Back to Search
Start Over
Seasonal variation of fine- and coarse-mode nitrates and related aerosols over East Asia: synergetic observations and chemical transport model analysis.
- Source :
- Atmospheric Chemistry & Physics; 2017, Vol. 17 Issue 23, p14181-14197, 17p, 2 Charts, 9 Graphs, 1 Map
- Publication Year :
- 2017
-
Abstract
- We analyzed long-term fine- and coarse-mode synergetic observations of nitrate and related aerosols (SO<subscript>4</subscript><superscript>2-</superscript>, NO<subscript>3</subscript><superscript>-</superscript>, NH<subscript>4</subscript><superscript>+</superscript>, Na<superscript>+</superscript>, Ca<superscript>2+</superscript>) at Fukuoka (33.52° N, 130.47° E) from August 2014 to October 2015. A Goddard Earth Observing System chemical transport model (GEOS-Chem) including dust and sea salt acid uptake processes was used to assess the observed seasonal variation and the impact of long-range transport (LRT) from the Asian continent. For fine aerosols (fSO<subscript>4</subscript><superscript>2-</superscript>, fNO<subscript>3</subscript><superscript>-</superscript>, and fNH<subscript>4</subscript><superscript>+</superscript>), numerical results explained the seasonal changes, and a sensitivity analysis excluding Japanese domestic emissions clarified the LRT fraction at Fukuoka (85% for fSO<subscript>4</subscript><superscript>2-</superscript>, 47% for fNO<subscript>3</subscript><superscript>-</superscript>, 73% for fNH<subscript>4</subscript><superscript>+</superscript>). Observational data confirmed that coarse NO<subscript>3</subscript><superscript>-</superscript> (cNO<subscript>3</subscript><superscript>-</superscript>) made up the largest proportion (i.e., 40-55%) of the total nitrate (defined as the sum of fNO<subscript>3</subscript><superscript>-</superscript>, cNO<subscript>3</subscript><superscript>-</superscript>, and HNO<subscript>3</subscript>) during the winter, while HNO<subscript>3</subscript> gas constituted approximately 40% of the total nitrate in summer and fNO<subscript>3</subscript><superscript>-</superscript> peaked during the winter. Large-scale dust-nitrate (mainly cNO<subscript>3</subscript><superscript>-</superscript>) outflow from China to Fukuoka was confirmed during all dust events that occurred between January and June. The modeled cNO<subscript>3</subscript><superscript>-</superscript> was in good agreement with observations between July and November (mainly coming from sea salt NO<subscript>3</subscript><superscript>-</superscript>). During the winter, however, the model underestimated cNO<subscript>3</subscript><superscript>-</superscript> levels compared to the observed levels. The reason for this underestimation was examined statistically using multiple regression analysis (MRA). We used cNa<superscript>+</superscript>, nss-cCa<superscript>2+</superscript>, and cNH<subscript>4</subscript><superscript>+</superscript> as independent variables to describe the observed cNO<subscript>3</subscript><superscript>-</superscript> levels; these variables were considered representative of sea salt cNO<subscript>3</subscript><superscript>-</superscript>, dust cNO<subscript>3</subscript><superscript>-</superscript>, and cNO<subscript>3</subscript><superscript>-</superscript> accompanied by cNH<subscript>4</subscript><superscript>+</superscript>), respectively. The MRA results explained the observed seasonal changes in dust cNO<subscript>3</subscript><superscript>-</superscript> and indicated that the dust-acid uptake scheme reproduced the observed dust-nitrate levels even in winter. The annual average contributions of each component were 43% (sea salt cNO<subscript>3</subscript><superscript>-</superscript>), 19% (dust cNO<subscript>3</subscript><superscript>-</superscript>), and 38% (cNH<subscript>4</subscript><superscript>+</superscript> term). The MRA dust-cNO<subscript>3</subscript><superscript>-</superscript> component had a high value during the dust season, and the sea salt component made a large contribution throughout the year. During the winter, cNH<subscript>4</subscript><superscript>+</superscript> term made a large contribution. The model did not include aerosol microphysical processes (such as condensation and coagulation between the fine anthropogenic aerosols NO<subscript>3</subscript><superscript>-</superscript> and SO<subscript>4</subscript><superscript>2-</superscript> and coarse particles), and our results suggest that inclusion of aerosol microphysical processes is critical when studying observed cNO<subscript>3</subscript><superscript>-</superscript> formation, especially in winter. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 16807316
- Volume :
- 17
- Issue :
- 23
- Database :
- Complementary Index
- Journal :
- Atmospheric Chemistry & Physics
- Publication Type :
- Academic Journal
- Accession number :
- 126865270
- Full Text :
- https://doi.org/10.5194/acp-17-14181-2017