乌鲁木齐市PM_(2.5)和PM_(2.5~10)中碳组分季节性变化特征

2011年1月至12月在乌鲁木齐市区用膜采样法采集了大气PM_(2.5)和PM_(2.5~10)样品,并利用热光/碳分析仪测定了其中有机碳(OC)和元素碳(EC)的质量浓度.通过OC与EC的粒径分布特征、比值和相关性的分析,初步分析了乌鲁木齐市大气可吸入颗粒物中碳质气溶胶污染特征,并用OC/EC比值法估算了二次有机碳(SOC)的浓度.结果表明,PM_(2.5)和PM_(2.5~10)的年平均质量浓度分别为92.8μg/m~3和64.7μg/m~3.PM_(2.5)中OC和EC的年平均浓度分别为13.85μg/m~3和2.38μg/m~3,PM_(2.5~10)中OC和EC的年平均浓度分别为2.63μg/m~3和0.57μg/m~3.OC和EC四季变化趋势基本一致,季浓度最高.碳组分主要集中于PM_(2.5)中,OC/EC比值范围为3.62~11.21.夏季和秋季的PM_(2.5)和PM_(2.5~10)中OC和EC的相关性较好(R20.65).估算得出的PM_(2.5)和PM_(2.5~10)中SOC的估算浓度为2.31~11.98μg/m~3和0.38~1.49μg/m~3.

Seasonal changes of carbonaceous speeies in PM2.5, PM2.5~10 in Urumqi

Filter-based PM_2.5~10 and PM_2.5 samples were collected at an urban site in Urumqi during January-December 2011, and analyzed for the organic carbon (OC) and elemental carbon (EC) mass concentrations by a thermal/optical carbon analyzer. The characteristics of carbonaceous aerosols in Urumqi were preliminarily investigated with the size distribution of OC and EC, OC/EC ratios and their correlations; and the mass concentrations of secondary organic carbon (SOC) were estimated by using the OC/EC ratio or EC-tracer method. The results showed that PM_2.5 and PM_2.5~10 had annual average mass concentrations of 92.8 μg/m³ and 64.7 μg/m³, respectively; while OC and EC had annual average mass concentrations of 13.85 μg/m³ and 2.38 μg/m³ in PM_2.5, and 2.63 μg/m³ and 0.57 μg/m³ in PM_2.5~10, respectively. OC and EC in PM_2.5 and PM_2.5~10 demonstrated similar seasonal variations with the highest values observed in winter. Carbonaceous aerosols were mainly concentrated in PM_2.5. OC/EC ratios ranged from 3.67 to 11.21. Good linear correlations were found between OC and EC in summer and autumn (R²>0.65). Estimated SOC in PM_2.5 and PM_2.5~10 ranged 2.31~11.98 μg/m³ and 0.38~1.49 μg/m³, respectively.