持久性有机污染物在水生食物网中的传递行为

食物网是持久性有机污染物(POPs)在水生生态系统中传递的重要途径,了解其传递行为与机制是POPs生态暴露风险评价的科学基础。从4个方面展开了讨论和分析:(1)食物网主要特征(营养级和食物链长度)与POPs环境行为的关系;(2)POPs在底栖及底栖-浮游耦合食物网中的环境行为;(3)微食物网对POPs环境行为的作用;(4)食物网的变化对POPs环境行为的影响。主要结论如下:(1)已有研究对水生生物中POPs生物放大作用存在较大争议。一般营养级越高,POPs生物富集性越强,但由于各种生态和生理性质的影响,也存在例外情况。食物链长度与POPs生物富集性呈正相关。(2)POPs通过底栖食物网将沉积物中的POPs向上传递,底栖-浮游食物网的耦合提高了高营养级消费者的暴露风险,目前就POPs在底栖食物网中的生物放大性是否大于浮游食物网存在争议。(3)微生物具有较大的比表面积,是吸附POPs的重要载体。另,沉积物中的微生物通过分解有机质,将POPs释放到水柱中。微生物降解也是环境中POPs脱离环境的重要途径。(4)在内、外压力下,食物网结构和功能发生变化,使物质和能量的传递方向和效率发生改变,并与环境理化性质的变化互相耦合,影响POPs的环境行为。当前研究的重点多集中在POPs在浮游食物网,尤其是高营养级浮游食物网中的环境行为,对POPs在底栖及底栖-浮游耦合食物网和微食物网中环境行为的研究相对缺乏。有关POPs在食物网中环境行为的研究多集中在食物网的某个部分,时间尺度较短,缺乏对POPs环境行为动态变化的研究,未来需深入开展多尺度和多角度的POPs在食物网中环境行为的动态变化研究。新型POPs的生产和使用量不断增加,但有关其在食物网中环境行为的相关分析还较为匮乏,需加强研究。

Environmental behavior of persistent organic pollutants in aquatic food web

Food web is an import transfer path in aquatic ecosystem. It is essential to explore the environmental behavior of persistent organic pollutants (POPs) along the food web, which will provides cientific foundations for risk evaluation of ecological exposure. Here, we analyzed and summarized the environmental behavior of POPs in aquatic food web, including (a) relationships between trophic levels and food chain length and biomagnification; (b) POPs transfer along benthic and benthic-pelagic coupling food web; (c) adsorption and degradation of POPs by microbes; (d) influences of food web changes caused by several common environmental pressures on the environmental behavior of POPs. The results showed increased bioaccumulation in higher trophic levels, but exceptions were noted because of ecological and physiological factors, such as diet, prey abundance, POPs degradation and isotope enrichment by microbial loop, growth rate, and lipid content. Food chain length was positively correlated with bioaccumulation. When POPs were transferred from the sediment to top consumers, the coupling of pelagic-benthic food web would enhance the exposure risks of higher trophic level consumers to POPs. Controversies existed whether the biomagnification of POPs along benthic food web was greater than that along the pelagic food web. Microbes could adsorb POPs more efficiently because of having a larger surface area. Microbes in the sediment decomposed organic materials, recycling POPs into the water column. Microbial degradation is an important way for POPs leaving aquatic ecosystem. Food web changes caused by seasonal succession, eutrophication and exotic invasions could change the direction and efficiency of energy transfer, and further resulted in changes of the environmental behavior of POPs. Most current studies mainly focused on the environmental behavior of POPs in pelagic food web, especially on the higher trophic levels, lacking researches on the environmental behavior of POPs in benthic and pelagic-benthic coupling food webs and microbial loops. Furthermore, the studies on environmental behaviors of POPs were always restricted to parts of the food web on small temporal and spatial scales, lacking researches on dynamic changes of the environmental behavior of POPs from multiple perspectives and large scales. New POPs have been increasing in production and usage, but studies about its environmental behavior along food web were still scare. Future studies should be conducted considering the above.