• 关键词：京津冀  PM_2.5  有机碳  元素碳  二次有机碳

• 基金项目：国家重点研发计划（No.2016YFC0208500，2016YFC0208506）；国家科技支撑计划（No.2014BAC23B01，2014BAC23B03）；天津市科技计划项目（No.16YFZCSF00260）

• 李立伟
• 天津市环境监测中心, 天津 300191

• 肖致美
• 天津市环境监测中心, 天津 300191

• 陈魁
• 天津市环境监测中心, 天津 300191

• 徐虹
• 天津市环境监测中心, 天津 300191

• 李鹏
• 天津市环境监测中心, 天津 300191

• 邓小文
• 天津市环境监测中心, 天津 300191

• 杨文
• 中国环境科学研究院, 北京 100012

• 孙韧
• 天津市环境保护局, 天津 300191

• 摘要：为了解京津冀区域PM_2.5中碳组分污染特征，于2015年7月和10月及2016年1月和4月在北京、天津、保定、石家庄、沧州5个城市同步采集PM_2.5样品，采用热/光分析法分析样品中有机碳（OC）和元素碳（EC），使用OC/EC最小比值法估算二次有机碳（SOC）.结果表明：京津冀区域主要城市OC、EC和SOC的年均浓度分别为12.9~28.5、4.1~7.9和3.3~10.4 μg·m^-3，OC/EC和SOC/OC的比值分别为2.4~3.0和0.26~0.32.OC和EC的浓度呈现保定 > 石家庄 > 沧州 > 天津 > 北京的空间分布特点和夏季 < 春季 < 秋季 < 冬季的季节变化特点.OC/EC的比值及OC和EC的相关性在夏季最低，冬季最高，这可能与京津冀区域冬季采暖燃煤有关，冬季不利的气象条件也加剧了碳质气溶胶污染.冬季较高的SOC浓度主要与低温、气态前体物的增加以及频繁出现的逆温、小风和混合层高度降低等不利气象条件有关.京津冀区域碳质气溶胶的污染特征具有空间相似性.

• Abstract：To investigate the characteristics of carbonaceous species in PM_2.5 in BTH (Beijing Tianjin and Hebei) area, ambient PM_2.5 samples were simultaneously collected in five urban sites (i.e. Beijing, Tianjin, Baoding, Shijiazhuang, Changzhou) from July 2015 to April 2016. The carbonaceous species including organic carbon (OC) and element carbon (EC) were analyzed by a thermal optical carbon analyzer (Model 2001A, DRI, USA). The EC tracer method was used to estimate the concentrations of secondary organic carbon (SOC) in PM_2.5. The results showed that the annual average concentrations of OC, EC and SOC were 12.9~28.5, 4.1~7.9 and 3.3~10.4 μg·m^-3, respectively; and the annual average values of OC/EC and SOC/OC were up to 2.4~3.0 and 0.26~0.32, respectively. The spatial variations of OC and EC concentrations were the same orders:Baoding > Shijiazhuang > Cangzhou > Tianjin > Beijing, and the seasonal variations of OC and EC concentrations were the also same order:summer < spring < autumn < winter. The OC/EC ratios were lowest in summer and highest in winter at all the sampling sites, likely due to the additional coal-combustion for heating and the adverse meteorological-conditions in winter. The highest correlation of OC and EC was found in winter and lowest in summer, which probably indicated that the sources of OC and EC were higher homology in winter, and the sources of OC were comparatively complicated in summer. The higher SOC concentrations in winter were likely due to the low temperature, the high concentrations of gaseous precursors resulted from coal combustion, and the unfavorable meteorological conditions such as the temperature inversion, the calm wind and the low height of mixed layer. Overall, the pollution characteristics of carbonaceous aerosols showed the spatial consistency in the plain area of BTH.

• Key words：Beijing,Tianjin and Hebei (BTH)  PM_2.5  organic carbon (OC)  element carbon (EC)  secondary organic carbon (SOC)

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