Temporal variation of atmospheric mercury over the northern South China Sea
Date Issued
2007
Date
2007
Author(s)
Liu, Chiuan-Sheng
DOI
zh-TW
Abstract
The distribution of gaseous elemental mercury (GEM) and particle-associated mercury (PM) were determined in the surface atmosphere of the northern South China Sea during 7 cruises of the SEATS (SouthEast Asian Time-series Study) between March 2005 and January 2007. In addition, there were 9 cruises for GEM investigation (Tseng et al., unpublished data) between May 2003 and March 2005. Therefore, the atmospheric Hg dataset were presented in this study a total of 15 and 7 cruises for GEM and PM, respectively. The sampling and analysis of the GEM were performed on board ship by using a custom-made on-line mercury analyzer based on gold (Au) amalgamation techniques together with cold vapor atomic fluorescence detection (CVAFS), while the analysis of the PM was performed in the laboratory by the closed microwave digestion, followed by the Au-CVAFS detection by using a customized on-line Hg analyzer.
Distinct inter-annual and seasonal patterns were observed for the GEM, which concentrations were higher in winter and lower in summer. The seasonal GEM averaged 3.7±1.1 (n=3), 3.4±1.3 (n=4), 4.2±1.5 (n=4) and 4.8±2.1 (n=4) ng/m3 in spring, summer, autumn, and winter, respectively. A significant diurnal variation in GEM was occurred in summer with a peak at noontime and a low at nighttime. The PM averaged 17.4±5.9, 17.6±7.1, 18.6±14.0 and 18.0±6.3 in spring (n=1), summer (n=2), autumn (n=1) and winter (n=2). No obviously seasonal variation in PM was observed, but its concentration was slightly higher in autumn and winter. However, both of the GEM and PM had the likely similar distribution trend in annual variability.
According to source tracking from the NOAA-HYSPLIT back trajectory and the NCEP wind vector, we found air masses in autumn, winter, and spring were from Eurasia continents, including Mongolia, China, Japan, and Korea, which exported the terrestrial and industrially anthropogenic materials to the SCS. On the other hand, air masses in summer were always from the Indochina Peninsula and Indian Ocean, which brought with the clean marine materials.
The results demonstrated that the East Asian monsoons with the prevailing northeast wind in winter and southwest in summer control the sources of the GEM and PM associated with fine particles and further the long-rang Hg transportation would affect the Hg atmospheric distribution and cycling in the South China Sea.
Subjects
大氣汞
氣態元素汞
懸浮微粒汞
南海
南海時序研究
Atmospheric Hg
gaseous elemental Hg (GEM)
particle-associated Hg (PM)
South China Sea(SCS)
SEATS (SouthEast Asian time-series Study)
SDGs
Type
thesis
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