Characteristics Of Water-soluble Orginic Nitrogen Of PM_2.5 In Taiyuan

In recent years,severe haze pollution involving atmospheric fine particulate matter(PM_2.5)has been paid widespread attention.As one of the important components of PM_2.5,water-soluble organic nitrogen?WSON?has a great impact on atmospheric nitrogen cycle,physical and chemical properties of secondary aerosols and human health.Taiyuan,the capital city of Shanxi province,China,is a typical northern industrial city,and the haze pollution of Taiyuan possesses a typically regional characteristic.The total characteristics,the concentration level and source analysis of WSON in PM_2.5 of Taiyuan are studied in this paper.It is hoped to be helpful for providing a scientific basis for the relevant departments to prevent and control haze.PM_2.5 samples were collected at a five-story building in Shanxi University using a medium-volume PM_2.5 impactor from December 1to December 31,2016,and April 1 to April 30,July 1 to July 31,and October 1to October 31,2017.The concentration of water-soluble organic carbon?WSOC?,water-soluble inorganic ion and water-soluble total nitrogen?WSTN?in PM_2.5 was measured with an organic carbon/total nitrogen analyzer and ion chromatography.The concentration of WSON was calculated to study the seasonal variation characteristics and concentration levels.Finally,the source and contribution of WSON were analyzed.by PCA/APCS?Principal component analysis/Absolutely principal component analysis?model.Results showed that:?1?The seasonal mean concentrations of WSON in PM_2.5 in Taiyuan during the sampling periods were significantly different,and the mean concentration were 0.90 ± 0.27?g·m^-3 in spring,2.49 ± 4.80?g·m^-3 in summer,2.84 ± 0.83?g·m^-3 in autumn,7.67 ± 7.13?g·m^-3 in winter,respectively.The mean concentration of WSON in winter was the highest.The contribution of WSON to WSTN were higher in winter and summer,followed by autumn,while the lowest in spring.The average contribution of WSON accounted for 30% of the WSTN.?2?The correlation between WSON and N/C in summer was the highest?R²=0.65?,indicating the sources of WSON in summer were relatively single,while the sources of other three seasons were plentiful.The meteorological conditions also affect the concentration of WSON,it showed that when the meteorological conditions was low wind speed and high relative humidity,the concentration of WSON was high.?3?The sources of WSON were analyzed with PCA/APCS model.The results showed that about 76% mixed pollution sources of coal combustion and automobile exhaust was the largest contribution to WSON in spring.In summer,the major pollution sources were coal combustion,automobile exhaust and biomass combustion,building dust and industrial combustion,with contribution of 44.8%,13.7%,10.2%,respectively.While in autumn expect the large part of mix pollution sources of coal combustion and automobile exhaust?40.6%?,building dust?4.9%?and biomass combustion?0.04%?also accounted for a certain proportion.In winter,the major pollution sources were coal combustion,biomass combustion and automobile exhaust,cooking,building dust,with contribution of 21.4%,1.7%,1.3%,respectively.