南京北郊冬春季大气颗粒物中含氮无机水溶性离子组分特征

Characteristic of Water-soluble Azotic Inorganic Ions in Atmospheric Particulate Matters during Winter and Spring in the North Suburb of Nanjing

为了解南京北郊大气颗粒物中含氮二次水溶性离子组分特征,2014年冬春两季使用Anderson 9级采样器对南京北郊大气颗粒物进行分级采样,利用离子色谱仪分析得到了各粒径范围颗粒物中的含氮二次无机组分质量浓度,结合能见度、相对湿度、颗粒物浓度等观测数据探讨了不同天气状况下大气颗粒物中含氮二次水溶性离子组分的含量及其粒径分布特征。结果表明:冬季和春季平均PM_(2.5)质量浓度分别达到了80.81μg·m^(-3)和52.57μg·m^(-3),明显超过二类标准限值。PM_(10)中NO_3^-和NH_4^+表现出较好的一致性,相关系数高达0.92,表明两种离子的来源比较相似;NO_2^-与NO_3^-和NH_4^+均呈现明显的负相关关系。就季节平均而言,冬季NO_3^-和NH_4^+质量浓度明显高于春季,尤其在0.43~2.1μm粒径范围内,这与冬季二次细颗粒物污染加剧有关;其他粒径段的浓度值季节差异不明显。不同能见度下,NO_3^-和NH_4^+质量浓度谱均呈三峰分布;当水平能见度>3 km时,NO_3^-和NH_4^+最大谱峰大多在9.0~10μm粗粒径段;能见度降至3 km以下时,谱最大峰值出现在1.1~2.1μm粒径段。能见度水平越低,NO_3^-和NH_4^+的质量浓度越高,表明随着NO_3^-和NH_4^+浓度增加气溶胶的消光作用有所增强,从而导致能见度降低。霾天细模态中NH_4^+和NO_3^-的浓度较非霾天明显增加,粗模态无明显变化。NO_2^-作为中间产物其性质极不稳定,谱分布也比较复杂,但任何天气状况下均在粗粒径段出现高峰值。

To investigate the water-soluble azotic inorganic ions component characteristics of atmospheric particulate matters,aerosol samples were collected by a9-stage Andersen cascade impactor from January to May in2014in north suburb of Nanjing,andazotic inorganic ions components of different size particulate matter were analyzed using IC(Ion Chromatography).Visibility(VIS),relative humidity(RH)and concentrations of particles were analyzed to explore mass concentration and size distribution ofwater-soluble azotic inorganic ions in different weather conditions.As the results showed,the average mass concentration of PM2.5was higher than the standard values of categoriesⅡand was80.81μg·m-3during winter and52.57μg·m-3during spring.The NO3-mass concentration of PM10were consistent with the NH4+(r=0.92)which indicated these two ions from the same source.There wereobviously negative correlations between NO2-and NO3-(NH4+).The average mass concentrations of NO3-and NH4+during winterwere obviously higher than those of spring,especially in the range of0.43~2.1μm,due to fine particle pollution was serious inwinter.NO3-and NH4+mass concentrations showed a significant increasing trend with the visibility deterioration.The sizedistributions of NO3-and NH4+followed three-peak distribution.The maximum peak of the size distributions most appeared in therange of9.0~10μm when the visibility greater than3km,and the maximum peak appered in the range of1.1~2.1μm when thevisibility less than3km.The NO3-and NH4+mass concentrations of fine particulate were comparatively high during haze days.Thesize distribution of NO2-was more complex,and the coarse mode was dominant in all weather conditions.