Photochemical emissions of HONO, NO<inf>2</inf> and NO from the soil surface under simulated sunlight: Fid-Bau Portal

Photochemical emissions of HONO, NO2 and NO from the soil surface under simulated sunlight

Yang, Wangjin / Yuan, Hua / Han, Chong / Yang, He / Xue, Xiangxin

Abstract Emissions of HONO, NO2 and NO from different soils under simulated sunlight were investigated using a flow reactor at ambient pressure. Enhanced emissions of HONO, NO2 and NO were observed when soils were exposed to the simulated sunlight. NO3 ⁻ and NO2 ⁻ partly contributed to the HONO and NO formations, whereas NH4 ⁺ and NH2OH played minor roles in HONO, NO2 and NO emissions from the soil. The emission flux densities of HONO (F HONO), NO2 ( $F_{N O_{2}}$ ) and NO (F NO) significantly depended on environmental conditions, including irradiation intensity, relative humidity (RH), temperature and pH. F HONO, $F_{N O_{2}}$ and F NO linearly increased with increasing irradiation intensity in the range of 0–320 W/m². Maximum values of F HONO, $F_{N O_{2}}$ and F NO appeared at RH = 55%. F HONO and F NO increased while $F_{N O_{2}}$ decreased with increasing the temperature in the range of 278–338 K. Maximum F HONO and $F_{N O_{2}}$ values appeared at pH = 8 while larger F NO values occurred at pH of 2 and 8. Atmospheric implications about the photochemical emission of HONO from soil contributing to HONO in the atmosphere were also discussed.

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Highlights • Light significantly enhanced HONO, NO2 and NO emissions from soils. • NO3 ⁻ and NO2 ⁻ partly contributed to the HONO and NO emissions from the soil. • HONO, NO2 and NO emission flux densities depended on the environmental conditions.