水、沉积物和土壤中重金属生物有效性／毒性的生物配体模型研究进展

PREDICTION OF BIOAVAILABILITY AND TOXICITY OF HEAVY METALS IN WATER,SEDIMENT AND SOIL ENVIRONMENTS USING BIOTIC LIGAND MODEL

重金属以多种化学形态存在于环境介质中,仅根据环境中重金属元素总量已不能对其生物效应进行良好预测,因此在制定重金属环境质量标准和进行环境风险评价时,明确考虑其生物有效性逐渐受到重视。水体重金属的生物有效性和毒性很早就被认识到是水化学性质的函数,并形成了一些机理描述模型,如自由离子活度模型(FIAM)、鱼鳃点位交互作用模型(GSIM)和生物配体模型(BLM)。BLM在FIAM和GSIM的基础上,同时考虑了水中金属离子的化学形态以及阳离子与金属离子在生物配体(BL)上的竞争对其毒性的影响,能成功预测水体金属的生物有效性/毒性,并被用于水质金属基准的制定。本文对BLM在水环境中的概念模型、发展状况及软件应用做了全面介绍,并对BLM在沉积物和陆地环境中的拓展作了综述,重点介绍了针对植物、土壤动物和微生物的陆地生物配体模型(t-BLM),提出了土壤重金属t-BLM的概念模型并对其构建方法学等进行了探讨。联合了土壤理化性质、金属形态及生物积累和毒性效应的t-BLM,将提供一个环境风险评价和制定更合理土壤环境质量标准的新工具。

In aquatic and soil systems, trace metals exist in a number of forms, soluble or particulate, that determine their effect on ecosystems. It is accepted that based on the content of total heavy metal alone, it is not feasible to make any good prediction of its biological effect. Consequently, in establishing environmental criteria for and executing risk assessment of heavy metals, more and more attention is being given to taking into account their bioavailability. Metal bioavailability and toxicity have long been recognized as a function of water chemistry. And models were proposed to describe its mechanisms, such as Free Ion Activity Model （FIAM）, Gill Site Interaction Model （GSIM） and Biotic Ligand Model （BLM）. Based on FIAM and GSIM, by taking into account the effects of chemical speciation of heavy metals in water and their competition with cations for biotic ligands, BLM was successfully used to predict bioavailability and toxicity of metals in waterbody. USEPA has recently adopted BLM in developing its water quality criteria for copper. In this paper, a complete introduction is presented to the conceptual model of BLM in aquatic environment, its development and application of software, and a review made of extrapolating BLM to the sediment and soil environments, with emphasis on the terrestrial biotic ligand models （t-BLM） for plants, soil animals and microorganisms. A conceptual model of t-BLM was proposed and its methodology discussed. T-BLM which integrates soil physicochemical properties, metal speciation, bioaccumulation and toxicity response, will serve as a new tool to develop the more rational soil quality criteria and to conduct risk assessment of heavy metals.