万州城区夏季、冬季PM_(2.5)中有机碳和元素碳的浓度特征

Characteristics of organic carbon and elemental carbon in PM_(2.5) in the urban Wanzhou area in summer and winter

在位于三峡库区腹心的山地城市万州城区采集夏季和冬季PM2.5样品,采用热光反射法(Thermal Optical Reflection,TOR)测定了PM2.5中有机碳(OC)和元素碳(EC)的浓度,探讨了其污染特征及来源.结果发现,OC和EC在夏季的平均浓度分别为(7.09±1.86)μg·m-3和(3.49±0.64)μg·m-3;冬季分别为(16.82±6.87)μg·m-3和(6.21±2.06)μg·m-3,高于夏季,这可能与冬季当地居民生物质燃烧的贡献显著增加有关.冬季OC和EC显著线性相关(r=0.89),表明冬季两者的一次污染来源相近.冬季PM2.5中总碳(TC)和水溶性K+含量的相关性(r=0.88)高于夏季(r=0.69),表明冬季生物质燃烧对碳污染贡献显著.利用OC/EC比值法对二次有机碳(SOC)进行估算,SOC的浓度均值在夏季为(2.17±1.46)μg·m-3,占OC比例为28.18%±13.85%;冬季为(4.46±3.69)μg·m-3,占OC的23.13%±12.30%.通过计算PM2.5中8个碳组分丰度,初步判断机动车尾气排放和生物质燃烧是万州城区碳组分的主要来源.

PM2.5samples were collected during summer and winter in Wangzhou,a mountainous city in Three Gorges Reservoir,China. Organic carbon( OC) and elemental carbon( EC) were analyzed by thermal optical reflection( TOR) and investigated for their pollution characteristics and sources. The average concentrations of OC and EC were( 7.09±1.86) μg·m-3and( 3.49± 0. 64) μg·m-3in summer,higher than that in winter of( 16. 82 ± 6. 87)μg·m-3and( 6.21±2.06) μg·m-3,respectively. This may be related to biomass burning by local residents. The concentrations of OC in PM2.5were significantly correlated with EC in winter( r = 0. 89),suggesting that they might have similar primary sources. The correlations between TC and K+in PM2.5were stronger in winter( r = 0. 88) than summer( r = 0. 69),suggesting biomass burning contributed significantly to the carbon pollution. The concentrations of secondary organic carbon( SOC) were estimated by OC / EC ratio method. The average concentration of SOC was( 2.17±1.46) μg·m-3in summer and( 4.46 ± 3. 69) μg·m-3in winter,contributed 28. 18% ± 13. 85% and 23. 13% ± 12. 30% to total OC,respectively. By calculating and analyzing the abundances of eight kinds of carbon components in PM2.5,motor vehicle emissions and biomass burning were indicated to be the major sources of carbon components in Wanzhou.