Differential Optical Absorption Spectroscopy (DOAS) is a technique that allows for the quantitative detection of trace gases in the atmosphere by spectrally resolving their characteristic absorption features. I will present several studies undertaken with ground-based DOAS spectrometers investigating tropospheric trace gases and their associated chemistry. I will discuss measurements that have been performed at three different sites at Cabauw, Netherlands, at Halifax, Nova Scotia, and at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut using a wide collection of DOAS instruments such as the University of Toronto Ground-Based Spectrometer (UT-GBS) and the PEARL-GBS, as well as two newly deployed instruments: an Airyx Skyspec 1D spectrometer and a Pandora instrument. These instruments have been involved in both campaign-based and long-term deployments from which I will present and summarize intercomparisons of NO₂, glyoxal, and vertical profiling retrievals from the CINDI-3 campaign; NO₂, SO₂, and O₄ measurements from shipping emissions in Halifax; and measurements of gaseous halogen species (BrO and IO) from Eureka discussing their role in Arctic ozone depletion.