2013年1月中国中东部大气重污染期间上海颗粒物的污染特征

The chemical characteristics of particulate matters in Shanghai during heavy air pollution episode in Central and Eastern China in January 2013

2013年1月,我国中东部地区连续遭受多场大范围、长时间、高强度的灰霾天气.期间,本研究采用在线连续观测手段测量了上海市城区大气中气态污染物、颗粒物的质量浓度、细颗粒物的化学组分等,获得了高污染过程中颗粒物的污染特征.观测结果显示,1月份期间PM10、PM2.5与PM1.0平均浓度分别为(125±75)μg·m-3、(82±54)μg·m-3和(44±27)μg·m-3,PM2.5/PM10为65.0%±13.0%,能见度小于10.0km的累计时间长达284 h,占整月小时数的38.2%.灰霾期间大气PM2.5中SO2-4、NO-3、NH+4和OM分别占PM2.5的21.5%±4.9%、22.8%±5.9%、15.9%±3.1%和20.4%±4.3%,其中,二次组分(SNA+SOA)占PM2.5的65.7%±8.4%,表明灰霾期间二次组分对PM2.5的贡献较大;灰霾期间还测得较高的SOR和NOR,分别为0.335±0.121和0.229±0.066,说明SO2-4和NO-3的生成效率较高;较高的[NO-3]/[SO2-4]比值(1.137±0.438)表明灰霾期间机动车的污染较明显.研究发现,随着PM2.5质量浓度不断地增加,SNA的比例明显上升,期间NH+4对SO2-4、NO-3等酸性物质的中和发挥了重要作用.研究结果显示,灰霾期间,因受低温和高浓度颗粒物的影响,上海地区的大气对有机物的氧化能力明显减弱,昼夜OC/EC值差别不大.

Intensive fog and haze shrouded central and eastern parts of China in Jan. 2013. In this study, characteristics of this severe pollution event were investigated based on in-situ measurement of gas and fine particulate pollutants in urban area of Shanghai. Results shown that average concentration of PM10, PM2.5 and PM1.0 in Jan. 2013 were （12575） μgm-3, （8254） μgm-3 and （4427） μgm-3, respectively, while PM2.5/PM10 ratio was about 65.0%13.0%. The accumulated duration with visibility less than 10.0 km was 284 hours, accounting for 38.2% of a month. SO42-, NO3-, NH4＋ and OM contributed 21.5%4.9%, 22.8%5.9%, 15.9%3.1% and 20.4%4.3% to PM2.5 in haze period, respectively. The proportion of secondary composition （SNA＋SOA） in PM2.5 was 65.7%8.4%, indicating the large contribution from secondary formation to PM2.5 during heavy air pollution episode. Meanwhile, the observed relatively high SOR （0.3350.121） and NOR （0.2290.066） suggested a high production rate of SO42- and NO3-, and the high ratio of/with 1.1370.438 implied that the pollution from vehicle emission was more obvious during the haze episode. The increase of PM2.5 mass concentration was in line with the rise of SNA proportion, while NH4＋ played a critical role in particle formation with SO42- or NO3-. Due to the low temperature, high humidity, and high concentration of particulate matter, atmospheric oxidization capability of organic matters was considerably weakened in haze period, and OC/EC ratio in day and night showed little difference.