| Organochlorine pesticides(OCPs) have been of great concern globally due to their high bioaccumulation, toxicity, semi-volatility and persistence in the environment. As one of the main economic crops, vegetables are of short growing duration, high pesticide consumption, and are usually grown in the suburbs to supply the local market. OCPs residues in peri-urban vegetable soils are closely related to the quality of vegetables and human health. Changchun, Jilin, and Siping are the three biggest and most economically prosperous cities in Jilin province, Northeast China, and have experienced a rapid expansion over the past decades. Based on field survey and lab analysis, this research studied the current residue levels, composition pattern, spatial distribution and possible sources of thirteen OCPs in peri-urban vegetable soils of Changchun, Jilin, and Siping. Also, correlation between OCPs concentrations and soil properties, and ecological and health effects of OCPs were studied in this work. All the results here can guide the safe production of vegetables and provide database and recommendation for decision-makers. The main results of this study are as follows:1. Concentrations of various OCPs all decreased in the order of DDTs > HCHs > Chlordanes > Aldrin > Dieldrin in peri-urban vegetable soils of Changchun, Jilin, and Siping. These two compounds of DDTs and HCHs together accounted for 88.29%, 82.05%, and 91.96% of the total OCPs residues, respectively. In addition, the coefficients of variation(C.V., calculated as [standard deviation]/ [mean]) of various OCPs ranged from 37.93% to 224.90%, showing the disorder and bad management of organochlorine pesticides application.2. Composition analysis showed that both HCHs and Chlordanes in peri-urban vegetable soils of Changchun, Jilin, and Siping derived from the historical and fresh input. Except for fresh input of dicofol in Jilin, it could be concluded that DDTs in peri-urban vegetable fields from Changchun and Siping were mainly from the historical application of technical DDT. In this study, aldrin and dieldrin were found in high detection frequencies but low concentrations. This may be attributed to the atmospheric deposition as these compounds are still used in some developing countries around the tropical belt. Affected by wind and human activities, spatial distribution patterns for various OCPs deserved to be discussed compound by compound.3. Percentages above MRL(maximum residue limit) for different kinds of vegetables decreased in the order: leaf vegetable > root vegetable > fruit vegetable. The order of percentages of OCPs above MRL(maximum residue limit) was as follows: green onion > radish > Chinese vegetable > red pepper > cucumber > eggplant > tomato.4. Correlation analysis showed that various OCPs in peri-urban vegetable soils of Changchun were closely related, which might suggest a common source. Except for α-HCH and γ-HCH, soil organic matter showed significant and extremely significant positive correlation with all the rest of OCPs. Soil p H did not present any correlation with OCPs except for γ-HCH. Actually, the residue levels and composition pattern of OCPs in soils were affected by so many factors that, at a regional scale, it was hard to use soil geochemical factor alone to predict residual variation of OCPs.5. HCHs residues in peri-urban vegetable soils of Changchun showed low potential ecological risk, but β-HCH in individual samples had bad influence on soil invertebrates; DDTs showed certain ecological risk on birds and soil organisms, but were safe to the mammals. HCHs residues in peri-urban vegetable soils of Jilin showed low potential ecological risk; DDTs showed certain ecological risk on birds and soil organisms, but were safe to the mammals. HCHs residues in peri-urban vegetable soils of Siping showed low potential ecological risk, but β-HCH in individual samples had bad influence on soil invertebrates; DDTs showed certain ecological risk on birds and soil organisms, and low potential ecological risk on the mammals except for individual samples.6. Both cancer risk and non-cancer risk in different exposure pathways showed in the order of ingestion > dermal absorption > inhalation. The risk for children was 2.33 times higher than that for adults via ingestion, while it was 1.64 times higher than adults via dermal absorption. But for inhalation, the risk for children was lower than adults. To sum up, the total risks for children through three exposure pathways were higher than that for adults. Health risk assessment showed that the total risks of cancer and hazard indexes(HIs) of non-cancer caused by various OCPs were lower than 10-6 and 1, respectively, suggesting that there is no significant potential health risk for adults and children in Changchun, Jilin, and Siping. Target hazard quotients(THQ) for individual OCPs decreased in the order: Chlordane > Heptachlor > HCHs > Diedrin = Aldrin > DDTs. THQs for various OCPs were lower than 1, which indicated that residents around Changchun did not confront with a significant potential health risk by intake of individual OCPs via vegetables. For adults and children, the total THQ through consuming vegetables is less than 1, indicating that there is no significant potential health risk for adults and children by consuming vegetables. Actually, the TTHQ for adults is higher than children.7. According to the single factor pollution index, the environmental quality of peri-urban vegetable fields of Changchun was in no pollution level except for few samples in light pollution, while it was totally in no pollution level for Jilin. The environmental quality of peri-urban vegetable fields of Siping was in no pollution level except for few samples in light and heavy pollution. According to the synthetic pollution index, the soil environmental quality of Changchun and Jilin was in safety level, while only a few vegetable fields was at guard line and light pollution levels, and little fields in Siping reached heavy pollution grade. As shown in the spatial distribution of the synthetic pollution index, vegetable fields in southwest of Changchun and Longtan district of Jilin city should be taken seriously. With reference to the soil environment quality standard(GB15618-2008), the vast majority of the vegetable fields in the study area were non-pollution vegetable production bases, more than half of them can be used as organic and green vegetables bases, and few fields required risk assessment before being used to plant vegetables.Although HCHs and DDTs have been banned for more than 30 years, they are still the main OCPs residues in soils and vegetables. Therefore, we ought to strengthen supervision of the manufacture, sale and application of OCPs. |
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