采集兰州冬季采暖期及夏季PM2.5样品共60个,通过DRI 测定有机碳(OC)和元素碳(EC). 结果显示:冬季OC和EC平均质量浓度分别为(35.39±13.88)μg/m3和(13.80±5.41)μg/m3,夏季分别为(9.74±3.30)μg/m3和(4.44±2.00)μg/m3,冬季污染远高于夏季. 冬夏季OC和EC相关系数分别为0.91和0.76,表明冬季兰州PM2.5中OC和EC的来源相似. 二次有机碳质量浓度冬夏季分别为(8.48±6.10)μg/m3和(3.07±2.20)μg/m3,约占OC含量的(22.46±11.93)%和(31.29±18.51)%,表明兰州冬夏季PM2.5中OC的来源均以一次排放为主,夏季二次源贡献高于冬季. 对8种不同温度段碳质组分分析表明,兰州冬季生物质燃烧较夏季有所增加,夏季可能主要为机动车尾气.
A total of 60 PM2.5 samples were collected during winter and summer seasons in Lanzhou city. OC and EC were measured by the thermal/optical method using DRI-2001A. The results indicated that carbonaceous aerosol in winter was significantly higher than that in summer. The average concentrations of OC and EC were (35.39±13.88) μg/m3 and (13.80±5.41) μg/m3 in winter and (9.74±3.30) μg/m3 and (4.44±2.00) μg/m3 in summer, respectively. The correlation between OC and EC was 0.91 in winter and 0.76 in summer, which revealed that OC and EC had similar sources. The concentrations of SOC were (8.48±6.10)μg/m3 and (3.07±2.20)μg/m3 in winter and summer, and they were about (22.46±11.93)% and (31.29 + 18.51)% of OC in PM2.5, respectively, which manifested that OC was mainly from primary sources and the contribution of secondary transformation was higher in summer than in winter. Analysis on the eight fractions of carbonaceous aerosol within the different temperature ranges showed that biomass burning had a high contribution for carbonaceous aerosol in PM2.5 in winter, but vehicle emissions might be the major source in summer.
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