摘要
河流是有毒重金属汞跨圈层循环的重要通道,因而明确河流汞的迁移转化对了解其全球生物地球化学循环和生态环境效应至关重要。近十五年来,具有独特“三维”分馏体系的汞同位素已被证实是示踪河流汞来源-转化-归趋的有效手段。成熟的前处理和分析方法是开展河流汞同位素研究的前提。本文首先概括了适用于河流不同形态汞提纯和浓缩以进行同位素检测方法,包括用于溶解态总汞同位素分析的离子交换树脂法和吹扫捕集法、用于颗粒态总汞同位素分析的热解法和消解法以及用于甲基汞同位素分析的蒸馏-气相色谱法和蒸馏-离子交换树脂法。其次,本文系统讨论了汞同位素在河流汞来源解析、过程示踪和归趋判定三方面的应用成果,包括:(1)汇总河流样品和储库汞同位素组成,并定量解析了河流不同形态汞的来源及各端员的贡献比例;(2)依据不同转化过程的同位素分馏系数,揭示汞在储库释放、河流迁移及入海过程中的地球化学行为及其控制因素;(3)整合河流和海洋样品汞同位素组成,明确河流汞的环境归趋和生态效应。最后,本文将汞同位素嵌入河流-近海汞通量模型,进而评估了近海汞源汇平衡状态。目前,河流汞同位素研究仍处于起步阶段,未来研究应继续发展不同形态汞同位素分析方法和分馏机理,厘清人类活动和气候变化双重影响下大型河流与土壤、大气、海洋和生物等系统或圈层互作中汞的地球化学循环,为制定汞环境保护政策提供科学依据。
River plays a critical role in biogeochemical cycling of toxic heavy metal,mercury(Hg),across Earth’s surface spheres,thus it is important to identify the sources,transformations and fates of Hg in river system.Over the past fifteen years,the unique“three-dimensional”Hg isotopes system has been widely used as a powerful tool for tracing the biogeochemical cycling of Hg,which has largely improved the understanding of Hg systematics in rivers.In this study,the recent development of pretreatment and analysis methods essential for Hg isotopes study is first summarized,including the anion-exchange resin and purge and trap for dissolved Hg,the pyrolysis and digestion for particulate Hg,and the distillation-gas chromatography and distillation-ion exchange resin for methylmercury(MeHg).Then we introduce systematically three application aspects of Hg isotopes in rivers,with the first to quantitatively determine the sources of different Hg species and their contributions,the second to reveal the geochemical behavior of Hg and its migration into the ocean,and the third to clarify the environmental and ecological effects of riverine Hg.Finally,Hg isotopes are integrated into the river-coastal Hg flux model,and the source-sink balance is examined.As the study on Hg isotopes in rivers is still at the beginning,future research should be systematically performed not only to develop the analysis method,but also to advance our knowledge of Hg isotope fractionation mechanisms during the interaction between riverine Hg with other ecosystems such as soil,atmosphere,and ocean,with a goal to better constrain the fate of riverine Hg and its environmental and ecological effect.
作者
何晟
蔡虹明
袁玮
陈玖斌
HE Sheng;CAI Hongming;YUAN Wei;CHEN Jiubin(School of Earth System Science,Tianjin University,Tianjin 300072,China)
出处
《地学前缘》
北大核心
2025年第3期375-391,共17页
Earth Science Frontiers
基金
国家自然科学基金项目(42421003,42473007)。
关键词
汞同位素
质量分馏
非质量分馏
河流
mercury isotopes
mass-dependent fractionation
mass-independent fractionation
river
