Atmospheric wet and litterfall mercury deposition at urban and rural sites in China

Abstract

Abstract. Mercury (Hg) concentrations and deposition fluxes in precipitation and litterfall were measured at multiple sites (six rural sites and an urban site) across a broad geographic area in China. The annual deposition fluxes of Hg in precipitation at rural sites and an urban site were 2.0 to 7.2 and 12.6 ± 6.5 µg m −2 yr −1 , respectively. Wet deposition fluxes of Hg at rural sites showed a clear regional difference with elevated deposition fluxes in the subtropical zone, followed by the temporal zone and arid/semi-arid zone. Precipitation depth is the primary influencing factor causing the variation of wet deposition. Hg fluxes through litterfall ranged from 22.8 to 62.8 µg m −2 yr −1 , higher than the wet deposition fluxes by a factor of 3.9 to 8.7 and representing approximately 75 % of the total Hg deposition at the forest sites in China. This suggests that uptake of atmospheric Hg by foliage is the dominant pathway to remove atmospheric Hg in forest ecosystems in China. Wet deposition fluxes of Hg at rural sites of China were generally lower compared to those in North America and Europe, possibly due to a combination of lower precipitation depth, lower GOM concentrations in the troposphere and the generally lower cloud base heights at most sites that wash out a smaller amount of GOM and PBM during precipitation events.

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

“…Values at urban sites are high, likely reflecting local Hg II emissions, and are correlated with high concentrations of particulate Hg II (Fu et al, 2016). Values at rural sites are much lower and comparable to wet deposition observed in North America and Europe despite higher TGM concentrations in China (see Fig.…”

“…Observations of Hg wet deposition over China have recently become available (Fu et al, , 2016. Values at urban sites are high, likely reflecting local Hg II emissions, and are correlated with high concentrations of particulate Hg II (Fu et al, 2016).…”

“…We find that 80 % of global Hg II deposition is to the oceans, compared to 71 % in Holmes et al (2010), and that 60 % of this deposition is wet. Fu et al (2015Fu et al ( , 2016 over China (9 sites). In the China panel, circles represent rural sites, and diamonds represent urban sites as identified in Fu et al (2015Fu et al ( , 2016.…”

“…Fu et al (2015Fu et al ( , 2016 over China (9 sites). In the China panel, circles represent rural sites, and diamonds represent urban sites as identified in Fu et al (2015Fu et al ( , 2016. For the MDN and EMEP networks, which collect weekly or monthly integrated samples, we only include sites with at least 75 % of annual data for at least 1 year between 2007 and 2013; for China we only include sites with at least 9 months of data over the 2007-2013 period.…”

Subtropical subsidence and surface deposition of oxidized mercury produced in the free troposphere

“…Here, we use the 2009-2012 AMNet observations, as these data are publicly available. AMNet had 23 sites over the continental US and eastern Canada (Nova Scotia) operational during this period (Table S2 in Ground-based measurements of Hg wet deposition and Hg(II) surface concentration have been made as part of the Global Mercury Observations System (GMOS) network (Angot et al, 2014;Wängberg et al, 2016;Sprovieri et al, 2016Sprovieri et al, , 2017Travnikov et al, 2017) and at sites in Europe (Weigelt et al, 2013), Canada, and East Asia (Sheu et al, 2010;Sheu and Lin, 2013;Fu et al, 2015Fu et al, , 2016b. We use the 2013-2014 measurements wherever available but use all sites with 1 year or more of observations.…”