MEASUREMENT OF ATMOSPHERIC FORMIC AND ACETIC-ACIDS - METHODS EVALUATION AND RESULTS FROM FIELD STUDIES

Formic and acetic acids are important contributors to atmospheric acidity, present in low and subparts per billion by volume (ppbv) range. This paper presents the results of laboratory and field studies to evaluate the performance of an annular denuder system to collect gas-phase formic and acetic acids. The collection efficiencies for formic and acetic acids by a KOH-coated annular denuder have been determined to be 99.1 % and 98.5 %, with precisions of 1.9 % and 1.2 % and capacities greater than 5.08 and 1.36 mg, respectively. The extracts of samples with chloroform added as a biocide have been shown to be stable for storage periods of 4 months at 4-degrees-C in the dark. Interference by aldehydes with measurement of formic acid and acetic acid was determined to be small. Formic acid concentrations observed in Boston, MA, ranged between 1.8 and 14.8 ppbv, with limits of detection of 0.7 ppbv. Acetic acid concentrations observed ranged between 0.8 and 5.4 ppbv, with a detection limit of 0.2 ppbv. Formic acid concentrations measured in outdoor sampling in Uniontown, PA, ranged between not detectable and 44.6 ppbv. Acetic acid concentrations measured ranged between not detectable and 12.6 ppbv.