Regional precipitation and surface water chemistry trends in southeastern Canada (1983–1991)

Abstract

We analyzed for trends of acidification related variables from 1983 to 1992 in precipitation concentrations and deposition at six sites and surface water concentrations at 111 sites located from central Ontario to eastern Newfoundland. Precipitation showed significantly decreasing H+ and [Formula: see text] concentrations and deposition in central and eastern Ontario and at one of two sites in Québec (deposition only). For Ontario surface water sites, only increasing or stable [Formula: see text] trends were observed, and these had both concomitant increasing and decreasing trends for pH and (or) acid-neutralizing capacity (ANC). Despite a considerable number of lakes showing decreasing [Formula: see text] trends in Québec, pH and ANC also decreased. Québec was also the only region showing extensive evidence of increasing [Formula: see text]. The opposite situation was observed in Atlantic Canada lakes where despite increasing [Formula: see text], the dominant trend observed for pH and ANC was increasing. Trends observed for pH and ANC were used to classify the acidification status of our surface water sites: 60 of the 111 sites were found to be stable (i.e., showing no trends), 17 were continuing to acidify, and 34 were improving.