摘要
研究PM2.5中NO-3、NO-2、NH+4及其气态前体物HNO3、HNO2、NH3的浓度特征和气-粒平衡关系,对深入认识PM2.5的来源及控制因素具有重要意义.因此,本文利用2012年6—7月在青岛采集的denuder和PM2.5大气样品,分析了其中气态和颗粒态氮组分的浓度.结果发现,青岛大气中HNO3、HNO2和NH3浓度分别为(0.80±0.79)μg·m-3、(0.49±0.59)μg·m-3和(4.71±4.03)μg·m-3,PM2.5中NO-3、NO-2和NH+4的浓度分别为(7.50±9.00)μg·m-3、(0.07±0.02)μg·m-3和(8.23±5.57)μg·m-3.HNO3气体浓度的昼夜变化具有统计意义上的显著差异,白天平均为1.16μg·m-3,高于夜晚的0.44μg·m-3,但其他氮组分无显著昼夜差异.观测期间,青岛大气为富氨环境,PM2.5中NH+4主要以(NH4)2SO4的形式存在,NO-3生成主要受HNO3的限制.利用ISORROPIA II热力学平衡模型探讨了青岛PM2.5中氮组分的控制因子,通过敏感性实验发现,颗粒态NO-3和NH+4分别对总HNO3(TN)和总H2SO4(TS)的变化响应敏感,而对总NH3(TA)的变化响应不敏感,这暗示了减少大气中TN和TS而不是TA对降低青岛PM2.5浓度更有效.
Reactive nitrogen compounds consist of an important part of PM2.5and their gas-particle partitioning are usually associated with thermodynamic equilibrium.Characterization of NO-3,NO-2and NH+4concentrations in PM2.5and their partners(HNO3,HNO2 and NH3) in gas phase are important in improving understanding of source apportionment of PM2.5and determining factors controlling their partitioning in PM2.5.In this study,these gas and particulate species were collected in Qingdao from June to July 2012 using a PM2.5sampler equipped with two denuders.The averaged concentrations of HNO3,HNO2 and NH3were(0.80±0.79) μg·m-3,(0.49±0.59) μg·m-3and(4.71± 4.03) μg·m-3,respectively while they were(7.50±9.00)μg·m-3,(0.07±0.02) μg·m-3and(8.23±5.57) μg·m-3for NO-3,NO-2and NH+4in PM2.5.We also found that HNO3 showed statistically significant diurnal variation with higher concentration(1.16 μg·m-3) during daytime and low concentration(0.44 μg·m-3) at night,but there were no significant difference for other species between daytime and nighttime samples.During the study period,NH3 was rich and NH+4in PM2.5was mainly present in the form of(NH4)2SO4.The analysis results suggested that formation of NO-3were likely determined by availability of HNO3.To further explore the control factors of these species in PM2.5,the thermodynamic equilibrium model of ISORROPIA II was used.Through sensitivity analysis of single component,we found that formation of NO-3and NH+4was sensitive to the changes in total HNO3(TN) and total H2SO4(TS) respectively,and less sensitive to the change in total NH3(TA).This implies that reducing TN and TS rather than TA appears to be more effective in lowering mass concentrations of PM2.5 in Qingdao.
出处
《环境科学学报》
CAS
CSCD
北大核心
2014年第11期2869-2877,共9页
Acta Scientiae Circumstantiae
基金
国家自然科学基金(No.41176097)
国家重点基础研究发展计划(973)项目(No.2011CB409802)~~
