Mercury cycling and species mass balances in four North American lakes

Qureshi, Asif H.; MacLeod, Matthew; Scheringer, Martin; Hungerbühler, Konrad

doi:10.1016/j.envpol.2008.09.023

Cited by 17 publications

(9 citation statements)

References 49 publications

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“…MMHg residence times in the smaller Itenez floodplains are then insufficient to produce significant anomalies via photochemical demethylation. It is highly likely that the large MMHg MIF anomalies of +4.97 ‰ observed in Lake Michigan are due to the long MMHg residence time of approximately 0.5 years (42). Finally, it should be noted that Hg(II) photoreduction by formic acid, a simple carboxylic acid, led to MDF but not MIF (28).…”

Section: Resultsmentioning

confidence: 98%

Anomalous Mercury Isotopic Compositions of Fish and Human Hair in the Bolivian Amazon

Laffont

Sonke

Maurice

et al. 2009

Environ. Sci. Technol.

124

156

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We report mercury (Hg) mass-dependent isotope fractionation (MDF) and mass-independent isotope fractionation (MIF) in hair samples of the Bolivian Esse Ejjas native people and in several tropical fish species that constitute their daily diet. MDF with δ202Hg ranging from −0.40 to −0.92 ‰ for fish and +1.04 to +1.42 ‰ for hair was observed. Hair samples of native people with a fish-dominated diet are enriched by +2.0 ± 0.2 ‰ in δ202Hg relative to the fish consumed. Both odd Hg isotopes, 199Hg and 201Hg, display MIF in fish (from −0.14 to +0.38 ‰ for Δ201Hg and from −0.09 to +0.55 ‰ for Δ199Hg) and in hair (from +0.12 to +0.66 ‰ for Δ201Hg and from +0.14 to +0.81 ‰ for Δ199Hg). No significant difference in MIF anomalies is observed between Hg in fish and in human hair, suggesting that the anomalies act as conservative source tracers between upper trophic levels of the tropical food chain. Fish Hg MIF anomalies are 10-fold lower than those published for fish species from midlatitude lakes. Grouping all Amazonian fish species per location shows that Δ199Hg:Δ201Hg regression slopes for the clear water Itenez River basin (0.95 ± 0.08) are significantly lower than those for the white water Beni River basin (1.28 ± 0.12). Assuming that the observed MIF originates from aquatic photoreactions, we calculated limited photodemethylation of monomethylmercury (MMHg) in the Beni River floodplains and insignificant photodemethylation in the Itenez River floodplains. This is possibly related to lower residence times of MMHg in the Itenez compared to the Beni River floodplains. Finally, a significantly negative Δ201Hg of −0.14 ‰ in Beni River fish suggests that the inorganic Hg precursor to the MMHg that bioaccumulates up the food chain defines an ecosystem specific non-zero Δ201Hg baseline. Calculation of photodemethylation intensities from Hg or MMHg MIF, therefore, requires a baseline correction.

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Section: Resultsmentioning

confidence: 98%

Anomalous Mercury Isotopic Compositions of Fish and Human Hair in the Bolivian Amazon

Laffont

Sonke

Maurice

et al. 2009

Environ. Sci. Technol.

124

156

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“…These CR values are ratios of observed concentrations of Hg(0) and Hg(II)(g), or Hg(II)(aq) from field studies. They implicitly describe the net rate of interconversion between mercury species [ MacLeod et al , 2005b; Qureshi et al , 2009; Toose and Mackay , 2004]. Their use is valid if (i) the gross rates of interconversions between the mercury species are faster than the rates of processes transporting these species into or out of the air compartment [e.g., Selin et al , 2007, Figure 1] or (ii) the conditions in the air compartment are near steady state.…”

Section: Methodsmentioning

confidence: 99%

“…While CTMs explicitly model air and water flows in the environment at highly resolved temporal and spatial scales and implicitly calculate the mass balance of substance(s) being modeled, multimedia mass balance models use spatial and/or temporal averages of environmental flows estimated from GCMs and explicitly model the mass balance of the substance [ MacLeod et al , 2010]. The multimedia approach has been successfully evaluated for modeling regional mass balances of mercury and conducting regional uncertainty analysis [ MacLeod et al , 2005b; Qureshi et al , 2009].…”

Section: Introductionmentioning

confidence: 99%

“…We model elemental and divalent mercury, Hg(0) and Hg(II), species that are important from a mass flux perspective. We simplify the modeling of mercury species in the atmosphere by using observed average ratios of concentrations between Hg(0) and Hg(II) species to empirically describe atmospheric mercury reactions [ MacLeod et al , 2005b; Qureshi et al , 2009; Toose and Mackay , 2004]; reactions in other compartments and all mass transfer processes are represented by means of pseudo‐first order rate constants and mass transfer velocities. We then conduct a Monte Carlo uncertainty analysis on a unit‐world variant of WorM 3 that has high computational efficiency (25 000 Monte Carlo simulations in <10 h on a modern desktop computer).…”

Section: Introductionmentioning

confidence: 99%

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Quantifying uncertainties in the global mass balance of mercury

Qureshi

MacLeod

Hungerbühler

2011

Global Biogeochem. Cycles

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[1] We quantify uncertainties in the global mass balance of mercury and identify research priorities to reduce these uncertainties. This is accomplished by developing a new spatially resolved global multimedia model (WorM 3 ) that quantitatively describes the fate of mercury at a process level, and conducting an uncertainty analysis on its unit-world variant which computes similar global estimates. In our modeling approach, all mass transfer processes and reactions in ocean water, soil and vegetation, are represented as pseudo-first order; reactions in air are represented using the ratios of observed concentrations of mercury species. We use Monte Carlo analysis to estimate uncertainties in the unit-world modeled global mass balance of mercury and quantitatively identify the input parameters which contribute most to these uncertainties. A key finding is that uncertainties in input parameters that describe the rates of reduction and oxidation reactions in surface ocean contribute more than uncertainties in anthropogenic emissions to the total uncertainties in atmospheric concentration and depositional fluxes of mercury. More research should therefore be targeted toward understanding of these oceanic processes.Citation: Qureshi, A., M. MacLeod, and K. Hungerbühler (2011), Quantifying uncertainties in the global mass balance of mercury, Global Biogeochem. Cycles, 25, GB4012,

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“…(Wang et al, 2009). It can be accumulated through aquatic biota food webs and thus pose a detrimental threat to humans and other piscivorous wildlife (Ullrich et al, 2001;Qureshi et al, 2009). Many studies have identified that sediment is the predominant methylation site, and that the distribution and concentration of Hg in sediment and pore water have significant effects on Hg distribution in water column (Choe et al, 2004;Hines et al, 2004;Rothenberg et al, 2008).…”

Section: Introductionmentioning

confidence: 99%