蔬菜大棚种植区土壤与地下水中典型有机污染物健康风险评价

在对石家庄某蔬菜大棚种植区进行采样测试分析的基础上,针对其表层土壤及地下水有机污染特征,依托美国环保局(U.S.EPA)所提健康风险评价四步法,以菜农为敏感人群,尝试开展蔬菜大棚种植区的健康风险评价工作。在评价过程中,主要考虑经口摄入土壤和饮用地下水两种暴露途径,而鉴于蔬菜大棚内表层土壤与大棚周围表层土壤中污染物种类和含量存在明显差异这一事实,又将经口摄入土壤途径细分为经口摄入大棚内表层土壤和经口摄入大棚外表层土壤。评价结果显示,菜农的非致癌风险和致癌风险目前均处于可接受风险水平;邻苯二甲酸二正丁酯是最主要的非致癌污染物,其非致癌风险贡献率高达84.2%,狄氏剂是最主要的致癌污染物,其致癌风险贡献率为51.35%;饮用地下水途径是最主要的非致癌风险贡献途径,其非致癌风险贡献率高达94.42%;经口摄入棚外表层土壤途径是最主要的致癌风险贡献途径,其致癌风险贡献率为47.14%。

Health risks of typical soil and groundwater organic pollutants in greenhouse vegetables growing area

Nine groups of groundwater samples and two groups of soil samples were collected in greenhouse areas in Shijiazhuang and analyzed for organic pollutants. Two groups of groundwater samples were sampled from drinking water wells and seven groups from irrigation wells. Soil samples were surface soils inside greenhouse and farmland outside greenhouse respectively. About 20 organic pollutants were detected in the surface soil, 8 of which also occurred in groundwater with PAEs as the main pollutant. There were obvious differences in the pollutant species and content from surface soils between outside and inside greenhouse. There were more OCPs in farmland soils than inside greenhouse soils and the reverse was the general trend for PAEs and PAHs. Based on standard health risk assessments, the target pollutants for health risk were dieldrin, benzo a-anthracene, benzo a-pyrene, indeno 1,2,3-cd-pyrene, dimethyl phthalate and dibutyl phthalate. The test results showed that the characteristics of the above organic pollutants in surface soils and groundwater systems in studying area posed health risks to greenhouse farmers and sensitive population. The exploration assessment of cultivated greenhouse soils followed the four steps of Health Risk Assessment certified by US EPA. The steps include data collection and evaluation, toxicity assessment, exposure assessment and risk attribute. The major exposure pathways included oral ingestion of soil and drinking groundwater. Then oral ingestion of soil was subdivided into oral ingestion of greenhouse surface soil and that of surface soil of farmland outside greenhouse. The results of the health risk assessment showed that in this area, both non-carcinogenic risk and carcinogenic risk of greenhouse farmers were at acceptable levels. The contribution rate of dibutyl phthalate to non-carcinogenic risk, which was the most dangerous non-carcinogenic risk contaminant, was nearly 84.2%, while that of dieldrin was only 15.8%. Also the contribution rate of dieldrin to carcinogenic risk, which was the most dangerous carcinogenic contaminant, was 51.35%. That of benzo a-pyrene, the second largest rate, was about 39.75%. Then those of benzo a-anthracene and indeno 1,2,3-cd-pyrene were the least, with contribution rates of only 4.89% and 4.01%. Drinking groundwater was the main pathway for non-carcinogenic risk, with a contribution rate of about 94.42%. The contribution rates of the other two exposure pathways (oral ingestion of greenhouse surface soil and that of surface soil in farmland outside greenhouse) to non-carcinogenic risk were 5.578% and 0.002%, respectively. Oral ingestion of surface soil in farmland outside greenhouse was the main pathway for carcinogenic risk, with a contribution rate of about 47.14%. The contribution rates of the other two exposure pathways (drinking groundwater and oral ingestion of greenhouse surface soil) to carcinogenic risk were 33.2% and 19.66%, respectively.