Five-year records of mercury wet deposition flux at GMOS sites in the Northern and Southern hemispheres

Sprovieri, Francesca; Pirrone, Nicola; Bencardino, Mariantonia; D’Amore, Francesco; Angot, Hélène; Barbante, Carlo; Brunke, Ernst-Günther; Árcega-Cabrera, Flor; Cairns, Warren R. L.; Comero, Sara; Diéguez, María del Carmen; Dommergue, Aurélien; Ebinghaus, Ralf; Feng, Xizeng; Fu, Xuewu; García, Pérez; Bernd, Gawlik; Hageström, Ulla; Hansson, Katarina; Horvat, Milena; Kotnik, Jože; Labuschagne, Casper; Magand, Olivier; Martin, Lynwill; Mashyanov, Nikolay; Mkololo, Thumeka; Munthe, John; Оболкин, В. А.; Islas, Martha Ramirez; Sena, Fabrizio; Somerset, Vernon; Spandow, Pia; Vardè, Massimiliano; Walters, Chavon; Wängberg, Ingvar; Weigelt, Alexandra; Yang, Xu; Zhang, Hui

doi:10.5194/acp-17-2689-2017

Cited by 73 publications

(61 citation statements)

References 79 publications

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“…We used the PCA component 1 (explaining 60% of total variances, Table S7) of δ 202 Hg in soil, the shift of δ 202 Hg between litterfall and soil, and k d to represent the long‐term effect induced by precipitation. Precipitation intensity can infer the wet Hg deposition variations as earlier studies suggest that variation of seasonal or spatial wet Hg deposition is controlled by the precipitation intensity (X. W. Fu, Yang, et al, ; Sprovieri et al, ; X. Wang, Lin, et al, ).…”

Section: Resultsmentioning

confidence: 99%

Effects of Precipitation on Mercury Accumulation on Subtropical Montane Forest Floor: Implications on Climate Forcing

et al. 2019

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Processes facilitated by precipitation play an important role on mercury (Hg) accumulation on forest floor and therefore key to Hg cycling in forest ecosystems. Sites along the windward slope of 1,250 to 2,400 m at Mt. Ailao, Southwestern China, have higher precipitation than the leeward slope sites. In this study, measurements of Hg concentration and associated stable isotope composition for soil, fresh, and degraded litterfall samples were made at sites along two slopes of Mt. Ailao to quantify the direct and indirect effects of precipitation on Hg accumulation on forest floor. Higher soil Hg concentrations, larger litterfall Hg depositions, and faster litter decomposition rates were observed on the windward slope (1,250-2,400 m). Data of Hg isotopic signatures suggest that Hg in surface soils is mainly derived from litterfall Hg input. Precipitation enhances litterfall Hg deposition by increasing litter biomass production, reduces litter decomposition rate, facilitates short-term Hg uptake to decomposing litter, and potentially increases microbial activity that increases Hg loss via microbial reduction or runoff. Structural equation modeling results support that the indirect effect of precipitation on increased biomass production merge as the most important factor controlling soil Hg variation. Given the climate forcing on global precipitation pattern and vegetation growth cycle, Hg biogeochemical cycling is likely to continue to evolve under the changing climate.Plain Language Summary Precipitation has direct and indirect effects on Hg accumulation and transformation on forest floor. The direct effect is that atmospheric Hg enters into forest floor via precipitation, throughfall, and cloud water deposition. In addition, precipitation likely has an indirect effect on Hg accumulation by influencing litter biomass production and postdepositional processes of Hg, such as litter decomposition, Hg reemission, and surface runoff. The objective of this study is to better quantify the direct and indirect effects of precipitation on Hg accumulation on forest floor. The study sites are located along the leeward and windward slopes of Mt. Ailao in Southwest China. Precipitation intensity is the main variable at the same altitude between two slopes. Our results showed that influences from precipitation on soil Hg accumulation are largely through the indirect effects caused by influencing litterfall Hg deposition. We also suggest that the changed precipitation pattern can force variations of litterfall Hg deposition and soil Hg accumulation globally.

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Section: Resultsmentioning

confidence: 99%

Effects of Precipitation on Mercury Accumulation on Subtropical Montane Forest Floor: Implications on Climate Forcing

et al. 2019

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“…Mercury (Hg) is a potent neurotoxin and a pervasive global pollutant that poses a risk to ecosystem and human health (Driscoll et al 2013). Research on environmental cycling and trophic uptake of Hg has increased greatly over the last 25 years, but most research has focused on mid-and highlatitude ecosystems; Hg researchers have paid relatively scant attention to tropical landscapes (Sprovieri et al 2017). The tropics merit greater attention because they are a reservoir for biodiversity and hold about half of the world's human population, including groups with diets high in fish, one of the main pathways of human exposure to Hg.…”

Section: Introductionmentioning

confidence: 99%

Resolving a paradox—high mercury deposition, but low bioaccumulation in northeastern Puerto Rico

et al. 2019

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At a "clean air" trade winds site in northeastern Puerto Rico, we found an apparent paradox: atmospheric total mercury (THg) deposition was highest of any site in the USA Mercury Deposition Network, but assimilation into the local food web was quite low. Avian blood THg concentrations (n = 31, from eight species in five foraging guilds) ranged widely from 0.2 to 32 ng g−1 (median of 4.3 ng g−1). Within this population, THg was significantly greater at a low-elevation site near a wetland compared to an upland montane site, even when the comparison was limited to a single species. Overall, however, THg concentrations were approximately an order of magnitude lower than comparable populations in the continental U.S. In surface soil and sediment, potential rates of demethylation were 3 to 9-fold greater than those for Hg(II)-methylation (based on six radiotracer amendment incubations), but rates of change of ambient MeHg pools showed a slight net positive Hg(II)-methylation. Thus, the resolution of the paradox is that MeHg degradation approximately keeps pace with MeHg production in this landscape. Further, any net production of MeHg is subject to frequent flushing by high rainfall on chronically wet soils. The interplay of these microbial processes and hydrology appears to shield the local food web from adverse effects of high atmospheric mercury loading. This scenario may play out in other humid tropical ecosystems as well, but it is difficult to evaluate because coordinated studies of Hg deposition, methylation, and trophic uptake have not been conducted at other tropical sites.

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“…Here, we use the 2009-2012 AMNet observations, as these data are publicly available. AMNet had 23 sites over the continental US and eastern Canada (Nova Scotia) operational during this period (Table S2 in Ground-based measurements of Hg wet deposition and Hg(II) surface concentration have been made as part of the Global Mercury Observations System (GMOS) network (Angot et al, 2014;Wängberg et al, 2016;Sprovieri et al, 2016Sprovieri et al, , 2017Travnikov et al, 2017) and at sites in Europe (Weigelt et al, 2013), Canada, and East Asia (Sheu et al, 2010;Sheu and Lin, 2013;Fu et al, 2015Fu et al, , 2016b. We use the 2013-2014 measurements wherever available but use all sites with 1 year or more of observations.…”

Section: Introductionmentioning

confidence: 99%

Subtropical subsidence and surface deposition of oxidized mercury produced in the free troposphere

Shah

Jaeglé

2017

Atmos. Chem. Phys.

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Abstract. Oxidized mercury (Hg(II)) is chemically produced in the atmosphere by oxidation of elemental mercury and is directly emitted by anthropogenic activities. We use the GEOS-Chem global chemical transport model with gaseous oxidation driven by Br atoms to quantify how surface deposition of Hg(II) is influenced by Hg(II) production at different atmospheric heights. We tag Hg(II) chemically produced in the lower (surface-750 hPa), middle (750-400 hPa), and upper troposphere (400 hPa-tropopause), in the stratosphere, as well as directly emitted Hg(II). We evaluate our 2-year simulation (2013)(2014) against observations of Hg(II) wet deposition as well as surface and free-tropospheric observations of Hg(II), finding reasonable agreement. We find that Hg(II) produced in the upper and middle troposphere constitutes 91 % of the tropospheric mass of Hg(II) and 91 % of the annual Hg(II) wet deposition flux. This large global influence from the upper and middle troposphere is the result of strong chemical production coupled with a long lifetime of Hg(II) in these regions. Annually, 77-84 % of surface-level Hg(II) over the western US, South America, South Africa, and Australia is produced in the upper and middle troposphere, whereas 26-66 % of surface Hg(II) over the eastern US, Europe, and East Asia, and South Asia is directly emitted. The influence of directly emitted Hg(II) near emission sources is likely higher but cannot be quantified by our coarse-resolution global model (2 • latitude × 2.5 • longitude). Over the oceans, 72 % of surface Hg(II) is produced in the lower troposphere because of higher Br concentrations in the marine boundary layer. The global contribution of the upper and middle troposphere to the Hg(II) dry deposition flux is 52 %. It is lower compared to the contribution to wet deposition because dry deposition of Hg(II) produced aloft requires its entrainment into the boundary layer, while rain can scavenge Hg(II) from higher altitudes more readily. We find that 55 % of the spatial variation of Hg wet deposition flux observed at the Mercury Deposition Network sites is explained by the combined variation of precipitation and Hg(II) produced in the upper and middle troposphere. Our simulation points to a large role of the dry subtropical subsidence regions. Hg(II) present in these regions accounts for 74 % of Hg(II) at 500 hPa over the continental US and more than 60 % of the surface Hg(II) over high-altitude areas of the western US. Globally, it accounts for 78 % of the tropospheric Hg(II) mass and 61 % of the total Hg(II) deposition. During the Nitrogen, Oxidants, Mercury, and Aerosol Distributions, Sources, and Sinks (NOMADSS) aircraft campaign, the contribution of Hg(II) from the dry subtropical regions was found to be 75 % when measured Hg(II) exceeded 250 pg m −3 . Hg(II) produced in the upper and middle troposphere subsides in the anticyclones, where the dry conditions inhibit the loss of Hg(II). Our results highlight the importance the subtropical anticyclones as the primary conduits for t...

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Five-year records of mercury wet deposition flux at GMOS sites in the Northern and Southern hemispheres

Cited by 73 publications

References 79 publications

Effects of Precipitation on Mercury Accumulation on Subtropical Montane Forest Floor: Implications on Climate Forcing

Effects of Precipitation on Mercury Accumulation on Subtropical Montane Forest Floor: Implications on Climate Forcing

Resolving a paradox—high mercury deposition, but low bioaccumulation in northeastern Puerto Rico

Subtropical subsidence and surface deposition of oxidized mercury produced in the free troposphere

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