Collett’s research interests include pollution processing by clouds and fogs, nitrogen deposition, aerosol chemistry, air quality impacts from unconventional oil and gas development, emissions from wild and prescribed fires, precipitation chemistry and physics, dew chemistry, bi-directional exchange of ammonia between the atmosphere and surface, regional air quality, aerosol impacts on visibility, and instrument development.

Recent studies have characterized (1) emissions of air toxics, ozone precursors, and methane from specific processes (drilling, fracking, flowback and production) associated with unconventional oil and gas development; (2) the increasing contributions of ammonia to reactive nitrogen deposition in the Rocky Mountain region and across the U.S.; (3) contributions of biomass burning to reactive nitrogen and brown carbon; (4) the organic chemistry of clouds and fogs; (5) impacts of oil and gas development on fine particle and haze formation in the Bakken oil patch; (6) the role of dew as a temporary, nighttime reservoir for atmospheric ammonia; and (7) international air quality issues in China and Korea.