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The location of the Dianshan Lake (DSL) site in Shanghai, China. Different colors in the map represent different land cover types.
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Mercury (Hg) is a global toxic pollutant that can be released into the
atmosphere through anthropogenic and natural sources. The uncertainties in
the estimated emission amounts are much larger from natural than
anthropogenic sources. A method was developed in the present study to
quantify the contributions of natural surface mercury emissions to am...
Contexts in source publication
Context 1
... situated in the YRD region, is one of the most developed cities in China. Like in many other cities in China, severe air pollution events have occurred frequently in this city in the past decades. A supersite has been set up next to the Dianshan Lake in Qingpu District of rural Shanghai (Fig. 1) as part of the framework of the State Environmental Protection Scientific Observation and Research Station. This supersite is designed to represent the regional-scale air pollution characteristics in the YRD region based on the following two considerations: (1) it is located in the conjunction area of Shanghai, Jiangsu, and Zhejiang ...
Context 2
... natural surface emissions on ambient GEM concentration was important in the warm seasons but may not be the case in the cold seasons. The seasonal bivariate polar plots of GEM showed that high GEM concentrations were associated frequently with airflows from the south and southwest and occasionally with those from the north, particularly in summer (Fig. S1 in the Supplement). This was consistent with the findings in previous studies which showed stronger natural surface emissions in southern and southwestern China than northern China ( Wang et al., 2016Wang et al., , 2006Feng et al., 2005;Sommar et al., 2016). Hence, in the context of significant reduction of anthropogenic mercury ...
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... further verify the reliability of the resolved factors, the correlations between the mass contributions of all factors to GEM and temperature were examined on the basis of diurnal profiles. As shown in Fig. S19, positive correlation was only found between the natural surface emissions factor and temperature, while the other resolved factors (i.e. vehicle emission, coal combustion, shipping activities, cement production, and iron and steel production) did not show this relationship. In addition, the relationship between particulate black ...
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... shown in Fig. S30, the potential source regions of shipping GEM were found mainly over coastal and oceanic areas, indicating the shipping factor resolved in this study was also valid. Figures S31 and S32 show that the potential source contribution function (PSCF) signals of cement production GEM were relatively weak in the YRD region, while there were substantial high-PSCF signals for iron and steel production GEM in eastern China. All the results above collectively confirmed that the PMF results were robust. ...
Citations
... Y. Liu et al., 2019). Existing studies have reported the trends in GEM concentrations at three sites in eastern China covering a few (≤4) years (Qin et al., 2020;Tang et al., 2018;Wu et al., 2020). Analysis of these data using multiple source identification methods, including trajectory-based source identification, positive matrix factorization, and statistical models, helps to understand the mechanisms controlling GEM concentrations. ...
... Y. Liu et al., 2019), but considerably lower than those (−22.3%-−8.0% yr −1 ) observed at sites close to major anthropogenic source regions in eastern and northern China (e.g., Chongming Island during 2014-2016, Dianshan Lake during 2015-2018, and Beijing during 2015-2018)(Qin et al., 2020;Tang et al., 2018;Wu et al., 2020). ...
... Such a finding is broadly in agreement with modeling studies which showed that atmospheric GEM levels responded quickly to anthropogenic emissions abatements(Amos et al., 2013; Y. X.. Considering the expected increase in China's anthropogenic Hg emissions before 2015 due to the rapid economic development and its big contribution to the global total anthropogenic Hg emissions (AMAP/UNEP, 2019; K. Y.Liu et al., 2019;Streets et al., 2019a), abatement of anthropogenic Hg emissions in China would have significant impact on global Hg cycling. The observations in this study, together with GEM declines reported in previous studies(Nguyen et al., 2019;Qin et al., 2020;Tang et al., 2018;Wu et al., 2020), indicate the trends in Chinese anthropogenic GEM emissions probably have reversed from early years increasing to recent years declining. Previous studies on Hg emission inventory showed that global anthropogenic Hg emissions increased during 2010-2015, largely (∼50%) driven by the increases in East Asia (essentially China) (AMAP/UNEP, 2019; Streets et al., 2019a). ...
China is the largest contributor to the global total anthropogenic mercury (Hg) emissions. However, the trend in anthropogenic Hg emissions in recent years in China has not been effectively evaluated due to the lack of long‐term atmospheric Hg observations. This study documents the changes in atmospheric gaseous elemental mercury (GEM) concentrations and isotopic compositions at Mt. Changbai (MCB) in northeastern China during 2015–2021 and Mt. Ailao (MAL) in southwestern China during 2017–2021, and explores the potential factors controlling these changes. GEM concentrations showed continuous declines from 2015 to 2021 (−2.1 ± 0.6% yr⁻¹) at MCB and from 2017 to 2021 (−4.0 ± 1.4% yr⁻¹) at MAL. Accompanied with these GEM declines are positive shifts in δ²⁰²Hg (medians: from 0.42 to 0.46‰ at MCB and from 0.17 to 0.57‰ at MAL), and negative shifts in Δ¹⁹⁹Hg (medians: from −0.17‰ to −0.21‰ at MCB and from −0.10‰ to −0.17‰ at MAL) and Δ²⁰⁰Hg values (medians: from −0.07‰ to −0.08‰ at MCB and from −0.03‰ to −0.05‰ at MAL) (at significant levels for Δ¹⁹⁹Hg at MCB and δ²⁰²Hg and Δ¹⁹⁹Hg at MAL). These changes were mainly caused by the decreases in regional anthropogenic emissions in the study areas. Based on a ternary mixing model with Δ¹⁹⁹Hg and Δ²⁰⁰Hg as input, we estimate decline rates of 5.8 ± 2.8 and 4.8 ± 3.0% yr⁻¹ for the regional anthropogenic GEM emissions in northeastern and southwestern China, respectively.
... S3, 4). Recent studies have indicated either a stable or a slight decreasing trend for GEM or TGM concentrations in Chinese cities after 2013 due to China having applied vigorous measures to control air pollution (Qin et al., 2020;Wu et al., 2020;Yin et al., 2020). For instance, it was reported that GEM concentrations at Chongming Island in East China significantly decreased from 2014 to 2016, and the inflection point occurred before 2014 (Tang et al., 2018). ...
... The weights of CWT in January 2015 were higher than those of other study years, and the region of high CWT values spread over Fujian Province and EC. Previous studies have also reported high levels of GEM in 2015 among urban Beijing, Changdao Island, rural Shanghai, and Chongming Island (Tang et al., 2018;Qin et al., 2020;Wang et al., 2020;Wu et al., 2020), which suggests a heavy GEM pollution on a large regional scale during 2015. The high GEM concentrations in January 2015 were likely due to a combination of high-level Hg emissions and adverse meteorological conditions. ...
The long-term monitoring of atmospheric mercury is an important part of the effective evaluation of the Minamata Convention on Mercury. Gaseous elemental mercury (GEM), along with conventional air pollutants and meteorological parameters, was simultaneously observed in Xiamen, Southeast China, in January and July over the period 2012–2020. GEM concentrations in January were highest in 2015 (4.47 ng m−3) and decreased by 2020 (3.93 ng m−3), while GEM concentrations in July were highest in 2017 (2.65 ng m−3) and lowest in 2020 (1.56 ng m−3). The temporal variation of GEM was typically characterized by higher concentrations in winter than in summer and in nighttime than in daytime. Bivariate polar plots and the concentration-weighted trajectory (CWT) model were used to identify the source regions of GEM on a local and regional scale. The results indicate that the high GEM concentrations in January 2015 were likely due to a combination of high-level Hg emissions and adverse meteorological conditions. Generalized additive models (GAMs), which use a regression analysis method, were established and applied to investigate the influencing factors on the inter-annual variation of GEM. The factors anthropogenic emissions, meteorological conditions, and transportation explained 37.8 %±11.9 %, 31.4 %±9.0 %, and 30.8 %±9.9 % on average of the variation of GEM concentrations, respectively. There was a positive relationship of daily GEM concentrations with T and RH, mostly linking to natural surface emissions and Hg chemical transformations. The interpretation rate of anthropogenic emissions has significantly decreased since 2012, indicating the effectiveness of emission mitigation measures in reducing GEM concentrations in the study region.
The wide spread of the coronavirus (COVID-19) has significantly impacted the global human activities. Compared to numerous studies on conventional air pollutants, atmospheric mercury that has matched sources from both anthropogenic and natural emissions is rarely investigated. At a regional site in eastern China, an intensive measurement was performed, showing obvious decreases in gaseous elemental mercury (GEM) during the COVID-19 lockdown, while it was not as significant as most of the other measured air pollutants. Before the lockdown, when anthropogenic emissions dominated, GEM showed no correlation with temperature and negative correlations with wind speed and the height of the boundary layer. In contrast, GEM showed significant correlation with temperature, while the relationship between GEM and the wind speed/boundary layer disappeared during the lockdown, suggesting the enhanced natural emissions of mercury. By applying a machine learning model and the SHAP (SHapley Additive exPlanations) approach, it was found that the mercury pollution episodes before the lockdown were driven by anthropogenic
sources, while they were mainly driven by natural sources during and after
the lockdown. Source apportionment results showed that the absolute
contribution of natural surface emissions to GEM unexpectedly increased
(44 %) during the lockdown. Throughout the whole study period, a
significant negative correlation was observed between the absolute
contribution of natural and anthropogenic sources to GEM. We conclude that the natural release of mercury could be stimulated to compensate for the
significantly reduced anthropogenic GEM via the surface–air exchange in the balance of mercury.
The widespread of coronavirus (COVID-19) has significantly impacted the global human activities. Compared to numerous studies on conventional air pollutants, atmospheric mercury that has matched sources from both anthropogenic and natural emissions is rarely investigated. At a regional site in Eastern China, an intensive measurement was performed, showing obvious decreases of gaseous elemental mercury (GEM) during the COVID-19 lockdown, while not as significant as the other air pollutants. Before the lockdown when anthropogenic emissions dominated, GEM showed no correlation with temperature and negative correlations with wind speed and the height of boundary layer. In contrast, GEM showed significant correlation with temperature while the relationship between GEM and wind speed/boundary layer disappeared during the lockdown, suggesting the enhanced natural emissions of mercury. By applying a machine learning model and the Shapley Additive ExPlanation Approach, it was found that the mercury pollution episodes before the lockdown were driven by anthropogenic sources, while they were mainly driven by natural sources during and after the lockdown. Source apportionment results showed that the absolute contribution of natural surface emissions to GEM unexpectedly increased (44%) during the lockdown. Throughout the whole study period, a significant negative correlation was observed between the absolute contribution of natural and anthropogenic sources to GEM. We conclude that natural release of mercury could be stimulated to compensate the significantly reduced anthropogenic GEM via the surface - air exchange balance of mercury.
