Wet and dry deposition of sulphates and nitrates in Eastern Canada: 1979–1982

Abstract

Daily air and precipitation chemistry observations at six rural locations in eastern Canada were analyzed to obtain wet and dry deposition. Dry deposition was calculated from air concentrations using deposition velocities originating from a recent literature review and synthesis exercise involving land use types. Total annual deposition ranges for ${\text{SO}}_{\text{4}}^{\text{ = }}$ from 10 to 86 mmol m⁻² and for ${\text{NO}}_{\text{3}}^{\text{ - }}$ excluding N0₂ contributions to dry deposition from 13 to 62 mmol m⁻². Dry deposition accounts for an estimated 22 and 21% of the total ${\text{SO}}_{\text{4}}^{\text{ = }}$ and ${\text{NO}}_{\text{3}}^{\text{ - }}$ deposition, respectively. For ${\text{NO}}_{\text{3}}^{\text{ - }}$, this fraction increases to 30% if N0₂ concentration to dry deposition is included. There is a marked seasonal variation in total ${\text{SO}}_{\text{4}}^{\text{ = }}$ deposition but not in that of ${\text{NO}}_{\text{3}}^{\text{ - }}$. Both wet and dry deposition are episodic. 20% of daily events deliver between 47 and 70% of the deposition.