摘要
NH_(3)是PM_(2.5)重要前体物,并影响其理化性质.基于2021年12月至2022年2月江苏常州NH_(3)、SO_(2)、NO_(2)、PM_(2.5)及其水溶性离子在线观测,结合热力学平衡模型计算气溶胶酸度和气溶胶含水量(AWC),分析了富氨条件下NH_(3)-NH_(4)^(+)转化对AWC、酸度及二次反应的影响.结果表明,2021年冬季常州为富氨,富余程度随PM_(2.5)浓度升高而加强,NH_(4)^(+)以NH_(4)NO_(3)和和(NH_(4))_(2)SO_(4)为主,多数时段有少量NH_(4)Cl.气溶胶呈中等酸度,pH均值4.2±0.4,与大气NH_(3)浓度正相关,pH值变幅随污染升级收窄趋中至4~5之间;AWC随湿度和颗粒物二次离子浓度升高而指数级攀升,主要由NH_(4)NO_(3)、(NH_(4))_(2)SO_(4)和NH_(4)Cl吸湿贡献,占比分别为58.5%、18.4%和8.3%,污染条件下NH_(4)NO_(3)主导颗粒物吸湿增长.NH_(3)-NH_(4)^(+)促进SO_(2)非均相反应和NO_(3)^(-)均相反应生成.因富氨环境,需降低30%以上NH_(3)方可影响pH值和含水量等理化性质.该结果对理解二次反应影响、支撑当地空气质量改善提供了参考.
Ammonia(NH_(3))is an important alkaline reactive nitrogen,which,as a precursor of fine particulate matter,raises public health issues.In this study,online NH_(3),SO_(2),NO_(2),PM_(2.5),and its water-soluble inorganic ions were detected to deduce the influence of NH_(3)on aerosol liquid water content(AWC)and aerosol pH,including the formation of water-soluble secondary ions in PM_(2.5)in winter in Changzhou,an ammonia-rich city in the Yangtze River Delta area in winter.The results showed that NH_(4)^(+)mainly existed in the form of NH_(4)NO_(3)and(NH_(4))_(2)SO_(4),and the remaining NH_(4)^(+)existed as NH_(4)Cl.Owing to the NH_(3)-NH_(4)^(+)buffer system,the aerosol pH values were found at 4.2±0.4,which was positively correlated with the NH_(3)content.The aerosol pH value variation narrowed with the increase in PM_(2.5)concentration and tended to be between 4 to 5.AWC increased exponentially with the increase in humidity and SNA content,among which NH_(4)NO_(3),(NH_(4))_(2)SO_(4),and NH_(4)Cl contributed 58.5%,18.4%,and 8.3%,respectively,due to their hygroscopicity.Aerosol pH,AWC,and NH_(3)-NH_(4)^(+)conversion promoted the gas-to-particle conversion of SO_(2)and NO_(2).In Changzhou,rich NH_(3)-NH_(4)^(+)were found to maintain relatively high pH values,push up AWC,and promote the heterogeneous reaction of SO_(2),whereas NO_(3)-generation was dominated by a homogeneous reaction,which was accelerated by NH_(3).According to the simulation results,relatively noticeable changes in aerosol pH and AWC could be found by the reduction of up to 30%of NH_(3).
作者
余益军
庄旻
王振
李锴基
杨卫芬
YU Yi-jun;ZHUANG Min;WANG Zhen;LI Kai-ji;YANG Wei-fen(Jiangsu Changzhou Environmental Monitoring Center,Changzhou 213004,China)
出处
《环境科学》
EI
CAS
CSCD
北大核心
2024年第8期4493-4501,共9页
Environmental Science
基金
常州科技计划项目(CE20225068)。
