Lake Recovery in Nova Scotia: A Longitudinal Review of Water Chemistry Data

Abstract

Emission control policies aimed at reducing the emission of sulfur oxides have been effective at reducing acid deposition, thereby allowing lakes to recover from acidification (as indicated by decreasing sulfate and increasing pH and alkalinity). In addition to improvements in pH and alkalinity, increasing dissolved organic carbon (DOC) content has also been observed in lakes recovering from acidification. Using long-term precipitation and lake water chemistry data, this work assessed trends in precipitation and lake water chemistry to evaluate the recovery of NS lakes from acidification. Trend testing revealed that precipitation sulfate decreased by approximately 66% between 1985 and 2016 and that recovery from acidification (decreasing sulfate, increasing alkalinity and pH) has occurred in most of the study lakes. In addition to increasing pH and alkalinity, widespread increases in NOM content (using colour as a proxy) and total phosphorus concentrations were found.