An Evaluation of the Contributions of Short and Long Range Pollutant Transport on Southern Ontario's Atmospheric Sulfur Content

Sulfur dioxide (SO2), particle sulfate (p-SO4-2), and total sulfur (SOx) were evaluated at York University, in Toronto, Canada, using a ThermoFisher SO2 analyzer and an Aerodyne Aerosol Mass Spectrometer. These measurements were compared with a dataset from 2002-2020, which demonstrated a downward trend in atmospheric sulfur. Toronto’s atmospheric sulfur decline has plateaued in recent years. Current mean SO2 was 0.37 ppb, p-SO4-2 was 0.60 μg/m3, and SOx was 1.6 μg/m3. There were no significant seasonal or daytime/nighttime differences. The effects of pollutant transport and major contributors to Toronto’s sulfur were determined. Major contributors to SO2 included Hamilton metal refineries, Greater Toronto Area chemical production facilities, the Nanticoke petroleum refinery, and vehicle emissions. Major contributors to p-SO4-2 are Sarnia petroleum and chemical production, Sudbury metal refineries, and long-range transport from the Ohio River Valley. A field study mass-balance determination of Sarnia’s SO2 emissions was estimated at 0.18 tonnes/hr (4,300 kg/day).