Dissolved gaseous mercury concentrations and mercury volatilization in a frozen freshwater fluvial lake

Department of Earth & Environmental Science, Room LL33 K.C Irving Environmental Science Center, Acadia University, Wolfville, Nova Scotia.
Environmental Science and Technology (Impact Factor: 5.48). 08/2008; 42(14):5125-30. DOI: 10.1021/es800216q
Source: PubMed

ABSTRACT In situ mesocosm experiments were performed to examine dissolved gaseous mercury (DGM), mercury volatilization, and sediment interactions in a frozen freshwater fluvial lake (Lake St. Louis, Beauharnois, QC). Two large in situ mesocosm cylinders, one open-bottomed and one close-bottomed (no sediment diffusion), were used to isolate the water column and minimize advection. Mercury volatilization over the closed-bottom mesocosm did not display a diurnal pattern and was low (mean = -0.02 ng m(-2) h(-1), SD = 0.28, n=71). Mercury volatilization over the open-bottom mesocosm was also low (mean = 0.24 ng m(-2) h(-1), SD = 0.08, n=96) however a diurnal pattern was observed. Low and constant concentrations of DGM were observed in surface water in both the open-bottomed and close-bottomed mesocosms (combined mean = 27.6 pg L(-1), SD = 7.2, n=26). Mercury volatilization was significantly correlated with solar radiation in both the close-bottomed (Pearson correlation = 0.33, significance = 0.005) and open-bottomed (Pearson correlation = 0.52, significance = 0.001) mesocosms. However, DGM and mercury volatilization were not significantly correlated (at the 95% level) in either of the mesocosms (significance = 0.09 in the closed mesocosm and significance = 0.9 in the open mesocosm). DGM concentrations decreased with depth (from 62 to 30 pg L(-1)) in the close-bottomed mesocosm but increased with depth (from 30 to 70 pg L(-1)) in the open-bottomed mesocosm suggesting a sediment source. DGM concentrations were found to be high in samples of ice melt (mean 73.6 pg L(-1), SD = 18.9, n=6) and snowmelt (mean 368.2 pg L(-1), SD = 115.8, n=4). These results suggest that sediment diffusion of mercury and melting snow and ice are important to DGM dynamics in frozen Lake St. Louis. These processes may also explain the lack of significant correlations observed in the DGM and mercury volatilization data.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Controlled experiments were performed with frozen and melted Arctic snow to quantify relationships between mercury photoreaction kinetics, ultra violet (UV) radiation intensity, and snow ion concentrations. Frozen (-10°C) and melted (4°C) snow samples from three Arctic sites were exposed to UV (280-400nm) radiation (1.26-5.78W·m(-2)), and a parabolic relationship was found between reduction rate constants in frozen and melted snow with increasing UV intensity. Total photoreduced mercury in frozen and melted snow increased linearly with greater UV intensity. Snow with the highest concentrations of chloride and iron had larger photoreduction and photooxidation rate constants, while also having the lowest Hg(0) production. Our results indicate that the amount of mercury photoreduction (loss from snow) is the highest at high UV radiation intensities, while the fastest rates of mercury photoreduction occurred at both low and high intensities. This suggests that, assuming all else is equal, earlier Arctic snow melt periods (when UV intensities are less intense) may result in less mercury loss to the atmosphere by photoreduction and flux, since less Hg(0) is photoproduced at lower UV intensities, thereby resulting in potentially greater mercury transport to aquatic systems with snowmelt.
    Science of The Total Environment 08/2014; 509-510:115-132. DOI:10.1016/j.scitotenv.2014.07.056 · 3.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Diurnal variations of water total Hg, reactive Hg, and dissolved gaseous Hg concentrations and mercury flux were monitored at 2 sites in warm and cold seasons in an alkaline reservoir in southwestern China. Concentrations of total Hg and reactive Hg, as well as Hg fluxes, usually exhibited a consistent diurnal trend, with elevated values observed during the day. The increasing reactive Hg concentrations and Hg fluxes were highly related to the incident intensity of solar radiation, suggesting that sunlight-induced processes played an important role in the transformation of Hg in the study area. Dissolved gaseous Hg concentrations experienced different diurnal variations among the sampling sites, with peak dissolved gaseous Hg at midday under sunny weather conditions and in the early morning under cloudy and/or partially cloudy weather conditions. The peak values of dissolved gaseous Hg observed at midday agree well with previous results and highlight the sunlight-induced production of dissolved gaseous Hg in freshwaters, whereas dissolved gaseous Hg peaks at night suggest that microbial activity might be an additional mechanism for dissolved gaseous Hg production in surface waters. Total Hg, reactive Hg, and dissolved gaseous Hg concentrations and Hg fluxes in the warm season were consistently higher than those in the cold season; this is probably attributable to the combined effect of seasonal variations of environmental parameters, transformation of Hg species, and microbial activities. Environ Toxicol Chem 2013;32:2256–2265. © 2013 SETAC
    Environmental Toxicology and Chemistry 10/2013; 32(10). DOI:10.1002/etc.2323 · 2.83 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Mercury is a toxic and bioaccumulative environmental contaminant, which may be transported to remote regions around the world such as the Arctic. Snow melt is a major source of mercury to many surface water environments, but the amount of mercury in snow varies considerably. This variation may be due to regulation of mercury retention and losses from snow being controlled largely by photochemical reactions, and the mechanisms of mercury movement being tied to its speciation. As such, quantifying these photochemical reaction rates and the factors affecting them will allow for the prediction of mercury speciation and movement into receiving water bodies, and consequently improve our ability to predict exposure of organisms to mercury. This review highlights knowledge gaps in the quantification of mercury photochemical kinetics and the specific research required to advance the science of mercury photochemistry in snow, by examining the physical and chemical snowpack variables that influence snowpack mercury reactions. At present, our lack of mechanistic and kinetic knowledge of mercury reactions in snow is one of the greatest gaps preventing accurate predictions of mercury fate in regions containing seasonal snowpacks.
    Environmental Reviews 10/2014; 22(4):331-345. DOI:10.1139/er-2014-0006 · 2.36 Impact Factor

Full-text (3 Sources)

Available from
May 26, 2014