MEASUREMENT AND SPECIATION OF GAS AND PARTICULATE PHASE ORGANIC ACIDITY IN AN URBAN-ENVIRONMENT .1. ANALYTICAL

Organic acids are important contributors to ambient acidity, in both g as and particulate phase. Particulate phase organic acids represent an important fraction of organic particulate matter. This paper presents the results of a field study conducted in Philadelphia, Pennsylvania, during the summer of 1992. The purpose of this study was to measure t he concentrations of gas and particulate phase organic acids. Formic a cid was found to be the most abundant gas phase organic acid, with ace tic and propionic acids detected at lower concentrations. Dicarboxylic acids and even-carbon monocarboxylic acids were found to be present a t relatively high concentrations in the particulate phase; odd-carbon monocarboxylic acids were present at much smaller concentrations. This paper discusses the measurement and analytical techniques used in thi s study. A subsequent paper will address the data analysis and discuss the chemistry and origins of organic acids.