Atmospheric Nitrate Formation through Oxidation by Carbonate Radical

Abstract

The carbonate radical (CO3 •–) has been proved to be of great significance in the water environment. However, a few studies concerned with its contribution to atmospheric heterogeneous chemistry. Here, we report the pathway for the first time for CO3 •– generation by interfacial photogenerated hole/hydroxyl radical (•OH) transfer between the photoactive component and (bi)­carbonate (CO3 2–/HCO3 –) of mineral dust under atmospherically relevant actinic irradiation. By combining laboratory simulation, nanosecond transient absorption spectroscopy (NTAS), and field observation, we demonstrate that (bi)­carbonate in the atmosphere not only has a pH buffering effect in the uptake of NO2 but more importantly directly participates in the photochemical reactions by generating CO3 •– under irradiation. CO3 •– can play an important role by facilitating nitrite transformation to nitrate, especially under a lower light intensity (15 mW/cm2) and a higher humidity (60% RH). Diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) was used to detect the surface species generated on simulated mineral dust. Under irradiation, the time-dependent reactive uptake coefficient for the first-order reaction of NO2 uptake on simulated mineral dust was found to be 2.817 × 10–8 × e–t/6559. These results highlight the important role of CO3 •– in atmospheric photochemistry, which could act as a reactive radical and influence secondary aerosol formation.

A Novel Pathway of Atmospheric Sulfate Formation Through Carbonate Radical

“…In fact, either CO2 or carbonate salt is able to produce the active CO3 •under the ambient circumstance and increase the oxidative capacity in the atmosphere. Combined with our earlier investigation of CO3 •- (Fang et al, 2021), this https://doi.org/10.5194/acp-2021-564 Preprint. Discussion started: 2 August 2021 c Author(s) 2021.…”

“…However, it is only regarded as an intermediate in tropospheric anion chemistry so far (Graedel and Weschler, 1981a;Dotan et al, 1977;Lehtipalo et al, 2016;Beig and Brasseur, 2000) and its underlying role as an active oxidant for heterogeneous reaction in the atmosphere is barely explored. Very recently, our group observed the promotional effect of CO3 •on atmospheric nitrate formation (Fang et al, 2021). Motivated by this finding, attempts were made to further explore its role in other important atmospherically-relevant reactions.…”

In-depth study of the formation processes of single atmospheric particles in the southeastern margin of Tibetan Plateau

“…S10). Meanwhile, high RH could promote organonitrates formation (Fang et al, 2021;Fry et al, 2014). No obvious change and insignificant correlation between NO3 − and RH during E1, potentially attributed to the decreases of NO2 concentration (3.7 ± 0.4 ppb) in the local atmosphere.…”

Unveiling the Role of Carbonate Radical Anions in Dust‐Driven SO2 Oxidation

“…The surface pH of authentic dust and clay particles was estimated on the basis of charge conservation law, which is extensively applied for the quantification of the water-soluble ions that are not readily or directly determined (Fang et al, 2021;Palmer & Cherry, 1984;T. Zhang et al, 2011).…”

“…In addition, this radical ion can trigger ferrous oxidation, which can strengthen Fe(II)/Fe(III) redox circle in the atmosphere. Accumulating studies demonstrate that $${\mathrm{C}{\mathrm{O}}_{3}}^{.-}$$ gains its importance in atmospheric anion or cation formation, especially those reactions mediated by dust particle surfaces (Fang et al., 2021; Y. Liu et al., 2022), where they efficiently create the localized relatively high pH micro‐aqueous medium (M. Tang et al., 2016; Y. Wang et al., 2005), which goes beyond aqueous droplets and fog of a rather low pH.…”