郑州市灰霾天气过程PM_(2.5)水溶性无机离子污染分析

Characteristic features of the watersoluble inorganic ions in PM_(2.5) in the process of a severe haze episode in Zhengzhou

利用离子色谱技术对郑州市2014年10月一次严重灰霾天气过程的PM_(2.5)中的水溶性无机离子(F-、Cl^-、Br-、NO_3^-、SO_4^(2-)、Li^+、Na^+、K^+、NH_4~^+、Mg^(2+)及Ca^(2+))进行了分析测定,并结合大气质量监测数据及气团轨迹分析讨论了水溶性无机离子的质量浓度变化、来源及影响因素。结果表明,样品中Li^+、Mg^(2+)、Ca^(2+)、Br-均低于检测限,水溶性离子平均质量浓度从大到小依次为NH_4^+(36.33μg/m^3)、NO_3^-(30.4μg/m^3)、SO_4^(2-)(26.91μg/m^3)、Cl^-(12.43μg/m^3)、K^+(5.275μg/m^3)、Na^+(1.198μg/m^3)、F^-(0.626 4μg/m^3),水溶性离子质量分数为PM_(2.5)的47.2%~88.2%,平均为66.1%。随着灰霾天气的延续,水溶性离子在细颗粒物中所占比例逐渐增大,这表明来源于人为活动排放的二次污染物是PM_(2.5)主要贡献成分,采样时间段采样点PM_(2.5)污染受到了交通的严重影响,同时郑州市大气细颗粒物污染受周边农村农业生产影响严重,尤其是秸秆燃烧影响非常大。

The main objective of this paper is to investigate and explore the formation and evolution mechanism of the fine particulates （PM2.5） during a severe haze that took place in Oct, 2014, in Zhengzhou. For this purpose, we have collected enough PM2.5 samples in the process of that severe haze episode in the city in the previous years. It is well known that in the past few years, it was often the case in Zhengzbou that some severe long lasting haze events hit the capital city of Henan province. When we analyze such water-soluble inorganic ions （WSIIs） of PM2.5 with an ion-chromatograph, they can be found containing F-, Cl-, Br-, NO3-, SO42-, Li ＋, Na ＋, K ＋ NH4＋ Mg2＋ as well as Ca2＋ respectively. Furthermore, close investigations done together with the data of ambient air quality and backward trajectories let us notice that they are in various concentrations, origins and effects of WSIIs. We have also made comparison and contrast of the concentrations of WSIIs in PM2.5 in Zhengzhou with other cities in China. The results of our investigation have shown that the concentrations of Li＋ , Mg2＋, Ca2＋ and Brin the samples analyzed are all below the detection limits. The concentrations of the WSIIs have been found decreasing in a descending order, that is, NH4＋ （36.33μg/m3） 〉NO3-（30.4μg/m3） 〉SO]-（26.91μg/m3） 〉 Cl- （ 12.43μg/m3 ） 〉 K＋ （ 5. 275μg/m3 ） 〉 Na＋（ 1. 198μg/m3 ） 〉 F- （0. 626 4μg/m3 ）. WSIIs have been discovered up to 47.2% -88. 2%, with amean rate of 66.1% of PM2.5. The results indicate that the longer the haze particles tend to last, more the PM2.5 contains WSIIs, which implies that the secondary pollutant origins from the anthropogenic emission are the principal constituent of PM2.5- As a matter of fact, PM2.5 has been greatly impacted by the transportation and communications of the city, and also been seriously impacted by the agricultural production around the city during the sampling periods. The fine particulate matters, particularly the particulates of the biomass burning, have brought about serious effects on the air quality pollution of the city.