in edible parts of vegetable and soil were found, suggesting that bioaccumulation from contaminated soil derived from sediment dredging is important sources of PCDD/Fs and Hg in vegetable. Much higher PCDD/Fs (12 ± 9 pg/g dw) and Hg (THg, 0.14 ± 0.23 μg/g dw; MeHg,12.63 ± 13.31 ng/g dw) levels in vegetable were found compared with those from other contaminated regions, indicative of serious PCDD/Fs and Hg pollution in vegetable harvested from contaminated soil. Finally, the calculated provisional tolerable daily intake (PTDI) values showed higher health risk of PCDD/Fs and Hg exposure to local residents through consumption of purple and white flowering stalk, and oilseed rape. Our study established a good model to evaluate the long-term risks of PCDD/Fs and Hg. Moreover, the results indicate that the oxidation pond method and dredging programme were not effective to remove PCDD/Fs and Hg in sediment, which shed new light on management strategy of PCDD/Fs and Hg pollution in contaminated regions.
Keywords: Concentrations; Health risk; Hg; PCDD/Fs; Sources; Vegetable.
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