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Volume 16, issue 21
Atmos. Chem. Phys., 16, 13807–13821, 2016
https://doi.org/10.5194/acp-16-13807-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 16, 13807–13821, 2016
https://doi.org/10.5194/acp-16-13807-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 08 Nov 2016

Research article | 08 Nov 2016

Speciated atmospheric mercury on haze and non-haze days in an inland city in China

Qianqian Hong1,3, Zhouqing Xie1,2,3, Cheng Liu1,2,3, Feiyue Wang4, Pinhua Xie2,3, Hui Kang1, Jin Xu2, Jiancheng Wang1, Fengcheng Wu2, Pengzhen He1, Fusheng Mou2, Shidong Fan1, Yunsheng Dong2, Haicong Zhan1, Xiawei Yu1, Xiyuan Chi1, and Jianguo Liu2 Qianqian Hong et al.
  • 1School of Earth and Space Sciences, University of Science and Technology of China, 230026 Hefei, China
  • 2CAS Center for Excellence in Regional Atmospheric Environment& Institute of Urban Environment of CAS, 361021 Xiamen, China
  • 3Key Lab of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, 230031 Hefei, China
  • 4Centre for Earth Observation Science, and Department of Environment and Geography, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

Abstract. Long-term continuous measurements of speciated atmospheric mercury were conducted from July 2013 to June 2014 in Hefei, a midlatitude inland city in eastern central China that experiences frequent haze pollution. The mean concentrations (±standard deviation) of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particle-bound mercury (PBM) were 3.95 ± 1.93 ng m−3, 2.49 ± 2.41 and 23.3 ± 90.8 pg m−3, respectively, on non-haze days, and 4.74 ± 1.62 ng m−3, 4.32 ± 8.36 and 60.2 ± 131.4 pg m−3, respectively, on haze days. Potential source contribution function (PSCF) analysis suggested that atmospheric mercury pollution on haze days was caused primarily by local emissions, instead of via long-range transport. The poorer mixing conditions on haze days also favored the accumulation of atmospheric mercury. Compared to GEM and GOM, PBM was especially sensitive to haze pollution. The mean PBM concentration on haze days was 2.5 times that on non-haze days due to elevated concentrations of particulate matter. PBM also showed a clear seasonal trend; its concentration was the highest in fall and winter, decreased rapidly in spring and was the lowest in summer, following the same order in the frequency of haze days in different seasons. On both non-haze and haze days, GOM concentrations remained low at night, but increased rapidly just before sunrise, which could be due to diurnal variation in air exchange between the boundary layer and free troposphere. However, non-haze and haze days showed different trends in daytime GEM and GOM concentrations. On non-haze days, GEM and GOM declined synchronously through the afternoon, probably due to the retreat of the free tropospheric air as the height of the atmospheric boundary layer increases. In contrast, on haze days, GOM and GEM showed opposite trends with the highest GOM and lowest GEM observed in the afternoon, suggesting the occurrence of photochemical oxidation. This is supported by simple box-model calculations, which showed that oxidation of GEM to GOM does occur and that the transport of free tropospheric GOM alone is not large enough to account for the observed increase in daytime GOM. Our results further postulate that NO2 aggregation with the HgOH intermediate may be a potential mechanism for the enhanced production of GOM during daytime.

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It is known that rapid industrialization in developing countries has led to an increase in air pollution. Here we firstly report the speciated atmospheric mercury during haze days based upon 1-year synchronous observations in an inland city in China. The findings provide direct evidence to understand the biogeochemical cycles of atmospheric mercury related to air pollution and an opportunity to evaluate the potential health risks of atmospheric mercury.
It is known that rapid industrialization in developing countries has led to an increase in air...
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