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。尽管自前工业时代以来，人为汞排放急剧增加，但自然排放对全球汞总量和通量的贡献很大。这给负责管理环境中汞的监管机构带来了相当大的挑战，因为通常无法区分自然汞来源和人为汞来源。因此，详细了解汞的地球化学循环至关重要，但并不总是足够的。汞稳定同位素比值的测定和汞同位素分馏的确定是一种新的有前途的工具，以追踪汞的来源，并获得新的见解，他们的相对重要性，总汞迁移。 拟议的研究将结合联合收割机实地研究，包括从自然环境中收集和测量样本，并进行专门的受控实验室实验，以调查特定的过程。特别重点将放在新的和仍然无法解释的观测异常分馏甚至汞同位素（即200-汞），这是迄今为止主要是在水样品（降水，雪，地表水）检测。实地研究将调查汞同位素在水生食物网生物累积过程中的分馏情况，并将得到利用特伦特大学微环境实验室新安装的大气室进行的受控实验室实验的支持。我们将专门研究元素汞的大气反应物，如溴原子和BrOx自由基的（光）化学氧化，并确定其潜在的质量依赖和质量无关的分馏。 这里提出的基础研究是至关重要的，最终能够采用测得的汞同位素指纹作为一种工具，跟踪汞从其来源到环境中的各种受体网站，并最终能够区分自然和人为来源的汞。

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.