南京北郊冬夏季大气PM_(2.5)中碳质组分浓度及同位素组成研究

Concentration and isotopic composition of carbonaceous components in PM_(2.5) during winter and summer in the northern suburb of Nanjing

为研究南京北郊不同季节PM_(2.5)中碳质组分的主要来源,分别在2014年1月1—23日和2014年7月3—22日进行PM_(2.5)样品采集,并分析其中有机碳(OC)、元素碳(EC)浓度及总碳同位素组成.结果表明,冬季PM_(2.5)浓度高于夏季,平均值为(146.69±64.67)μg·m-3,OC、EC浓度较高,分别为(14.77±5.58)μg·m-3与(9.01±4.74)μg·m-3;而夏季PM_(2.5)浓度为(57.69±23.80)μg·m-3,OC、EC浓度分别为(5.94±2.20)μg·m-3和(2.78±1.25)μg·m-3.二次有机碳(SOC)占OC比重较小,冬、夏两季分别为36.99%与27.37%,这与采样点紧邻公路主干道使颗粒物未得到充分的二次反应有关.南京北郊冬季δ13C平均值为-25.38‰±0.36‰,夏季为-26.50‰±0.58‰,通过与潜在污染源的δ13C值对比,推断出采样期间冬季主要的潜在碳质污染源为煤炭燃烧及机动车尾气,夏季主要的潜在碳质污染源为生物质燃烧及汽车尾气.

To understand the main sources of carbonaceous components in PM2.5 in the northern suburbs of Nanjing,PM2.5 samples were collected from January 1 to January 23,2014 and from July 3 to July 22,2014,respectively,and were analyzed for organic carbon（ OC）,elemental carbon（ EC）content and total carbon isotopic composition. The results showed that PM2.5 had higher levels in winter（ 146. 69 ± 64. 67） μg·m^-3 than in summer（ 57.69±23.80） μg·m^-3,and the average concentrations of OC and EC were（ 14.77±5.58） μg·m^-3 and（ 9.01±4.74） μg·m^-3 in winter and（ 5.94±2.20） μg·m^-3 and（ 2.78 ± 1. 25） μg·m^-3 in summer. The fractions of OC accounted for by SOC in winter and summer were 36. 99% and 27. 37%,respectively. The low SOC contribution to OC might be due to the fact that the sampling site was close to a main road with heavy traffic,and the OC in PM2.5 was less oxidized and mainly associated with primary emissions. The average δ13 C in the northern suburb of Nanjing is-25.38‰±0.36‰ in winterand-26.50‰±0.58‰ in summer. With the comparison of the δ13 C value between this work and that for specific pollution source,we inferred that the main sources of carbonaceous components in PM2.5 in winter were coal combustion and motor vehicle emission; biomass burning and motor vehicle emission were the main sources of PM2.5 carbon contents in summer.