Application of multi-axis differential optical absorption spectroscopy (MAX-DOAS) to Canadian rural and urban sites

A novel technique: Multi-axis differential optical absorption spectroscopy (MAX-DOAS) was used for the first time in urban Canada to gain information on the vertical and spatial distribution of airborne pollutant species. Spectra at several elevation angles were collected at six different sites over the time period August 2005--August 2006 and resolved into differential slant column densities (DSCDs) using the DOAS technique. DSCDs of NO2, O3, HCHO and O4 were analyzed as a function of location, time of day, elevation angle and azimuth using average DSCD values. Correlations were found between daily DSCD averages and independent measurements of the same species. Mixing height information was elicited via radiative transfer modeling for two days, one in an urban environment and the other in a rural environment. The results demonstrate that MAX-DOAS can be used as a low-cost, automated tool to obtain useful information on pollutant variability in multiple dimensions.