中文摘要：

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.

英文摘要：

PM10 and PM2.5 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 PM10 and PM2.5 at urban site were higher than those at suburb site in each period. PM2.5/PM10 ratio in May was the lowest, mainly because soil dust had a large contribution to PM10 in this period. Average concentrations of organic carbon （OC） and elemental carbon （EC） in PM10 and PM2.5 had the similar variation trend, and the highest values were all observed in December. OC/TC ratios in PM10 and PM2.5 ranged 0.60-0.83, 0.55-0.81, respectively. About 76% of OC in PM10 was associated with the fine particle （PM2.5） mode. Concentration of SOC was highest in December due to the potential effect of meteorological condition and local pollution sources.