Long-term response in episodic acidification to declining SO₄^2– deposition in two streams in Nova Scotia

Abstract

Trends in anthropogenically driven episodic acidification associated with extended winter snow melt/rain episodes between 1983 and 1998 were investigated for two streams in Nova Scotia, Canada. The anthropogenic contribution to Acid Neutralization Capacity (ANC) was analysed using the Boreal Dilution Model (Bishop et al., 2000) modified by applying a sea-salt correction to all input hydrochemistry. The anthropogenic contribution to episodic ANC decline was statistically significant and strongly correlated with the decline in acid deposition, which decreased by approximately 50% during the period of record. Sensitivity analysis demonstrated that the BDM can be applied to surface waters with sea-salt contributions although the correction increases model uncertainty. Results of this study demonstrate the effectiveness of reduced emissions in North America in the last decades in decreasing the severity of episodic acidification in the Atlantic region of Canada. Keywords: episodic acidification, acidification recovery, Nova Scotia, snowmelt, winter