The study of NOy serves as an important undertaking in the understanding of both night and daytime atmospheric processes. Two separate datasets were collected over the course of this research using Differential Optical Absorption Spectroscopy. In the first study, NO3 vertical column densities (VCDs) determined using lunar DOAS were analysed in conjunction with surface mixing ratios found using active DOAS on two separate nights during the summer of 2015 to quantify the NO3 vertical profile present at York University. The second study focused on the determination of HONO mixing ratios based on full-day active DOAS measurements performed in a forested region at the AMS13 site near Fort McMurray, Alberta during a joint field study with Environment Canada. The average diurnal profile of HONO found in this study (and various other species) was used for calculating the daytime production of OH radical through HONO photolysis compared to other OH production mechanisms
