Observations of high rates of NO2-HONO conversion in the nocturnal atmospheric boundary layer in Kathmandu, Nepal

Yong, Yu,1972Chalmers tekniska högskola,Chalmers University of Technology (author)

Nitrous acid (HONO) plays a significant role in the atmosphere, especially in the polluted troposphere. Its photolysis after sunrise is an important source of hydroxyl free radicals (OH). Measurements of nitrous acid and other pollutants were carried out in the Kathmandu urban atmosphere during January-February 2003, contributing to the sparse knowledge of nitrous acid in South Asia. The results showed average nocturnal levels of HONO (1.7+/-0.8 ppbv), NO2 (17.9+/-10.2 ppbv), and PM10(0.18+/-0.11 mg m(-3)) in urban air in Kathmandu. Surprisingly high ratios of chemically formed secondary [HONO] to [NO2] (up to 30%) were found, which indicates unexpectedly efficient chemical conversion of NO2 to HONO in Kathmandu. The ratios of [HONO]/[NO2] at night were found to be much higher than previously reported values from measurements in urban air in Europe, North America and Asia. The influences of aerosol surface, ground reactive surface, and relative humidity on NO2-HONO chemical conversion were discussed. The high humidity, strong and low inversion layer at night, and high aerosol pollution burden in Kathmandu may explain the particularly efficient conversion of NO2 to HONO.

TEKNIK OCH TEKNOLOGIER Annan teknik Övrig annan teknik hsv//swe
ENGINEERING AND TECHNOLOGY Other Engineering and Technologies Other Engineering and Technologies not elsewhere specified hsv//eng
simulated vertical profiles
absorption cross-sections
mass accommodation coefficients
air-water-interface
conversion
mineral dust particles
heterogeneous no2
nitric-acid
differential
nitrous-acid hono
path field-measurements
optical-absorption

Galle, Bo,1952Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)galle (author)
Panday, A.Massachusetts Institute of Technology (MIT),Princeton University (author)
Hodson, E.Eidgenossische Forschungsanstalt fur Wald, Schnee Und Landschaft Eth-Bereichs,Massachusetts Institute of Technology (MIT) (author)
Prinn, R.Massachusetts Institute of Technology (MIT) (author)
Wang, S. (author)
Chalmers tekniska högskolaMassachusetts Institute of Technology (MIT) (creator_code:org_t)

In:Atmospheric Chemistry and Physics: Copernicus GmbH9:17, s. 6401-64151680-73161680-7324

By the author/editor: Yong, Yu, 1972; Galle, Bo, 1952; Panday, A.; Hodson, E.; Prinn, R.; Wang, S.

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