文献阅读笔记：矿尘气溶胶相关文献泛读合辑

矿尘气溶胶相关文献泛读合辑。

因为遇到一些有关矿尘气溶胶的问题，最近一段时间都在看这方面的相关文献。前几日刚看完 Sullivan-2007-ACP 这篇文章，因文章太长，信息量过大，加之生活上的种种因素，以致累计下来在这篇文章上花费了将近两周的时间。虽然收获颇丰，但也对自己的计划安排产生了较大干扰，而且文中能对我解决眼下困难所提供的帮助也仅有那么几点。思来想去，决定改变一下阅读策略。文献繁多，逐一精读怕是一辈子也读不完，适当结合泛读，提纲挈领的总结主旨要义与创新点，不失为一种聪明的做法。

Paper 1

Ma-2021-EST: Comprehensive Study about the Photolysis of Nitrates on Mineral Oxides

1. The heterogeneous reactions of reactive nitrogen species on mineral dust have been recognized as a significant sink of NO_x and HNO₃. Consequently, mineral dust mixing with nitrate is ubiquitous in the atmosphere. The average lifetime of mineral dust in the troposphere is about a few days or weeks, which can be transported to thousands of kilometers or more, having an important impact on atmospheric chemistry globally. When passing through the industrial or urban regions with high NO_x concentration, the heterogeneous reaction on mineral particles leads to their mixing with nitrate. The nitrate aged mineral dust can export NO_x in remote areas with low NO_x concentration through the photolysis renoification process, which could then affect the regional air quality.
2. The results in the present study indicate that the photolysis of nitrate can be accelerated under complex air pollution conditions with the coexistence of mineral dust and high concentrations of NH₃ and SO₂, for example, in the North China plain. Thus, the NO_x migration and transformation accompanied by mineral dust transportation and its impact on regional and global atmospheric environment are worthy of further study.
3. TiO₂ was found much more reactive than Al₂O₃ and SiO₂ with both NO₂ and HONO as the two major photolysis products. The yields of NO₂ and HONO depend on the cation basicity of the nitrate salts or the acidity of particles. As such, NH₄NO₃ is much more productive than other nitrates like Fe(NO₃)₃, Ca(NO₃)₂, and KNO₃. It is found that the alkalinity of cation and coexistence of SO₂ and H₂O are important factors affecting the observed production rates of NO₂ and HONO in the photolysis of nitrates on mineral dust containing TiO₂. SO₂ and water vapor promote the photodegradation by increasing the surface acidity due to the photoinduced formation of H₂SO₄/sulfate and H⁺, respectively. O₂ enables the photo-oxidation of NO_x to regenerate nitrate and thus inhibits the NO_x yield.
4. In addition to NH₄NO₃, there are other types of nitrates in the atmosphere. When the concentration of ammonia in the air is insufficient or the concentration of sulfuric acid is high, the conversion of gaseous HNO₃ to NH₄NO₃ will be inhibited. At this time, the condensation of HNO₃ on mineral particles could result in the formation of various nitrate species, such as Ca(NO₃)₂, KNO₃, and Fe(NO₃)3 on mineral dust.
5. Ammonium is an important chemical to neutralize sulfate and nitrate in the atmosphere. The ratio of the equivalents of ammonium to the sum of sulfate plus nitrate is always close to one in PM_2.5 samples, indicating that nitrate mainly exists in the form of ammonium nitrate. While in ammonium-poor samples, some metal ions (e.g., Ca²⁺,K⁺,Fe³⁺) in the crystal may be involved in the neutralization of sulfate and nitrate.

Paper 2

Jia-2021-JGR-A: Heterogeneous Reaction of CaCO₃ With NO₂ at Different Relative Humidities: Kinetics, Mechanisms, and Impacts on Aerosol Hygroscopicity

1. During transport, mineral dust particles may undergo heterogeneous and multiphase reactions with trace gases, such as nitrogen oxides (NO_x). Heterogeneous reaction of mineral dust with NO₂, an important nitrogen oxide in the troposphere, may contribute significantly to the formation of aerosol nitrate and HONO (an important precursor of OH radicals), and could thus affect the formation of O₃, and secondary aerosols.
2. Mineral dust is very complex and contains a variety of minerals, among which calcite (CaCO₃) is abundant and reactive. ... The hygroscopicity of unreacted CaCO₃ is very low. Heterogeneous reactions of CaCO₃ with acidic trace gases produce more soluble and hygroscopic specie (for example, Ca(NO₃)₂). This is supported by a number of field studies which found that some Ca-containing dust particles in the troposphere may exist as aqueous droplets, instead of solid particles as they were when freshly emitted. Laboratory work also showed that heterogeneous reactions with acidic trace gases could significantly enhance hygroscopicity of CaCO₃ and authentic mineral dust particles.
3. The change in nitrate with reaction time, can be used to calculate the average pseudo-first-order formation rate of nitrate (k_net, s^-1) in a given period, which is equal to the gas-particle reactive collision frequency: k_net = d[NO₃^-] / dt. The reactive uptake coefficient of NO₂, γ(NO₂), defined as ratio of the reactive collision frequency to the total collision frequency, can thus be determined: γ(NO₂) = k_net / Z. The total collision frequency between NO₂ molecules and particles, Z, can be calculated using: Z = 0.25·A_s·[NO₂]·c(NO₂). where c(NO₂) is the average molecular speed of NO₂ (37,043 cm s⁻¹ at 298 K), and [NO₂] is the NO₂ concentration (molecule cm⁻³). The surface area of CaCO₃ particles available for NO2 uptake, As, is equal to the mass (∼5 mg) of CaCO₃ on the filter multiplied by its BET surface area (2.18 m²/g), assuming that all the CaCO₃ particles on the filter are available for NO₂ uptake.
4. When NO₂ concentration was ∼10 ppmv (∼2.5×10¹⁴ molecule cm⁻³), CaCO₃ showed very low reactivity toward NO₂ at < 1% RH, and γ(NO₂) was estimated to be < 2 × 10⁻⁸; consequently, no significant change in hygroscopicity of CaCO₃ particles was observed after reaction with NO₂ for 24 h at < 1% RH, as the amount of nitrate formed was very limited.
5. Increase in RH to 20% or higher would substantially promote heterogeneous uptake of NO₂ onto CaCO₃, and no surface saturation was observed after reaction for 24 h; the average γ(NO₂) was determined to be (1.21±0.45)×10⁻⁷, independent of RH (20%–80%) and reaction time (3–24 h).
6. We found that during heterogeneous reaction with NO₂ at 20%–80% RH, reacted CaCO₃ took up considerable amounts of water due to the formation of nitrate, and therefore would be covered by a deliquesced Ca(NO₃)₂/H₂O layer, which further drove NO₂ uptake via heterogeneous hydrolysis. ... This provides further support to our proposed mechanism that heterogeneous reaction of NO₂ with CaCO₃ at elevated RH is driven by heterogeneous hydrolysis of NO₂ in the deliquesced layer formed on CaCO₃ particles.
7. It should be pointed out that NO₂ concentrations (2.5–10 ppmv) used in our study were significantly higher than those in the troposphere. ... Therefore, one may conclude that essentially no change (or slight increase) in γ(NO₂) was observed when NO₂ concentrations were decreased from ∼10 to ∼2 ppmv (by a factor of five).
8. In addition, although concentrations of HNO₃ and N₂O₅ in the troposphere are lower than NO₂, their heterogeneous reactivity toward mineral dust is much higher (Crowley et al., 2010); as a result, heterogeneous reactions of HNO₃ and N₂O₅ may substantially increase hygroscopicity of CaCO₃ particles and should be investigated in future.

Paper 3

Hrdina-2021-ACP: The role of coarse aerosol particles as a sink of HNO₃ in wintertime pollution events in the Salt Lake Valley

1. During the two persistent cold-air pool (PCAP) events captured, the fine particulate matter was dominated by secondary NH₄NO₃. The comparison of total nitrate (HNO₃ + PM_2.5 NO₃⁻) and total NH_x (NH₃ + PM_2.5 NH₄⁺) showed NH_x was in excess during both pollution events. However, chemical composition analysis of the snowpack during the first PCAP event revealed that the total concentration of deposited NO₃⁻ was 2.8 times larger than that of deposited NH₄⁺, implying there is additional NO₃^- that is not observed by PM_{2.5 P}NO₃^- and gas-phase HNO₃ measurements alone. Daily snow composition measurements showed a strong correlation between NO₃⁻ and Ca²⁺ in the snowpack.
2. Taken together, these observations imply that atmospheric measurements of the gas-phase and fine-mode particle nitrate may not represent the total burden of nitrate in the atmosphere, implying a potentially significant role for uptake by coarse-mode dust.
3. Using the NO₃^-:NH₄⁺ ratio observed in the snowpack to estimate the proportion of atmospheric nitrate present in the coarse mode, we estimate that the amount of secondary NH₄NO₃ could double in the absence of the coarse-mode sink.
4. The detection of non-volatile cations (_PNa⁺, _PK⁺, _PCa²⁺, and _PMg²⁺) in PM_2.5 by the AIM-IC suggests the presence of mineral dust and/or salt during PCAP pollution events, which can potentially impact the availability of HNO₃. This is due to the reactive uptake of HNO₃ onto NaCl— and CaCO₃—containing particles, which can be predominantly found in the coarse mode. This can introduce a permanent sink for HNO₃.