聊城市冬季PM2.5及水溶性离子污染特征及来源分析

为研究聊城市冬季PM_2.5污染特征，于2016年1月7-29日在聊城市区对PM_2.5样品进行了采集，并对其水溶性离子（包括F-、Cl-、NO₃-、SO₄2-、NH₄+、Ca2+、Na+、Mg2+、K+）进行了分析.结果显示:观测期间聊城市ρ（PM_2.5）平均值为（192.4±88.9）μg/m3，超过GB 3095-2012《环境空气质量标准》日均二级标准限值的1.6倍.水溶性离子质量浓度为（77.4±46.9）μg/m3，占ρ（PM_2.5）的40.2%，其中SNA（NO₃-、SO₄2-和NH₄+）为主要离子，占水溶性离子比例达82.5%.轻度、中度、重度及严重污染时PM_2.5中水溶性离子质量浓度分别为（32.49±3.67）（46.26±17.66）（77.11±11.64）和（139.21±51.71）μg/m3，SNA分别占ρ（PM_2.5）的24.4%、26.7%、30.4%和39.0%，随着污染程度加重，SNA比例升高.观测期间SOR（硫转化率）与NOR（氮转化率）的平均值分别为0.18和0.20，随着ρ（PM_2.5）升高，SOR及NOR明显上升，表明冬季PM_2.5污染越严重时SO₂与NO₂的转化速率越强，二次无机污染严重.主成分分析结果表明，二次转化、扬尘源及工业生产为水溶性离子的主要来源.后向气流轨迹结果显示，观测期间污染气团主要来源于西北方向，受内蒙古及河北城市影响较大，但当污染气团来源于周边城市且天气静稳时，颗粒物浓度最高.研究显示，聊城市冬季PM_2.5污染较为严重. 

Characterization and Source Analysis of PM2.5 and Water-Soluble Ions during Winter in Liaocheng City

PM_2.5 samples were collected in Liaocheng City on January 7th to 29th, 2016, and the water-soluble ions in PM_2.5 include F-, Cl-, NO₃-, SO₄2-, NH₄+, Ca2+, Na+, Mg2+ and K+ were analyzed. The results showed that ρ(PM_2.5) was (192.4±88.9)μg/m3 in Liaochengcity during sample collecting period, exceeding the National Ambient Air Quality Standard (GB 3095-2012) more than 1.6 times. The total water-soluble ions concentration was (77.4±46.9)μg/m3, accounting for 40.2% of PM_2.5, NO₃-, SO₄2- and NH₄+(SNA) were the main ions and accounted for 82.5% of the total ions. During mild, moderate, severe and extremely severe contamination level, the water-soluble ions concentration was (32.49±3.67)(46.26±17.66)(77.11±11.64) and (139.21±51.71)μg/m3 respectively, the ratio of SNA accounted for PM_2.5 were 24.4%, 26.7%, 30.4% and 39.0%, respectively. The mean values of SOR and NOR were 0.18 and 0.20 respectively during research period, and with the increase of PM_2.5 concentration, SOR and NOR increased obviously, indicating that the secondary transformation rate was promoted under severe pollution, and the secondary inorganic pollution was serious during winter. The results of principal component analysis showed that the secondary transformation, dust source and industrial production were the main sources of water-soluble ions. The backward trajectories of air mass result showed that the polluted air mass mainly came from northwest direction during observation period, which was influenced by Inner Mongolia and Hebei cities. However, when the air mass came from the surrounding cities and the weather was stable, the PM_2.5 concentration was highest. The result showed PM_2.5 pollution was serious in Liaocheng City.