合肥市郊夏季PM10浓度及其与能见度的关系

Observation Study on PM_(10) Concentration and Its Relationship with Visibility in Hefei Suburban Area in Summer

2010年8—9月在合肥市郊对ρ(PM10)进行了观测,并分析了其中9种水溶性离子(NO2-、Cl-、NO3-、SO42-、NH4+、Ca2+、Na+、Mg2+、K+)质量浓度.结果表明:采样期间该地区ρ(PM10)日均值为78.9μg/m3,9种水溶性离子的平均质量浓度为18.93μg/m3,占ρ(PM10)的26.6%,表明水溶性组分是PM10的重要组成之一.SO42-、NO3-、NH4+和Ca2+是主要的阴、阳离子,日均质量浓度分别为8.14、4.81、3.46和1.33μg/m3.不同RH(相对湿度)下PM10对能见度的影响不同,RH小于80%时,二者呈显著的线性负相关〔R(相关系数)为-0.80〕;RH大于80%时,二者呈指数负相关(R为-0.48).离子间相关性分析显示,PM10中水溶性离子的主要结合方式为(NH4)2SO4、NH4HSO4、NH4NO3、KCl及K2SO4.采样期间ρ(NO3-)/ρ(SO42-)平均值为0.59,说明在该地区固定源对水溶性组分的贡献大于移动源.另外,扬尘也是PM10重要来源之一.

PM10 was measured from August to September 2010 in a suburb of Hefei,and the water-soluble ions such as NO2-,Cl-,NO3-,SO42-,NH4＋,Ca2＋,Na＋,Mg2＋,K＋ in PM10 were analyzed.The results showed that the average PM10 concentration in summer was 78.9 μg/m3.The mean concentration of the nine ions was 18.93 μg/m3,comprising 26.6% of the PM10.SO42-,NO3-,NH4＋ and Ca2＋ were the major water-soluble ions,with concentrations of 8.14,4.81,3.46 and 1.33 μg/m3,respectively.The relationship between PM10 and visibility was found to vary with the relative humidity.They were linearly correlated（R=-0.80） when RH was less than 80%,and exponentially correlated（R=-0.48） when RH was larger than 80%.The correlation among the ions showed that the water-soluble ions mainly existed in the forms of（NH4）2SO4,NH4HSO4,NH4NO3,KCl and K2SO4.The ratio between NO3-and SO42-（0.59） suggested that the contribution of sulfur-rich point sources was larger than that of mobile source emissions on the ion concentrations in PM10.Additionally,dust was another important source of PM10.