Spatiotemporal distribution and long-range transport of atmospheric speciated mercury at three remote islands in Taiwan Strait and South China Sea

Temporal variation and potential origins of atmospheric speciated mercury at a remote island in South China Sea based on two-year field measurement data

“…It showed that the two-year averaged GEM concentrations at the Taiping Island were 1.37 ± 0.48 ng/m 3 , respectively (see Table 1), which were as high as the background GEM concentration (1.3-1.5 ng/m 3 ) of the Northern Hemisphere. As far as other remote islands and coastal areas in the East Asia was concerned, the concentration of GEM at the Taiping Island was generally lower than those at other East Asian islands, but similar to that at the Nansha Islands 26 , indicating that mercury emissions from the surrounding countries of the SCS were much lower than other Asian remote islands and coastal areas.…”

“…Comparing with the remote continental sites such as Mt. Lulin 59 , Checheng 27 , and Dongsha Islands 26,59 in Taiwan, and Mt. Changbai 60 and Waliguan 30 in China, we found that the concentration of GEM at the Taiping Island was relatively low.…”

“…Oppositely, the relatively low GEM concentrations at the Taiping Island were mostly observed for Routes B and C that occurred frequently in winter and spring. Although Routes B and C could apparently blow GEM from anthropogenic sources located at the Northeast Asia to the leeward northern South China Sea 22,26 , the concentrations of GEM measured at the Taiping Island were much lower than those at the Dongsha Island, and close to the GEM background level of Northern Hemisphere in all seasons. Therefore, we concluded that Asian Northern Monsoons derived from Mongolian high pressure systems seemed not strong enough to transport the polluted air masses down to the Taiping Island in the central SCS.…”

“…This section attempts to plot a series of regional fire maps in the East and South Asia to compare their spatial distribution www.nature.com/scientificreports/ in four seasons during the two-year sampling periods, which can be further applied to identify the potential origins of atmospheric mercury sampled at the Taiping Island for the following relevant discussion. The global fire maps have been widely used by numerous studies to locate the burning sources over the ground surface in a large geological scale 26 . According to the fire maps in fall season, the fire spots (i.e.…”

“…PM 2.5 ) could be transported easterly from the East Asian continent to the leeward areas of Korea Peninsula, Japan Islands, Hawaii Islands, and even the West Coast of the United States [23][24][25] . Additionally, atmospheric speciated mercury could be transported southerly from the Northeastern Asia to the Taiwan Strait and even the northern SCS 22,26 . The emissions of mercury-containing pollutants from East Asian as a continental outflow to the leeward marine regions have been increasing in the past decades.…”