广州干湿季典型灰霾过程水溶性离子成分对比分析

利用广州气象台2011年地面逐时能见度和相对湿度数据,以及广州番禺南村大气成分站2011年逐时Marga数据、PM数据,对比分析了一次湿季(4—9月)灰霾过程和干季(10月—次年3月)灰霾过程的污染特征.研究表明,相对干季灰霾过程,湿季灰霾过程颗粒物浓度较低,且细粒子所占比例较高;由于湿季较干季光化学反应较为活跃及可能受气象因素的不同影响,导致干湿季灰霾过程颗粒物浓度的总体变化趋势相反;湿季灰霾过程二次无机离子(SO_4~(2-)、NH_4~+和NO_3~-)占PM_(2.5)质量百分比的76%,是PM_(2.5)的主要成分;干季灰霾过程二次无机离子(SO_4~(2-)、NH_4~+和NO_3~-)仅占PM_(2.5)质量百分比的34%;湿季硫氧化率(Sulfur Oxidation Ratio,SOR)、氮氧化率(Nitrogen Oxidation Ratio,NOR)值大于干季,说明二次离子对湿季灰霾的贡献比干季要大;湿季灰霾过程中气溶胶酸性比干季弱.根据相关性分析结果可知,湿季灰霾过程中,NH_4~+主要与SO_4~(2-)结合,Na+主要与Cl-及NO_3~-结合,K+主要与Cl-和NO_3~-结合,极少部分与SO_4~(2-)结合;而在干季灰霾过程中,NH_4~+除了与SO_4~(2-)结合之外,还以NH_4NO_3和NH_4Cl的形式存在,K~+主要与Cl~-和SO_4~(2-)结合,Na+主要与Cl~-及SO_4~(2-)结合.

Comparative analysis of water-soluble ions during typical haze processes in dry and wet seasons in Guangzhou

The hourly water-soluble ions (obtained by Marga) and particulate matter (PM) mass data from Panyu atmospheric components observatory of China Meteorological Agency in 2011 were analyzed together with the hourly visibility and relative humidity data provided by Guangzhou meteorological observatory. Haze processes during the wet season (April to September) and the dry season (October to next March) were further characterized. It was found that compared to the dry season, PM concentrations in the wet season were significantly lower, whereas the proportion of fine particles was higher. This may be because the photochemical reaction in the wet season is more active. In addition, the contribution from the meteorological factors should also be considered. In the wet season, the secondary inorganic ions (SO₄^2-, NH₄⁺ and NO₃^-) contributed 76% of PM_2.5 (mass ratio). In contrast, the secondary inorganic ions (SO₄^2-, NH₄⁺ and NO₃^-) contributed only 34% of PM_2.5 in the dry season. The values of sulfur and nitrogen oxidation ratio (SOR and NOR) in the wet season were greater than those in the dry season, suggesting a higher contribution of secondary ions to the haze process in the wet season. The acidity of aerosols in haze processes in the wet season was weaker than that in the dry season. In the wet season, NH₄⁺ was mainly coexisted with SO₄^2-, Cl^- and NO₃^-, and K⁺ was with Cl^- and NO₃^-. In comparison, NH₄⁺ was still coexisted with SO₄^2-, Cl^- and NO₃^-, but both K⁺ and Na⁺ were observed with Cl^- and SO₄^2- in the dry season.