Recent modernisation of an aluminum smelting facility in Kitimat, British Columbia, has resulted in a permitted increase in sulphur dioxide (SO₂) emissions from 27 to 42 tonnes per day. Prior to modernisation, a broad environmental assessment to identify potential impacts focused on modelled atmospheric dispersion and deposition of sulphur (S) throughout the Kitimat region. One major limitation of this investigation was the lack of observational data to evaluate modelled atmospheric S along the smelter’s predominant emission plume. In lieu of this knowledge gap, a network of passive and active air samplers was deployed along the Kitimat Valley to evaluate atmospheric dispersion, conversion, and total S deposition during 2017-2018. The network consisted of ion-exchange-resin columns to capture wet deposition, passive-diffusive samplers to capture ambient SO₂ air concentrations, and portable active samplers equipped with two-stage filterpacks capable of measuring ambient SO₂ and particulate sulphate (pSO₄^2–). Estimated annual wet S deposition ranged from 14.0 – 1.4 kg S/ha/yr with distance from the smelter (~40 km) and exhibited a non-linear decline (logarithmic decline; R²= 0.70) with increased distance. Ambient SO₂ ranged from 10.26–0.76 µg/m³ during the June–October 2017 sampling period and similarly displayed decreasing concentration away from the emissions source. Average pSO₄^2– varied between seasonal exposures, ranging from 0.134, 0.088, 0.184, and 0.255 µg/m³ during June and October 2017, and February and June 2018 respectively. The highest concentrations of pSO₄^2– were observed within the plume path further down-wind from the emissions source.