Seasonal and Spatial Variations of Carbon Fractions in PM2. 5 in Ningbo and the Estimation of Secondary Organic Carbon

为了研究 Pm2.5中碳质组分的时空分布特征,于2012年12月至2013年10月4个季度典型时段在宁波市5个采样点采集环境大气中的 Pm2.5,分析了样品中有机碳(OC)和元素碳(EC)的质量浓度,并估算二次有机碳(SOC)对 OC 的贡献.结果表明：①宁波市 Pm2.5年均质量浓度为51.6μg·m -3,其中 OC 和 EC 的比例分别为17％和6％.反向轨迹模型的分析结果表明,来自内陆地区的区域传输可能是冬季和春季 Pm2.5浓度较高的主要原因.②OC/ EC 比值和 OC 与 EC 的相关性分析结果表明,夏季有大量 SOC 生成,而冬季则可能受华北地区燃煤供暖的显著影响.③用 EC 示踪法对宁波市的 SOC 进行了估算,结果表明宁波冬季和春季受到区域传输的显著影响,污染源较不稳定,不宜使用该估算方法.夏季和秋季的 SOC 质量浓度分别为2.5μg·m -3和2.3μg·m -3,占 OC 的42％和28％.To investigate the seasonal and spatial variations of carbon fractions in Pm2. 5 in Ningbo, Pm2. 5 samples were collected at 5 sites in typical periods of 4 seasons from December 2012 to October 2013. The concentrations of organic carbon (OC) and elemental carbon (EC) were determined and the contribution of secondary organic carbon (SOC) was estimated. The result shows that: ①the annual average of Pm2. 5 in Ningbo is 51. 6 μg·m - 3 . OC and EC account for 17% and 6% respectively. According to the result of the backward trajectory model, the concentrations of Pm2. 5 in winter and spring are higher mainly because of regional transport from inland China. ② the OC/ EC ratio and the correlation between OC and EC indicate that in summer a large sum of SOC is generated while in winter the influence of coal burning emission for heating in North China may be the main reason for high OC/ EC ratio. ③ the contribution of SOC was estimated using an EC tracer method. The result shows that this method is not suitable for both winter and spring because of significant regional transport. The average concentrations of SOC in summer and autumn are 2. 5 μg·m - 3 and 2. 3μg·m - 3 , accounting for 42% and 28% of total OC respectively.宁波市 Pm2.5污染特征与大气监测网络优化研究项目中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)93128-31343