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。

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.