Particulate Amines in the Background Atmosphere of the Yangtze River Delta, China: Concentration, Size Distribution, and Sources

Abstract

Amines are important for new particle formation and subsequent growth in the atmosphere. Consequently, the processes involved are receiving more attention in recent years. Here, we conduct a field observation in order to investigate the atmospheric particulate amines at a background site in the Yangtze River Delta (YRD) during the summer of 2018. Four amines in PM_2.5, i.e., methylamine (MA), dimethylamine (DMA), diethylamine (DEA), and trimethylamine (TMA), were collected, twice daily and analyzed. During the campaign, our measurements found the concentrations of MA, DMA, DEA, and TMA of 15.0 ± 15.0, 6.3 ± 6.9, 20.4 ± 30.1, and 4.0 ± 5.9 ng m⁻³, respectively, and the four amines correlated well with each other. The concentration of amines appear to be independent of whether they were collected during the day or night. Both MA and DMA exhibited a bimodal size distribution that had peaks at 0.67 and 1.1 µm, suggesting amines preferably distribute on submicron particles. Boundary layer height (BLH), relative humidity, and pH of aerosols were found have a negative relationship with amines, while aerosol liquid water content (ALWC) was found to have a positive relationship with amines. The PMF (positive matrix factorization) source apportionment results showed that the main source of amines in Chongming Island was of anthropogenic origin such as industrial and biomass emission, followed by marine sources including sea salt and marine biogenic sources. Given that the YRD region is still suffering from complex atmospheric pollution and that the knowledge on aerosol amines is still limited, more field studies are in urgent need for a better understanding of the pollution characteristics of amines.

摘要

有机胺在大气新粒子形成和增长过程中起着重要作用,近年来备受关注。为研究长三角地区大气有机胺的污染特征,于2018年夏季在长三角背景点地区进行了颗粒态有机胺的野外观测。结果表明观测期间细颗粒物上甲胺、二甲胺、二乙胺和三甲胺浓度分别为15.0±15.0、6.3±6.9、20.4±30.1和 4.0±5.9 ng/m³,且四种有机胺互相相关。除二甲胺外,其余几种有机胺没有显著的昼夜差别。就不同粒径上浓度而言,甲胺和二甲胺呈双峰分布特征,但主要分布在07–1.1 μm粒径段,说明有机胺更倾向于分布于超细颗粒物上。边界层高度、相对湿度和颗粒物pH与有机胺浓度负相关,颗粒物液态水含量与有机胺浓度正相关。利用PMF源解析初步探究有机胺来源,发现包括生物质燃烧和工业排放在内的人为源是长三角背景点有机胺的主要来源,以海盐和海洋生物源在内的自然源也有较大贡献。目前,对大气有机胺的认知尚不充分,考虑到长三角地区大气污染的严重性和复杂性,希望未来有更多研究关注长三角地区有机胺污染特征。