摘要
为系统反映太原市春季PM_(2.5)中无机水溶性离子的特征,采用在线气体/气溶胶监测仪(Marga)分析了太原市2016年3月1日至5月31日期间PM_(2.5)中无机水溶性离子的变化情况,研究表明二次离子(SO_4^(2-)、NO_3^-、NH_4^+)是无机水溶性离子的主要组成部分,它们在监测期间的均值分别为13.7μg·m^(-3)、14.7μg·m^(-3)以及10.4μg·m^(-3),整个观测期间三者的浓度之和(SNA)占总无机水溶性离子值的百分数为81.0%,占PM_(2.5)百分数为68.5%.三者浓度的日变化特征均呈单峰的形式存在,NO_3^-变化略有不同.热力学研究表明,由于NH_4NO_3分解平衡常数(Ke)与观测期间NH_3与HNO_3的浓度积(Km)的不同,导致了不同监测期间NO-3浓度变化不一致.观测期间硫氧化率(SOR)和氮氧化率(NOR)的值都大于0.1,说明太原市大气气溶胶中硫酸盐和硝酸盐主要都是经过转化形成的二次污染物.在典型空气污染过程中,SO_4^(2-)、NO_3^-、NH+4与能见度、相对湿度的变化有很好的对应关系,说明太原市低能见度与二次离子的生成有关.
In order to reflect the characteristics of inorganic water-soluble ions of PM_（2.5）in Taiyuan systematically,the variation characteristics of the inorganic water-soluble ions were measured and analyzed by online gas and aerosol monitoring instrument（ Marga） from March 1 to May 31 in 2016.Results showed that secondary aerosol ions SO4^2-,NO3^- and NH4^＋ were the main components of inorganic water-soluble ions,with the mean values of 13.7 μg·m^-3,14.7 μg·m^-3and 10.4 μg·m^-3during the observation period,respectively. The sum of SO4^2-,NO-3and NH4^＋（ SNA） accounted for81.0% of the total inorganic water-soluble ions during the observation period,and the ratio was68.5% in PM_（2.5）. The diurnal variation of SO4^2-,NO3^- and NH4^＋ showed a single peak. However,NO3^- was slightly different. Thermodynamics analysis indicated that the theoretical equilibrium constant（ Ke） of NH_4NO_3 was different from the observed concentration product（ Km=[NH3]×[HNO3]） in spring,which lead to the different variation of NO3^- in different months. The sulfur oxidation rate（ SOR） and nitrogen oxidation rate（ NOR） were both greater than 0.1 during the observation period,which indicated that both sulphate and nitrate in atmospheric aerosols were mainly secondary pollutants formed by conversion in Taiyuan. In the process of typical air pollution,SO4^2-,NO-3andNH＋4were well correlated with the visibility and relative-humidity,implying the strong association between the low visibility in Taiyuan and the formation of the secondary inorganic ions.
出处
《环境化学》
CAS
CSCD
北大核心
2017年第8期1777-1784,共8页
Environmental Chemistry
