上海秋季典型大气高污染过程中有机碳和元素碳的变化特征

The variation characteristics of organic and element carbon during air pollution episodes in autumn in Shanghai,China

于2011年10月1日至10日在上海市城区对大气中细粒子的质量浓度和含碳气溶胶进行了在线连续观测,获得了秋季典型大气灰霾污染过程中含碳气溶胶的变化特征.观测结果显示,在大气灰霾过程中PM2.5中有机碳(OC)和元素碳(EC)的质量浓度分别为(20.38±7.11)μg·m-3和(4.07±1.97)μg·m-3,浓度显著高于非霾过程.以非霾天气的起始点作为参照点,得出灰霾期间OC和EC的增长率分别为641%±258%和409%±246%,本次灰霾过程中OC的污染累积与二次生成作用分别占63.8%和36.2%,污染过程以累积为主.灰霾期间OC/EC与O3具有良好的线性关系,且相关分析表明二者之间呈正相关,OC浓度的升高与含碳组分的光化学反应有关.采用EC示踪法估算短期大气过程中有机碳(SOC)含量,灰霾天气和非霾天气PM2.5中的SOC浓度分别为1.64～17.96μg·m-3和0.25～2.83μg·m-3,分别占OC的10.7%～66.7%和9.2%～52.5%.

Continuous measurements were conducted to investigate the characteristics of PM2.5 and carbonaceous aerosol during a haze episode in Shanghai urban from October 1st to October 10th , 2011. The mass concentrations of organic carbon （OC） and elemental carbon （EC） were （20.38 ± 7. 11 ）μg·m-3 and （4.07±1.97） μg·m-3, respectively, higher than those in clear day. Compared to 9：00 AM on October 1st（ the reference point） , the growth factors of OC and EC were 641% ± 258% and 409% ± 246% during the haze episode. It was estimated that the accumulation processes were more important than the secondary formation for the increase of OC during the haze episode, accounting for 63.8%. Additionally, the OC-to-EC ratio was positively correlated with ozone, maybe due to the strong photochemical processes of carbonaceous species, According to the EC-traeer method, the concentrations of secondary organic carbon （SOC） both in this haze episode and clear day were estimated to be 1.64 N 17.96 μg·m-3 and 0.25 - 2.83μg·m-3, accounting for 10.7% - 66.7% and 9.2% - 52.5% to OC, respectively.