Anthropogenic lead pervasive in Canadian Arctic seawater.

Anthropogenic Pb is widespread in the environment including remote places. However, its presence in Canadian Arctic seawater is thought to be negligible based on low dissolved Pb (dPb) concentrations and proxy data. Here, we measured dPb isotopes in Arctic seawater with very low dPb concentrations (average ∼5 pmol ⋅ kg) and show that anthropogenic Pb is pervasive and often dominant in the western Arctic Ocean.

Isotopic Characterization of Atmospheric Gaseous Elemental Mercury by Passive Air Sampling.

Tracing emission sources and transformations of atmospheric mercury with Hg stable isotopes depends on the ability to collect amounts sufficient for reliable quantification. Commonly employed active sampling methods require power and long pumping times, which limits the ability to deploy in remote locations and at high spatial resolution and can lead to compromised traps. In order to overcome these limitations, we conducted field and laboratory experiments to assess the preservation of isotopic composition during sampling of gaseous elemental mercury (GEM) with a passive air sampler (PAS) that uses a sulfur-impregnated carbon sorbent and a diffusive barrier.

Mercury isotopic signatures of tailings from artisanal and small-scale gold mining (ASGM) in southwestern Ecuador.

Artisanal and small-scale gold mining (ASGM) is currently one of the largest anthropogenic sources of mercury (Hg) to the atmosphere and a significant source to downstream terrestrial aquatic systems. Given the potential toxicity of Hg when it is released to aquatic ecosystems, both scientific and regulatory communities have interest in the development of tools and methods for understanding the fate and transport of Hg in the environment. Although Hg isotopes are applied extensively to trace other anthropogenic point sources of Hg in aquatic ecosystems, few studies have used isotopic analyses to investigate the downstream impacts of ASGM.

Mercury Stable Isotope Fractionation during Abiotic Dark Oxidation in the Presence of Thiols and Natural Organic Matter.

Mercury (Hg) stable isotope fractionation has been widely used to trace Hg sources and transformations in the environment, although many important fractionation processes remain unknown. Here, we describe Hg isotope fractionation during the abiotic dark oxidation of dissolved elemental Hg(0) in the presence of thiol compounds and natural humic acid. We observe equilibrium mass-dependent fractionation (MDF) with enrichment of heavier isotopes in the oxidized Hg(II) and a small negative mass-independent fractionation (MIF) owing to nuclear volume effects.

An investigation of mercury sources in the Puyango-Tumbes River: Using stable Hg isotopes to characterize transboundary Hg pollution.

Mercury (Hg) concentrations and stable isotopes along with other trace metals were examined in environmental samples from Ecuador and Peru's shared Puyango-Tumbes River in order to determine the extent to which artisanal- and small-scale gold mining (ASGM) in Portovelo-Zaruma, Ecuador contributes to Hg pollution in the downstream aquatic ecosystem. Prior studies investigated the relationship between ASGM activities and downstream Hg pollution relying primarily on Hg concentration data. In this study, Hg isotopes revealed an isotopically heavy Hg signature with negligible mass independent fractionation (MIF) in downstream sediments, which was consistent with the signature observed in the ASGM source endmember.

Mercury anomalies and the timing of biotic recovery following the end-Triassic mass extinction.

The end-Triassic mass extinction overlapped with the eruption of the Central Atlantic Magmatic Province (CAMP), and release of CO2 and other volcanic volatiles has been implicated in the extinction. However, the timing of marine biotic recovery versus CAMP eruptions remains uncertain. Here we use Hg concentrations and isotopes as indicators of CAMP volcanism in continental shelf sediments, the primary archive of faunal data.

Mercury Stable Isotopes in Ornithogenic Deposits As Tracers of Historical Cycling of Mercury in Ross Sea, Antarctica.

Production of methylmercury (MeHg) in ocean waters and its bioaccumulation in marine organisms are critical processes controlling the fate and toxicity of mercury (Hg). However, these processes are not well understood in the Antarctic, where high levels of MeHg are observed in the subsurface ocean (100-1000 m). We explored the use of Hg stable isotope compositions in historical and modern biological deposits as a new approach for discerning Hg sources and tracing MeHg cycling in the ocean and bioaccumulation in marine biota.

Mercury isotope fractionation during aqueous photoreduction of monomethylmercury in the presence of dissolved organic matter.

Monomethylmercury (MMHg) is a toxic pollutant that bioaccumulates in aquatic food webs. A major mechanism that limits MMHg uptake by biota is photodemethylation in surface waters. Recently, the extent of mass-independent fractionation (MIF) of Hg isotopes preserved in fish is being used to quantify this MMHg sink.

Mass-dependent and -independent fractionation of hg isotopes by photoreduction in aquatic systems.

Mercury (Hg) isotopes can be used as tracers of Hg biogeochemical pathways in the environment. The photochemical reduction of aqueous Hg species by natural sunlight leads to both mass-dependent fractionation (MDF) of Hg isotopes and mass-independent fractionation (MIF) of the odd-mass isotopes, with the relation between the MIF for the two odd isotopes being distinct for different photoreduction pathways. Large variations in MDF and MIF are observed in fish and provide new insights into the sources and bioaccumulation of Hg in food webs.

Mercury stable isotope fractionation during reduction of Hg(II) to Hg(0) by mercury resistant microorganisms.

Mercury (Hg) undergoes systematic stable isotopic fractionation; therefore, isotopic signatures of Hg may provide a new tool to track sources, sinks, and dominant chemical transformation pathways of Hg in the environment. We investigated the isotopic fractionation of Hg by Hg(II) resistant (HgR) bacteria expressing the mercuric reductase (MerA) enzyme. The isotopic composition of both the reactant Hg(II) added to the growth medium and volatilized product (Hg(0)) was measured using cold vapor generation and multiple collector inductively coupled plasma mass spectrometry.

Reporting of variations in the natural isotopic composition of mercury.

High-precision measurements of natural variations in the stable isotopic composition of mercury show great promise as a new tracer of mercury sources and chemical transformations in the environment. We strongly suggest that all laboratories adopt a common means of data correction, standardization, and nomenclature in order to ensure that data from various laboratories can be easily evaluated and compared. We make suggestions for mass bias correction, reporting of mass-dependent and mass-independent isotope variations, and a standard protocol for reporting analytical uncertainties.