Reactivity and Mobility of New and Old Mercury Deposition in a Boreal Forest Ecosystem during the First Year of the METAALICUS Study

Hintelmann, Holger; Harris, R. O.; Heyes, Andrew; Hurley, James P.; Kelly, Carol A.; Krabbenhoft, David P.; Lindberg, S. E.; Rudd, John W. M.; Scott, Kevin R.; Louis, Vincent L. St.

doi:10.1021/es025572t

Cited by 251 publications

(213 citation statements)

References 27 publications

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“…Thus, after 3 years of loading, most of the spike mercury remained bound to vegetation and soils, and Ϸ99% of the mercury in runoff was older, preexisting ambient mercury. A similar result was seen in a pilot study on an upland microcatchment (16) in which spike mercury worked its way into the soils and was incorporated into the much larger preexisting pool of soil mercury before exiting the catchment.…”

Section: Resultssupporting

confidence: 74%

Whole-ecosystem study shows rapid fish-mercury response to changes in mercury deposition

Harris

Rudd²,

Amyot

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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400

333

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Methylmercury contamination of fisheries from centuries of industrial atmospheric emissions negatively impacts humans and wildlife worldwide. The response of fish methylmercury concentrations to changes in mercury deposition has been difficult to establish because sediments/soils contain large pools of historical contamination, and many factors in addition to deposition affect fish mercury. To test directly the response of fish contamination to changing mercury deposition, we conducted a whole-ecosystem experiment, increasing the mercury load to a lake and its watershed by the addition of enriched stable mercury isotopes. The isotopes allowed us to distinguish between experimentally applied mercury and mercury already present in the ecosystem and to examine bioaccumulation of mercury deposited to different parts of the watershed. Fish methylmercury concentrations responded rapidly to changes in mercury deposition over the first 3 years of study. Essentially all of the increase in fish methylmercury concentrations came from mercury deposited directly to the lake surface. In contrast, <1% of the mercury isotope deposited to the watershed was exported to the lake. Steady state was not reached within 3 years. Lake mercury isotope concentrations were still rising in lake biota, and watershed mercury isotope exports to the lake were increasing slowly. Therefore, we predict that mercury emissions reductions will yield rapid (years) reductions in fish methylmercury concentrations and will yield concomitant reductions in risk. However, a full response will be delayed by the gradual export of mercury stored in watersheds. The rate of response will vary among lakes depending on the relative surface areas of water and watershed.bioaccumulation ͉ mercury methylation ͉ stable isotopes ͉ whole-ecosystem experimentation ͉ methylmercury

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Section: Resultssupporting

confidence: 74%

Whole-ecosystem study shows rapid fish-mercury response to changes in mercury deposition

Harris

Rudd²,

Amyot

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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400

333

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“…The impact of this process has been estimated to contribute 256-1400 Mg a −1 to worldwide emission of mercury from terrestrial surfaces, based on 20 % prompt reemission of deposited mercury (Selin et al, 2008;Kikuchi et al, 2013;Simone et al, 2014). Evidence for this process came from isotopic measurements (Hintelmann et al, 2002;Graydon et al, 2006), where newly deposited mercury was found to be more susceptible to re-emission to the atmosphere on a scale of days to months. Data from the Mercury Experiment to Assess Atmospheric Loadings in Canada and the US (METAALICUS) study suggest between 5 and 40 % of mercury newly deposited over terrestrial surfaces is promptly recycled (Hintelmann et al, 2002;Amyot et al, 2004;Selin et al, 2008).…”

Section: Howard and G C Edwards: Mercury Fluxes Over An Australimentioning

confidence: 99%

“…Evidence for this process came from isotopic measurements (Hintelmann et al, 2002;Graydon et al, 2006), where newly deposited mercury was found to be more susceptible to re-emission to the atmosphere on a scale of days to months. Data from the Mercury Experiment to Assess Atmospheric Loadings in Canada and the US (METAALICUS) study suggest between 5 and 40 % of mercury newly deposited over terrestrial surfaces is promptly recycled (Hintelmann et al, 2002;Amyot et al, 2004;Selin et al, 2008). Further evidence has since been compiled during observations taken during atmospheric mercury depletion events (AMDEs), which are characterised by the rapid oxidation of gaseous elemental mercury (GEM) to the more reactive gaseous oxidised mercury (GOM) and subsequent deposition to the surface (Steffen et al, 2008, and references within).…”

Section: Howard and G C Edwards: Mercury Fluxes Over An Australimentioning

confidence: 99%

“…In their isotopic investigations, Hintelmann et al (2002) observed that 66 % of wet-deposited mercury was bound within vegetation, suggesting this may be a significant sink of GOM formed near the surface. Figure 5 shows that, following the significant deposition during dew nights, an emission pulse is observed shortly after sunrise.…”

Section: Howard and G C Edwards: Mercury Fluxes Over An Australimentioning

confidence: 99%

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Mercury fluxes over an Australian alpine grassland and observation of nocturnal atmospheric mercury depletion events

Howard

Edwards

2018

Atmos. Chem. Phys.

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Abstract. Aerodynamic gradient measurements of the airsurface exchange of gaseous elemental mercury (GEM) were undertaken over a 40 ha alpine grassland in Australia's Snowy Mountains region across a 3-week period during the late austral summer. Bi-directional GEM fluxes were observed throughout the study, with overall mean value of 0.2 ± 14.5 ng m −2 h −1 and mean nocturnal fluxes of −1.5 ± 7.8 ng m −2 h −1 compared to diurnal fluxes of 1.8 ± 18.6 ng m −2 h −1 . Deposition velocities ranged from −2.2 to 2.9 cm s −1 , whilst ambient GEM concentrations throughout the study were 0.59 ± 0.10 ng m −3 . Cumulative GEM fluxes correlated well with 24 h running mean soil temperatures, and one precipitation event was shown to have a positive impact on diurnal emission fluxes. The underlying vegetation had largely senesced and showed little stomatal control on fluxes. Nocturnal atmospheric mercury depletion events (NAMDEs) were observed concomitant with O 3 depletion and dew formation under shallow, stable nocturnal boundary layers. A mass balance box model was able to reproduce ambient GEM concentration patterns during NAMDE and non-NAMDE nights without invoking chemical oxidation of GEM throughout the column, indicating a significant role of surface processes controlling deposition in these events. Surface deposition was enhanced under NAMDE nights, though uptake to dew likely represents less than one-fifth of this enhanced deposition. Instead, enhancement of the surface GEM gradient as a result of oxidation at the surface in the presence of dew is hypothesised to be responsible for a large portion of GEM depletion during these particular events. GEM emission pulses following nights with significant deposition provide evidence for the prompt recycling of 17 % of deposited mercury, with the remaining portion retained in surface sinks. The long-term impacts of any sinks are however likely to be minimal, as cumulative GEM flux across the study period was close to zero.

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“…Therefore, the watershed could remain a major source of Hg to lakes and rivers for many years and delay the response of aquatic ecosystems to changes in emissions (Yang et al 2002). However, recent Hg emissions appear to be more readily methylated, suggesting at least an initial rapid decrease in fish Hg concentration after reductions in Hg emissions Hintelmann et al 2002). As a result of these complexities and uncertainties, Hg concentrations in fish could respond over months, years, or decades following changes in atmospheric Hg emissions.…”

Section: Comparison To Wet Depositionmentioning

confidence: 99%

Mercury trends in fish from rivers and lakes in the United States, 1969–2005

Chalmers

Argue

Brigham

et al. 2010

Environ Monit Assess

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A national dataset on concentrations of mercury in fish, compiled mainly from state and federal monitoring programs, was used to evaluate trends in mercury (Hg) in fish from US rivers and lakes. Trends were analyzed on data aggregated by site and by state, using samples of the same fish species and tissue type, and using fish (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) were compared to wet Hg deposition data from the Mercury Deposition Network (MDN) over the same period. Downward trends in Hg concentrations in fish from data collected during 1969-1987 exceeded upward trends by a ratio of 6 to 1. Declining Hg accumulation rates in sediment and peat cores reported by many studies during the 1970s and 1980s correspond with the period when the most downward trends in fish Hg concentrations occurred. Downward Hg trends in both sediment cores and fish were also consistent with the implementation of stricter regulatory controls of direct releases of Hg to the atmosphere and surface waters during the same period. The southeastern USA had more upward Hg trends in fish than other regions for both site and state aggregated data. Upward Hg trends in fish from the southeastern USA were associated with increases in wet deposition in the region and may be attributed to a greater influence of global atmospheric Hg emissions in the southeastern USA. No significant trends were found in 62% of the fish species from six states from 1996 to 2005. A lack of Hg trends in fish in the more recent data was consistent with the lack of trends in wet Hg deposition at MDN 176 Environ Monit Assess (2011) 175:175-191 sites and with relatively constant global emissions during the same time period. Although few significant trends were observed in the more recent Hg concentrations in fish, it is anticipated that Hg concentrations in fish will respond to changes in atmospheric Hg deposition, however, the magnitude and timing of the response is uncertain.

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Reactivity and Mobility of New and Old Mercury Deposition in a Boreal Forest Ecosystem during the First Year of the METAALICUS Study

Cited by 251 publications

References 27 publications

Whole-ecosystem study shows rapid fish-mercury response to changes in mercury deposition

Whole-ecosystem study shows rapid fish-mercury response to changes in mercury deposition

Mercury fluxes over an Australian alpine grassland and observation of nocturnal atmospheric mercury depletion events

Mercury trends in fish from rivers and lakes in the United States, 1969–2005

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