洞庭湖主要河口区表层沉积物与河蚬中砷的污染特征及风险评价

Characteristics and risk assessment of arsenic contamination from surface sediments and clams(Corbicula fluminea) in the main estuaries of Lake Dongting

水体砷污染及其健康危害已成为一个备受关注的环境问题.本研究通过测定洞庭湖主要河口区表层沉积物砷含量、河蚬砷及砷形态(亚砷酸盐As(Ⅲ)、砷酸盐As(Ⅴ)、甲基砷酸MMA、二甲基砷酸DMA和砷甜菜碱As B)含量,对表层沉积物砷的潜在生态风险和河蚬食用健康风险进行评价.结果表明,洞庭湖主要河口区表层沉积物砷含量在11.47～61.20 mg/kg之间,其水平分布规律表现为:南洞庭湖>东洞庭湖>西洞庭湖.河蚬砷含量范围为6.36～11.15 mg/kg,各砷形态含量排序为:As B> As(Ⅴ)> DMA> As(Ⅲ)> MMA,各样地间不存在显著性差异.应用潜在生态风险指数法对表层沉积物中砷的潜在生态风险进行评价,各样地的潜在生态风险指数均值为23.09,潜在生态风险程度属于轻微级别.同时,利用致癌风险指数(CR)和危熵系数(HQ)评价经河蚬摄入无机砷给人体带来的潜在健康风险.洞庭湖主要河口区河蚬中无机砷的致癌风险CRiAs值达到了1.36×10-3～3.43×10-3(平均值为2.24×10-3),均显著超过USEPA推荐的可接受风险水平上限值(1×10-4),其危熵系数HQiAs值达到3.01～7.61(平均值为4.98,约为标准值的5倍),说明长期食用当地河蚬具有较高的致癌和非致癌健康风险.本研究结果对于了解洞庭湖沉积物和底栖动物的砷污染现状和风险水平具有重要意义,为该流域的砷污染控制及治理提供科学依据.

Arsenic contamination in water bodies and associated health hazards has become an important environmental issue. In this study, the total arsenic concentrations in surface sediments as well as clams and the arsenic species (arsenite (As(Ⅲ)), arsenate (As(Ⅴ)), monomethylarsonate (MMA), dimethylarsinate (DMA) and arsenobetaine (AsB)) in clams from the main estuaries of Lake Dongting were investigated. Meanwhile, both the potential ecological risk of arsenic in surface sediments and the health risk of eating clams were assessed. The results showed that the total arsenic concentrations in surface sediments were 11.47-61.20 mg/kg, and the horizontal distribution pattern of arsenic was as follows: South Lake Dongting > East Lake Dongting > West Lake Dongting. The total arsenic concentrations in clams were 6.36-11.15 mg/kg, and no significant difference was found among sampling sites. The arsenic species distribution in the clams was AsB > As(Ⅴ)> DMA > As(Ⅲ)> MMA. The Hakanson potential ecological risk index ( E r ) was applied for assessing the extent of potential ecological risk of arsenic in surface sediments. The average of E r was 23.09, indicating that the potential ecological risk of arsenic in surface sediments belonged to low level. Meanwhile, both the carcinogenic risk ( CR ) and hazard quotient ( HQ ) were used to assess the potential health risks of human dietary exposure to inorganic arsenic (iAs) through clam. The CR iAs values reached 1.36×10^-3 -3.43×10^-3 , and the mean value was 2.24× 10^-3 , of which all exceeded the upper limit of USEPA’s acceptable risk range (1×10^-4 ). The HQ iAs values also reached 3.01- 7.61 , and the average of HQ iAs was 4.98, which was 5 times of standard value. It was suggested that long-term intake of native clam from the main estuaries of Lake Dongting was associated with increased both carcinogenic and non-carcinogenic health risk. The results of this study are of great significance for understanding the status and risk level of arsenic contamination from surface sediments and benthos in the main estuaries of Lake Dongting, and provide scientific basis for the control and treatment of arsenic contamination in this basin.