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. 2022 Nov 17;6(11):2666-2672.
doi: 10.1021/acsearthspacechem.2c00221. Epub 2022 Oct 21.

Reactive Uptake of Gas-Phase NO2 by Urban Road Dust in the Dark

Zoë M Golay  1 , Stephanie H Jones  1   2 , D James Donaldson  1   3
Affiliations

Reactive Uptake of Gas-Phase NO2 by Urban Road Dust in the Dark

Zoë M Golay et al. ACS Earth Space Chem. .

Abstract

Road dust constitutes a prominent source of anthropogenic particulate matter, making its heterogeneous interactions with common atmospheric gas-phase compounds important. Here, we show that three distinct samples of urban road dust-including dust samples collected from city streets in summer and winter, and an urban park in summer-react with NO2 in the dark, forming NO and surface nitrite. The loss of NO2 ranged from ∼2 to 13% of its gas-phase concentration and scaled with its concentration as well as with the mass of the road dust sample. The uptake of NO2 by the winter dust was ∼4 times greater than that seen from summer street dust, which was in turn greater than that by the park dust. The conversion ratio of NO2 → NO ranged from 0.06 to 0.8 NO produced per NO2 lost and was greatest for the summer park dust. Exposure of the summer road dust to NO2 roughly doubles the concentration of inorganic nitrite anion in the dust but does not produce nitrate. The formation of NO and photolabile nitrite products means that heterogeneous NO x reactions occurring on the surface of road dust in the dark could have wide implications for the oxidative potential of urban areas.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
NO2 (orange; left axis) and NO (blue; right axis) concentrations when 1.0 g of road dust was exposed to a 50 ppb NO2 gas at 50% RH. An uptake of NO2 and a simultaneous release of NO were observed when road dust was put into contact with the gas flow. Yellow-highlighted area indicates the time at which the sample was in contact with NO2, while gray-highlighted area indicates no contact. Note that the NO and NO2 scales are different on their respective axes.
Figure 2
Figure 2
Changes in NO2 (orange, left axis) and NO (blue, right axis) concentrations when 1.0 g of HS road dust was exposed to 35–150 ppb NO2 at 50% RH.
Figure 3
Figure 3
Changes in NO2 (orange, left axis) and NO (blue, right axis) concentrations when 0.5–3.0 g of HS road dust samples was exposed to 50 ppb NO2 at 50% RH.
Figure 4
Figure 4
Changes in NO2 (orange) and NO (blue) concentrations when 0.5 g of SD road dust was exposed to 50 ppb NO2 at 50% RH. A clear increase in the magnitude of the NO changes with increasing exposure of NO2 to the dust can be seen, while the magnitude of the NO2 changes remains constant. Yellow-highlighted areas indicate the times at which the sample was in contact with NO2, while gray-highlighted areas indicate no contact.
Figure 5
Figure 5
Changes in NO2 (orange, left axis) and NO (blue, right axis) concentrations when 1.0 g of HP road dust was exposed to 50 ppb NO2 at 50% RH. The NO concentration initially spikes when the gas is first diverted into the chamber but quickly stabilizes. Yellow-highlighted area indicates the time at which the sample was in contact with NO2, while gray-highlighted area indicates no contact.
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