Dissolved organic matter thiol concentrations determine methylmercury bioavailability across the terrestrial-marine aquatic continuum.

The most critical step for methylmercury (MeHg) bioaccumulation in aquatic food webs is phytoplankton uptake of dissolved MeHg. Dissolved organic matter (DOM) has been known to influence MeHg uptake, but the mechanisms have remained unclear. Here we show that the concentration of DOM-associated thiol functional groups (DOM-RSH) varies substantially across contrasting aquatic systems and dictates MeHg speciation and bioavailability to phytoplankton.

An examination of the factors influencing the bioaccumulation of methylmercury at the base of the estuarine food web.

Estuarine systems have received ongoing mercury (Hg) inputs from both point sources and regional contamination and have high legacy Hg in sediments. This is an environmental concern given that coastal seafood is an important vector for human exposure to methylmercury (MeHg). The base of the food chain represents the most important trophic steps for MeHg bioaccumulation.

Historic contamination alters mercury sources and cycling in temperate estuaries relative to uncontaminated sites.

Mercury (Hg) is a global and persistent pollutant which can be methylated to more toxic forms (methylmercury; MeHg) in natural systems. Both forms pose a health risk to humans and wildlife, and exposure often begins in aquatic environments. Therefore, quantifying aquatic concentrations and identifying source pathways is important for understanding biotic exposure.

The interaction of mercury and methylmercury with chalcogenide nanoparticles.

Mercury (Hg) and methylmercury (CHHg) bind strongly to micro and nano (NP) particles and this partitioning impacts their fate and bioaccumulation into food webs, and, as a result, potential human exposure. This partitioning has been shown to influence the bioavailability of inorganic Hg to methylating bacteria, with NP-bound Hg being more bioavailable than particulate HgS, or organic particulate-bound Hg. In this study we set out to investigate whether the potential interactions between dissolved ionic Hg (Hg) and CHHg and NPs was due to incorporation of Hg into the core of the cadmium selenide and sulfide (CdSe; CdS) nanoparticles (metal exchange or surface precipitation), or due purely to surface interactions.

Role of Sediment Resuspension on Estuarine Suspended Particulate Mercury Dynamics.

Coastal sediments are an important site for transient and long-term mercury (Hg) storage, and they foster a geochemical environment optimal for Hg methylation. Therefore, efforts have been taken to constrain the role of sediments as a source of methylmercury (MeHg) to the estuarine water column. This study employed the Gust Microcosm Erosion Core system capable of quantifying particle removal from undisturbed cores under measurable shear stress conditions to assess particulate Hg and MeHg exchange between sediments and the water column.

The precipitation, growth and stability of mercury sulfide nanoparticles formed in the presence of marine dissolved organic matter.

The methylation of mercury is known to depend on the chemical forms of mercury (Hg) present in the environment and the methylating bacterial activity. In sulfidic sediments, under conditions of supersaturation with respect to metacinnabar, recent research has shown that mercury precipitates as β-HgS(s) nanoparticles (β-HgS(s)nano). Few studies have examined the precipitation of β-HgS(s)nano in the presence of marine dissolved organic matter (DOM).

Contemporary Mobilization of Legacy Pb Stores by DOM in a Boreal Peatland.

We examined how different landscape areas in a catchment containing a northern ombrotrophic peatland and upland mineral soils responded to dramatic decreases in atmospheric deposition of lead (Pb). Pb concentrations in the outflow stream from the peatland measured from 2009-2015 indicated continued mobilization and export of Pb derived from historic inputs to the bog. In contrast, Pb concentrations in surface peat and runoff from upland mineral soils have declined in response to reductions in atmospheric deposition.