1Institute of Oceanography, National Taiwan University, P.O. Box 23-13, Taipei 106, Taiwan, China
2Woods Hole Oceanographic Institute, MS 51, Woods Hole, MA 02543, USA
Received: 17 Apr 2012 – Discussion started: 11 May 2012
Abstract. The distribution of gaseous elemental mercury (GEM) was determined in the surface atmosphere of the northern South China Sea (SCS) during 12 SEATS cruises between May 2003 and December 2005. The sampling and analysis of GEM were performed on board ship by using an on-line mercury analyzer (GEMA). Distinct annual patterns were observed for the GEM with a winter maximum of 5.7 ± 0.2 ng m−3 (n = 3) and minimum in summer (2.8 ± 0.2; n = 3), with concentrations elevated 2–3 times global background values. Source tracking through backward air trajectory analysis demonstrated that during the northeast monsoon (winter), air masses came from Eurasia, bringing continental- and industrial-derived GEM to the SCS. In contrast, during summer southwest monsoon and inter-monsoon, air masses were from the Indochina Peninsula and Indian Ocean and west Pacific Ocean. This demonstrates the impact that long-range transport, as controlled by seasonal monsoons, has on the Hg atmospheric distribution and cycling in the SCS.
Revised: 19 Jul 2012 – Accepted: 06 Aug 2012 – Published: 16 Aug 2012
Tseng, C. M., Liu, C. S., and Lamborg, C.: Seasonal changes in gaseous elemental mercury in relation to monsoon cycling over the northern South China Sea, Atmos. Chem. Phys., 12, 7341-7350, doi:10.5194/acp-12-7341-2012, 2012.