| Dicarboxylic acids are important organic components in atmospheric particulates.Special double carboxyl structure which has strong polarity and hygroscopicity,can affect the activity of cloud condensation tuberculosis and the pH value of rainfall.Dicarboxylic acids have a certain impact on human health and environment since it contributes to heterogeneous chemical reaction of aerosol.of Wuhan,In order to study the chemical compositions and pollution level of dicarboxylic acids in atmospheric particulates in Wuhan,particulate matter samples were collected for a year in typical areas,following discussion of their sources and the impact of regional transmission in typical pollution events.Result shows that the annual PM2.5 concentrations of Wuhan is 81.32?g/m3,and the maximum is 131.41?g/m3 in winter,minimum is 42.14?g/m3 in summer.Meteorological conditions and pollution diffusion dilution may affect the PM2.5concentrations.The mass concentration the total dicarboxylic acids of PM2.5 in Wuhan city is797 ng/m3,which oxalic acid get the highest proportion?71%?as the annual average concentration was 550.14 ng/m3.Distinct seasonal differences were observed that concentrations of dicarboxylic acids in summer is 1434.93 ng/m3 while 133.11 ng/m3in winter.Meteorological conditions in summer such as high temperature,high relative humidity and strong radiation intensity in Wuhan are in favor of a series of complex photochemical transformations of the dicarboxylic acids precursors in the atmosphere,leading to dicarboxylic acids eventually.The seasonal variations of the dicarboxylic acids and PM2.5were differed,indicating that diverse sources.The characteristic ratio shows that the aging process of aerosol in summer is the most obvious one in Wuhan,that dicarboxylic acids is mainly affected by the vehicle exhaust,that the anthropogenic sources and biological source for dicarboxylic acids.According to correlation analysis,correlation is highly significant between the dicarboxylic acids,indicating dicarboxylic acids may have similar sources.Dicarboxylic acids have high correlation with SO42-and NO3-,indicating that the secondly source transformation may be an important source of dicarboxylic acids.There is a certain correlation between dicarboxylic acids with K+and Cl-,indicating that biomass combustion has effect on dicarboxylic acids in Wuhan.The correlation between the acids and Mg2+,Ca2+and Na+is poor,indicates that the effect of sea salt and building dust on the acids in Wuhan is not significant.The source of dicarboxylic acids in Wuhan is relatively extensive according to the result of PMF model,including vehicle emissions?41.57%?,biomass combustion?22.09%?,building dust?12.89%?,and sources?23.45%?.The potential source area of dicarboxylic acids in PM2.5 are simulated by Trajstat,Jiangxi,Anhui and Gansu provinces were the main potential source area of dicarboxylic acids of Wuhan in winter.while Shanxi,Shanxi and Guizhou provinces were the main contributors in summer..According to the PM2.5 mass balance study during intensive sampling period,organic matte were the highest proportion component,accounting for 29.43%and25.57%respectively in summer?16.43?g/m3?and winter?29.65?g/m3?.accounted for the largest proportion of PM2.5,highest quality components,The proportion of EC in PM2.5 is the smallest,which is 7.13%and 2.17%respectively.Biomass combustion and incomplete combustion of fossil fuels is the major source of EC.The contribution of biomass combustion to OC and EC is 22.96%,39.66%respectively in summer.while 40.58%,46.09%respectively in winter.Analysis of satellite fire map of NOAA and straw burning test report of Ministry of Ecology and Environment of the People republic of China,combined with back trajectory model,proves that the pollution event in summer may mainly affected by Hubei,Hunan,Hebei Province;as for winter,Liaoning,Hebei,Shaanxi province have obvious influence on air quality in Wuhan since dense fire spots were observed in those areas in winter. |
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