嘉兴市冬季不同空气质量等级下大气污染物的分布特征

Characteristics of Atmospheric Pollutants under Different Air Quality Levels of Jiaxing City in Winter

为研究浙江省嘉兴市冬季PM、污染气体和含碳气溶胶在不同空气质量等级下的分布特征,于2013年11月28日—12月28日使用SHARP测尘仪、热电EMS系统和Sunset在线OCEC分析仪观测了PM(PM_(10)和PM_(2.5))、污染气体(SO_2、NO_2、CO和O_3)和含碳气溶胶[OC(有机碳)、EC(元素碳)和TC(总碳)]的质量浓度,结合气象数据和HYSPLIT模式,分析了霾污染过程中大气污染物浓度变化、日变化及其来源特征.结果表明:嘉兴市冬季霾天ρ(PM_(2.5))、ρ(PM_(10))、ρ(SO_2)、ρ(NO_2)、ρ(O_3)、ρ(OC)、ρ(EC)、ρ(POC)和ρ(SOC)分别为167.90、248.86、77.79、、97.16、28.50、27.09、7.72、7.50和19.59μg/m^3,ρ(CO)为1.47 mg/m^3,分别是空气质量为良时的3.00、2.50、1.29、1.84、0.86、2.59、2.19、2.13、2.82和1.50倍.降雨对不同大气污染物的清除作用不同,对粗粒子的清除作用较大,而对二次产物O_3的影响较小.高ρ(PM)是造成能见度降低的主要原因,随着污染程度的加剧,PM中细粒子占比越来越高,在严重污染过程中ρ(PM_(2.5))/ρ(PM_(10))可达70.31%,比空气质量为良时高14.04%;不同污染气体的日变化不同,OC和EC的来源逐渐趋于一致,ρ(SOC)呈现出积累-爆发-积累-爆发的往复过程,边界层的日变化对污染物浓度的影响逐渐减弱.研究显示,随着霾污染的加剧,SOC气溶胶占比逐渐增加、EC和POC等一次碳气溶胶占比逐渐降低.

In order to investigate the pollution characteristics of particulate matter（PM）,gas pollutants and carbonaceous aerosol under different air quality levels,PM（PM（10） and PM2.5）,gas pollutants（SO2,NO2,CO and O3） and carbonaceous aerosol（OC,EC and TC）were measured by SHARP monitoring instrument,Thermo EMS system and Sunset online OC/EC analyzer instrument from November 28 th to December 28 th,2013. Furthermore,combining with the meteorological data and back-trajectory model（HYSPLIT）,the diurnal variations and sources of air pollutants were discussed in haze episodes. Results showed that the average concentrations of PM2.5,PM（10）,SO2,CO,NO2,O3,OC,EC,POC and SOC were 167. 90 μg/m3,248. 86 μg/m3,77. 79 μg/m3,1. 47 mg/m3,97. 16 μg/m3,28. 50μg/m3,27. 09 μg/m3,7. 72 μg/m3,7. 50 μg/m3 and 19. 59 μg/m3 during the haze episode in Jiaxing City,which were 3. 00,2. 50,1. 29,1. 84,1. 50,0. 86,2. 59,2. 19,2. 13 and 2. 82 times higher than the standard concentrations respectively,when the air quality index was good（51AQI100）. The rainfall showed different scavenging effects on air pollutants,which had greater scavenging impactson coarse particles and had weak impacts on O3. High concentrations of PM were responsible for the reduced visibility. The proportions of fine particles in PM increased with the increase of air pollution levels. The PM2.5/PM（10） ratio reached to 70. 31% when the air quality index was seriously polluted（AQI〉300）,14. 04% higher than that when the air quality index was good. With the exacerbation of air quality,the effects of boundary layer became weak to air pollutants. Gas pollutants showed different diurnal variations but the sources of OC and EC were gradually consistent,the concentrations of SOC showed features of accumulation-explosion-accumulation-explosion. With the increase of haze pollution,the proportion of SOC gradually increased but that of primary carbonaceous aerosol（EC and POC） gradually decreased.