中文摘要：

基于污染物浓度、颗粒物化学组分及气象参数等观测数据,综合分析天津市2015年冬季典型重污染过程成因及污染特征,结果表明:天津市冬季重污染期间风速0~4.0m/s,相对湿度80%以上,混合层高度仅为清洁天气的1/3~1/2,静稳高湿的大气环境对重污染影响较大.重污染过程NO2/SO2比值较清洁天气低,NO3-/SO42-比值大于1,表明重污染期间天津市移动源与固定源并重.重污染PM2.5/PM10比值较清洁天气高,PM1/PM2.5比值较清洁天气低,可能与重污染过程期间细粒子的吸湿增长以及散煤燃烧排放有关.污染初期NOR大于SOR,随着重污染持续,由于受制于氨,SOR要高于NOR,需关注气态前体物尤其是SO2排放.OC与EC浓度高时二者相关性较低,SOC占OC的20%~54%,说明冬季重污染期间散煤燃烧源和二次有机化学反应对冬季重污染影响较大.

英文摘要：

To study the characteristics and causes of atmospheric heavy pollution episodes in winter of Tianjin,the concentrations of air pollutants,chemical characteristics of particulate matter and the meteorological parameters were analyzed in this study.The major conclusions were obtained as follows.During the heavy pollution episodes,the wind speeds kept below4.0m/s the relative humidity were larger than80%,and the mixing heights were only one third to one second of that in the clean days.The NO2/SO2ratios were lower in heavy pollution days than that in clean days,and the NO3-/SO42-ratios were larger than1during pollution days,indicating that both vehicle exhaust and stationary sources were dominant in Tianjin.Compared to clean days,the PM2.5/PM10ratios during the heavy pollution episodes were larger while the PM1/PM2.5ratios were relatively lower,probably because of the hygroscopic behavior of fine particles and the coarse particles from coal combustion.At the beginning of pollution processes,the NOR values were larger than SOR,however,as the development of pollution,the SOR values exceeded NOR due to the limit of ammonia's concentration,indicating that more attention should be focused on gaseous precursors especially sulfur dioxides.OC and EC were weakly correlated when both of them have high concentrations.SOC contributed20%to54%of OC,indicating that the residential bulk coal burning and secondary organic reactions greatly affected heavy pollution episodes.