Comparison of Three Methods for Measurement of Atmospheric Nitric Acid and Aerosol Nitrate and Ammonium

摘要

Three methods for measuring gaseous ambient nitric acid in the low concentration range 0-15 mcg/cum were compared under field conditions in southwestern Ontario during June 1-14, 1982. The methods employed were (1) tunable diode laser absorption, (2) a tungstic acid denuder tube, and (3) a filter pack containing a Teflon-nylon-W41 filter combination operated over 3-hour sampling periods. In general, the three methods measured nitric acid with adequate sensitivity (sub ppb) and they correlated reasonably over the low ambient concentrations considered here. However, there were some notable differences (up to a factor of 2 at night) by the tungstic acid and filter pack methods. These correlated well but again some differences were observed. During the field comparison, particulate nitrate and ammonium were also measured (0-6 mcg/cu m range) by the tungstic acid and filter pack methods. These correlated well but again some differences were observed. (Copyright (c) 1985 Pergamon Press Ltd.)