武汉市春季大气PM_(2.5)中水溶性离子特征

Characteristic Analysis of Water-Soluble Lons in Atmospheric Fine Particles in Spring Wuhan

运用大气PM_(2.5)水溶性组分及其气态前体物在线监测系统(GAC-IC)于2017年3月5—12日对武汉市大气PM_(2.5)中水溶性组分进行了在线监测,分析了PM_(2.5)中主要水溶性离子的化学特征和作用机制。结果表明:实验期间武汉市大气PM_(2.5)中水溶性组分与气态前体物间存在明显的二次转化过程,二次反应是PM_(2.5)的重要来源。监测期间,PM_(2.5)中NO_3^-、SO_4^(2-)和NH_4^+的平均质量浓度分别为24.3、16.9、15.0μg/m^3,是PM_(2.5)中重要的水溶性无机离子,占PM_(2.5)质量浓度的40%~70%。硫氧化率(SOR)和氮氧化率(NOR)平均值分别为0.52和0.27,表现出较为明显的二次污染特征。通过相关性分析发现:监测点位周边大气PM_(2.5)中NH_4^+与NO_3^-、SO_4^(2-)有良好的相关性,且表现为富氨状态,大气中铵能较好地中和SO_4^(2-)和NO_3^-。

Simultaneously on-line measurements of major water-soluble inorganic ions and gaseous pollutants were performed from March 5 to 12,2017 in Wuhan,using a gas-aerosol collector（ GAC） and ion chromatograph（ IC）,aiming to track the chemical characteristics and reaction mechanism of secondary inorganic components in fine particles（ PM（2.5））. The results showed that there was an obvious quadratic transformation process between water-soluble ions in PM（2.5）and their gas-phase precursors,which was the important source of PM（2.5）. As the dominant ionic components of PM（2.5）（ accounting for 40%-70%）,the average concentrations of NO3-、SO4（2-）、NH4＋were 24. 3,16. 9 and 15. 0 μg/m3 respectively. The average fine sulfate and nitrate oxidation ratios（ SOR and NOR） were SOR = 0. 52,NOR = 0. 27,revealing the remarkable characteristics of quadratic pollution. The correlation analysis showed that NH4＋ got well relations with NO3-and SO4（2-）,and the environment was rich of ammonia,NH3 in atmosphere could neutralize sulfate and nitrate.