Geochemistry of Mercury Along a Soil Profile Compared to Other Elements and to the Parental Rock: Evidence of External Input

Fiorentino, Janaina Correa; Enzweiler, Jacinta; Angélica, Rômulo Simões

doi:10.1007/s11270-011-0769-x

Cited by 34 publications

(25 citation statements)

References 55 publications

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“…Hg concentrations across the six weathering profiles (0.4 to 282 ng/g) were comparable to the range of values reported by previous studies on nonpoint source polluted forested soils in North America (e.g., Obrist et al, 2009;Obrist et al, 2011;Richardson et al, 2013;Smith et al, 2013), tropical South America (e.g., Fiorentino et al, 2011), temperate and subtropical China (Luo et al, 2014), and temperate and Mediterranean Europe (Peña-Rodríguez et al, 2012;Schwesig & Matzner, 2001). Furthermore, Hg concentrations were generally lower than those reported in point-source polluted areas such as soils near artisanal gold mining (e.g., 70-420 ng/g of soils in French Guyana studied by Guedron et al, 2009) and soils near metropolitan areas in China (e.g., 110-2178 ng/g in Shi et al, 2013).…”

Section: Mercury Concentrations and Inventories In Weathering Profilessupporting

confidence: 87%

Mercury Sourcing and Sequestration in Weathering Profiles at Six Critical Zone Observatories

Richardson

Aguirre

Buss

et al. 2018

Global Biogeochemical Cycles

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Mercury sequestration in regolith (soils + weathered bedrock) is an important ecosystem service of the critical zone. This has largely remained unexplored, due to the difficulty of sample collection and the assumption that Hg is predominantly sequestered within surface soils (here we define as 0–0.3 m). We measured Hg concentrations and inventories in weathering profiles at six Critical Zone Observatories (CZOs): Boulder Creek in the Front Range of Colorado, Calhoun in the South Carolina Piedmont, Eel River in coastal northern California, Luquillo in the tropical montane forest of Puerto Rico, Shale Hills of the valley and ridges of central Pennsylvania, and Southern Sierra in the Sierra Nevada range of California. Surface soils had higher Hg concentrations than the deepest regolith samples, except for Eel River, which had lower Hg concentrations in surface soils compared to regolith. Using Ti normalization, CZOs with <12% rock‐derived Hg (Boulder Creek, Calhoun, and Southern Sierra) had Hg peaks between 1.5 and 8.0 m in depth. At CZOs with >50% rock‐derived Hg, Eel River Hg concentrations and pools were greatest at >4.0 m in the weathering profile, while Luquillo and Shale Hills had peaks at the surface that diminished within 1.0 m of the surface. Hg and total organic C were only significantly correlated in regolith at Luquillo and Shale Hills CZOs, suggesting that Hg sorption to organic matter may be less dominant than clays or Fe(II) sulfides in deeper regolith. Our results demonstrate the importance of Hg sequestration in deep regolith, below typical soil sampling depths.

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Section: Mercury Concentrations and Inventories In Weathering Profilessupporting

confidence: 87%

Mercury Sourcing and Sequestration in Weathering Profiles at Six Critical Zone Observatories

Richardson

Aguirre

Buss

et al. 2018

Global Biogeochemical Cycles

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“…Mercury concentration in crustal rocks is still poorly defined, but a recent study on arc crustal rocks reported much lower Hg concentration (2.9 ± 2.6 ppb) [ Canil et al ., ] than most of our mineral soil samples. In addition, previous studies on Hg sources in soils using geochemical ratios also show that the dominant source of Hg in upper soils is from exogenic (i.e., atmospheric) inputs rather than from geogenic sources [ Grimaldi et al ., ; Fiorentino et al ., ; Peña‐Rodríguez et al ., ]. Note that the contribution of geogenic Hg may vary between sites.…”

Section: Resultsmentioning

confidence: 99%

Mercury isotope compositions across North American forests

Zheng

Obrist

Weis

et al. 2016

Global Biogeochemical Cycles

184

195

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Forest biomass and soils represent some of the largest reservoirs of actively cycling mercury (Hg) on Earth, but many uncertainties exist regarding the source and fate of Hg in forest ecosystems. We systematically characterized stable isotope compositions of Hg in foliage, litter, and mineral soil horizons across 10 forest sites in the contiguous United States. The mass‐independent isotope signatures in all forest depth profiles are more consistent with those of atmospheric Hg(0) than those of atmospheric Hg(II), indicating that atmospheric Hg(0) is the larger source of Hg to forest ecosystems. Within litter horizons, we observed significant enrichment in Hg concentration and heavier isotopes along the depth, which we hypothesize to result from additional deposition of atmospheric Hg(0) during litter decomposition. Furthermore, Hg isotope signatures in mineral soils closely resemble those of the overlying litter horizons suggesting incorporation of Hg from litter as a key source of soil Hg. The spatial distribution of Hg isotope compositions in mineral soils across all sites is modeled by isotopic mixing assuming atmospheric Hg(II), atmospheric Hg(0), and geogenic Hg as major sources. This model shows that northern sites with higher precipitation tend to have higher atmospheric Hg(0) deposition than other sites, whereas drier sites in the western U.S. tend to have higher atmospheric Hg(II) deposition than the rest. We attribute these differences primarily to the higher litterfall Hg input at northern wetter sites due to increased plant productivity by precipitation. These results allow for a better understanding of Hg cycling across the atmosphere‐forest‐soil interface.

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“…The magmatic and metamorphic rocks making up the Guiana and Brazilian shields, which border the Amazon basin to the northeast and south, have low concentrations of Hg, ranging from 4 to 7 ng g -1 for granites, basalts and andesites in French Guiana (Guédron et al, 2006). These concentrations are lower than, or equal to, those obtained for rocks of a comparable nature found in Brazil (Fiorentino et al, 2011) and on other continents (Gao et al, 1998). Except for certain minerals, which are generally sulfur (S)-bearing (cinnabar: HgS), Mercury is present as impurities in the crystalline lattices of minerals (Andersson, 1979).…”

Section: Origins and Carrier Phases Of Mercury Accumulated In Soilsmentioning

confidence: 75%

Impact of gold mining on mercury contamination and soil degradation in Amazonian ecosystems of French Guiana.

Grimaldi

Guédron²,

Grimaldi³

2015

Land-Use Change Impacts on Soil Processes: Tropical and Savannah Ecosystems

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This chapter focuses on the impact of artisanal small-scale gold mining (ASGM) on the Hg contamination of tropical soils, with special attention on how the change in land use (i.e., gold extraction practices) alters the soil processes that affect Hg fate and behaviour. The chapter explains the soil formation and transformation processes that determine the accumulation or mobilization of Hg, reflecting the dual role of soils as both 'sink' and 'source' of Hg. First, it compares the fate and behaviour of Hg from ASGM with that from the natural geochemical background, considering the nature and abundance of carrier phases and soil functioning. Then, it describes how former and current ASGM activities intensify the soil processes that favour Hg mobilization by surface and near-surface runoff to watercourses, Hg emission to the atmosphere and production of monomethyl-Hg. Further, this chapter combines research carried out in French Guiana, a territory located in northern South America with studies from Brazilian Amazonia. French Guiana, like much of Amazonia, is greatly impacted by ancient and current, legal and illegal ASGM activities. The impact on tropical soils, as well as on ecosystems as a whole, has been well studied in these areas. Furthermore, as the environmental legislation in force since 2006 in French Guiana prohibits the use of Hg at gold mining sites, it is relevant to compare ASGM with or without the amalgamation practice. For a better understanding of the soil processes involved, the main research issue is to promote mining practices that can reduce health and environmental risks. The chapter established that although the use of Hg has been officially prohibited in French Guiana since 2006, being replaced by techniques combining concentration by gravity and centrifugation, its use is common in other parts of the developing world. However, even when Hg amalgamation is not used, gold mining without any precautions creates conditions that favour the transport of Hg already present in the soils to river systems and its transformation into monomethyl-Hg. The risk of Hg contamination for humans thus tends to eclipse the other problems arising from ASGM operations. In fact, ASGM also causes complete deforestation of the areas exploited and consequently a loss of biodiversity and ecosystem functions, landscape modifications and soil degradation.

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Geochemistry of Mercury Along a Soil Profile Compared to Other Elements and to the Parental Rock: Evidence of External Input

Cited by 34 publications

References 55 publications

Mercury Sourcing and Sequestration in Weathering Profiles at Six Critical Zone Observatories

Mercury Sourcing and Sequestration in Weathering Profiles at Six Critical Zone Observatories

Mercury isotope compositions across North American forests

Impact of gold mining on mercury contamination and soil degradation in Amazonian ecosystems of French Guiana.

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