中国保护水生生物的甲基汞水质标准制订初探

甲基汞是具较强生物有效性和毒性的有机汞形态,其具有高生物累积性和生物放大效应,能对水生态系统中高营养级生物产生极高的危害,对脊椎动物造成神经毒性、内分泌干扰和生殖毒性等。我国不同环境介质(水、沉积物和生物体组织)中均检测到了甲基汞的存在。传统的水质基准仅依据水环境中水生生物急慢性毒性数据推导得到,未考虑污染物的生物有效性和生物累积性,采用该水质基准可能会对水生态系统造成欠保护。组织浓度是累积性物质生物有效性的直接体现,使用基于组织浓度的毒性数据推导水质基准进而确定水质标准,科学性更强,能更加合理、可靠地保护水生态系统。综述了甲基汞暴露最新毒性研究,在此基础上,采用物种敏感度分布法计算了甲基汞基于组织浓度的基准值为23.15 μg/kg,确定了其保护水生生物的水质基准值为0.12 ng/L,由此推导了其适合我国水环境的水生生物水质标准值为0.35 ng/L。研究结果可为甲基汞水质基准向水质标准的转化及生物累积性物质的水环境质量管理提供思路和支持。

Study on methylmercury water quality standards for aquatic life protection in China

Methylmercury is a kind of organic mercury with strong bioavailability and toxicity. Because of high bioaccumulation and bioavailability, methylmercury can pose serious harmful effects to aquatic life at higher trophic levels and cause neurotoxicity, endocrine disruption and reproductive toxicity to vertebrates. The presence of methylmercury has been detected in various environmental media (water, sediments and organisms) in China. The traditional water quality criteria for methylmercury was only derived from the acute and chronic toxicity data of aquatic organisms in water that did not take bioaccumulation and bioavailability into account, which may cause lower-protection problem to aquatic ecosystem. As the tissue concentrations could directly reflect the bioavailability of cumulative substances, water quality criteria deriving from toxic data based on tissue was more scie.pngic, and could provide protection for aquatic ecosystem more reasonably and reliably. Based on a review of the latest toxic data for methylmercury exposure, the criteria value of methylmercury based on tissue concentration was calculated at 23.15 μg/kg, the water quality criteria for protection of aquatic life was determined at 0.12 ng/L, and the water quality standard value of methylmercury of aquatic organisms suitable for Chinese aquatic environment was derived at 0.35 ng/L. The results can provide a new method and support for the transformation of methylmercury water quality criteria to the water quality standards and for the water environmental management of bioaccumulative chemicals.