Distribution and air-sea exchange of mercury (Hg) in the Yellow Sea

Abstract

Abstract. The Yellow Sea, surrounded by East China and the Korea Peninsula, is a potentially important receptor for anthropogenic mercury (Hg) emissions from East Asia. However, there is little documentation about the distribution and cycle of Hg in this marine system. During the cruise covering the Yellow Sea in July 2010, gaseous elemental mercury (GEM or Hg(0)) in the atmosphere, total Hg (THg), reactive Hg (RHg) and dissolved gaseous mercury (DGM, largely Hg(0)) in the waters were measured aboard the R/V Kexue III. The mean (±SD) concentration of GEM over the entire cruise was 2.61 ± 0.50 ng m −3 (range: 1.68 to 4.34 ng m −3 ), which were generally higher than other open oceans. The spatial distribution of GEM generally reflected a clear gradient with high levels near the coast of East China and low levels in open waters, suggesting the significant atmospheric Hg outflow from East China. The mean concentration of THg in the surface waters was 1.69 ± 0.35 ng l −1 and the RHg accounted for a considerable fraction of THg (RHg: 1.08 ± 0.28 ng l −1 , %RHg/THg = 63.9%). The mean concentration of DGM in the surface waters was 63.9 ± 13.7 pg l −1 and always suggested the supersaturation of Hg(0) in the surface waters with respect to Hg(0) in the atmosphere (the degree of saturation: 7.8 ± 2.3 with a range of 3.6-14.0). The mean Hg(0) flux at the air-sea interface was estimated to be 18.3 ± 11.8 ng m −2 h −1 based on a two-layer exchange model. The high wind speed and DGM levels induced the extremely high Hg(0) emission rates. Measurements at three stations showed no clear vertical patterns of DGM, RHg and THg in the water column. Overall, the elevated Hg levels in the Yellow Sea compared with other open oceans suggested that the human activity has influenced the oceanic Hg cycle downwind of East Asia.

Air–sea exchange of gaseous mercury in the tropical coast (Luhuitou fringing reef) of the South China Sea, the Hainan Island, China

“…Our concentrations were also higher than the mean concentrations (36.5 ± 14.9 pg L −1 ) of the northern SCS in the summer cruise but were very similar to those of stations near the Hainan Island (~40-80 pg L −1 , Fu et al 2010). Many field measurements also widely reported that the water Hg(0) concentrations in nearshore environments were generally higher than those in the open water (e.g., Mason et al 2001;Ci et al 2011d). The field observations and incubation experiments suggest that the special properties of nearshore environment, such as the enhanced THg levels, the estuarine mixing, and the high biological activity, can either promote the production of water Hg(0) and/or increase the Hg(0) input to the coastal water (Amyot et al 1997;Lanzillotta et al 2002;Rolfhus et al 2003;Covelli et al 2008;Fantozzi et al 2009;Schartup et al 2015;Ci et al 2016).…”

“…A 47-mmdiameter Teflon pre-filter was placed in the inlet to remove the particle matter (including particulate Hg). This measurement was considered as that of atmospheric Hg(0) (Ci et al 2011d;Tseng et al 2012;Gustin et al 2015).…”

Elemental mercury (Hg(0)) in air and surface waters of the Yellow Sea during late spring and late fall 2012: Concentration, spatial-temporal distribution and air/sea flux

“…These GEM concentrations are statistically lower (t-test, P < 0.05) than our previous summer cruise (July 2010) covering the similar sea region (2.61 ± 0.50 ng m À3 , Ci et al, 2011d). The GEM data of the three cruises suggest the high concentrations during the summer cruise and low concentrations during the spring cruise and fall cruise.…”

“…However, the accuracy of the modeling result is difficult to evaluate because of limited field data, especially those related to marine system (Jaffe and Strode, 2008;Ci et al, 2012). At present, most atmospheric Hg measurements focused on the coastal region of East Asia (e.g., Wang et al, 2007;Ci et al, 2011b;Nguyen et al, 2010;Xiu et al, 2009), but the investigations focusing on the open ocean are limited (Friedli et al, 2004;Ci et al, 2011d;Nguyen et al, 2011;Fu et al, 2010;Tseng et al, 2012;Sheu et al, 2013). The lack of Hg knowledge in the open ocean of East Asia has become a critical barrier to the current understanding of the regional and global Hg cycles (Jaffe and Strode, 2008;Ci et al, 2012).…”

“…This marine system has great economic, climatic and ecologic importance for the half billion population living in its surrounding regions. As the downwind and downstream of East Asia, the Yellow Sea receives high Hg input from atmospheric deposition and river/wastewater discharge (Ci et al, 2011d). Many studies also highlight that the anthropogenic Hg emission from East Asia will continue to increase (e.g., Streets et al, 2009;Pacyna et al, 2010).…”