Assessment of Regional Mercury Deposition and Emission Outflow in Mainland China

Wang, Xun; Lin, Che‐Jen; Feng, Xinbin; Yuan, Wei; Fu, Xuewu; Zhang, Hui; Wu, Qingru

doi:10.1029/2018jd028350

Cited by 30 publications

(24 citation statements)

References 148 publications

(410 reference statements)

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“…As mentioned before, during the cold season, air masses that carry some air pollutants from the Asian continent are transported to our monitoring site by westerlies and northwestern monsoons. In the East Asian region, China is one of the major contributors of atmospheric Hg emissions [57], although the estimated emission amounts [58] and emission outflow [59] have been reported to have slightly decreased due to emission controls in recent years. In addition, the Hg emissions in East Asia slightly increased in the period between 2010 (901.4 Mg) and 2015 (1012.3 Mg), although its growth rate has slowed in recent years [60].…”

Section: Long-term Trends Of Atmospheric Gem Gom and Pbm25 Concentrationsmentioning

confidence: 99%

Long-Term Observation of Atmospheric Speciated Mercury during 2007–2018 at Cape Hedo, Okinawa, Japan

et al. 2019

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The concentrations of atmospheric gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle-bound mercury (particles with diameter smaller than 2.5 μm; PBM2.5) were continuously observed for a period of over 10 years at Cape Hedo, located on the north edge of Okinawa Island on the border of the East China Sea and the Pacific Ocean. Regional or global scale mercury (Hg) pollution affects their concentrations because no local stationary emission sources of Hg exist near the observation site. Their concentrations were lower than those at urban and suburban cities, as well as remote sites in East Asia, but were slightly higher than the background concentrations in the Northern Hemisphere. The GEM concentrations exhibited no diurnal variations and only weak seasonal variations, whereby concentrations were lower in the summer (June–August). An annual decreasing trend for GEM concentrations was observed between 2008 and 2018 at a rate of −0.0382 ± 0.0065 ng m−3 year−1 (−2.1% ± 0.36% year−1) that was the same as those in Europe and North America. Seasonal trend analysis based on daily median data at Cape Hedo showed significantly decreasing trends for all months. However, weaker decreasing trends were observed during the cold season from January to May, when air masses are easily transported from the Asian continent by westerlies and northwestern monsoons. Some GEM, GOM, and PBM2.5 pollution events were observed more frequently during the cold season. Back trajectory analysis showed that almost all these events occurred due to the substances transported from the Asian continent. These facts suggested that the decreasing trend observed at Cape Hedo was influenced by the global decreasing GEM trend, but the rates during the cold season were restrained by regional Asian outflows. On the other hand, GOM concentrations were moderately controlled by photochemical production in summer. Moreover, both GOM and PBM2.5 concentrations largely varied during the cold season due to the influence of regional transport rather than the trend of atmospheric Hg on a global scale.

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Section: Long-term Trends Of Atmospheric Gem Gom and Pbm25 Concentrationsmentioning

confidence: 99%

Long-Term Observation of Atmospheric Speciated Mercury during 2007–2018 at Cape Hedo, Okinawa, Japan

et al. 2019

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“…Recent global Hg models estimate that 3600 Mg yr −1 of atmospheric Hg is deposited to terrestrial surfaces, with 1000 Mg yr −1 being re-emitted back to the atmosphere (Outridge et al, 2018). Moreover, compared to primary anthropogenic emissions of Hg (2500 Mg yr −1 ), estimates of re-emissions from soil surfaces are highly uncertain (Outridge et al, 2018;Wang et al, 2018). Compiling data from 132 studies, Agnan et al (2016) found that the Earth's surface (particularly in East Asia) is an increasingly important source of TGM emissions, with up to half of the global emissions derived from natural sources.…”

Section: Introductionmentioning

confidence: 99%

“…The annual loading of total mercury (THg) to subtropical forests in China has been shown to be much higher than forest catchments in Europe and North America (Wright et al, 2016;Zhou et al, 2020a). High Hg deposition has resulted in elevated soil Hg pools in Chinese subtropical forests (Wang et al, 2018;Wang et al, 2009). In contrast, a recent study showed that the Hg deposition and soil Hg concentrations at a temperate forest in China were similar to those in Europe and North America (Zhou et al, 2020a).…”

Section: Introductionmentioning

confidence: 99%

Soil–atmosphere exchange flux of total gaseous mercury (TGM) at subtropical and temperate forest catchments

et al. 2020

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Abstract. Evasion from soil is the largest source of mercury (Hg) to the atmosphere from terrestrial ecosystems. To improve our understanding of controls and in estimates of forest soil–atmosphere fluxes of total gaseous Hg (TGM), measurements were made using dynamic flux chambers (DFCs) over 130 and 96 d for each of five plots at a subtropical forest and a temperate forest, respectively. At the subtropical forest, the highest net soil Hg emissions were observed for an open field (24 ± 33 ng m−2 h−1), followed by two coniferous forest plots (2.8 ± 3.9 and 3.5 ± 4.2 ng m−2 h−1), a broad-leaved forest plot (0.18 ± 4.3 ng m−2 h−1) and the remaining wetland site showing net deposition (−0.80 ± 5.1 ng m−2 h−1). At the temperate forest, the highest fluxes and net soil Hg emissions were observed for a wetland (3.81 ± 0.52 ng m−2 h−1) and an open field (1.82 ± 0.79 ng m−2 h−1), with lesser emission rates in the deciduous broad-leaved forest (0.68 ± 1.01 ng m−2 h−1) and deciduous needle-leaved forest (0.32 ± 0.96 ng m−2 h−1) plots, and net deposition at an evergreen pine forest (−0.04 ± 0.81 ng m−2 h−1). High solar radiation and temperature during summer resulted in the high Hg emissions in the subtropical forest and the open field and evergreen pine forest at the temperate forest. At the temperate deciduous plots, the highest Hg emission occurred in spring during the leaf-off period due to direct solar radiation exposure to soils. Fluxes showed strong positive relationships with solar radiation and soil temperature and negative correlations with ambient air TGM concentration in both the subtropical and temperate forests, with area-weighted compensation points of 6.82 and 3.42 ng m−3, respectively. The values of the compensation points suggest that the atmospheric TGM concentration can play a critical role in limiting TGM emissions from the forest floor. Climate change and land use disturbance may increase the compensation points in both temperate and subtropical forests. Future research should focus on the role of legacy soil Hg in reemissions to the atmosphere as decreases in primary emissions drive decreases in TGM concentrations and disturbances of climate change and land use.

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“…Recent global Hg models estimate that 3600 Mg yr −1 of atmospheric Hg is deposited to terrestrial surfaces, with 1000 Mg yr −1 reemitted back to the atmosphere (Outridge et al, 2018). Additionally, compared to anthropogenic emissions of Hg (2500 Mg yr −1 ), estimates of re-emissions from soil surfaces are highly uncertain (Agnan et al, 2016;Outridge et al, 2018;Wang et al, 2018). Compiling data from 132 studies, Agnan et al (2016) found that the Earth's surface (particularly in East Asia) is an increasingly important source of total gaseous Hg (TGM) emissions, contributing up to half of the global emissions from natural sources.…”

Section: Introductionmentioning

confidence: 99%

“…Forests experience highly elevated Hg loads, especially in China (Fu et al, 2015;Wang et al, 2016). The annual loading of THg to subtropical forests in China have been shown to be much higher than some forest catchments in Europe and North America (Wright et al, 2016;Larssen et al, 2008) and high Hg deposition has resulted elevated the soil Hg pools in Chinese subtropical forests (Wang et al, 2018;Wang et al, 2009). However, recent studies showed that the Hg deposition and soil Hg concentration in temperate forest were similar to those in Europe and North America (Zhou et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Soil-atmosphere exchange flux of total gaseous mercury (TGM) in subtropical and temperate forest catchments

Zhou¹,

Wang²,

Zhang³

et al. 2020

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Abstract. Evasion from soil is the largest source of mercury (Hg) to the atmosphere in terrestrial ecosystems. To improve understanding of controls and reduce uncertainty in estimates of forest soil-atmosphere exchange, soil-air total gaseous Hg (TGM) fluxes were measured for 130 and 96 days for each of four plots at a subtropical forest and a temperate forest, respectively. The soil-air TGM fluxes, measured using dynamic flux chambers (DFC), showed patterns of both emission and deposition at five study plots, with an area-weighted net emission rate of 3.2 and 0.32 ng m−2 hr−1 for the entire subtropical and temperate forests, respectively. At the subtropical forest, the highest fluxes and net soil Hg emission were observed for an open field, with lesser emission rates in coniferous (Masson pine) and broad-leaved (camphor) forests, and net deposition in a wetland. At the temperate forest, the highest fluxes and net soil Hg emission were observed for a wetland and an open field, with lesser emission rates in deciduous broad-leaved and deciduous needle-leaf (larch) forests, and net deposition in an evergreen pine forest (Chinese pine). High solar radiation and temperature in summer resulted in the high Hg emission at the subtropical forest, and open field and evergreen pine forest in the temperate forest. In the temperate deciduous plots, the highest Hg emission was in spring during leaf-off period due to direct solar radiation exposure to soils. Fluxes showed strong positive relationships with solar radiation and soil temperature, and negative correlations with ambient-air TGM concentration in both subtropical and temperate forests, with area-weighted compensation points of 6.82 and 3.42 ng m−3, respectively. The compensation points implicated that the atmospheric TGM concentration plays a critical role in inhibiting the TGM emission from forest floor. More attention should pay to the legacy Hg stored in terrestrial surface as a more important increasing Hg emission source with the decreasing air TGM concentration recently.

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Assessment of Regional Mercury Deposition and Emission Outflow in Mainland China

Cited by 30 publications

References 148 publications

Long-Term Observation of Atmospheric Speciated Mercury during 2007–2018 at Cape Hedo, Okinawa, Japan

Long-Term Observation of Atmospheric Speciated Mercury during 2007–2018 at Cape Hedo, Okinawa, Japan

Soil–atmosphere exchange flux of total gaseous mercury (TGM) at subtropical and temperate forest catchments

Soil-atmosphere exchange flux of total gaseous mercury (TGM) in subtropical and temperate forest catchments

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