Ground and shipboard measurements of atmospheric gaseous elemental mercury over the Yellow Sea region during 2007–2008

The first ever shipboard measurements of atmospheric gaseous elemental mercury (GEM) over the Yellow Sea were carried out. Ground measurements were also performed at background and urban sites surrounding the Yellow Sea during 2007–2008. The GEM mean concentrations obtained from ground measurements at Ningbo, Chengshantou, and Deokjeok, and from shipboard measurements for the routes of Incheon–Qingdao, Incheon–Weihai, and Incheon–Jeju were 3.79 ± 1.29, 2.07 ± 0.91, 1.79 ± 0.80, 1.82 ± 0.51, 2.03 ± 0.66, and 2.43 ± 0.59 ng m−3, respectively. Compared with the GEM background concentration in the northern hemisphere, the slightly higher GEM regional background concentration of 2.08 ± 0.85 ng m−3 over the Yellow Sea region, based on shipboard measurements and ground measurements at background sites, gave implications for the impact of anthropogenic mercury sources surrounding the Yellow Sea. Shipboard measurements over the Yellow Sea showed a decrease of mercury concentration compared with aircraft measurements during ACE-ASIA campaign in 2001, though it was still generally higher than those from other seas or oceans around the world. The contrasting patterns in seasonal and diurnal variations of GEM concentration between background and urban sites were apparent due to the influence of different sources; for example, natural sources, such as vegetative and foliar emissions in background area, and local anthropogenic sources, such as coal combustion in urban area. The significantly elevated GEM concentrations at Deokjeok, a Korean background site, during the spring of 2008 were attributed to the long-range transport from the southern part of Liaoning province, one of the heaviest mercury-polluted areas in China.