西安冬春季PM10中碳气溶胶的昼夜变化特征

为探讨西安市大气碳气溶胶的季节变化和昼夜变化特征及来源,于2006-12-19~2007-01-21(冬季)和2007-04-01~2007-04-30(春季)连续采集了大气可吸入颗粒物(PM10)样品,并采用IMPROVE热光分析法分析了其中有机碳(OC)和元素碳(EC)的昼夜浓度.结果显示,冬季白天PM10及其中OC和EC的平均浓度分别为455.0、62.4和7.5μg/m3,夜晚的平均浓度分别为448.7、66.1和6.9μg/m3,对应春季白天的平均浓度分别为397.9、26.7和6.9μg/m3,夜晚分别为362.1、31.9和8.6μg/m3.冬季白天OC与EC的相关系数为0.44,较之春季0.81要差,主要与冬季采暖期燃料的多样性有关.碳气溶胶组分中,冬季白天和晚上二次有机碳气溶胶(SOC)的平均浓度为8.9和10.2μg/m3,远高于春季(2.8和3.4μg/m3),说明冬季较高的OC排放及较低的大气扩散能力利于碳气溶胶中SOC的生成.对碳气溶胶8种组分的因子分析结果表明,冬季燃煤排放及郊区的生物质排放对碳气溶胶有重要的贡献,而春季机动车的贡献明显增加.

Day-Night Variation of Carbonaceous Aerosols in PM10 During Winter and Spring over Xi'an

The purpose of this study was to investigate the day-night variation of carbonaceous aerosols in PM10 during spring and winter over Xi'an.PM10 samples were collected during 19 Dec 2006 to 21 Jan 2007(Winter) and 1 Apr 2007 to 30 Apr 2007 (Spring).Organic carbon (OC) and elemental carbon (EC) concentrations were measured using thermal-optical method.PM10,OC,and EC concentrations in winter were 455.0,62.4,and 7.5 μg/m3 during daytime,and 448.7,66.1,and 6.9 μg/m3 for nighttime,respectively,while in spring were 397.9,26.7,and 6.9 μg/m3 for daytime,and 362.1,31.9,and 8.6 μg/m3 for nighttime.The correlation coefficient of OC and EC during daytime in winter was 0.44,while a strong relationship between OC and EC was observed in spring daytime,indicating that the emission sources of carbonaceous aerosol in winter were more complicated than those in spring.Due to high OC levels and the weaker dispersal ability of atmosphere,the mean concentrations of SOC during winter (8.9 and 10.2 μg/m3 at daytime and nighttime) were much higher than those in spring (2.8 and 3.4 μg/m3).Factor analysis on the eight carbon fraction indicated that coal combustion and biomass burning were the major sources for carbonaceous aerosol in winter,while vehicle exhaust played an important role in spring.