Unraveling the biogeochemical cycling of mercury using stable mercury isotopes as source tracers

汞污染在地方、区域和全球范围内对人类健康和自然生态系统构成重大威胁。虽然自前工业化时代以来，人为汞排放急剧增加，但自然排放对全球总体存量和通量的贡献很大。这对负责管理环境中汞的监管机构构成了相当大的挑战，因为通常不可能区分天然汞源和人为汞源。因此，详细了解汞的生物地球化学循环是至关重要的，但并不总是足够的。稳定汞同位素比的测量和汞同位素分异的测定是一种新的有前途的工具，可以追踪汞的来源，并获得它们对汞总输运的相对重要性的新见解。拟议的研究将结合实地研究，包括从自然环境中收集和测量样本，以及专门的受控实验室实验来调查特定过程。特别的重点将是对汞同位素（即200-Hg）异常分馏的最新和尚未解释的观察，迄今为止主要在水样（降水、雪、地表水）中检测到异常分馏。实地研究将调查水食物网生物积累过程中汞同位素的分馏，并将得到使用特伦特大学微环境实验室新安装的大气室的受控实验室实验的支持。我们将特别研究（照片）元素汞被大气反应物（如溴原子和溴自由基）化学氧化，并确定它们产生质量依赖和质量独立分馏的潜力。这里提出的基础研究至关重要，最终能够利用测量的汞同位素指纹作为一种工具，追踪汞从其来源到环境中的各种受体位点，并最终能够区分自然来源和人为来源的汞。

Mercury contamination poses a significant threat for human health and natural ecosystems at local, regional and global scales. Although man-made mercury emissions have increased dramatically since pre-industrial times, natural emissions represent a substantial contribution the overall global inventory and fluxes. This poses a considerable challenge for regulators tasked with managing mercury in the environment, as it is often impossible to distinguish natural from anthropogenic mercury sources. Thus, a detailed understanding of the biogeochemical cycle of mercury is crucial, but not always sufficient. The measurement of stable mercury isotope ratios and determination mercury isotope fractionation is a new promising tool to trace sources of mercury and to gain new insights into their relative importance to the total mercury transport.The proposed research will combine field studies, including collection and measurement of samples from natural environments, with dedicated controlled laboratory experiments to investigate specific processes. Special focus will be on the newly and still unexplained observation of anomalous fractionation of even mercury isotopes (i.e. 200-Hg), which so far has been predominantly detected in aqueous samples (precipitation, snow, surface water). Field studies will investigate fractionation of mercury isotopes during bioaccumulation in aqueous food webs and will be supported by controlled laboratory experiments using the newly installed atmospheric chamber in Trent University's Micro-Environmental Laboratory. We will specifically investigate the (photo)chemical oxidation of elemental mercury by atmospheric reactants such as bromine atoms and BrOx radicals and determine their potential to create mass dependent and mass independent fractionation.The fundamental research proposed here is critical to eventually be able to employ measured mercury isotope fingerprints as a tool to track mercury from its source to various receptor sites in the environment and to finally be able to distinguish natural from anthropogenic sources of mercury.