Particle-Phase Photoreactions of HULIS and TMIs Establish a Strong Source of H2O2 and Particulate Sulfate in the Winter North China Plain.
Environ Sci Technol
; 55(12): 7818-7830, 2021 06 15.
Article
en En
| MEDLINE
| ID: mdl-34019409
ABSTRACT
During haze periods in the North China Plain, extremely high NO concentrations have been observed, commonly exceeding 1 ppbv, preventing the classical gas-phase H2O2 formation through HO2 recombination. Surprisingly, H2O2 mixing ratios of about 1 ppbv were observed repeatedly in winter 2017. Combined field observations and chamber experiments reveal a photochemical in-particle formation of H2O2, driven by transition metal ions (TMIs) and humic-like substances (HULIS). In chamber experiments, steady-state H2O2 mixing ratios of 116 ± 83 pptv were observed upon the irradiation of TMI- and HULIS-containing particles. Correspondingly, H2O2 formation rates of about 0.2 ppbv h-1 during the initial irradiation periods are consistent with the H2O2 rates observed in the field. A novel chemical mechanism was developed explaining the in-particle H2O2 formation through a sequence of elementary photochemical reactions involving HULIS and TMIs. Dedicated box model studies of measurement periods with relative humidity >50% and PM2.5 ≥ 75 µg m-3 agree with the observed H2O2 concentrations and time courses. The modeling results suggest about 90% of the particulate sulfate to be produced from the SO2 reaction with OH and HSO3- oxidation by H2O2. Overall, under high pollution, the H2O2-caused sulfate formation rate is above 250 ng m-3 h-1, contributing to the sulfate formation by more than 70%.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Contaminantes Atmosféricos
/
Material Particulado
País/Región como asunto:
Asia
Idioma:
En
Revista:
Environ Sci Technol
Año:
2021
Tipo del documento:
Article
País de afiliación:
China