| In order to study the chemical characteristics of particulates during the dust storm in Shanghai, we had continuous ground observation in urban area of Shanghai from January,2010to December,2012. Observing program include particulate matter mass concentration (PM10and PM2.5and PM1.0), chemical composition of PM2.5(water soluble inorganic ions, OC and EC), the concentration of gas pollutions (NO2, SO2, O3and CO) and meteorological data (RH, ats, WD and WS). The article summarize air condition and distribution characteristics of particulate matter in Shanghai from2010to2012..Besides, the mass concentration and chemical composition characteristics of PM2.5during the dust storm episodes were analyzed. This study results show that:(1) During the observation, the primary air quality of Shanghai was good. Air quality varied with the change of seasons.The frequency of pollution days in spring,autumn and winter were higher than5days, while in summer, they were lower than2days,and all the heavy pollution weather occurred in the spring.(2) The average mass concentration of PM10, PM2.5and PM1.0was76,43.7and29.3g·m-3,respectively. The variation trend of PM10mass concentration were the same as PM2.5,they were higher in winter and spring, compare with summer.while the variation trend of PM1.0is not obvious with the change of seasons, winter were a little higher than spring and autumn, and summer were a little lower than spring and autumn. The mass concentration of particulate in winter half year (November, December, January, February, march and April) were significantly higher than the summer half year (may, June, July, August, September, and October).(3) According to statistic analysis, we found that Shanghai were affected by dust episode for16times during observation, including eight times in spring, three times in autumn and five times in winter. There were43floating dust weather days in total. During the dust episodes, the average mass concentration of PM10, PM2.5and Pm1.0were136.0to1005.4μg·m-3,44.0to172.3μg·m-3and17.4-44.4μg·m-3respectively.while in clean days, they were30.5to66.6μg·m-3,22.2to45.2μg·m-3and13.3to29.1μg·m-3.The former were1.8-13.2、1.0-3.9and0.6-1.5times of the latter respectively.(4) The concentration of secondary water soluble inorganic components SNA (SO42-, NO3-, NH4+) increased as the rise of mass concentration of PM2.5most of the time during the dust episode. Meanwhile, the mass concentration of Cl-and Na+varied from the path of the dust arrived at Shanghai. The mass concentration of Ca2+, Mg2+, K+and OC in the dust storm were higher than cleaning period, while the change of EC was not stable.(5) Dust particles have acidic buffer effect. The particles appeared alkaline during the dust episode on May1-4,2011, while particles was acid On May12-15(the second dust episode), but weaker than clean days (May6-9). Factor analysis showed that NH4+was the major neutralizing substances weather it was dust day or not. The neutralization of Ca2+during dust days was obviously higher than nondust days, and the other metal cation’s neutralization has strengthened. What’s more, the SO42-, NO3-was mainly existed as the form of NH4HSO4, NH4NO3and (NH4)2SO4during nondust days, but they will combine with other mineral ions during dust days. |
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