摘要
本研究于2018年秋季利用在线气体和气溶胶组分监测仪以高时间分辨率连续测定南京市大气中的气体(主要是NH3)与二次无机气溶胶(主要是NH4+、NO3-和SO42-)浓度,借此研究污染和非污染期城市大气NH3和NH4+的演化规律,进而探讨NH3-NH4+气粒转化过程中的化学机制.结果表明,观测期间NH3和NH4+浓度的平均值(±1σ)分别为(15. 3±6. 7)μg·m-3和(11. 3±7. 8)μg·m-3,且日变化在污染和非污染事件中呈现出显著的差异.综合在线观测的NH3和NH4+浓度数据,通过计算潜在源贡献因子,分析了NH3和NH4+的潜在贡献源区在重污染过程受长距离污染传输影响较小,证明城市也是NH3排放的重要热点地区.进一步分析发现,NH3-NH4+的气粒转化是影响NH3和NH4+日变化的主要驱动因子.具体体现在:低温、高湿(温度在7. 5~12. 5℃,湿度在50%~90%)时,NH3和NH4+的气固转化速度较快,NH3与酸性物质反应生成更多的NH4+,使得(NH4)2SO4和NH4NO3的形成从而导致污染事件的加剧.研究结果有助于厘清城市大气NH3的来源和转化机制及其对颗粒物的潜在贡献.
In this study,hourly mass concentrations of atmospheric gases(mainly NH3)and secondary inorganic aerosols(mainly NH4+,NO3-,and SO42-)in Nanjing City were continuously measured during the fall of 2018 by an online gas and aerosol chemical component monitor.The dataset was used to investigate the variation characteristics of ambient NH3 and NH4+during polluted and nonpolluted periods,and to explore the potential chemical mechanism during gas-to-particle conversion between NH3 and NH4+.The results show that throughout the sampling period,the mean values(±1σ)of the mass concentrations of NH3 and NH4+were(15.3±6.7)μg·m-3 and(11.3±7.8)μg·m-3,respectively,and that their diurnal profiles were distinct between pollution and nonpollution periods.Analysis of the potential contribution sources indicated that local contributions exceeded long-range transport as the dominant source of measured NH3 and NH4+,suggesting that urban areas can be hotspots of NH3 emissions.Further in-depth analysis revealed that the process of gas-to-particle conversion was the main driving force with respect to controlling diurnal variations in NH3 and NH4+.Specifically,pollution episodes were characterized by low temperature(7.5-12.5℃)and high humidity(50%-90%)meteorological conditions.These conditions tended to accelerate the reaction rate of gas-to-particle conversion and facilitate the formation of aerosol ammonium,leading to pronounced(NH4)2 SO4 and NH4 NO3 increases during pollution events.These findings clarify the sources of NH3 in the urban atmosphere and its potential contribution to the formation of particulate matter.
作者
邵生成
常运华
曹芳
林煜棋
范美益
谢锋
洪一航
章炎麟
SHAO Sheng-cheng;CHANG Yun-hua;CAO Fang;LING Yu-qi;FAN Mei-yi;XIE Feng;HONG Yi-hang;ZHANG Yan-lin(Yale-NUIST Center on Atmospheric Environment,International Joint Laboratory on Climate and Environment Change(ILCEC),School of Applied Meteorology,Nanjing University of Information Science&Technology,Nanjing 210044,China;Key Laboratory of Meteorological Disasters(CIC-FEMD),Nanjing University of Information Science&Technology,Nanjing 210044,China)
出处
《环境科学》
EI
CAS
CSCD
北大核心
2019年第10期4355-4363,共9页
Environmental Science
基金
国家重点研发计划项目(2017YFC0210101)
国家自然科学基金项目(91644103,41761144056,41705100)
江苏省自然科学杰出青年基金项目(BK20180040)
江苏省高校自然科学基金项目(17KJB170011)
关键词
氨气
铵根
污染事件
气粒转化
潜在源贡献因子法(PSCF)
NH3
NH4+
pollution episode
gas to particle conversion
potential source contribution function(PSCF)
