成都平原大气颗粒物中无机水溶性离子污染特征

Pollution Characteristics of Inorganic Water-soluble Ions in Atmospheric Particulate Matter in Chengdu Plain

为探讨成都平原大气颗粒物中水溶性离子的污染特征,识别水溶性离子的组成、分布和时空变化,有针对性地控制重污染和灰霾天气,于2013年8月~2014年7月,在成都平原的5个监测点位共采集1 476个颗粒物样品,应用离子色谱法对PM10和PM_(2.5)中8种无机水溶性离子(SO_4^(2-)、NO_3^-、NH_4^+、K^+、Na^+、Ca^(2+)、Mg^(2+)、Cl^-)进行测量.结果表明在观测期间,PM_(2.5~10)和PM_(2.5)中无机水溶性离子总量分别为11.35μg·m-3和36.93μg·m-3,分别占ρ(PM_(2.5)~10)和ρ(PM_(2.5))的37.8%和46.6%;其中二次离子(SO_4^(2-)、NO_3^-和NH^+4,SNA)约占各自水溶性离子总量的81.1%和89.9%.水溶性离子质量浓度冬季最高,春秋季相当,夏季最低.ρ(SO2-4)/ρ(PM_(2.5))夏秋季较高,而ρ(NO_3^-)/ρ(PM_(2.5))冬季最高,夏季最低.SNA、Cl^-、K^+大多分布在PM_(2.5)中,Ca^(2+)和Mg^(2+)主要分布在PM_(2.5~10)中.PM_(2.5)基本呈中性,水溶性离子主要以(NH_4)_2SO_4、NH_4NO_3、KNO_3、NaCl、KCl等形式存在.ρ(NO_3^-)/ρ(SO_4^(2-))揭示固定源依然是PM_(2.5)的主要来源.硫氧化速率(SOR)和氮氧化速率(NOR)年均值分别为0.31和0.13,SOR夏季最高,NOR冬季最高,二者变化趋势相反.成都平原PM_(2.5)呈区域性复合污染特征,SNA是造成ρ(PM_(2.5))增加的主导因素.

To study the pollution characteristics of water-soluble ions in atmospheric particulate matter in Chengdu Plain,and identify the composition,distribution,time and spatial variation,achieve targeted control of heavy pollution and haze days,1 476 samples were collected at five monitoring sites during August 2013-July 2014,in which eight kinds of inorganic water-soluble ions（ SO42-,NO3-,NH4＋,K＋,Na＋,Ca2＋,Mg2＋,Cl-） were determined by ion chromatography. The results showed that the total mass concentrations of 8 ions in PM2.5-10 and PM2.5were 11. 35 and 36. 93 μg·m^-3,accounting for 37. 8% and 46. 6% respectively,and SNA（ SO_4^（2-）,NO_3^-and NH_4~＋） in PM_（2.5-10） and PM_（2.5）contributed 81. 1% and 89. 9% to the total ions,respectively. The concentration of watersoluble ions was highest in winter and lowest in summer. ρ（ SO4~2-） /ρ（ PM2.5） was highest in summer and autumn,while ρ（ NO-3） /ρ（ PM_（2.5）） was highest in winter and lowest in summer. SNA,Cl-,K＋mostly distributed in PM2.5,Ca^2＋ and Mg^2＋ in PM2.5-10. PM2.5was generally neutral,the water-soluble ions in which existed as（ NH4）2SO4,NH4NO3,KNO3,NaCl,KCl and so on. ρ（ NO-3） /ρ（ SO2-4） revealed that the main source of PM2.5was given priority to fixed sources. Sulfur oxidation ratio（ SOR） and nitrogen oxidation ratio（ NOR） were 0. 31 and 0. 13,respectively,which had opposite changing trend with a highest SOR in summer and NOR in winter. PM2.5had the characteristics of regional pollution complex,and SNA was the dominant factor causing the increase ofρ（ PM2.5）.