Yu Xu, Wong Yee Ka, Yu Jian Zhen
Division of Environment and Sustainability, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Division of Environment and Sustainability, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China; Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Sci Total Environ. 2023 Nov 25;901:165880. doi: 10.1016/j.scitotenv.2023.165880. Epub 2023 Aug 2.
Organic nitrogen (ON) in atmospheric particles is much less monitored compared to inorganic nitrogen (IN), despite its significant contribution to atmospheric N deposition budget. In this study, we expanded a newly developed instrumental method for IN and ON in PM samples to PM samples. We determined the quantities of ON and IN for paired PM and PM samples collected at an urban coastal site in Hong Kong, southern China over a year. These measurements also allowed the determination of IN and ON abundance in the coarse PM (i.e., PM) by taking the difference between PM and PM. The measurement results show that ON accounted for 27.6 % and 21.1 % of total N in fine and coarse particles, respectively, and was mainly (87.7 %) distributed in the fine mode at the site. The seasonal variation of ON/total N was relatively small in PM (23.6-30.4 %) while considerably larger in coarse PM (4.3-42.1 %). Analysis aided by concurrently measured source indicators revealed that sea spray, biological particle emissions, and dust mixed with anthropogenic pollutants are potentially significant sources of ON in coarse particles. Positive matrix factorization (PMF) source apportionment further revealed that industrial emissions/coal combustion (43.6 %), soil dust emission (16.3 %), fresh sea salt emission (15.2 %), and aged sea salt (24.9 %) are major sources of PM-bound ON at the site. The contributions of industrial emissions/coal combustion and soil dust emission to ON were significantly higher in autumn and winter. Fresh sea salt emissions contributed greater proportions to ON in spring and summer, while ON associated with the aged sea salt source was higher in spring and autumn. These findings have advanced our quantitative understanding of the sources of PM-bound ON, which was scarcely determined in the past. Furthermore, the ON measurement data in fine and coarse particles helps estimate ON deposition, which has been previously under-evaluated.
尽管大气颗粒物中的有机氮（ON）对大气氮沉降收支有重大贡献，但与无机氮（IN）相比，其监测程度要低得多。在本研究中，我们将一种新开发的用于测定PM样品中IN和ON的仪器方法扩展应用于PM样品。我们测定了一年内在中国南方香港一个城市沿海站点采集的成对PM和PM样品中ON和IN的含量。通过计算PM和PM之间的差值，这些测量还能确定粗颗粒物（即PM）中IN和ON的含量。测量结果表明，ON分别占细颗粒物和粗颗粒物中总氮的27.6%和21.1%，且在该站点主要（87.7%）分布在细模态中。PM中ON/总氮的季节变化相对较小（23.6 - 30.4%），而在粗PM中则大得多（4.3 - 42.1%）。同时测量的源指标辅助分析表明，海沫、生物颗粒物排放以及与人为污染物混合的灰尘可能是粗颗粒物中ON的重要潜在来源。正定矩阵因子分解（PMF）源解析进一步表明，工业排放/煤炭燃烧（43.6%）、土壤扬尘排放（16.3%）、新鲜海盐排放（15.2%）和老化海盐（24.9%）是该站点PM结合态ON的主要来源。工业排放/煤炭燃烧和土壤扬尘排放对ON的贡献在秋季和冬季显著更高。新鲜海盐排放在春季和夏季对ON的贡献比例更大，而与老化海盐源相关的ON在春季和秋季更高。这些发现加深了我们对PM结合态ON来源的定量理解，而这在过去几乎未被确定。此外，细颗粒物和粗颗粒物中的ON测量数据有助于估算ON沉降，而此前ON沉降一直被低估。
