| PM2.5 is one of the main factors causing haze,and water-soluble inorganic ions(K+,Na+,Ca2+,Mg2+,NH4+,SO42-,NO3-,Cl-,F-,et al.)are important for PM2.5.The components can affect the pH of atmospheric particulate matter and have an impact on human health.In most parts of China,atmospheric PM2.5 particles have a high proportion of nitrogen,which is one of the important atmospheric pollutants.The sources of nitrogen in the atmosphere can be divided into natural sources and anthropogenic sources.The sources of atmospheric nitrogen may have large differences in different regions.Compared with natural systems such as forests,urban atmospheric nitrogen is mainly based on human sources.such as the release of fossil fuels,nitrogen fertilizer plant and human and animal manure.Generally,the nitrogen isotope composition of different sources has obvious differences in a specific area,and the screening of nitrogen sources can be effectively identification.PM2.5 samples were collected at Guiyang urban,and determined 9 kinds of water-soluble ions and?15N-TN values respectively in this study.The characteristics of water-soluble ion composition and main sources of nitrogen in PM2.5 were discussed,and the following conclusions were obtained:?1?The concentration of PM2.5 in winter is significantly higher than other seasons,and these ranked as winter,spring,autum,summer.Compared with other cities,Guiyang's PM2.5 average mass concentration is lower than domestic,higher than foreign countries.?2?The concentration of NH4+,SO42-,and NO3-were much higher than others in Guiyang's PM2.5 composition,accounting for 83%.The sequences of those ions were:SO42->NH4+>NO3->Ca2+>K+>Cl->Mg2+>Na+>F-.The seasons change of the total ions concentration of PM2.5 represented as follows:winter>spring>autumn>summer and the concentration were 26.39±10.94?g·m-3,18.87±8.17?g·m-3,17.93±9.23?g·m-3,11.21±5.01?g·m-3,respectively.?3?The NH4+may exist mainly in the form of?NH4?2SO4,NH4NO3,and partially in the form of NH4HSO4 and NH4NO3 in PM2.5.The seasons change of NOR?Nitrogen oxidation rate?and SOR?Sulfur oxidation rate?of PM2.5 represented as follows:winter>autumn>spring>summer,summer>spring>winter>autumn,respectively.?4?The average value of NO3-/SO42-is 0.31±0.26,which is much low than unit,may indicate that Guiyang PM2.5 mainly suffering stationary pollution during this time.NO3-/SO42-has obvious seasonal variation characteristics,and these ranked as winter,autum,spring,summer.?5?Combined correlation analysis and principal component analysis showed that NH4+may be contribution from automobile exhaust,biomass combustion and coal combustion.The total types of water-soluble ion sources in autumn,winter,spring and summer are similar,the contribution main from secondary sources,coal incineration,dust and biomass burning.?6?Base on the backward trajectory model combined with PSCF and CWT analysis,the distribution of NO3-,SO42-,and NH4+source regions was similar,and the regional transmission potential hotspot source regions appear in Chongqing and Chengdu.The western part of Guangxi,eastern Yunnan,and southern Guizhou are potential regional transmission sources of Ca2+in PM2.5.?7?The total nitrogen isotope(?15N-TN)showed obvious seasonal variation in PM2.5,and it can be found that the most positive values in summer and the most negative values in winter in this study,they were+15.59‰,+7.65‰,respectively.The?15N-TN isotope values in the warm season are significantly more positive than the?15N-TN isotope values in the cold season.Combined with previous studies,it is found that the total nitrogen in PM2.5 is mainly contribution from coal combustion,automobile exhaust,biomass burning and soil nitrogen sources. |
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