Vegetation Mediated Mercury Flux and Atmospheric Mercury in the Alpine Permafrost Region of the Central Tibetan Plateau

Sun, Shiwei; Ma, Ming; He, Xiaobo; Obrist, Daniel; Zhang, Qianggong; Yin, Xiufeng; Sun, Tao; Huang, Jie; Guo, Junming; Kang, Shichang; Qin, Dahe

doi:10.1021/acs.est.9b06636

Cited by 20 publications

(24 citation statements)

References 47 publications

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“…During the month of July in this study, when the solar radiation was at the maximum level during the entire growing season, the Hg 2+ photo-reduction had proceeded at the highest rate. This was similar to the results of a study conducted in Australian alpine grasslands by Howard et al [ 26 ]. In addition, it has been determined that intense solar radiation levels will lead to higher air and soil temperatures, which tend to accelerate the biotic or abiotic transformation of Hg 0 and enhance the mercury vapor pressure to facilitate the volatilization of mercury [ 50 ].…”

Section: Discussionsupporting

confidence: 92%

“…In addition, depositions were observed to occur during nighttime hours and colder seasons. However, no clear agreement has been reached on the aforementioned characteristics [ 26 ]. In summary, the large uncertainties caused by different measurement methods, along with a lack of knowledge of soil-air Hg exchanges in grassland regions (particularly whole ecosystem soil-plus-vegetation flux data), have resulted in substantial controversy regarding the roles played by global grassland surfaces.…”

Section: Introductionmentioning

confidence: 99%

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Gaseous Elemental Mercury Exchange Fluxes over Air-Soil Interfaces in the Degraded Grasslands of Northeastern China

Zhang

Zhou

et al. 2021

Biology

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Mercury (Hg) is a global pollutant that may potentially have serious impacts on human health and ecologies. The gaseous elemental mercury (GEM) exchanges between terrestrial surfaces and the atmosphere play important roles in the global Hg cycle. This study investigated GEM exchange fluxes over two land cover types (including Artemisia anethifolia coverage and removal and bare soil) using a dynamic flux chamber attached to the LumexR RA915+ Hg analyzer during the growing season from May to September of 2018, in which the interactive effects of plant coverage and meteorological conditions were highlighted. The daily mean ambient levels of GEM and the total mercury concentrations of the soil (TSM) were determined to be 12.4 ± 3.6 to 16.4 ± 5.6 ng·m−3 and 32.8 to 36.2 ng·g−1, respectively, for all the measurements from May to September. The GEM exchange fluxes (ng·m−2·h−1) during the five-month period for the three treatments included the net emissions from the soil to the atmosphere (mean 5.4 to 7.1; range of −27.0 to 47.3), which varied diurnally, with releases occurring during the daytime hours and depositions occurring during the nighttime hours. Significant differences were observed in the fluxes between the vegetation coverage and removal during the growing months (p < 0.05). In addition, it was determined that the Hg fluxes were positively correlated with the solar radiation and air/soil temperature levels and negatively correlated with the air relative humidity and soil moisture under all the conditions (p < 0.05). Overall, the results obtained in this study demonstrated that the grassland soil served as both a source and a sink for atmospheric Hg, depending on the season and meteorological factors. Furthermore, the plants played an important inhibiting role in the Hg exchanges between the soil and the atmosphere.

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Gaseous Elemental Mercury Exchange Fluxes over Air-Soil Interfaces in the Degraded Grasslands of Northeastern China

Zhang

Zhou

et al. 2021

Biology

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“…In addition, the combination of rapidly uplifting terrain and abundant rainfall produces great evergreen forests in the low-altitude areas in the grand canyon, in contrast to the alpine meadows in the central Tibetan Plateau . Vegetation is a dominant sink for GEM in the vegetation-covered land. ,− The roles of various climates and vegetation coverages shaped by landforms and monsoons during the transport of atmospheric Hg and their influence on atmospheric Hg levels in the Tibetan Plateau regions remain unclear.…”

Section: Introductionmentioning

confidence: 99%

Tracing the Transboundary Transport of Mercury to the Tibetan Plateau Using Atmospheric Mercury Isotopes

Bao

Yang

Liu

et al. 2022

Environ. Sci. Technol.

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Deposition of atmospheric mercury (Hg) is the most important Hg source on the high-altitude Himalayas and Tibetan Plateau. Herein, total gaseous Hg (TGM) at an urban and a forest site on the Tibetan Plateau was collected respectively from May 2017 to October 2018, and isotopic compositions were measured to clarify the influences of landforms and monsoons on the transboundary transport of atmospheric Hg to the Tibetan Plateau. The transboundary transported anthropogenic emissions mainly originated over Indo-Gangetic Plain and carried over the Himalayas by convective storms and mid-tropospheric circulation, contributing over 50% to the TGM at the Lhasa urban site, based on the binary mixing model of isotopes. In contrast, during the transport of TGM from South Asia with low altitude, the uptake by evergreen forest in Yarlung Zangbo Grand Canyon largely decreased the TGM level and shifted isotopic compositions in TGM at the Nyingchi forest site, which are located at the highaltitude end of the canyon. Our results provided direct evidence from Hg isotopes to reveal the distinct patterns of transboundary transport to the Tibetan Plateau shaped by landforms and climates, which is critical to fully understand the biogeochemical cycling of Hg in the high-altitude regions.

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“…Net daytime GEM emission has already been reported for other vegetated mountain environments, such as a high-610 altitude meadow in the US (-2.1 to 6.6 ng m -2 h -1 , depending on the season; Converse et al, 2010), and an alpine meadow in the central Tibetan plateau (0.12 to 5.96 ng m -2 h -1 , depending on the growing period; Sun et al, 2020).…”

mentioning

confidence: 76%

Mercury in the Free Troposphere and Bidirectional Atmosphere-Vegetation Exchanges – Insights from Maïdo Mountain Observatory in the Southern Hemisphere Tropics

Koenig

Magand

Verreyken

et al. 2022

Preprint

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Abstract. Atmospheric mercury (Hg) observations in the lower free troposphere (LFT) can give important insights into Hg redox chemistry and can help constrain Hg background concentrations on a regional level. Relatively continuous sampling of LFT air, inaccessible to most ground-based stations, can be achieved at high-altitude observatories. However, such high-altitude observatories are rare, especially in the Southern Hemisphere (SH), and atmospheric Hg in the SH LFT is unconstrained. To fill this gap, we continuously measured gaseous elemental mercury (GEM; hourly) and reactive mercury (RM; integrated over ~6–14 days) for 9 months at Maïdo mountain observatory (2160 masl) on remote Réunion Island (21.1° S, 55.5° E) in the tropical Indian Ocean. GEM exhibits a marked diurnal variation characterized by a midday peak (mean: 0.95 ng m-3; SD: 0.08 ng m-3) and a nighttime low (mean: 0.78 ng m-3; SD: 0.11 ng m-3). We find that this diurnal variation is likely driven by the interplay of important GEM photo-reemission from the islands’ vegetated surface during daylight hours (8–22 ng m-2 h-1), boundary layer influences during the day, and predominant LFT influences at night. We estimate GEM in the LFT based on nighttime observations in particularly dry airmasses and find a notable seasonal variation, with LFT GEM being lowest from December to March (mean 0.66 ng m-3; SD: 0.07 ng m-3) and highest from September to November (mean: 0.79 ng m-3; SD: 0.09 ng m-3). Such a clear GEM seasonality contrasts the weak seasonal variation reported for the SH marine boundary layer, but goes in line with modeling results, highlighting the added value of continuous Hg observations in the LFT. Maïdo RM is 10.6 pg m-3 (SD: 5.9 pg m-3) on average, but RM in the cloud-free LFT might be about twice as high, as weekly-biweekly sampled RM observations are likely diluted by low-RM contributions from the boundary layer and clouds.

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Vegetation Mediated Mercury Flux and Atmospheric Mercury in the Alpine Permafrost Region of the Central Tibetan Plateau

Cited by 20 publications

References 47 publications

Gaseous Elemental Mercury Exchange Fluxes over Air-Soil Interfaces in the Degraded Grasslands of Northeastern China

Gaseous Elemental Mercury Exchange Fluxes over Air-Soil Interfaces in the Degraded Grasslands of Northeastern China

Tracing the Transboundary Transport of Mercury to the Tibetan Plateau Using Atmospheric Mercury Isotopes

Mercury in the Free Troposphere and Bidirectional Atmosphere-Vegetation Exchanges – Insights from Maïdo Mountain Observatory in the Southern Hemisphere Tropics

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