Enhanced biomass burning as a source of aerosol ammonium over cities in central China in autumn
Enhanced biomass burning as a source of aerosol ammonium over cities in central China in autumn
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秋季，中国中部城市上空生物质燃烧加剧，成为气溶胶铵的来源
DOI：
10.1016/j.envpol.2020.115278
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发表时间：
2020
影响因子：
8.9
通讯作者：
Xiao Hua-Yun
中科院分区：
文献类型：
--
作者：
Xiao Hong-Wei;Wu Jing-Feng;Luo Li;Liu Cheng;Xie Ya-Jun;Xiao Hua-Yun
大气环境气态氨（NH3）是最丰富的碱性气体，通过与酸性气体反应形成二次气溶胶的关键作用，影响公众健康和气候变化。估算城市大气中氨源的贡献是非常具有挑战性的。稳定氮同位素比（δ15N）测量表明，城市气溶胶NH4+和气态nh3来源于化石燃料燃烧相关（FF）来源，如煤燃烧、nh3滑出和汽车尾气，以及与挥发相关的来源，如农业和城市水挥发。生物质燃烧（BB）来源，特别是住宅生物燃料，可以产生大量的nh3和其他污染物，并可能极大地影响空气质量并导致城市nh3排放增加。本研究在秋季连续采集了中国中部3个城市的pm2.5样本，分析了主要水溶性离子和气溶胶NH4+的δ15N值。接近冬季时，NH4+浓度随温度的降低而升高，而δ15N值则没有这种规律。经同位素分异校正后的贝叶斯模型显示，南昌、武汉和长沙的FF源对秋季气溶胶NH4+的贡献率分别为56.4±17.1%、46.4±18.2%和51.8±14.9%。南昌、武汉和长沙的BB源贡献率分别为34.5±20.4%、46.4±21.4%和40.4±17.4%。我们还发现，从2017年9月到11月，这三个城市的BB气溶胶NH4+的比例都有所增加，这可能是由于季节温度下降导致供暖需求增加所致。此外，BB对南昌的严重雾霾事件（最大pm2.5为205.69 μg/m3）负责。这些发现表明，政府改善空气质量的控制措施除了FF源外，还应包括BB源。
Atmospheric ambient gaseous ammonia (NH3), the most abundant alkaline gas, affects public health and climate change through its key role in the formation of secondary aerosols via reactions with acidic gases. Estimation of the contributions of ammonia sources is very challenging in the urban atmosphere. Stable nitrogen isotope ratio (δ15N) measurements have shown that urban aerosol NH4+and gaseous NH3are derived from fossil fuel combustion-related (FF) sources, such as coal combustion, NH3slip, and vehicle exhaust, and volatilization-related sources, such as agriculture and urban water volatilization. Biomass burning (BB) sources, especially residential biofuel, can produce vast quantities of NH3and other pollutants and may greatly influence air quality and contribute to increased urban NH3emissions. In the present study, we continually collected PM2.5samples at three urban sites in Central China during autumn and analyzed the major water-soluble ions and δ15N values of aerosol NH4+. The concentrations of NH4+increased as the temperature decreased close to winter, whereas the δ15N values did not show this pattern. According to the Bayesian model after isotope fractionation correction, FF sources contributed to 56.4 ± 17.1%, 46.4 ± 18.2%, and 51.8 ± 14.9% of aerosol NH4+in Nanchang, Wuhan, and Changsha, respectively, throughout autumn. The contributions from BB sources were 34.5 ± 20.4%, 46.4 ± 21.4%, and 40.4 ± 17.4% for Nanchang, Wuhan, and Changsha, respectively. We also found the fraction of aerosol NH4+from BB increased in all three cities from September to November 2017, which was likely caused by increased heating demands with the decrease in temperature during the season. Furthermore, BB was responsible for a severe haze event (maximum PM2.5of 205.69 μg/m3) in Nanchang. These findings suggest government controls to improve air quality should include BB sources in addition to FF sources.