Intercomparison of Nitrous Acid Measurement Methods during the SHARP Campaign in Houston

Nitrous acid is a known source of radicals in urban air. During the SHARP campaign, nitrous acid was measured to understand its contribution to the radical levels in Houston. Measurements were carried out using six different methods to analyze the impact of the methods on the measured values. The methods included a pulsed quantum cascade laser (QCL) instrument operated by Aerodyne Inc.; long path DOAS operated by University of California, Los Angeles; long path absorption photometry (LOPAP) instrument operated by University of Miami; long path absorption photometry (LOPAP) instrument operated by University of Houston; mist chamber ion chromatography instrument operated by University of New Hampshire and ion drift-chemical ionization mass spectrometry instrument operated by Texas A&M University. This study compares the measurements done by these instruments and examines the measurement inconsistencies, if there exists any, between instruments or within the instrument.