NOz Interference in Measuring NO2 by Molybdenum Oxide Conversion and Chemiluminescence at a coastal site in Nova Scotia, Canada

Abstract

The common method of monitoring NO2 (Nitrogen dioxide) in Canada may be subject to error by interference from other oxides of nitrogen. These other compounds are capable of causing instruments to over-report NO2 concentrations. NO2 is a toxic gas, a reasonable surrogate measure for mixed-pollutant air masses, and one of the pollutants used to calculate Canada's air quality risk communication tool, the AQHI (Air Quality Health Index). It is one of the pollutants commonly modelled in air chemistry models. The level of interference has been reported to be half or more of measured NO2 in a variety of locations, from the Swiss Alps to Mexico City. Using measurements with some unknown amount of positive interference has the potential to introduce artifacts into air quality forecasts or induce model error. It is expected that there may be a significant, albeit poorly characterised, interference in NO2 monitoring in Canada.