Acidification and other chemical changes Halifax County lakes after 21 years

Abstract

Sixteen of 23 lakes sampled in 1955 show no sign of significant physical alterations within their drainage basins over a 21‐year interval, so that chemical changes in these lakes can be assumed to reflect changes in atmospheric inputs. In all 16, the pH levels have declined, with greater declines in the higher pH (near neutrality) lakes. After correction for sea‐salt input, concentrations of sodium, magnesium, calcium, potassium, and sulfate show no significant change. Sulfate and hydrogen ions are significantly correlated and both show significant regressions on distance from the major sulfur‐emitting industrial sources in the Halifax area. Although the area as a whole may be subject to an influx of acid pollutants via long distance atmospheric transport, for lakes near Halifax the high acid levels are largely due to local pollution.

The impact of atmospheric deposition on the aquatic ecosystem with special emphasis on lake productivity, Newfoundland, Canada

“…1933 to 1944 this part of the Newfoundland's island was receiving acid precipitation at pH values above 4.5. This observation is in accordance with Watt et al, (1979), who reported no apparent increase in Ca and Mg content in Nova Scotia lakes, which had undergone a significant pH decline over a 21 year period (1955 to 1977). Martin & Brydges (1986), in reviewing long term trends in sulfur emissions in North America, have reported increasing deposition over the 1950's and 1960's to reach a maximum level in the early 1970's, with declining deposition since the mid 1970's.…”

Freshwater acidification research in Atlantic Canada: a review of results and predictions for the future

“…Marine aerosols generated by ocean waves are deposited over terrestrial catchments in Atlantic Canada and elsewhere and contribute ions to drainage waters (Watt et al 1979;Farrell et al 1998). The ionic composition of the marine aerosols has been measured, and is consistent with that in seawater (Junge 1972), so that in assessing marine influence, Cl -measured in freshwaters can be generally used as a quantitative indicator of marine ionic contribution.…”

“…Shaw (1979) showed that Atlantic Canada, the eastern-most part of the North American continent, received low, but measurable acid deposition originating mostly in central Canada, the Ohio Valley and the eastern seaboard of the United States. Later studies by Watt et al (1979Watt et al ( , 1983 and Kerekes et al (1982) showed that some surface waters were very acidic in the region, and that deleterious effects to aquatic ecosystems from acid rain could be measured. The main objectives of aquatic chemistry research in the early part of the 1980s were to (a) follow up on the earlier work of Gorham (1957) and Hayes and Anthony (1958) to better understand how water chemistry in the region differed from that of other regions in North America and Europe, (b) delineate the spatial extent of acidification effects in Atlantic Canada, and (c) assess long-term and seasonal trends in water chemistry to see if changes attributable to acid rain could be detected.…”

Long-term response in episodic acidification to declining SO<sub>4</sub><sup>2–</sup> deposition in two streams in Nova Scotia

“…A complication in assessing ∆ANC (poll) in the two streams is that the sea-salt-correction occasionally produces negative values of Na + during winter episodes. Assuming that the sea-salt-correction of major chemical constituents should be in equal proportions to sea water (Watt et al, 1979; …”

“…Water samples were analysed for major ions, dissolved organic carbon (DOC), and nitrate at an Environment Canada's laboratory in Moncton, New Brunswick (Table 1). Sea-salt-correction was made for all major ions, using ion to chloride ratios (SO (Watt et al, 1979) and assuming that all chloride is of marine origin.…”