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

Formic and acetic acids are important contributors to atmospheric acid ity, present in low and subparts per billion by volume (ppbv) range. T his paper presents the results of laboratory and field studies to eval uate the performance of an annular denuder system to collect gas-phase formic and acetic acids. The collection efficiencies for formic and a cetic 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 w ith chloroform added as a biocide have been shown to be stable for sto rage periods of 4 months at 4-degrees-C in the dark. Interference by a ldehydes with measurement of formic acid and acetic acid was determine d to be small. Formic acid concentrations observed in Boston, MA, rang ed between 1.8 and 14.8 ppbv, with limits of detection of 0.7 ppbv. Ac etic acid concentrations observed ranged between 0.8 and 5.4 ppbv, wit h a detection limit of 0.2 ppbv. Formic acid concentrations measured i n outdoor sampling in Uniontown, PA, ranged between not detectable and 44.6 ppbv. Acetic acid concentrations measured ranged between not det ectable and 12.6 ppbv.