Organic versus anthropogenic acidity in tributaries of the kejimkujik watersheds in Western Nova Scotia

Dilute waters (Ca = 0.3 to 0.8 mg L^?1) respond by depressed pH levels throughout the year to existing atmospheric wet deposition of sulphate (20 kg ha^?1yr^?1).This occurs in southwest Nova Scotia particularly during the cold, wet season when runoff is high. Colored waters of similar Ca levels receiving runoff from peaty catchments exhibit pH values one unit lower (4.7 to 4.1) than those of catchments of similar Ca levels but free from peat deposits (pH > 5.3). In colored streams sulphate and organic anions show opposing cyclic patterns while the negative gran alkalinity is the near mirror image of sulphate. Sulphate anion peaks during the high spring discharge when the organic anion concentration is lowest. Sulphate suddenly drops during the summer months during periods of high evapotranspiration, low water table and runoff, when the concentration of organic anions is highest. Both Al and Fe follow cyclic patterns similar to that of the organic anions while H⁺ reflects that of the sulphate anion. Hydrogen ion concentration is always higher than that of sulphate in very colored waters, particularly during the summer months when organic anion concentrations are very high. Analysis of data in the tributaries in the Kejimkujik watersheds indicates that while considerable organic acidity is present in colored waters, anthropogenic sulphate further increases the free acidity of these waters, particularly at times of high discharge.     

Meteorological characteristics of large acidic deposition events at Kejimkujik,Nova Scotia

The characteristics of acidic deposition at Kejimkujik National Park, a rural site in south-central Nova Scotia, were determined for the period from May 1979 to December 1983. The acidifying pollutants investigated were H⁺, sulphate ion and nitrate ion. Thirty per cent of the total annual amount of acidifying pollutants deposited by precipitation at Kejimkujik was deposited by only about 8% of the precipitation events during the year. These occasions of large deposition are referred to as episodes and occurred, on average, about five times per year, usually between March and November. The precipitation events that produced episodes were almost always rain events. The major meteorological feature producing deposition episodes at Kejimkujik is the sequence of a large high pressure area from mid-continent moving south of Nova Scotia, producing a prolonged southwesterly to westerly flow over the site, and then a weak frontal system, usually from south of the Great Lakes region, bringing moderate amounts of precipitation to the site. Since deposition episodes were almost always preceded by the above sequence of events, the ability to predict episodes was investigated. The results indicate that many “false alarms” could be anticipated because this sequence also occurs for non-episodes.     

Changes in Freshwater Acidification Trends in Canada's Atlantic Provinces: 1983–1997

Sixty-three lakes were sampled semi-annually for acid precipitation – related variables in Canada's Atlantic Provinces,Nova Scotia and Newfoundland from 1983 to 1997. A further 31 sites were sampled beginning in 1989 in Nova Scotia. We analyzedthe water chemistry data for trends in pH, acid neutralization capacity, sulfate and base cations using the whole data set for the original 63 sites and the most recent eight years' data for all sites. We also analyzed acid deposition at two CAPMoN precipitation chemistry sites located at the two extremes of thesampling region for trends. We found that hydrogen deposition decreased by 20% in Newfoundland and 30% in Nova Scotia, and sulfate decreased by 36 and 34%, respectively. Sulfate and basecations in lake waters showed decreases as expected, though lakeacidity and acid neutralization capacity did not show improvements. The conflicting trends in chemical variables suggest that though anthropogenically-induced weathering is diminishing in this region, conditions have not returned to `natural' background conditions.     

Precipitation and streamwater chemistry from undisturbed watersheds in the cascade mountains of Oregon

Long-term records of precipitation and streamwater chemistry are rare; such records from forested watersheds relatively free of acidic deposition are even rarer. Precipitation and streamwater chemistry have been measured on two undisturbed forested watersheds at the H. J. Andrews Experimental Forest located on the western slopes of the Cascade Mountains of Oregon. Data from one watershed spans the period 1973–1985, the other 1969–1985. The mean annual pH of precipitation was 5.5 with a range of 4.7 to 6.0. HCO₃ ^? was the dominant anion; Ca²⁺ and Na⁺ were the dominant cations. The mean annual pH of streamwater was 7.3, and was dominated by HCO₃ ^? and Ca²⁺. These data contrast sharply with data from other calibrated watersheds in the north Cascade Mountains of Washington and British Columbia, and with data from New Hampshire and North Carolina where pH of precipitation averages 4.14 and 4.43, respectively, with SO₄ ^2? the dominant anion.     

A summary of the impact of acid rain on atlantic salmon (Salmo salar) in Canada

Within the present North American range of Atlantic salmon, severe acid rain effects are limited to the Southern Upland area of Nova Scotia. In the Southern Upland, long range transport of H₂SO₄ has caused many rivers to decline in pH to the point where their Atlantic salmon stocks have been destroyed or much diminished. Chemical records show a declining pH trend in N.S. rivers since the early 1950s. Eighty % of the annual variation in H⁺ concentration can be accounted for by a multiple linear regression model on excess sulphate, total Al and organic anions. It is technically feasible to restore the acidified salmon habitat by the addition of limestone; the total cost of mounting a liming program to restore the lost habitat has been estimated at $4.75 × 10⁶ yr^?1. The pre-acidification Atlantic salmon production capacity of the Southern Upland was estimated from physical habitat surveys and tag return data to be about 45 000 fish yr^?1. Acidification has caused a 50% decline to the current production level of about 23 000 fish yr^?1. The costs of the liming program, when compared to the economic benefits of the anticipated salmon enhancement, are economically unjustifiable. The eradication of salmon from such large regions will hinder future programs to reestablish the species in their former range when pollution of the atmosphere is eventually brought under control. Present plans are for a small liming program to establish a series of refuges for the preservation of nuclei of native salmon stocks.     

Ambient acid aerosols in rural Nova Scotia

During the summer months, Nova Scotia is downwind of many of the large industrial areas of the eastern United States and central Canada. The studies described here were carried out in the summers of 1983 and 1984 in Antigonish, a small rural town in northeastern Nova Scotia with no local sources. Twenty-four hour samples were collected on Teflon filters using a dichotomous sampler, and were analyzed for sulphate, nitrate and chloride by ion chromatography and for strong acid using Gran titrations. Sulphate episodes (up to 27 μg m^?3) were frequent. They usually occurred in warm, hazy weather and were often accompanied by strong acid (up to 9 μg m^?3 as H₂SO₄).     

Evidence for the recovery of the waters off the east coast of Nova Scotia from the effects of a major oil spill

The background levels of residual oils in the Western North Atlantic off the east coast of Nova Scotia decreased from approximately 6 to about 2 μgl^?1 during May 1970 to January 1971 following a major spill of Bunker C fuel oil from the tanker ARROW which was wrecked in Chedabucto Bay, Nova Scotia on February 4, 1970.     

Vegetation,soils, and ion transfer through the forest canopy in two Nova Scotia lake basins

Characterization of the forest vegetation and soils in two adjacent; contrasting headwater lake basins located in Kejimkujik National Park, Nova Scotia was completed in 1980. Precipitation chemistry was studied during May to November, 1981–83 at two forested plots in each basin. There were 2012 stems ha^-1 in Beaverskin basin and 1816 stems ha^-1 in Pebbleloggitch basin. Beaverskin species composition was predominantly coniferous (72% of stems) while Pebbleloggitch was predominantly deciduous (52% of stems). Thickness and mass of organic soil layers were greater in Beaverskin. Mineral soil cation concentrations were similar. There were no differences between the basins in mean incident bulk precipitation pH. Mean volume-weighted pH for the period (73 collections) was 4.80. Sixteen percent of collections had a pH < 4.25. Sulphate deposition in incident bulk precipitation (May – November) ranged from 5.4–8.5 kg ha^-1 during 1981–83 while NO _inf3 ^sup- ranged from 0.04–0.93 kg ha^-1. The partitioning of incident precipitation into throughfall varied considerably (69%–38%) year-to-year. Temporal flux of ions did not differ significantly. Amounts of all major ions in throughfall especially SO _inf4 ^sup2- and base cations(Ca²⁺ + Mg²⁺ + K⁺ + Na⁺) were enriched.     

Physical and chemical characteristics of three acidic,oligotrophic lakes and their watersheds in Kejimkujik National Park,Nova Scotia

Southwestern Nova Scotia receives acidic precipitation (average pH 4.5 to 4.6), and there are many waterbodies that are susceptible to acidification. This study characterizes the physical and chemical features of three remote, oligotrophic lakes and their watersheds in this region, in order to provide baseline information against which assessments can be made of changes caused by atmospheric depositions. Two of the lakes are small (<0.5 km²) and on headwater watersheds: Beaverskin Lake has an almost completely forested watershed and is moderately acidic and clear (pH 5.3, 5 Hazen units), while the watershed of Pebbleloggitch Lake is about 2/3 forested and 1/3 covered by a Sphagnum-heath bog, and its water is very acidic and highly colored (pH 4.3, 87 Hazen units). Kejimkujik Lake is much larger, its watershed is mostly forested but also contains some boggy terrain, its water is intermediate in acidity and color (pH 4.9, 65 Hazen units), and because it drains a much larger area of watershed it has relatively large concentrations of Ca, Mg, Na, Cl, and SO₄.     

pH profiles from diatom stratigraphies in sediment cores of selected lakes of new brunswick and Nova Scotia,Canada

Diatom-inferred pH profiles have been constructed using the log x index for three lakes in Nova Scotia and four lakes in New Brunswick, Canada. The profiles cover the last 150 yr, including the past 70 to 80 yr when acid precipitation was increasing. The diatom-inferred pH changed from 6.1 to 5.3 for an unbuffered lake and from 6.3 to 6.1 for the buffered lake near Halifax, Nova Scotia, during the past 70 yr but no change in pH occurred in an unbuffered lake situated in the south of the province. Since 1900, the acidity of two unbuffered lakes in New Brunswick has changed from 6.5 to 6.1 and 6.2 to 5.7. There was no change in pH for the naturally-buffered lake and a third unbuffered lake in New Brunswick. The study suggests that there was a decline in pH of lake water in some unbuffered lakes of New Brunswick and Nova Scotia.     

Acidification of Nova Scotia Lakes

Although water chemistry of precipitation and lakes in Nova Scotia is dominated by C1 from sea salt, correction for marine influence reveals that the dominant anion in acidified lakes is SO₄. Atmospheric deposition of non-marine SO₄ (SO₄) and NO₃- for the period 1977–1980 at 4 stations in southwest Nova Scotia averaged 47 meq SO₄ ^* m^?2 yr^?1 and 21 meq NI₃-m^?2 yr^?1 compared with 38 and 13 meq, respectively, for the average of 3 stations in the northeastern third of the province. Precipitation pH increased from 4.5 to 4.8 along the same axis. Almost 50% of the SO₄ deposition occurred when storms came from the southwest, indicating low pressure tracks which pass south of major Canadian sources of S. SO₄ ^* deposition in metropolitan Halifax (1982 bulk data) was 87 meq m^?2 yr^?1, due to local emissions of ca. 28 300 tonne S in the area, as well as LRTAP. Concurrent deposition of NO₃-N was 15 meq m^?2 yr^?1 (2.1 kg ha^?1 yr ^?1). Loadings from SO₄ deposition in the Halifax area amount to 42 kg ha^?1 yr^?1 and clearly exceed the federal guideline (M.O.I., 1983) of 20 kg ha^?1 yr^?1. Water chemistry of southwest, northeast, and Halifax area lakes show the same general SOI trends as observed for atmospheric deposition. In addition we find a positive relationship between SOI concentrations in the urban lakes and proximity to the center of the urban area.     

Aluminium sulphate solubility in acid forest soils in Denmark

Ion leaching in 3 sandy spruce forest soils of different origin and pH was investigated in the laboratory. Zero-tension lysimeters containing undisturbed soil columns of varying soil depth were subjected to H₂SO₄ loadings for a period of 9 weeks. The analysis of the resulting leachate supports the hypothesis that Al-sulphate minerals may form in acidic soils when exposed to acid (H₂SO₄) deposition. In the B horizon of a glaciofluvial sandy soil (pH 4.2), both H⁺ and sulphate ions were retained to maintain 2pH + PSO₄ = 11.9 in the leachate solutions. This relation between H⁺ and sulphate activity may be due to an adsorption mechanism or a precipitation mechanism. The precipitation mechanism is favored by the good fit of leachate composition to the conditions for jurbanite [AlOHSO₄] formation from gibbsite [Al(OH)₃]. In the B horizon of a sandy till at pH 3.7, the Al in soil solution (0.5 mmol L^?1) was leached with sulphate. As the sulphate load was increased, some sulphate was retained. This may also be due to the dissolution and precipitation of an Al-sulphate mineral. The ion activity products of leachate solutions from the B horizon of this soil were close to the pK_s reported for jurbanite. The conditions for the possible existence and/or formation of Al-sulphate minerals in acidic soils are discussed.     

The acidifying potential of atmospheric deposition in Canada

It is proposed that the value of ([SO₄ ^??] - [Ca⁺⁺ + Mg⁺⁺]) in precipitation is a suitable way to describe the acidifying potential (AP) of the wet desposition. In eastern North America, the AP of precipitation varies from 20 to 85% of the total sulphate, the remainder of the sulphate being neutralized H₂SO₄, sulphate from salts in dust or from sea salt. The AP ranges from 20 to 80% of the H⁺ in the wet deposition. The rest of the H⁺ is contributed by the net effect of N compounds. Ammonium and nitrate ions from ammonia and NO_Xemissions do not represent a net acidic loading to the terrestrial ecosystem if they are taken up by vegetation. However, when N leaches from watersheds in the form nitrate, it constitutes an acidifying demand on the ecosystem. Therefore, the overall net acidifying potential (NAP) applied to the terrestrial ecosystem is defined by the value of ([SO₄ ^??] - [Ca⁺⁺ + Mg⁺⁺]) in precipitation plus [NO₃ ^??] in runoff from the watershed.     

Determination and Mapping Critical Loads of Acidity and Exceedances for Upland Forest Soils in Eastern Canada

Critical loads of acidity were estimated for upland forests in Eastern Canada using the steady-state Simple Mass Balance (SMB) Model. A consistent methodology was applied to the entire region, although critical loads were estimated separately for the Atlantic provinces (New Brunswick, Nova Scotia, Prince Edward Island and Newfoundland), Quebec and Ontario using different data sources. In this project, critical load estimates and steady-state exceedance values did not include the effect of forest fire and forest harvesting, which could have a considerable impact on critical loads in Eastern Canada. The observed soil pH – base saturation relationship for forest soils indicated that the constants used into the calculation of alkalinity leaching should be set to 10 (M/M) for the molar Bc/Al ratio in soil leachate and 10⁹ (mol L^?1)² for the gibbsite dissolution constant. The area-weighted median critical load for each province varied between 519 (Quebec) and 2063 eq ha^?1 y^?1 (Prince Edward Island), with a median critical load value for Eastern Canada of 559 eq ha^?1 y^?1. It is estimated that approximately 52% of the mapped area is exceeded in terms of acidity according to the 1994–1998 average total (wet + dry) atmospheric deposition. Greatest exceedances occurred in Ontario and Quebec and in the south of Nova Scotia, due to low critical loads and high loads of acid deposition.     

Effect of Industrial Emission on Atmospheric Wet Deposition

In order to quantify the role of industries on atmospheric depositions, wet depositions were collected at different sites in Singrauli area of Sonbhadra district, U.P., India. Rainwater samples were collected on event basis and were analyzed for pH and concentration of H+ ion, cations and anions. The monthly variations in rainwater pH clearly indicate that early rainfall is more alkaline and as rainy season proceeds rainwater showed lower pH. The pH of rain from June to September varied from 6.6 to 4.8 at most polluted locality. Among different cations, Ca²⁺ showed maximum concentration followed by NH₄ ⁺,Na⁺, Mg²⁺ and then K⁺, whereas among anions sulphate concentration was maximum followed by nitrate and then chloride. A significant positive correlation observed between sulphate and accumulated rainfall suggests that the source of sulphate is mainly the industrial activities. While the negative correlations of other cations with accumulated rain suggest their additional sources in the area. The study clearly indicates that the abundance of alkaline substances reduces the acidity of wet depositions.     

Chloride cycling in two forested lake watersheds in the west-central adirondack mountains,New York,U.S.A.

The chemistry of precipitation, throughfall, soil water, ground water, and surface water was evaluated in two forested lake-watersheds over a 4-yr period to assess factors controlling Cl^? cycling. Results indicate that Cl^? cycling in these watersheds is more complex than the generally held view of the rapid transport of atmospherically derived Cl^? through the excosystem. The annual throughfall Cl^? flux for individual species in the northern hardwood forest was 2 to 5 times that of precipitation (56 eq ha^?1), whereas the Na⁺ throughfall flux, in general, was similar to the precipitation flux. Concentrations of soil-water Cl^? sampled from ceramic tension lysimeters at 20 cm below land surface generally exceeded the Na⁺ concentrations and averaged 31 μeq L^?1, the highest of any waters sampled in the watersheds, except throughfall under red spruce which averaged 34 μeq L^?1. Chloride was concentrated prior to storms and mobilized rapidly during storms as suggested by increases in streamwater Cl^? concentrations with increasing flow. Major sources of Cl^? in both watersheds are the forest floor and hornblende weathering in the soils and till. In the Panther Lake watershed, which contains mainly thick deposits of till (>3 m), hornblende weathering results in a net Cl^? flux 3 times greater than that in the Woods Lake watershed, which contains mainly thin deposits of till. The estimated accumulation rate of Cl^? in the biomass of the two watersheds was comparable to the precipitation Cl^? flux.     

The case for liming some Nova Scotia salmon rivers

Long range transport of H₂SO₄ has caused many Nova Scotian rivers to decline in pH to the point where their Atlantic salmon (Salmo salar) stocks have been destroyed or much diminished. Chemical records show a declining pH trend in N.S. rivers since the early 1950's. The annual variation in hydrogen ion activity is positively correlated with sulphate and Al and negatively correlated with organic anions. It is technically feasible to restore the acidified salmon habitat by the addition of limestone, and the total cost of mounting a liming program to restore the lost habitat has been calculated. The pre-acidification Atlantic salmon production capacity was estimated from physical habitat surveys and tag return data. The estimated costs of the liming program are much greater than the anticipated economic benefits of the salmon restoration. Present plans are for a small liming program to establish a series of refuges for the preservation of nuclei of native salmon stocks.     

Hydrogen ion input to the hubbard brook experimental forest,New Hampshire,during the last decade

Being downwind of eastern and midwestern industrial centers, the Hubbard Brook Experimental Forest offers a prime location to monitor long-term trends in atmospheric chemistry. Continuous measurements of precipitation chemistry during the last 10 yr provide a measure of recent changes in precipitation inputs of H ion. The weighted average pH of precipitation during 1964–65 to 1973–74 was 4.14, with a minimum annual value of 4.03 in 1970–71 and a maximum annual value of 4.21 in 1973–74. The sum of all cations except H ion decreased from 51 μeq 1^?1 in 1964–65 to 23 μeq 1^?1 in 1973–74 providing a significant drop in neutralizing capacity during this period. Based upon regression analysis, the input in equivalents of H ion and nitrate increased by 1.4-fold and 2.3-fold respectively, from 1964–65 to 1973–74. Input of all other ions either decreased or showed no trend. Based upon a stoichiometric formation process in which a sea-salt, anionic component is subtracted from the total anions in precipitation, SO₄ ⁼, contribution to acidity dropped from 83% to 66%, whereas NO₃ ^? increased from 15% to 30% during 1964–65 to 1973–74. The increased annual input of H ion at Hubbard Brook during the past 10 yr is highly correlated with the increased input of nitrate in precipitation.     

Acid Toxicity Levels in Nova Scotian Rivers Have Not Declined in Synchrony with the Decline in Sulfate Levels

The Atlantic salmon (Salmo salar) resource of eastern Canada is impacted by acid rain in the Southern Upland (Atlantic Coast) area of Nova Scotia. Salmon runs in this area have become extinct in 14 rivers, are severely impacted in 20 rivers, and lightly impacted in 15 rivers. Water chemistry and fish communities in nine Southern Upland salmon rivers were studied from 1982 to 1996 as part of the effort to monitor the effects of the emission controlprograms in Canada and the United States. There hasbeen no statistically significant change in total ioncontent of Southern Upland river water, but there wasa significant decline in sulfate levels that was balanced by an increase in organic anions, and declines in calcium and magnesium that were balanced by increases in sodium and potassium. A geochemical scenario is proposed to account for these chemical changes. River water pH levels showed no overall linear trend, but at borderline toxicity sites the year-to-year variations in pH were correlated withchanges in juvenile salmon population densities. Tenfish species were collected, but none showed anysignificant overall time trend in population density.Fish species diversity was positively correlated with pH.     

pH and hydrogen ion deposition patterns in precipitation for the continental United States and Canada

Maps of both volume-weighted mean pH and mean H⁺ deposition in precipitation were developed for the continental United States and Canada using data from 12 precipitation chemistry monitoring networks. The maps were constructed using 1981–1982 laboratory pH data from approximately 130 monitoring sites. The area of greatest acidity (lowest pH/highest H⁺ deposition) is located in the northern Ohio Valley and southeastern Ontario, an area corresponding to high SO_x and NO_x emissions.