Quantifying uncertainties in the global mass balance of mercury

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

doi:10.1029/2011gb004068

Cited by 24 publications

(25 citation statements)

References 60 publications

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“…5), which needs mechanistic refinement. Air-seawater exchange estimated by global models is subject to the uncertainties in (1) mechanisms of aqueous redox transformation and the associated kinetic parameters and (2) Hg 0 mass transfer rates as determined by surface fiction velocity (Qureshi et al, 2011a). Kinetic parameters of these processes largely rely on limited field data without experimental verification (AMAP/UNEP, 2013) and require further investigation.…”

Section: Source and Sink Characteristics Of Natural Surfaces In The Cmentioning

confidence: 99%

“…However, the kinetic description of these process is fundamentally unknown. The pseudo-first reduction rate constant of Hg II has been assumed to be in the range of 10 −11 to 10 −10 s −1 (Scholtz et al, 2003;Qureshi et al, 2011a). Under laboratory conditions at 100 W m −2 and 32 ± 7 • C, the pseudo-first reduction rate was estimated to be 2-8 × 10 −10 m 2 s −1 w −1 basing on 2 mm soil depth (the maximum depth for light penetration in soil) (Quinones and Carpi, 2011).…”

Section: Modeling Of Air-surface Hg 0 Exchange Fluxmentioning

confidence: 99%

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Global observations and modeling of atmosphere–surface exchange of elemental mercury: a critical review

et al. 2016

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Abstract. Reliable quantification of air-surface fluxes of elemental Hg vapor (Hg 0 ) is crucial for understanding mercury (Hg) global biogeochemical cycles. There have been extensive measurements and modeling efforts devoted to estimating the exchange fluxes between the atmosphere and various surfaces (e.g., soil, canopies, water, snow, etc.) in the past three decades. However, large uncertainties remain due to the complexity of Hg 0 bidirectional exchange, limitations of flux quantification techniques and challenges in model parameterization. In this study, we provide a critical review on the state of science in the atmosphere-surface exchange of Hg 0 . Specifically, the advancement of flux quantification techniques, mechanisms in driving the air-surface Hg exchange and modeling efforts are presented. Due to the semi-volatile nature of Hg 0 and redox transformation of Hg in environmental media, Hg deposition and evasion are influenced by multiple environmental variables including seasonality, vegetative coverage and its life cycle, temperature, light, moisture, atmospheric turbulence and the presence of reactants (e.g., O 3 , radicals, etc.). However, the effects of these processes on flux have not been fundamentally and quantitatively determined, which limits the accuracy of flux modeling.We compile an up-to-date global observational flux database and discuss the implication of flux data on the global Hg budget. Mean Hg 0 fluxes obtained by micrometeorological measurements do not appear to be significantly greater than the fluxes measured by dynamic flux chamber methods over unpolluted surfaces (p = 0.16, one-tailed, Mann-Whitney U test). The spatiotemporal coverage of existing Hg 0 flux measurements is highly heterogeneous with large data gaps existing in multiple continents (Africa, South Asia, Middle East, South America and Australia). The magnitude of the evasion flux is strongly enhanced by human activities, particularly at contaminated sites. Hg 0 flux observations in East Asia are comparatively larger in magnitude than the rest of the world, suggesting substantial re-emission of previously deposited mercury from anthropogenic sources. The Hg 0 exchange over pristine surfaces (e.g., background soil and water) and vegetation needs better constraints for global analyses of the atmospheric Hg budget. The existing knowledge gap and the associated research needs for future measurements and modeling efforts for the air-surface exchange of Hg 0 are discussed.

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Section: Source and Sink Characteristics Of Natural Surfaces In The Cmentioning

confidence: 99%

Section: Modeling Of Air-surface Hg 0 Exchange Fluxmentioning

confidence: 99%

Global observations and modeling of atmosphere–surface exchange of elemental mercury: a critical review

et al. 2016

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“…This suggests that ocean emissions, rather than mercury sinks, can account for the model deficiencies. Since ocean mercury modelling to date has been constrained mainly by observations and process studies in mid latitudes (Soerensen et al, 2010), there are large uncertainties in the tropical marine fluxes, as well as globally (Qureshi et al, 2011).…”

Section: Model Comparisonmentioning

confidence: 99%

Sources of atmospheric mercury in the tropics: continuous observations at a coastal site in Suriname

et al. 2012

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Abstract. Mercury measurements at a coastal site in Nieuw Nickerie (5 • 56 N, 56 • 59 W), Suriname, provide the only continuous records of atmospheric mercury in the tropics. Here we evaluate observations of total gaseous mercury (TGM) during 2007. Nieuw Nickerie typically samples marine air from the Atlantic Ocean, with occasional influence from continental South America. Over the year, average concentrations are 1.40 ng m −3 . As the intertropical convergence zone passes over Suriname twice each year, the site samples both northern and southern hemispheric air masses. We use back trajectories to classify each measurement by hemisphere, as well as continental or ocean. For air passing over ocean before sampling, TGM concentrations are 10 % higher in air coming from the Northern Hemisphere (1.45 ng m −3 ) than from the Southern Hemisphere (1.32 ng m −3 ). Air from the South American continent also carries higher TGM (1.43 ng m −3 ) than air from the South Atlantic Ocean, with most of these trajectories occurring in August and September. Biomass burning in Brazil peaks in the same months and likely contributes significantly to elevated concentrations seen in Nickerie. We also compare the observed seasonal cycle to two atmospheric mercury chemistry and transport models (GRAHM and GEOS-Chem). Both models simulate transition between northern and southern hemispheric air, thus capturing the seasonal cycle; however the models overestimate the TGM concentrations during months when Nickerie samples Northern Hemisphere air. It is difficult to determine whether the models' sources or sinks in the Northern Hemisphere tropics are responsible.

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“…Consequently, mercury oxidation processes have been the focus of the international mercury community in recent years Cohen et al, 2016;Amos et al, 2015;Dastoor et al, 2015;Song et al, 2015;Bieser et al, 2014a;De Simone et al, 2014;Qureshi et al, 2011;Travnikov et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Multi-model study of mercury dispersion in the atmosphere: vertical and interhemispheric distribution of mercury species

et al. 2017

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Abstract. Atmospheric chemistry and transport of mercury play a key role in the global mercury cycle. However, there are still considerable knowledge gaps concerning the fate of mercury in the atmosphere. This is the second part of a model intercomparison study investigating the impact of atmospheric chemistry and emissions on mercury in the atmosphere. While the first study focused on ground-based observations of mercury concentration and deposition, here we investigate the vertical and interhemispheric distribution and speciation of mercury from the planetary boundary layer to the lower stratosphere. So far, there have been few model studies investigating the vertical distribution of mercury, mostly focusing on single aircraft campaigns. Here, we present a first comprehensive analysis based on various aircraft observations in Europe, North America, and on intercontinental flights.The investigated models proved to be able to reproduce the distribution of total and elemental mercury concentrations in the troposphere including interhemispheric trends. One key aspect of the study is the investigation of mercury oxidation in the troposphere. We found that different chemistry schemes were better at reproducing observed oxidized mercury patterns depending on altitude. High concentrations of oxidized mercury in the upper troposphere could be reproduced with oxidation by bromine while elevated concentrations in the lower troposphere were better reproduced by OH and ozone chemistry. However, the results were not always conclusive as the physical and chemical parameterizations in the chemistry transport models also proved to have a substantial impact on model results.

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Quantifying uncertainties in the global mass balance of mercury

Cited by 24 publications

References 60 publications

Global observations and modeling of atmosphere–surface exchange of elemental mercury: a critical review

Global observations and modeling of atmosphere–surface exchange of elemental mercury: a critical review

Sources of atmospheric mercury in the tropics: continuous observations at a coastal site in Suriname

Multi-model study of mercury dispersion in the atmosphere: vertical and interhemispheric distribution of mercury species

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