青藏高原东缘冬季PM2.5中碳组分特征和来源解析

于2017年冬季12月13—21日在青藏高原东缘理塘地区分昼夜采集PM_2.5样品,并用DRI2001A热光碳分析仪测定了有机碳(OC)和元素碳(EC)的质量浓度,研究青藏高原PM_2.5中碳组分的化学特征及主要来源,以期为理塘地区制定污染排放政策提供参考。结果表明,2017年冬季青藏高原东缘理塘地区PM_2.5平均质量浓度为44.34μg·m^?3,OC和EC的质量浓度为12.72μg·m^?3和3.85μg·m^?3,分别占PM_2.5质量浓度的29.61%和8.96%。通过经验公式,计算得到总碳气溶胶(TCA)质量浓度为24.20μg·m^?3,占PM_2.5的54.84%,说明碳质气溶胶对青藏高原东缘理塘地区PM_2.5有着十分重要的贡献。OC和EC在白天和夜间都有较高的相关性(相关系数分别为0.74和0.91),表明OC和EC的来源基本一致,受燃烧源影响较大。其中白天的相关系数低于夜间,说明青藏高原东缘理塘地区白天碳组分来源相对复杂。昼夜浓度对比显示,青藏高原东缘理塘地区PM_2.5白天和夜间的质量浓度分别为53.88μg·m^?3和33.44μg·m^?3,OC和EC浓度白天高于夜间,表明白天人为排放相对较高。冬季观测期间,PM_2.5中二次有机碳(SOC)昼夜浓度分别为1.11μg·m^?3和3.03μg·m^?3,分别占OC质量浓度的7.09%、26.59%,表明青藏高原东缘理塘城区白天碳组分主要为一次源。利用PMF 5.0软件对理塘城区碳组分进行进一步的解析,结果显示燃煤和生物质燃烧的混合源对总碳(TC)的贡献高达47.84%,占比最高;其次是汽车尾气和柴油车尾气源,贡献率分别为28.62%和23.54%。

Characteristics and Sources Apportionment of Carbon Components of PM2.5in Winter over Eastern Tibetan Plateau

In order to study the chemical characteristics and main sources of carbon components of PM_2.5 in the Tibetan Plateau,PM_2.5 samples were collected day and night in Litang over eastern Tibetan Plateau during the winter of December 13–21,2017.The mass concentrations of organic carbon(OC)and element carbon(EC)were measured by DRI2001A thermos-optical carbon,so as to provide reference for the formulation of pollution emission policy in Litang area.The results showed that the average mass concentration of PM_2.5 in Litang over eastern Tibetan Plateau in winter of 2017 was 44.34μg·m^?3,and the mass concentrations of OC and EC were 12.72μg·m^?3 and 3.85μg·m^?3,respectively accounting for 29.61%and 8.96%.Through the empirical formula,the mass concentration of total carbon aerosol(TCA)was calculated to be 24.20μg·m^?3,accounting for 54.84%of PM_2.5,indicating that carbonaceous aerosol was very important for PM_2.5 in Litang over eastern Tibetan Plateau.OC and EC had a high correlation during the day and night(correlation coefficients of 0.74 and 0.91,respectively),indicating that the sources of OC and EC were basically the same and were greatly affected by combustion sources.The correlation coefficient during the day was lower than that in night,indicating that the source of carbon components during the day in Litang over eastern Tibetan Plateau ws relatively complex.Contrast between day and night showed that the daytime and nighttime mass concentrations of PM_2.5 in Litang over eastern Tibetan Plateau were 53.88μg·m^?3 and 33.44μg·m^?3,respectively.The OC and EC concentrations during the day were higher than those at night,indicating that the anthropogenic emissions during the day were relatively high.During the winter observation period,the diurnal and night-time concentrations of secondary organic carbon(SOC)in PM_2.5 were 1.11μg·m^?3 and 3.03μg·m^?3,respectively,accounting for 7.09%and 26.59%of the mass concentration of OC,indicating that the carbon component in the daytime in Litang urban area was mainly a primary source.Using PMF 5.0 software to further analyze the carbon components in Litang,the results showed that the combined source of coal and biomass combustion contributes up to 47.84%of total carbon(TC),accounting for the highest proportion,followed by automobile exhaust and diesel.The source of vehicle exhaust,the contribution rates were 28.62%and 23.54%.