文献阅读笔记：有机胺离线分析相关文献泛读合辑

有机胺离线分析相关文献泛读合辑。

Paper 1

Liu-2017-AE: Concentration, size distribution and dry deposition of amines in atmospheric particles of urban Guangzhou, China

阅读笔记：https://chihchao.cn/posts/8f88013f/

Paper 2

Tao-2016-JGR-A: Effects of amines on particle growth observed in new particle formation events

1. In this study, the cutoff size of 1.8 μm is chosen to categorize fine-mode and coarse-mode particles.
2. The major water-soluble species in PM_1.0 were SO₄^2- and NH₄⁺, which together contributed approximately 92% of the total inorganic ionic species. In contrast, the concentrations of the major water-soluble species in the coarse particles (PM_1.8–18) followed the sequence of NO₃^- > SO₄^2- > Ca²⁺ > Na⁺.
3. Regardless of heavy traffic and high NOx emissions, the concentration offine-mode nitrate was less than a tenth that of sulfate. It is interesting to note that 80% of nitrate was in the coarse mode, which is in contrast to the fact that 85% of sulfate was in the fine particles, suggesting different formation mechanisms between secondary sulfate and nitrate aerosols. ... The remarkably lower amount of nitrate in PM_1.8 indicated that the formation of ammonium nitrate during the period of continuous hot weather was suppressed. Due to its low thermodynamic stability, the formation of ammonium nitrate via homogeneous neutralization between ammonia and nitric acid preferentially occurs in ammonia-rich areas and at low temperatures. ... The dominant cations in particles larger than 1.8 μm were Ca²⁺ and Na⁺, suggesting that the coarse-mode nitrate predominantly existed as Ca(NO₃)₂ and NaNO₃. Gaseous HNO₃ prefers to react with alkaline species, such as sea salt and mineral aerosols, when homogeneous reactions with ammonia are unavailable.
4. The equivalent ratio of ammonium to the sum of sulfate and nitrate was much less than one, indicating that PM_1.0 was significantly acidic. ... It should be highlighted that the lower molar ratio (NH₄⁺/(2SO₄^2- + NO₃^-)) in particles larger than 1.8 μm did not cause particulate acidity because Ca²⁺ and Na⁺ rather than NH₄⁺ were the dominant species to balance anions in coarse-mode particles.
5. Six aminiums were detected in these MOUDI samples, among which the group of diethylaminium and trimethylaminium (DEAH⁺ + TMAH⁺) was the most abundant.
6. The maximum concentration for each of the remaining four aminiums was observed in the MOUDI size bin of 0.56–1.0 μm, corresponding to the droplet mode range. This feature suggests that the aqueous uptake of amines greatly contributes to aminium formation. ... The uptake of amines on deliquesced particles is possibly another significant source of particulate amines. ... The aqueous phase of hygroscopic particles provided a favorable environment for amine adsorption and subsequent neutralization reactions with acidic aerosols.
7. In addition to aqueous uptake, laboratory studies showed that particulate aminium salts were formed by acid-base reactions between amines with sulfuric acid and nitric acid at lower RH. ... Our results showed that the concentrations of DEAH⁺ + TMAH⁺, DMAH⁺, and MMAH⁺ in condensation mode (0.1–0.56 μm) were second only to those in droplet mode (0.56–1.8 μm), suggesting that the condensation on preexisting particles was an important mechanism of particulate aminium formation. ...
8. Figure 3b illustrates the size dependence of the mass ratio of total aminiums to NH₄⁺. The coarse-mode aminiums may be sourced from sea salt and crustal aerosols [Ge et al., 2011]. The reactive uptake of HNO₃-aged aerosols was possibly another important mechanism for coarse-mode aminium formation.
9. 2[SO₄^2-] +[NO₃^-] - [NH₄⁺], briefly noted as [H⁺]_Total, is the parameter for the total aerosol acidity contributed by strong acids such as sulfuric and nitric acids. ... A strong linear relationship was found for Aitken mode particles (56–100 nm), indicating that the reactive uptake of amines increased with increasing aerosol acidity. This finding provides clear evidence that aminium salts in Aitken mode particles were predominantly formed through acid-base reactions.
10. The very high level of aminiums (average concentration up to 86.4 ng m^-3 in PM_1.8), together with highly acidic aerosols, provided insight into the frequent NPF events. The high mass ratio of total aminiums to NH4⁺ (>0.2 for PM_0.056) further highlighted the important role of amines in promoting NPF.
11. A spike in the SO₂ concentration was observed in the early afternoon of 26 July, which indicated that a heavily polluted air mass passed through the measurement site. Favored by strong atmospheric oxidation, as indicated from the high O₃ concentration, a large amount of H₂SO₄ would be produced from the oxidation of SO₂. The highly acidic environment would promote the neutralization reaction with amines and ammonia. The average PM_1.0 mass loading was close to 60 μg m³ during the SO₂ episode, which favored condensation growth on preexisting particles while the NPF was suppressed. ... The unexpected enhancement of DEAH⁺ + TMAH⁺ on a nonevent day was attributed to the transportation of an SO₂ plume.