[en] Highlights: • Horse River Fire had a major air quality impact on the city of Fort McMurray. • PM_2.5 enhancements at the community monitoring sites ranged from a factor of 19–54. • Significant enhancements of NMHC, NH₃, BC, DC, TRS, NOx, and H₂S were observed. • First observations of reduced sulfur compounds (TRS/H₂S) emissions from a wildfire • Fire PM_2.5 profiles were uniform across the network, can be used as a fingerprint. An unprecedented wildfire impacted the northern Alberta city of Fort McMurray in May 2016 causing a mandatory city wide evacuation and the loss of 2,400 homes and commercial structures. A two-hectare wildfire was discovered on May 1, grew to ~ 157,000 ha by May 5, and continued to burn an estimated ~ 590,000 ha by June 13. A comprehensive air monitoring network operated by the Wood Buffalo Environmental Association (WBEA) in and around Fort McMurray provided essential health-related real-time air quality data to firefighters during the emergency, and provided a rare opportunity to elucidate the impact of gaseous and particulate matter emissions on near-field communities and regional air pollution concentrations. The WBEA network recorded 188 fire-related exceedances of 1-hr and 24-hr Alberta Ambient Air Quality Objectives. Two air monitoring sites within Fort McMurray recorded mean/maximum 1-hr PM_2.5 concentrations of 291/5229 μg m^{− 3} (AMS-6) and 293/3259 μg m^{− 3} (AMS-7) during fire impact periods. High correlations (r² = 0.83–0.97) between biomass combustion related gases (carbon monoxide (CO), non-methane hydrocarbons (NMHC), total hydrocarbons (THC), total reduced sulfur (TRS), ammonia) and PM_2.5 were observed at the sites. Filter-based 24-hr integrated PM_2.5 samples collected every 6 days showed maximum concentrations of 267 μg m^{− 3} (AMS-6) and 394 μg m^{− 3} (AMS-7). Normalized excess emission ratios relative to CO were 149.87 ± 3.37 μg m^{− 3} ppm⁻¹ (PM_2.5), 0.274 ± 0.002 ppm ppm⁻¹ (THC), 0.169 ± 0.001 ppm ppm⁻¹ (NMHC), 0.104 ± 0.001 ppm ppm⁻¹ (CH₄), 0.694 ± 0.007 ppb ppm⁻¹ (TRS), 0.519 ± 0.040 ppb ppm⁻¹ (SO₂), 0.412 ± 0.045 ppb ppm⁻¹ (NO), 1.968 ± 0.053 ppb ppm⁻¹ (NO₂), and 2.337 ± 0.077 ppb ppm⁻¹ (NO_X). A subset of PM_2.5 filter samples was analyzed for trace elements, major ions, organic carbon, elemental carbon, and carbohydrates. Sample mass reconstruction and fire specific emission profiles are presented and discussed. Potential fire-related photometric ozone instrument positive interferences were observed and were positively correlated with NO and NMHC.

[en] Increases in reactive nitrogen deposition are a growing concern in the U.S. Rocky Mountain west. The Rocky Mountain Airborne Nitrogen and Sulfur (RoMANS) study was designed to improve understanding of the species and pathways that contribute to nitrogen deposition in Rocky Mountain National Park (RMNP). During two 5-week field campaigns in spring and summer of 2006, the largest contributor to reactive nitrogen deposition in RMNP was found to be wet deposition of ammonium (34% spring and summer), followed by wet deposition of nitrate (24% spring, 28% summer). The third and fourth most important reactive nitrogen deposition pathways were found to be wet deposition of organic nitrogen (17%, 12%) and dry deposition of ammonia (14%, 16%), neither of which is routinely measured by air quality/deposition networks operating in the region. Total reactive nitrogen deposition during the spring campaign was determined to be 0.45 kg ha^-1 and more than doubled to 0.95 kg ha^-1 during the summer campaign. - The reactive nitrogen deposition budget for Rocky Mountain National Park.