| Water soluble materials, as an important part in aerosol’s composition, can change the particles’ hygroscopicity, increase intensity of light absorption and scattering, and aggravate the aging process of particles. It will also bring a significant impact on environment, climate and human’s health. Analysis of water soluble content’s seasonal mass size-distribution, and diurnal size-distribution can provide scientific foundation for the reseach about SOA formation mechanism and formulation of urban particulate pollution control measures. In this study, size-resolved atmospheric particle samples(in the size range of <10μm) were collected in a typical urban site during in all seasons. Mass concentration of water soluble inorganic ions and water soluble organic carbon were detected, along with meteorological condition were analyzed, chief conclusions were list as follow:(1) The results of atmospheric particle samples in Guangzhou urban region showed that seasonal variation of water soluble ions concentration was winter(50.4 μg/m3) > spring(35.1 μg/m3) > autumn(27.3 μg/m3) > summer(16.5 μg/m3). SO42-, NO3-, NH4+ and Na+ were the dominant ions. Seasonal variation of WSOC concentration was winter(9.9 μg/m3) > spring(7.0 μg/m3) > autumn(6.4 μg/m3) > summer(6.0 μg/m3). Concentration of water soluble content in dry season was much higher than that in wet season.(2) SO42-, NH4+ and WSOC showed unimodal distribution in four seasons(in the size range of 0.49~1.5μm). NO3- showed bimodal distribution in spring(in the size range of 0.49~1.5μm and 3.0~7.2μm) and unimodal distribution in other three seasons(in the size range of 0.49~1.5μm and 3.0~7.2μm). According to the correlation coefficient between ratios of [WSOC]/[OC] and [H+in-situ]/[OC], it can be concluded that in summer, WSOC was formed through heterogeneous acid-catalyzed reactions in particle-phase, and in spring and winter, WSOC possibly formed through WSOC in gas phase-particle phase conversion.(3) Higher concentration increase of SO42-, NO3-, NH4+ and WSOC in hazy days were found in comparison with that in non-hazy days. Concentration of SO42-, NO3-, NH4+ and WSOC in hazy days in winter were higher than that in other seasons. Average mass concentration of SO42-, NO3-, NH4+ and WSOC in winter hazy days were respectively 22.1μg/m3,19.5μg/m3,8.8μg/m3 and11.3μg/m3. Among all seasons, the highest concentration increase in SO42- and NH4+ was found in summer hazy days in comparison with that in corresponding sunny days. As for NO3- and WSOC, it was found in winter. Due to higher relative humidity in spring and winter hazy days, SO42- mainly existed in droplet mode in comparison with that in corresponding non-hazy days. As for that in summer and autumn, it was found in condensation mode. Due to higher temperature in summer and autumn, the higher peak of NO3- was found in coarse particle. As for that in spring and winter, it was found in fine particle. Changes in mass size distribution of NO3- were found in comparison of hazy and non-hazy days.(4) The result showed that concentration of SO42- were higher in daytime in spring(19.8 μg/m3) and summer(9.0 μg/m3), and nighttime in autumn(14.6 μg/m3), except for winter(22.1 μg/m3). Concentration of NO3- and NH4+ were higher in daytime in spring(25.4 μg/m3, 11.4 μg/m3) and summer(3.7 μg/m3, 2.3 μg/m3), and nighttime in autumn(7.0 μg/m3, 4.5 μg/m3) and winter(22.3 μg/m3, 8.8 μg/m3). As for WSOC, concentration were higher in nighttime in summer(7.9 μg/m3), autumn(7.3 μg/m3) and winter(12.3 μg/m3). Changes in mass size distribution of NO3- were found in comparison of daytime and nighttime. |
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