树木年轮汞记录:进展、问题和展望

Mercury in tree rings:Advances,problems and prospects

汞作为生物毒性较强的金属元素之一,通过食物链富集进而威胁生态系统健康。汞在森林生态系统中的通量以及储量变化成为汞地球化学循环的重要影响因素。受汞监测记录的时空分布限制,对汞的时空分布变化认识尚不全面。分布广泛的树木是环境汞污染的有效生物监测器之一,能够利用树轮中的汞记录开展汞的时空分布变化研究。环境中的汞通过根系、叶片、树皮等组织吸收富集,最终在树木年轮中得以保存。因此,树轮能够重建污染历史并根据同位素比率反映地球化学循环特征。本文综述树木年轮汞浓度和汞同位素比率测量方法以及树轮汞浓度重建的应用,探讨树轮汞同位素记录在环境重建中以及森林生态系统汞的地球化学循环研究潜力,指出今后研究需要关注的问题。

As a highly biotoxic element,mercury(Hg)can be enriched by the food chain and has negative effect on ecosystems.Changes of Hg flux and reserves in forest have important effects on its biogeochemical cycle in forest ecosystem.Due to limitation of temporal and spatial monitoring,there is not comprehensive understanding on Hg distribution.Widely distributed trees can be used as effective bio-monitors and Hg records in tree rings can be used to study Hg temporal and spatial distribution.Hg accumulated by root,leaf,bark,and other tissues can be detained in bole and record environmental Hg variations.Therefore,historical Hg trends can be restructured by analyzing Hg concentration in tree rings and the biogeochemical characteristics can be understood with Hg isotope ratio.We reviewed the method of measurement of Hg concentration and isotope ratio and application of reconstruction using Hg concentration in tree ring.We suggested the great application potential of Hg isotope ratio in atmospheric Hg construction and biogeochemistry cycle and raised concerns in further studies.