使用离子色谱监测长三角地区PM_2.5中的有机胺。

Information for the paper

Title: Chemical composition and sources of amines in PM_2.5 in an urban site of PRD, China

Author: Huang, Shan

Year: 2022

Journal: Environmental Research

Introduction

Gaseous amines, as strong alkaline substances, can entry particulate phase via (i) acid-base reactions with strong acid vapors, (ii) uptake on acidic aerosols through heterogeneous processes, (iii) oxidation reactions to form non-volatile secondary organic aerosols by oxidants such as OH radical and ozone, (iv) direct condensation to existing liquid particles. (De Haan et al., 2011; Ge et al.,2011a; Murphy et al., 2007; Qiu and Zhang, 2013).)
A recent study found that septic system is a potent source of urban gaseous amines in Shanghai (Chang et al., 2021)
Also, amines could distribute in coarse mode via heterogeneous reactions with big particles such as soil dust and sea salt (Liu et al., 2017).

In general, MA was the dominated amine species in PRD urban area, accounting for 81.8% of the mass concentration of all measured amines with a remarkable amount of 243 ± 179 ng/m³ (ranging from 67 ng/m³ to 733 ng/m³). The predominance of MA in urban site of Guangzhou has been observed in previous studies in Guangzhou (Liu et al., 2017), Beijing, Xi’an, Xiamen and HongKong (Ho et al., 2016), as well as at a mountain site in South China (Liu et al.,2018).
As the second most abundant species, DMA contributed 16.5% of total measured amines with an average mass concentration of 49 ± 30 ng/m³, varying from 15 to 111 ng/m³.
This might infer marine emissions were not the major source for amines detected in this study since much higher mass concentration of TMA (280 ± 180 ng/m³) associated with marine air mass have been observed (Chen et al., 2021a; Hu et al., 2018).
while TMA was not detected or reported in Beijing, Xian, Xiamen, Hong Kong and Yangzhou (Cheng et al., 2020; Ho et al., 2016; Shen et al., 2017).
In total, the four detected amine species (Σ_amines) have an average concentration of 297 ± 209 ng/m³ (87–853 ng/m³), and contributed only 0.76 ± 0.33% (0.29–1.62%) of total PM_2.5, or 1.76% of total organic matters (OM) which were calculated by OC multiplying OM:OC ratio (2.0 as reported by Chen et al., 2021b).

It indicates that MA, DMA, and TMA were possibly from the same source or chemical transformation process， while DEA was contributed by different sources or pathways.
It indicates that MA and DMA might be mainly presented as nitrate amine salts and/or sulfate amine salts in particles as ammonium nitrate and ammonium sulfate.
Both MA and DMA varied more in association with NOR (0.37–0.56) rather than with SOR (-0.14–0.15), implying that amines might tend to react with gas-phase HNO₃ or particle phase nitrate to form amine salts via local process in Guangzhou.
This suggests that the amine salts in PM_2.5 in Guangzhou are easy to be scavenged at high wind speed and are not likely contributed by photochemical process.
This implies soil surface could not be fully excluded from the potential sources of amine, since the amine emission of soil was mainly controlled by the temperature

The amines roughly increased with the elevating RH, and similar variations were also observed for individual MA, TMA and DEA species.
It is interesting to find out that the DMA only existed in particle when daily average RH was larger than ~70%.
NPF events likely happened every noon time, which was overlapped with the low RH periods (~40%). The DMA was not observed (or below detection limit) during the NPF events in this study, indicating the NPF events during low RH periods were more likely driven by the lower ambient aerosol condensation sink and/or the oxidation products from photochemistry (Lehtipalo et al., 2018).

Considering that the offline samples in this study are insufficient for receptor models such as positive matrix factorization, a simple multiple linear regression approach is applied here to estimate the sources of amines in Guangzhou.

Liu, F., Bi, X., Zhang, G., Peng, L., Lian, X., Lu, H., Fu, Y., Wang, X., Peng, P.a., Sheng, G., 2017. Concentration, size distribution and dry deposition of amines in atmospheric particles of urban Guangzhou, China. Atmos. Environ. 171, 279–288. https://doi.org/10.1016/j.atmosenv.2017.10.016.
Ho, K.-F., Ho, S.S.H., Huang, R.-J., Chuang, H.-C., Cao, J.-J., Han, Y., Lui, K.-H., Ning, Z., Chuang, K.-J., Cheng, T.-J., Lee, S.-C., Hu, D., Wang, B., Zhang, R., 2016. Chemical composition and bioreactivity of PM_2.5 during 2013 haze events in China, Atmos. Environ. Times 126, 162–170. https://doi.org/10.1016/j.atmosenv.2015.11.055.
Shen, W., Ren, L., Zhao, Y., Zhou, L., Dai, L., Ge, X., Kong, S., Yan, Q., Xu, H., Jiang, Y., He, J., Chen, M., Yu, H., 2017. C1-C2 alkyl aminiums in urban aerosols: insights from ambient and fuel combustion emission measurements in the Yangtze River Delta region of China. Environ. Pollut. 230, 12–21. https://doi.org/10.1016/j.envpol.2017.06.034.