title: Temporal variation in daily concentrations of ozone and acid-related substances at Saturna Island, British Columbia.
abstract: A multiple linear regression model was used to investigate seasonal and long-term trends in concentrations of ozone (O3) and acid-related substances at the Saturna Island monitoring station in southwestern British Columbia from 1991 to 2000. Statistically significant primary (dominant) cycles with a period of 1 yr were found for O3, sulfur dioxide (SO2), nitric acid (HNO3), and aerosol concentrations of sulfate (SO4(2-)), calcium (Ca2+) and chloride (Cl-). Of these, peak median concentrations occurred during the spring for O3 and Ca2+, during the warmer, drier months (April-September) for SO4(2-) and HNO3, and during the cooler, wetter months (October-March) for SO2 and Cl-. Statistically significant secondary cycles of 6 months duration were seen for concentrations of O3, SO4(2-), HNO3, Ca2+, and Cl-. Daily maximum O3 concentrations exhibited a statistically significant increase over the period of record of 0.33 +/- 0.26 ppb/yr. Statistically significant declines were found for concentrations of SO2, SO4(2-), HNO3, Ca2+, and potassium, ranging from 20 to 36% from levels at the start of the sampling period. Declines in ambient concentrations of SO2, SO4(2-), and HNO3 reflect local declines in anthropogenic emissions of the primary precursors SO2 and NOx over the past decade. Trends in Ca2+ and potassium ion concentrations are in line with a broader North American declining trend in acid-neutralizing cations.
authors.affiliation: Aquatic and Atmospheric Sciences Division, Environment Canada, Vancouver, British Columbia, Canada. roxanne.vingarzan@ec.gc.ca
authors.forename: Roxanne
authors.initials: R
authors.lastname: Vingarzan
authors.forename: Bruce
authors.initials: B
authors.lastname: Thomson
mesh_terms: D015258:Acid Rain; D000143:Acids / Q000032:analysis; D000393:Air Pollutants / Q000032:analysis*; D001955:British Columbia; D017753:Ecosystem; D004784:Environmental Monitoring; D005068:Eutrophication; D010083:Oxidants, Photochemical / Q000032:analysis*; D010126:Ozone / Q000032:analysis*; D010507:Periodicity; D012621:Seasons
chemical_list: D015258:Acid Rain; D000143:Acids; D000393:Air Pollutants; D010083:Oxidants, Photochemical; D010126:Ozone