Mercury concentration and speciation in the coastal and open ocean boundary layer

Abstract

[1] Atmospheric elemental mercury and reactive gaseous mercury (RGHg) concentrations, as well as ancillary parameters and meteorological data, were collected during a cruise in the North Atlantic Ocean between Bermuda and Barbados and at two land-based sites: the Chesapeake Biological Laboratory (CBL), a semirural, coastal site, and a site within the city of Baltimore, Maryland. There were two deployments at CBL, including a 6-month deployment in 2003/2004. Wet deposition samples were collected and analyzed for mercury where possible. A diurnal change in RGHg concentration was found at both CBL and over the North Atlantic Ocean, with maxima in the afternoon that coincided with maximum UV radiation, demonstrating the importance of in situ formation of RGHg. The maxima in RGHg concentration did not coincide with elevated Hg 0 but were often found under conditions of low wind speed, and over the ocean, under low ozone conditions. In contrast, at the urban site there was more evidence of local sources. The data collected at the sites are contrasted and compared and used to examine the factors controlling the formation of RGHg in open ocean and nearshore locales and to estimate the importance of the dry deposition of RGHg to surface waters.

Mercury deposition in Southern New Hampshire, 2006–2009

“…Sigler et al (2009a, b) and Mao and Talbot (2011) observed RGM depletion during precipitation events at this site and others have made similar observations at diverse locations (Lindberg and Stratton, 1998;Yatavelli et al, 2006;Laurier and Mason, 2007). Despite this indication of RGM scavenging during precipitation events at TF, correlations between Hg wet deposition and Hg concentration in precipitation versus daily maximum RGM and RGM depletion during precipitation events were not statistically significant (Table 2).…”

Speciated atmospheric mercury in the marine boundary layer of the Bohai Sea and Yellow Sea

“…Changbai (Wan et al, 2009 , n ¼ 50) (ttest, p < 0.01). The mean concentration of RGM during the entire study period was 3.3 ± 2.3 pg m À3 (n ¼ 110), which was comparable to the global mean concentration of RGM in the MBL (Soerensen et al, 2010), and somewhat higher than those of rural or coastal areas in North America (Table 1), such as the Ontario Lake (Cheng et al, 2012), several coastal sites in Nova Scotia (Cheng et al, 2013a(Cheng et al, , 2014, and slightly lower than those of other seas, such as the Mediterranean Sea , the Weeks Bay (Engle et al, 2008), the Adriatic Sea (Sprovieri and Pirrone, 2008), the subtropical North Atlantic (Laurier and Mason, 2007), the Okinawa Island (Chand et al, 2008), and the North Pacific Ocean (Laurier et al, 2003). But RGM concentrations measured in this study area were much lower than those of urban or rural sites in China and South Korea, such as Guiyang Liu et al, 2011), Xiamen (Xu et al, 2015), Mt.…”

“…The mean GEM concentration during spring (2.03 ± 0.72 ng m À3 , n ¼ 5243) was comparable to that during fall (2.09 ± 1.58 ng m À3 , n ¼ 4413) (t-test, p > 0.05). The mean GEM level during the whole study period was 2.07 ± 1.16 ng m À3 , which was higher than those in some other open oceans (see Table 1), such as the Atlantic Ocean (Laurier and Mason, 2007;Soerensen et al, 2013), the equatorial Pacific Ocean (Soerensen et al, 2014), the Adriatic Sea (Sprovieri and Pirrone, 2008), and the Indian Ocean (Witt et al, 2010), even higher than those of rural coastal sites in Canada (Cheng et al, 2014), and was comparable to those of coastal sites, such as the Hedo Station (Chand et al, 2008) in Japan, and the Augusta basin (Bagnato et al, 2013) in Italy, but lower than those reported in the northern South China Sea (Fu et al, 2010;Tseng et al, 2012 Fig. 3).…”

“…This enables GEM to undergo a long-range transport and makes it well-mixed on a global scale. The atmospheric lifetime of RGM is shorter (hours to several days) than that of GEM due to its higher solubility and lower volatility (Holmes et al, 2009;Laurier and Mason, 2007). The composition of RGM (e.g., HgBr 2 , HgCl 2 , HgBrOH) varies across space and time .…”

“…Recently, speciated atmospheric Hg concentrations have been monitored at many locations with various site characteristics, such as remote oceans, Arctic and Antarctic, coastal, rural, and urban sites (Chand et al, 2008;Cheng et al, 2012Cheng et al, , 2013aCheng et al, ,b, 2014Choi et al, 2008;Fu et al, 2011Fu et al, , 2012Gabriel et al, 2005;Kim et al, 2009;Laurier and Mason, 2007;Liu et al, 2007Liu et al, , 2011Liu et al, , 2010Soerensen et al, 2010;Valente et al, 2007;Wan et al, 2009;Xu et al, 2015;Zhang et al, 2012). However, study on the knowledge of the speciated atmospheric Hg over the East Asia MBL is limited.…”