摘要
藻类能直接吸附吸收水体中的汞,是汞进入水生食物链的关键入口,并在摄食的消费者中富集和放大,控制着整个水生食物链中汞的水平.本文总结了野外调查与分析的有关藻中汞含量及其汞稳定同位素组成的最新研究结果,概述了藻细胞吸附吸收汞的可能机制.结果表明:①藻类中的汞含量比水相中汞浓度高2~3个数量级,自藻类以上各营养级生物对汞的生物累积和放大模式基本相似,即随着营养级的提高,汞含量和放大倍数也会升高,且甲基汞占总汞的比例也随之升高,但其生物累积和放大倍数远低于藻类对水体中汞的累积和放大倍数.②藻类主要通过细胞壁的表面吸附和细胞内的主动吸收两种方式富集和累积水体中的汞.藻类细胞壁上多种带负电荷的官能团与多糖能够吸附结合水体中的无机汞和少部分有机汞,藻类细胞的代谢过程通过载体蛋白把藻体外的无机汞和有机汞转运至细胞内而富集汞.③藻类是目前唯一确认∆^(199)Hg为正值的植物.无论是淡水微型藻类还是海洋大型藻类中的汞稳定同位素非质量分馏信息均为明显的正值,与高等植物的∆^(199)Hg为负值有显著差异.④淡水微型藻类和海洋大型藻类的汞稳定同位素质量分馏信息均为负值.随着食物链营养级的提高,浮游动物和鱼虾类的汞稳定同位素质量分馏信息逐渐偏正,汞在食物链的生物富集和传递过程中相对富集偏重的汞稳定同位素.鉴于分离野外采集的藻类样品较为困难,室内模拟实验研究可评估藻类在水生态系统中的重要作用,研究汞同位素进入藻细胞的分配与机制.
Algae can directly absorb mercury in water bodies,which is the key entrance for mercury to enter the aquatic food chain.Mercury absorbed by algae bioaccumulates and biomagnifies in consumers,thereby controlling mercury levels in throughout the aquatic food chain.We reviewed recent research results on mercury content in algae,possible mechanisms of mercury uptake by algae cells,and mercury isotopic signals in algae.The results indicate that:(1)The accumulation of mercury by algae is 2-3 orders of magnitude higher than that in the water phase.The mercury bioaccumulation and biomagnification patterns above phytoplankton are relatively similar.As the trophic level increases,the bioaccumulation and biomagnification of mercury also increase,and the proportion of methylmercury in total mercury also increases,but the bioaccumulation and biomagnification factors are much lower than those of mercury in the water bodies by algae.(2)Algae enrich and accumulate dissolved mercury in water through surface adsorption by the cell wall and active absorption within the cells.A variety of negative functional groups and polysaccharides on the algae cell wall can adsorb and bind inorganic mercury and small amounts of organic mercury in the water.The metabolic process of cells transports inorganic mercury and organic mercury outside the algae into the cells through carrier proteins,thereby accumulating mercury.(3)Algae are the only plant for whichΔ^(199)Hg has been detected as a positive value.The mercury non-mass fractionation signals in freshwater microalgae and marine macroalgae is both obviously positive,which is significantly different from the negative value ofΔ^(199)Hg in higher plants.The mercury mass fractionation signals are negative for both freshwater microalgae and marine macroalgae.As the trophic level of the food chain increases,the mercury mass fractionation signals of zooplankton,fish and shrimp gradually becomes positive.The heavy mercury isotopes are relatively enriched during the bioaccumulation and transportation
作者
李鹏高
汤顺林
LI Penggao;TANG Shunlin(Institute of Resources and Environment,Henan Polytechnic University,Jiaozuo 454000,China)
出处
《环境科学研究》
CAS
CSCD
北大核心
2024年第4期776-786,共11页
Research of Environmental Sciences
基金
国家自然科学基金项目(No.41573006,41372360)。
关键词
藻类
汞
吸附吸收机制
汞稳定同位素组成
algae
mercury
absorption mechanism
mercury stable isotopic signals
