dc.description.abstract | This work collected filter-based PM10 and PM2.5 samples at Son La (682 m a.s.l., Vietnam) in March 2011 and Mt. Lulin (2,862 m a.s.l., Taiwan) from March to April 2011 for analyzing their chemical compositions. The aim of this work is to understand aerosol characteristics from near-source biomass burning (BB) and BB plume after long-range transport.
The results showed that Son La aerosol was simultaneously influenced by BB and transported dust in the front observation period to result in the dominance of carbonaceous content both in PM10-2.5 and PM2.5 as well as higher PM10-2.5 mass than PM2.5 from March 18 to 21, 2011. In contrast, the proportion of water-soluble ions was increased to dominate aerosol chemical speciation in the rear observation period from March 22 to 31, 2011, especially for the apparent change of SO42- over PM2.5 mass, which was due to the influence of BB coupling with the pollution transported from the southern China. The slight greater C3/C4 ratio (0.4) in rear than front (0.34) periods implies aerosol component is inclined to be more water-soluble and with greater degree of photochemical oxidation. The moderate high correlations (R2>0.5) for nss-K+ vs. levoglucosan and Char-EC/Soot-EC, respectively, validate the influence of BB activities during the observation period.
The enhancements of Mt. Lulin PM2.5 mass, total carbon, total ion, levoglucosan, and K+ were 4.1, 3.8, 3.1, 4.3, and 5.4 folds when under the influence of BB plume transport. This fact identifies aerosol BB tracers from transported airmasses. Ammonia deficient was found for Son La and Mt. Lulin aerosols under the influence of BB; however, aerosol was almost completely neutralized when Mt. Lulin was not affected by the transported BB plume. This indicates that BB plume aerosol tends to be acidic.
For Son La aerosol, PM2.5 copound form was Oxalic‧2H2O(s) when atmospheric relative humidity (RH) exceeded 60% in the front period and were (NH4)2SO4 and (NH4)3(H)(SO4)2 in the rear period. For comparison, the copound form of Mt. Luin PM2.5 was always (NH4)2SO4 regardless of the influences of BB. Different compound forms of aerosol exert deviations in the degradation of solar radiation and thus important in the assessment of environmental effect.
Aerosol water content is capable of representlin hygroscopic growth under high atmospheric RH and consequently plays an important role for evaluating solar radiation attenuation. This work compiled aerosol water content measured at Mt. Luin from 2008 to 2011. Linear regression analyses show that SO42- and WSOC-HULIS_C are chosen as significant predictors for BB and NBB periods in PM10, while NH4+ is considered as the important predictor for all time. The results imply aerosol water content is determined by speciation and concentration. | en_US |