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

Gang Zhang,Rongfang Hu,Zheng Luo,Zhanhui Tang,Xu Li,Xiangyun Li,Xuhang Zhou,Zhaojun Wang,Yangjie Zhang,Deli Wang,Zhiyun Yang,Lei Wang

doi:10.3390/biology10090917

Gang Zhang, Rongfang Hu + Show 10 more

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https://doi.org/10.3390/biology10090917

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Abstract

Simple SummaryThis study investigated the gaseous elemental mercury exchange fluxes over 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 results showed that the net emissions from the soil to the atmosphere, 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. In addition, it was determined that the mercury fluxes were positively correlated with the solar radiation and air/soil temperature levels and negatively correlated with the air humidity and soil moisture. The grassland soil served as both a source and a sink for atmospheric mercury, depending on the season and meteorological factors. The plants played an important inhibiting role in the mercury exchanges between the soil and the atmosphere. This research will potentially assist in the development of more accurate local and regional estimates of mercury emissions from degraded grassland areas and the terrestrial environment as a whole.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.

Highlights

Mercury (Hg) is considered to be a significant global pollutant due to its biochemical properties [1]
Since the data followed normal distribution patterns, independent-samples t-tests were applied in order to analyze the differences in gaseous elemental mercury (GEM) and TSM
The GEM concentrations were generally higher than background levels for the northern hemisphere, which is considered to be approximately

Summary

Introduction

Mercury (Hg) is considered to be a significant global pollutant due to its biochemical properties [1]. Studies have estimated that as much as 80% of the Hg deposited on terrestrial surfaces will be re-emitted to the atmosphere through surface emissions [7]. Those results have further indicated the importance of terrestrial environments as significant Hg sources in the global Hg cycle. The gaseous mercury exchange fluxes between atmospheric and terrestrial sources serve as important examples Those fluxes have been poorly characterized, and the routes by which Hg enters and exits the Earth’s different ecosystems require further clarification [8]. It is expected that by improving the current quantification of fundamental ecosystems, accurate predictions can be made regarding the impacts that climate change will have on the global Hg cycle [9]

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