临沂市冬季环境空气PM2.5中水溶性离子污染特征及来源分析

为探究临沂市冬季环境空气PM_2.5中水溶性离子污染特征及来源，于2016年12月11日—2017年1月9日在临沂大学、兰山区政府、高新区翠湖嘉园、汤庄办事处、河东区政府、临沂开发区6个采样点开展样品采集.结果表明:①采样期间全市ρ（PM_2.5）日均值的平均值为144.86 μg/m3，ρ（PM_2.5）日均值在2016年12月20日和2017年1月4日出现峰值，分别为304.46和341.65 μg/m3.②水溶性离子日均质量浓度大小顺序依次为ρ（NO₃-）> ρ（SO₄2-）> ρ（NH₄+）> ρ（Cl-）> ρ（K+）> ρ（Ca2+）> ρ（Na+）> ρ（F-）> ρ（Mg2+）> ρ（NO₂-），其中，在PM_2.5中w（NO₃-）、w（SO₄2-）、w（NH₄+）分别为22.33%、16.57%、13.62%，说明NO₃-、SO₄2-和NH₄+是临沂市PM_2.5的主要组成部分.③临沂市污染天和非污染天ρ（PM_2.5）日均值分别为164.00和56.86 μg/m3.随污染水平增加，PM_2.5中w（NO₃-）明显增高，w（SO₄2-）和w（NH₄+）基本不变，说明w（NO₃-）的增加导致ρ（PM_2.5）的升高.污染天和非污染天的NOR（氮氧化率）分别为0.28和0.11，SOR（硫氧化率）分别为0.34和0.28，说明污染越重，NOR和SOR越高，并且NO_x的气-粒转化速率较SO₂慢.污染天ρ（Cl-）和ρ（K+）分别为7.22和1.77 μg/m3，分别是非污染天的2.5和3.0倍.④采样期间非污染天和污染天的N/S〔ρ（NO₃-）/ρ（SO₄2-）〕分别为0.85和1.39，说明非污染天时固定源对PM_2.5的贡献相对较大，而污染天时移动源对PM_2.5的贡献相对较大.⑤通过PMF模型法解析出3个因子.因子1对PM_2.5中水溶性离子的贡献率为56.13%，代表二次源和生物质燃烧源；因子2的贡献率为25.22%，代表工业源和垃圾焚烧源；因子3的贡献率为18.65%，代表扬尘源.研究显示，临沂市冬季PM_2.5污染严重，水溶性离子来源复杂，应采取多源控制的污染防治对策. 

Characteristics and Sources Analysis of Water-Soluble Ions of Ambient Air PM2.5 in Winter in Linyi City

To explore the pollution characteristics of soluble inorganic ions (WSⅡs) in PM_2.5 from December 11th, 2016 to January 9th, 2017 in Linyi City, PM_2.5 samples were collected during wintertime at 6 sampling sites (Linyi University, Lanshan District Government, High-tech Zone Cuihu Jiayuan, Tangzhuang Office, Hedong District Government, Linyi Development Zone) in Linyi City, and the WSⅡs associated with PM_2.5 were analyzed. (1) The results showed that the average concentration of PM_2.5 was 144.86 μg/m3 during sampling periods, with the peak values of 304.46 μg/m3 on December 20th, 2016 and 341.65 μg/m3 on January 4th, 2017, respectively. (2) The daily average mass concentration order of water-soluble ions was ρ(NO₃-) > ρ(SO₄2-) > ρ(NH₄+) > ρ(Cl-) > ρ(K+) > ρ(Ca2+) > ρ(Na+) > ρ(F-) > ρ(Mg2+) > ρ(NO₂-). NO₃-, SO₄2- and NH₄+ accounted for 22.33%, 16.57% and 13.62% of the total mass of PM_2.5, respectively, which indicated that NO₃-, SO₄2-, NH₄+ were the main components of PM_2.5 in Linyi City. (3) The daily averages of PM_2.5 mass concentrations in polluted and non-polluted days were 164.00 and 56.86 μg/m3, respectively. The mass percentage of NO₃- increased obviously with the increase of PM_2.5 pollution levels, and the mass percentage of SO₄2- and NH₄+ remained largely unchanged, indicating that the obvious increase of the mass percentage of NO₃- led to the increase of the mass concentration of PM_2.5. The NOR values of polluted and non-polluted days were 0.28 and 0.11, and SOR values were 0.34 and 0.28, respectively, showing the conversion rate from NO_x to NO₃- was slower than that from SO₂ to SO₄2-. The average concentrations of Cl- and K+ on polluted days were 7.22 and 1.77 μg/m3 respectively, which were 2.5 and 3.0 times higher than those on non-polluted days. (4) The ρ(NO₃-)/ρ(SO₄2-) (N/S) values of non-polluted days and polluted days were 0.85 and 1.39 respectively, indicating that coal combustion contributed more to PM_2.5 on non-polluted days, and mobile source contributed more on polluted days. (5) Three factors were isolated by PMF. The contributions of each factor to WSⅡs in PM_2.5 were 56.13% (secondary source and biomass burning), 25.22% (industries and waste incineration), 18.65% (fugitive dust). In conclusion, the PM_2.5 pollution was heavy during winter in Linyi City, and the sources of WSⅡs varied. Different countermeasures should be taken according to the pollution characteristics.