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Surface measurements of formaldehyde and formic and acetic acids at a subtropical semiarid site in India

1997; American Geophysical Union; Volume: 102; Issue: D15 Linguagem: Inglês

10.1029/97jd00735

2156-2202

Puja Khare, Gur Sumiran Satsangi, N. Kumar, K. Maharaj Kumari, S. S. Srivastava,

Air Quality and Health Impacts

Vapor phase formaldehyde, formic acid, and acetic acid (HCHO, HCOOH, and CH 3 COOH) were measured at Dayalbagh, a suburban site in Agra. The average mixing ratios of formaldehyde, formic acid and acetic acid for the entire data set (N=60) were 0.8±0.5 parts per billion by volume (ppbv), 1.4±0.8 ppbv, and 0.9±0.3 ppbv, respectively. Maximum levels of HCHO were observed between 1500 and 1900 hours (LT) possibly because of an increase in in situ formation up to 1600 hours. The extension of maximum concentration up to 1900 hours was probably due to low rates of HCHO removal as a result of diminished insolation and a decrease in OH concentration. Formic and acetic acids showed elevated levels between 1000 and 1600 hours, probably due to active photochemistry and direct emissions. HCOOH and CH 3 COOH correlated significantly with each other but not with HCHO. This finding suggested the origin of both the acids from the same sources, while HCHO had different pathways. Rates of direct emission, in situ formation, and removal by dry deposition were estimated for both acids. In situ reaction produced more formic acid than acetic acid. Production of acetic acid was seen to be dominated by direct emissions. The production estimates exceed removal by a factor of ≈2.5; these fall within the uncertainty limits.