Heterogeneous photochemical uptake of NO2 on the soil surface as an important ground-level HONO source. (15th February 2021)

• Record Type: Journal Article
• Authors: Yang, Wangjin; Han, Chong; Zhang, Tingting; Tang, Ning; Yang, He; Xue, Xiangxin
• Is Part Of: Environmental pollution. Volume 271(2021)
• Publication Date: 2021-02-15
• Subjects: Nitrogen-containing gases -- Photochemistry -- Organic species -- Product yield -- Environmental conditions; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2020.116289
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Nitrous acid (HONO) production from the heterogeneous photochemical reaction of NO2 on several Chinese soils was performed in a cylindrical reactor at atmospheric pressure. The NO2 uptake coefficient ( γ ) and HONO yield (YHONO ) on different soils were (0.42–5.16) × 10 −5 and 6.3%–69.6%, respectively. Although the photo-enhanced uptake of NO2 on different soils was observed, light could either enhance or inhibit the conversion efficiency of NO2 to HONO, depending on the properties of the soils. Soils with lower pH generally had larger γ and YHONO . Soil organics played a key role in HONO formation through the photochemical uptake of NO2 on soil surfaces. The γ showed a positive correlation with irradiation and temperature, while it exhibited a negative relationship with relative humidity (RH). YHONO inversely depended on the soil mass (0.32–3.25 mg cm −2 ), and it positively relied on the irradiance and RH (7%–22%). There was a maximum value for YHONO at 298 K. Based on the experimental results, HONO source strengths from heterogeneous photochemical reaction of NO2 on the soil surfaces were estimated to be 0.2–2.7 ppb h −1 for a mixing layer height of 100 m, which could account for the missing daytime HONO sources in most areas. Graphical abstract: Image 1 Highlights: Light enhanced or hindered the reduction of NO2 to HONO, relying on soil property. Soil organics were key species for photochemical uptake of NO2 to HONO on soils. Environmental factors led to the variation of NO2 uptake coefficient in 0.5–6 × 10 −5 . HONO yield ranged from 2.8% to 67.6% under various environmental factors. Photochemical NO2 uptake on soils caused a 0.2–2.7 ppb h −1 HONO source strength.