南京江北新区PM_(2.5)中水溶性有机氮的污染特征及其来源

Pollution Characteristics and Sources of Water-soluble Organic Nitrogen in PM_(2.5) in Jiangbei New Area,Nanjing

以南京江北新区2019年4、7、11和12月为代表分析了大气PM_(2.5)中水溶性有机氮(WSON)的季节变化特征,探讨了WSON与水溶性无机氮(WSIN)的关系.结果表明,南京江北新区PM_(2.5)中WSON的变化范围为0.446~4.200μg·m^(-3),平均值为2.04μg·m^(-3),略高于北京、上海和常州的观测结果.秋季PM_(2.5)中的WSON平均值最高[(2.967±0.643)μg·m^(-3)],约为其他3个季节的1.7倍.南京细粒子中WSON对水溶性总氮(WSTN)的平均贡献率占到25%,并表现出夏秋高、冬春低的特点,如冬季该占比仅为夏秋季的50%左右.WSON与WSIN中的NO_(2)^(-)-N相关性最高,与NO_(3)^(-)-N的相关性最低,可能与夏季高温导致NO_(3)^(-)-N的挥发有关.通过主成分分析(PCA)表明,南京江北新区细粒子中WSON主要来源于二次转化、海盐、扬尘和生物质燃烧.

The seasonal variation characteristics of water-soluble organic nitrogen(WSON)in PM_(2.5)were analyzed in the Nanjing Jiangbei new area.The relationship between WSON and water-soluble inorganic nitrogen(WSIN)was also discussed.The results showed that the variation range of WSON in PM_(2.5)was 0.446 to 4.200μg·m^(-3),with an average value of 2.04μg·m^(-3).This value was slightly higher than the observed results in Beijing,Shanghai,and Changzhou.The average value of WSON was the highest in autumn[(2.967±0.643)μg·m^(-3)],which was approximately 1.7 times that of the other three seasons.The average contribution ratio of WSON to water-soluble total nitrogen(WSTN)in fine particles of Nanjing accounted for 25%,with high ratios in summer-autumn and low ratios in winter-spring.For example,the proportion of WSON/WSTN in winter was only approximately 50%of that in summer and autumn.WSON had the highest correlation with NO_(2)^(-)-N and the lowest correlation with NO_(3)^(-)-N in WSIN,which may be related to the volatilization of NO_(3)^(-)-N caused by high temperatures in summer.Principal component analysis(PCA)showed that WSON of PM_(2.5)in Nanjing was mainly derived from secondary transformation,sea salt,dust,and biomass combustion.