常州市大气PM_(2.5)中水溶性离子组成及来源

于2013年3月~2014年4月采集常州市郊区、工业区、居民区和背景点的春季、秋季大气PM_(2.5)样品,用离子色谱法分析其中水溶性离子成分,对其组成、分布特征及来源等进行研究。结果表明:SO_4~(2–)、NO_3~–和NH_4~+是常州市PM_(2.5)中的主要水溶性离子,3种离子在PM_(2.5)中占比为18%~33%。不同功能区之间水溶性离子的占比和差异较小,常州背景点可能受到周边城市污染输送的影响。在PM_(2.5)中,NH_4~+与SO_4~(2–)和NO_3~–主要以(NH_4)_2SO_4和NH_NO_3存在;硫转化率(SOR)和氮转化率(NOR)是衡量二次无机粒子转化的有效手段,常州市各功能区的SOR均大于NOR;春季SOR0.25,NOR0.1,满足发生强烈光化学氧化反应的条件。

CHARACTERISTICS AND SOURCES ANALYSIS OF WATER-SOLUBLE IONS IN PM2.5 IN CHANGZHOU

Atmospheric PM_2.5 samples were collected from suburban areas, industrial areas, residential areas and background points in the Changzhou City from March 2013 to April 2014 during spring and autumn. Ion chromatography was used to analyze the composition, distribution characteristics and sources of water-soluble ions in PM_2.5. The results indicated that SO₄^2-, NO₃^-and NH₄⁺ were the main components of water-soluble ions in PM_2.5, contributing to 18%-33% of the mass of PM_2.5. The proportion and concentration difference of water-soluble ions between different functional areas was small, which showed that background points in Changzhou can be affected by pollutants transferred from surrounding cities. NH₄⁺, SO₄^2- and NO₃ mainly existed in PM_2.5 as (NH₄)₂SO₄ and NH₄NO₃. SOR and NOR are effective methods for evaluating the transformation ratio of secondary inorganic particles. The value of SOR was higher than that of NOR in all areas. In spring, the value of SOR was greater than 0.25, the value of NOR was greater than 0.1, which met the strong photochemical oxidation reaction conditions.