FIELD MEASUREMENT EVIDENCE FOR AN ATMOSPHERIC CHEMICAL SOURCE OF FORMIC AND ACETIC-ACIDS IN THE TROPIC

The simultaneous measurements of atmospheric HCOOH, CH3COOH, H2O2, org anic peroxides, HCHO, CH3CHO and isoprene made in the Venezuelan savan nah region, in the wet season (September, 1993) and during the period of high solar irradiation is reported. The average concentrations (in ppbv) between 10:00 and 16:00 were: HCOOH 0.75 +/- 0.32, CH3COOH 0.56 +/- 0.28, H2O2 1.37 +/- 0.48, the total peroxides 1.83 +/- 0.60, HCHO 1.38 +/- 0.43, CH3CHO 0.35 +/- 0.15, and isoprene 2.18 +/- 0.78. A goo d correlation was observed between the concentrations (15 min averages ) of both acids. The acids also correlate with isoprene (the most abun dant olefin in the savannah atmosphere), H2O2 and the total peroxides. HCOOH also correlates well with HCHO and CH3CHO. These results suppor t the hypothesis that significant amount of formic and acetic acids ar e produced in the tropical atmosphere as a result of the oxidation of reactive hydrocarbons.