Heterogeneous reactions of NO2 with CaCO3–(NH4)2SO4 mixtures at different relative humidities
Item
Title (Dublin Core)
Heterogeneous reactions of NO2 with CaCO3–(NH4)2SO4
mixtures at different relative humidities
mixtures at different relative humidities
Description (Dublin Core)
In this work, the heterogeneous reactions of NO<sub>2</sub> with CaCO<sub>3</sub>–(NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> mixtures with a series of weight percentage (wt %) of (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> were investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at different relative humidity (RH) values. For comparison, the heterogeneous reactions of NO<sub>2</sub> with pure CaCO<sub>3</sub> particles and pure (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> particles, as well as the reaction of CaCO<sub>3</sub> with (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> particles, were also studied. The results indicated that NO<sub>2</sub> did not show any significant uptake on (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> particles, and it reacted with CaCO<sub>3</sub> particles to form calcium nitrate under both dry and wet conditions. The heterogeneous reactions of NO<sub>2</sub> with CaCO<sub>3</sub>–(NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> mixtures were markedly dependent on RH. Calcium nitrate was formed from the heterogeneous reactions at all the RHs investigated, whereas CaSO<sub>4</sub> ⋅ 0.5H<sub>2</sub>O (bassanite), CaSO<sub>4</sub> ⋅ 2H<sub>2</sub>O (gypsum), and (NH<sub>4</sub>)<sub>2</sub>Ca(SO<sub>4</sub>)<sub>2</sub> ⋅ H<sub>2</sub>O (koktaite) were produced depending on RH. Under the dry condition, the heterogeneous uptake of NO<sub>2</sub> on the mixtures was similar to that on CaCO<sub>3</sub> particles with neglectable effects from (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>; the duration of initial stages and the NO<sub>3</sub><sup>−</sup> mass concentrations had a negative linear relation with the mass fraction of (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> in the mixtures. Under wet conditions, the chemical interaction of (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> with Ca(NO<sub>3</sub>)<sub>2</sub> enhances the nitrate formation, especially at medium RHs, while the coagulation of (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> with CaCO<sub>3</sub> exhibits an increasing inhibiting effects with increasing RH at the same time. In addition, the heterogeneous uptake of NO<sub>2</sub> on the mixtures of CaCO<sub>3</sub> and (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> was found to favor the formation of bassanite and gypsum due to the decomposition of CaCO<sub>3</sub> and the coagulation of Ca<sup>2+</sup> and SO<sub>4</sub><sup>2−</sup>. A possible reaction mechanism was proposed and the atmospheric implications were discussed.
Creator (Dublin Core)
Tan, Fang
Tong, Shengrui
Jing, Bo
Hou, Siqi
Liu, Qifan
Li, Kun
Zhang, Ying
Ge, Maofa
Date (Dublin Core)
2018-10-22
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-16-8081-2016
https://acp.copernicus.org/articles/16/8081/2016/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
