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Measurements of speciated atmospheric mercury play a key role in identifying mercury behavior in the atmosphere. In this study, we measured speciated atmospheric mercury, including gaseous elemental mercury (GEM), reactive gaseous mercury (RGM), and particulate bound mercury (PBM) (<2.5 μm), in 2015 and 2016 at an urban site in Beijing, China. The mean concentrations of GEM, RGM, and PBM were 4.70 ± 3.53 ng m−3, 18.47 ± 22.27 pg m−3, and 85.18 ± 95.34 pg m−3, respectively. The concentration of PM 2.5 significantly affected the distribution of reactive mercury between the gaseous and particulate phases. With the raising of PM 2.5 levels, PBM concentrations increased, on the contrary, the concentrations of RGM decreased gradually. The mean concentration of PBM during air-pollution events was more than three times that during clear days. During days with air pollution, the relative humidity significantly affected the gas-particle partitioning of reactive mercury. The linear relationships between gas-particle partitioning coefficient and meteorological factors (air temperature and relative humidity) were obtained over the four seasons. The data also showed that the gas-particle partitioning coefficient of reactive mercury was related to particle composition (e.g., Cl−, BC). The data present in this paper suggested the influence of anthropogenic emissions on reactive mercury in Beijing urban. And the findings will contribute to understand the gas-particle partitioning of reactive mercury and its influencing factors with complex urban pollution. Image 1 • Three speciated atmospheric mercury exhibited obviously seasonal and diurnal variations. • Increasing PM 2.5 led to a decrease in RGM levels and an increase in PBM levels. • Temperature, relative humidity, and particle composition were important factors in determining the reactive mercury gas-particle partitioning. PM 2.5 levels influenced the RGM and PBM concentrations, and the important factors that affect the reactive mercury gas-particle partitioning were discussed. [ABSTRACT FROM AUTHOR]

Atmospheric mercury was measured at an urban site in Beijing during the 2022 Beijing Olympic Winter Games (BOWG) to explore their sources and risks. The mean gaseous elemental mercury (GEM) and particulate bound mercury (PBM) concentrations were 2.75 ± 0.99 ng m−3 and 25.4 ± 67.1 pg m−3, respectively. The implementation of control measures was the dominant reason for low GEM during the BOWG. Similar temporal patterns (GEM, CO, NO 2 , and SO 2) and significant strong positive correlations between them reveal that they had common sources. Based on potential source contribution function and cluster analyses, central/southeastern Hebei, Tianjin, and southern Beijing were the dominant source areas. Air masses associated with high GEM during pollution event (>3.1 ng m−3) generally passed over polluted regions at low speeds and heights. Positive matrix factorization analysis reveals that surrounding coal fired and local vehicle emissions contributed approximately 58% and 30% to the sources, respectively. The PBM risk was higher than that of GEM, and children were more sensitive to atmospheric mercury. Mercury exposure is chronic at a low dosage, resulting loss of malaise, appetite, gastrointestinal upset, and weight. Although atmospheric mercury risk exhibits a decline trend over the past two decades and the current risk is generally low, the cumulative effect over decades or more shouldn't be ignored. The current occasionally high risk values warn people to avoid high-pollution periods. [Display omitted] • GEM level was significantly lower during the BOWG (winter) than during other seasons. • Tianjin and Hebei were identified as dominant source areas for high GEM in Beijing. • External coal burning and local vehicle emissions were major atmospheric Hg sources. • Children were more sensitive to atmospheric Hg risk, and it was great two decades ago. • A decline trend was found for winter atmospheric Hg risk, but summer risk was stable. [ABSTRACT FROM AUTHOR]

Gaseous elemental Hg (GEM), particulate bound Hg (PBM), and gaseous oxidized Hg (GOM) were monitored at an urban site in Beijing, China during wet seasons (July–November) of 2021. The mean (± standard deviation) GEM, PBM, and GOM concentrations were 3.45 ± 1.27 ng m−3, 48.2 ± 88.6 pg m−3, and 13.7 ± 55.0 pg m−3, respectively. GEM level was stable (generally 3.0–4.0 ng m−3) and the average concentration was about twice that of the background level in Beijing, while the occasionally very high PBM and GOM concentrations (>1000 pg m−3) suggest pollution events. Moreover, GEM, CO, and NO 2 exhibit a conspicuous similar diurnal trend with lower values during daytime compared to nighttime under the combined influence of anthropogenic emissions and meteorological factors, and the significantly positive relationship between them indicates that they had similar or common sources. However, the diurnal pattern of reactive Hg (i.e., RM = PBM + GOM) was not pronounced. Both cluster and potential source contribution function analyses show that southern Beijing, Tianjin, as well as central and east Hebei provinces were the dominant source regions for elevated GEM at this monitoring site. The dominant reason for the elevated GEM level (generally >3.5 ng m−3) during pollution event is that majority of air masses originated from the southern polluted regions of this sampling site and traveled at low heights, while the long-range transport of upper clean air masses and continuous high traveling heights were attributed to the low GEM level (<2.0 ng m−3) during clean event. Positive matrix factorization results reveal that regional transport of coal fired air pollutants and local vehicle emissions were the dominant contributors to elevated GEM level, while RM mainly originated from local sources. • Anthropogenic emissions have doubled the gaseous elemental Hg level in Beijing. • The diurnal pattern is pronounced for Hg0, but not for atmospheric reactive Hg. • Southern Beijing, Tianjin, and central Hebei were the dominant potential source areas. • Local vehicle emissions and regional coal fired were the dominant sources for Hg0. • Majority of the atmospheric reactive Hg originated from the local sources. [ABSTRACT FROM AUTHOR]

Speciated atmospheric mercury (Hg) was measured at an urban site in Beijing, China from February to March 2018. The mean concentrations of gaseous elemental Hg (GEM), gaseous oxidized Hg (GOM), and fine particulate bound mercury (PBM 2.5) were 2.81 ± 0.90 ng m−3, 10.7 ± 8.5 pg m−3, and 60.6 ± 43.5 pg m−3, respectively. Reactive Hg (i.e., RM=GOM+PBM 2.5) only represented ~2.4% of total atmospheric Hg. The GEM concentration at the monitoring site was 1.7 times higher than the average value in the Northern Hemisphere. In particular, the mean GEM and PBM 2.5 concentrations were significantly higher during haze period (hourly average AQI value > 100 for at least consecutive 24 h) (3.65 ± 0.76 ng m−3 and 93.0 ± 37.1 pg m−3) than during non-haze period (2.42 ± 0.73 ng m−3 and 48.5 ± 39.5 pg m−3). One possible explanation is the strong subsidence of air masses during haze period could lead to the accumulation of air pollutants. However, there was no significant difference in GOM concentration between haze and non-haze periods. Although the ozone, relative humidity (RH), and planetary boundary layer (PBL) all followed a clear diurnal cycle, while for RM no distinct diurnal pattern was observed. Additionally, GEM was significantly positively correlated with CO, indicating that they had homogeneous sources; whereas, they were all negatively correlated with wind speed and PBL height. Based on the combination of potential source contribution function and clustering analyses, we found that high atmospheric Hg events during haze days were more likely caused by the domestic sources in the Circum-Bohai-Sea region, while the transboundary transport of the clean air masses originating from Siberia was attributed to the low GEM and PBM 2.5 levels during non-haze days. Unlabelled Image • GEMand PBM2.5levels were 1.5 times higher during hazeperiod than non-haze period. • Elevated GEMand PBM2.5events oftencoincided with high trace gasesvalues. • There was no significance in RGM concentration between haze and non-haze periods. • Temperature inversionand lower PBL aggravated the atmospheric Hg pollution.5 • Anthropogenic Hg emissions in Circum-Bohai-Searegionwere the dominant sources. [ABSTRACT FROM AUTHOR]