天津市大气中PM10、PM2.5及其碳组分污染特征分析

2007年12月~2008年10月期间,分3个时段,设置2个点位,采集了天津市大气环境中PM10和PM2.5样品.用热光反射分析仪测定样品中的碳组分含量,并用OC/EC最小比值法估算二次有机碳(SOC)的浓度.结果表明,市区采样点颗粒物浓度高于郊区,2个采样点的颗粒物浓度变化趋势一致.5月份 PM2.5/PM10比值最小,主要由于土壤风沙尘对PM10的贡献较大.PM10和PM2.5中的有机碳(OC)、元素碳(EC)浓度12月份最高,且变化趋势相同.OC占总碳(TC)比例较高,PM10中OC/TC为0.60~0.83,PM2.5中OC/TC为0.55~0.81.碳组分主要集中在PM2.5中,PM10中约有76%的OC存在于PM2.5中.12月份的SOC浓度最高,与12月份的气象条件和污染源排放等因素有关.

Characteristics of PM10, PM2.5 and their carbonaceous species in Tianjin City

PM_(10) and PM_(2.5) samples were collected at two sites of Tianjin in three periods during December 2007～October 2008. Carbonaceous species were analyzed by thermal optical reflection analyzer, and concentrations of secondary organic carbon (SOC) were estimated by using OC/EC minimum ratio method. Concentrations of PM_(10) and PM_(2.5) at urban site were higher than those at suburb site in each period. PM_(2.5)/PM_(10) ratio in May was the lowest, mainly because soil dust had a large contribution to PM_(10) in this period. Average concentrations of organic carbon (OC) and elemental carbon (EC) in PM_(10) and PM2.5 had the similar variation trend, and the highest values were all observed in December. OC/TC ratios in PM_(10) and PM_(2.5) ranged 0.60～0.83, 0.55～0.81, respectively. About 76% of OC in PM_(10) was associated with the fine particle (PM_(2.5) mode. Concentration of SOC was highest in December due to the potential effect of meteorological condition and local pollution sources.