Maier K J, Knight A W
Department of Land, Air and Water Resources; Hydrologic Sciences, University of California, Davis 95616.
Rev Environ Contam Toxicol. 1994;134:31-48. doi: 10.1007/978-1-4684-7068-0_2.
The toxicology, environmental impacts and risk assessment of Se in freshwater systems are a high priority for research and regulatory agencies. However, understanding Se in freshwater systems is a challenging endeavor. The accurate risk assessment and determination of a water-quality criterion for any freshwater ecosystem are difficult for many reasons. First, the understanding of the structure and energy dynamics in ecosystems is limited. Second, knowledge of Se cycling and transformations in aquatic ecosystems is rudimentary. Third, the role of various environmental factors affecting its bioaccumulation, biotransformation, and toxicology in aquatic ecosystems is largely unknown. Fourth, the extrapolation and use of existing data in commonly used formulas for risk assessment and calculations of water quality criteria is difficult because of the demonstrated species differences in the bioaccumulation, metabolism, and tolerance of Se. There are many aspects of Se ecotoxicology that need to be addressed to develop more accurate environmental risk assessments and determine appropriate water-quality criteria to protect aquatic ecosystems. Studies evaluating the biochemical speciation of Se in aquatic ecosystems, and determination of the role of microbial communities in its cycling, bioaccumulation, transformation, transfer, and toxicity in aquatic systems, appear to be priorities for future research. These would include a broad exploration of Se effects on ecosystems, e.g., exposure regime, direct and indirect biologic effects, and ecosystem level effects. There are, however, ecological uncertainties that tend to confound such endeavors, e.g., insufficient data, extrapolation issues, and environmental stochasticity (Harwell and Harwell 1989). There are several concepts concerning the ecotoxicology of Se that can be stated. Elevated concentrations have degraded many freshwater ecosystems throughout the United States, and additional systems are expected to be affected as anthropogenic activities increasingly mobilize Se into aquatic systems. Se is a very toxic essential trace element. Toxic threshold concentrations in water, dietary items, and tissues are only 2-5 times normal background concentrations. Toxicity in freshwater ecosystems is the result of bioaccumulation, biotransformation, and cycling of Se in aquatic food chains. Thus, environmental risk assessment and development of effective water-quality criteria to protect freshwater ecosystems become formidable tasks.
硒在淡水系统中的毒理学、环境影响及风险评估是研究机构和监管机构的高度优先事项。然而，了解淡水系统中的硒是一项具有挑战性的工作。由于多种原因，准确评估任何淡水生态系统的风险并确定水质标准都很困难。首先，对生态系统结构和能量动态的理解有限。其次，关于硒在水生生态系统中的循环和转化的知识尚不完善。第三，各种环境因素对其在水生生态系统中的生物累积、生物转化和毒理学的作用很大程度上未知。第四，由于已证明在硒的生物累积、代谢和耐受性方面存在物种差异，因此难以将现有数据外推并用于常用的风险评估公式和水质标准计算。为了开展更准确的环境风险评估并确定保护水生生态系统的适当水质标准，硒生态毒理学的许多方面都需要解决。评估硒在水生生态系统中的生化形态以及确定微生物群落对其在水生系统中的循环、生物累积、转化、转移和毒性的作用的研究，似乎是未来研究的重点。这些研究将包括对硒对生态系统影响的广泛探索，例如暴露方式、直接和间接生物学效应以及生态系统层面的效应。然而，存在一些生态不确定性因素往往会干扰此类工作，例如数据不足、外推问题和环境随机性（哈韦尔和哈韦尔，1989年）。关于硒的生态毒理学有几个概念可以阐述。在美国，硒浓度升高已使许多淡水生态系统退化，随着人为活动越来越多地将硒排入水生系统，预计还会有更多系统受到影响。硒是一种毒性很强的必需微量元素。水中、食物和组织中的毒性阈值浓度仅为正常背景浓度的2至5倍。淡水生态系统中的毒性是硒在水生食物链中生物累积、生物转化和循环的结果。因此，进行环境风险评估和制定有效的水质标准以保护淡水生态系统成为艰巨的任务。
