Diatom-inferred pH history of Kejimkujik Lake,Nova Scotia: A reinterpretation

A reanalysis of the diatom-inferred pH profile from a sediment core collected in 1980 from Kejimkujik Lake has been made in the light of improved techniques and ecological information. Using Index B calibrated for lakes in Atlantic Canada, the lake pH was 4.6 to 4.7 before anthropogenic disturbances in the watershed began ca. 1850. These disturbances had little immediate impact on pH, but minima of pH 4.5 were evident in the period 1916 to 1950. A diatom-inferred pH of 4.75 in the surface sediments compares with a measured pH of 4.96 in 1980. Disturbances in the watershed since ca. 1850 resulted in a large increase in a form of Asterionella ralfsii, a diatom associated with colored, humic water. A decline in this diatom since 1950 and an increase in taxa less typical of humic water is consistent with the hypothesis of loss of organic matter accompanying acidification from acidic precipitation.     

Chemical characterization of several wetlands in Kejimkujik National Park,Nova Scotia

Results are presented from an investigation of wetland chemistry in Kejimkujik National Park, Nova Scotia. Significant differences in the major ionic constituents occurred between wetlands classified as bogs and those classified as fens, indicating the more minerotrophic status of the latter. The fens, however, were categorized as extremely poor, being very low in pH and base cations, indicating almost no buffering capacity. This type of wetland is regarded as transitional to bog and is viewed as highly sensitive to acid deposition by Gorham et al. (1987). Further alkalinity losses may result in abrupt changes in floral assemblages with rapid invasion of carpet forming Sphagnum species.     

Surface-water Acidification and Reproducibility of Sediment Cores from Kejimkujik Lake, Nova Scotia, Canada

A total of nine sediment cores were collected from the five deep basins of Kejimkujik Lake, located in southwestern Nova Scotia, Canada, in order to track changes related to surface-water acidification and to test reproducibility of results between sediment cores from different basins in a large lake. Present-day and pre-industrial (c. 1850) samples were analyzed from all cores and detailed diatom profiles were undertaken on three cores to determine the timing of acidification. All three detailed diatom profiles show declines in inferred pH starting in the early 1930–1940s. Since the 1940s, diatom-inferred lakewater pH has declined from a background pH of ～5.8 (± 0.4) to a current diatom-inferred pH of ～4.9 (± 0.1). This corresponds to the current (2001–2002) range of measured lakewater pH?=?4.7–5.2 with a mean pH?=?4.9. Species diversity of diatoms also declines markedly in all cores with the Hill’s N2 index decreasing from ～5 to near 1. The pre-impact diatom assemblages were dominated by Aulacoseira spp. and have since changed to dominance by Asterionella ralfsii var. americana (>45 μm). All nine sediment cores showed similar changes in diatom assemblages, diatom-inferred pH, and timing of the onset of acidification. Thus, paleolimnological inferences from deepwater sediment cores were highly reproducible in this large, morphometrically complex lake system.     

Mercury Flux Measurements over Air and Water in Kejimkujik National Park,Nova Scotia

Mercury flux measurements were conducted at two lakes and three soil sites in Kejimkujik National Park, located in the eastern Canadian province of Nova Scotia. One of the lakes had high levels of both mercury and Dissolved Organic Carbon (DOC). Two of the soil sites were located under the forestcanopy, while the other was in a small clearing surrounded by forest. Flux measurements were performed using the dynamic chamber method. Mercury concentrations in the air were measured with a TEKRAN mercury analyzer. Mercury fluxes over the two lakes were most strongly correlated with solar radiation, although the flux was also significantly correlated with water temperature, air temperature, and negatively correlated with relative humidity. The flux from the high DOC lake (Big Dam West) was especially high when the conditions were both sunny and windy (wind speed greater than 1.3 m s^-1) and the average flux measured was 5.4 ng m^-2 h^-1. The mercury flux from this lake was wellparameterized in terms of a simple expression involving solar radiation and a nonlinear dependence on wind speed. The flux measured from the low DOC lake (North Cranberry) tended to be lower than from the high DOC lake. The averageflux measured was 1.1 ng m^-2 h^-1, but was again strongly correlated with solar radiation. The flux was low during windy conditions in the absence of sunlight, suggesting that wind enhances mercury evasion from lakes only in the presence of solar radiation. Mercury fluxes measured over the soil sites tended to be smaller than those over water (a range of –1.4–4.3 ng m^-2 h^-1). At one of the forest sites, mercury flux was very strongly correlated with 0.5 cm soil temperature, and this dependence was well described by an Arrhenius-typeexpression with an activation energy of 14.6 kcal^-1 mole, quite close to the heat of vaporization of mercury (14.5 kcal^-1 mol^-1 at 20 °C). At the clearing, where there was direct exposure to the sun, the mercury flux was most strongly correlated with solar radiation.     

Seasonal variations of water chemistry in oligotrophic streams and rivers in Kejimkujik National Park,Nova Scotia

The seasonal patterns of flow and the concentrations of color, Mg, Ca, H⁺, Na, Cl, organic anions, SO₄, and Gran alkalinity are examined for five streams or rivers in Kejimkujik National Park (Lower Mersey River, Atkins Brook, Grafton Brook, Pebbleloggitch Brook, and Beaverskin Brook). These range in organic color and acidity from very darkwater Atkins Brook (average 191 Hazen units, pH 4.2) to clearwater Beaverskin Brook (5 Hazen units, pH 5.5). In general, most dissolved substances are present in a relatively large concentration during the high-flow period of winter-spring (most notably color, Mg, H⁺, Ca, Na, organic anions, and SO₄). In contrast, Gran alkalinity generally occurs in its highest concentration during the lowflow period. These observations suggest that during the high-flow period, substances are “flushed” from the terrestrial watersheds of these rivers and streams.     

Comparison of the macrophyte communities of a clearwater and a brownwater oligotrophic lake in Kejimkujik National Park,Nova Scotia

Beaverskin and Pebbleloggitch Lakes are small, proximate, acidic, oligotrophic, headwater lakes located in southwestern Nova Scotia. Beaverskin Lake has clear water, its euphotic zone is deep, and it has extensive beds of macrophytic vegetation that cover most of its bottom to a depth of 6.5 m. In contrast, the water of Pebbleloggitch Lake is highly colored by dissolved humic substances, and macrophytes are restricted to a narrow littoral fringe in depths of less than about 1.8 m. The most widespread macrophyte community in Beaverskin Lake occurs at depths of 2.0–6.5 m and is dominated by Sphagnum macrophyllum and Utricularia vulgaris, while the second most prominent community is littoral and is dominated by Eriocaulon septangulare, Lobelia dortmanna, and Eleocharis acicularis. The most prominent community in Pebbleloggitch Lake is dominated by the floating-leaved Nuphar variegatum rooted as deep as 1.8 m, while communities dominated by E. septangulare and Sphagnum spp. occur in water less than about 0.7 m deep.     

Ecological and physiological responses of Atlantic salmon in acidic organic rivers of Nova Scotia,Canada

Ecological and toxicological data from field studies on acidic rivers of Nova Scotia were examined to review the effects of low pH on Atlantic salmon (Salmo salar) populations in waters rich in organic acids where noexchangeable forms of Al dominate at all times. There were no survival of salmon past the dry stage at pH <4.7, and survival rates for salmon from egg to smolt only increased at pH >4.9. Annual production of juvenile salmon and potential yield of smolts were lower at pH 4.7 to 5.4 than at pH 5.6 to 6.3 because of reduced densities attributable to the high mortality of fry at pH ≤5.0. However, acidity episodes to pH <4.7 also resulted in mortality of parr, reducing densities and often completely eliminating year-classes. The physiological responses of juvenile salmon to chronic acid conditions and to acute acidity typical of episodic events were also reviewed in relation to toxicity. Decreased in plasma Na and Cl were well correlated with ambient pH, but not with exchangeable Al concentrations in rivers. These plasma electrolytes provided reliable indicators of the thresholds for sublethal effects on ionoregulatory mechanisms. There was no morphological evidence of damage or lesions in gill epithelia, indicating that accumulation of Al in the gills of parr was not a significant factor in the lethal effects observed in acidic rivers. High organic matter content in the water apparently protected gills from adverse Al effects. Toxicity was considered to result from the effect of low ambient pH on branchial ionoregulatory mechanisms.     

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.     

Patterns and importance of dissolved organic carbon in four acidic brownwater streams in Nova Scotia,Canada

The temporal variation and importance of dissolved organic carbon (DOC) was investigated in four brownwater streams in Nova Scotia, Canada, in basins receiving approximately 20 kg/ha/yr wet deposition of sulfate. Organic anions contributed an average of 23% of total equivalents.Within each waterbody, correlations of H+ with DOC were insignificant, whereas they were significant with sulfate. DOC was consistently correlated with concentrations Ca and Mg, suggesting that they occur as organic complexes. DOC concentrations and thus organic anions were inversely correlated with stream flow.     

Spatial Variation and Correlations of Mercury Levels in the Terrestrial and Aquatic Components of a Wetland Dominated Ecosystem: Kejimkujik Park,Nova Scotia,Canada

This study investigates the ranges and spatial variation ofmercury in various media in the wetland ecosystems ofKejimkujik Park, Nova Scotia. Mercury concentrations infive-year-old yellow perch (age based on regression analysesof existing data) ranged from 0.12–0.72 μgg^-1(wet weight basis) in 24 lakes. Mercury concentrations inred maple ranged from 5 to 41 ng g^-1 and levels inwhite pine ranged from 5 to 58 ng g^-1, dry weight.Concentrations of total mercury were found to besignificantly higher in epiphytic lichens (maximum of 660 ngg^-1) and in feather mosses (maximum of 395 ng g^-1)compared to vascular species. The soil Ah horizon exhibitsthe highest concentrations for both mercury and gold, withmaximum values of 466 and 42.8 ng g^-1 respectively;whereas the C-horizon appears to host the most Zn (maximum209.9 μg g^-1). Lake water pH and dissolved organic carbon (DOC) were thevariables most highly correlated with mercury in lake watersand yellow perch. No correlations were observed betweenmercury in terrestrial components and mercury in yellowperch; however, mercury in yellow perch was correlated withP in leaf tissues of both red maple and white pine. Theimportance of understanding linkages between terrestrial andaquatic ecosystems is emphasized through this study.     

Local patterns of sulphur deposition around Halifax/Dartmouth,Nova Scotia: 1979–83.

Five years of sampling support earlier findings that SO₂ emissions from Halifax/Dartmouth, Nova Scotia (population 270,000) cause wet sulphate deposition within 40 or 50 km of the city to be twice regional values. The urban effect is greatest within the city itself. Mean monthly sulphate concentrations in precipitation are usually more highly correlated among stations than is monthly deposition; the highest correlations are among concentrations in and around the city. Month to month variations in sulphate concentration in the city and at Oyster Pond (50 km east of the city) appear to be affected mainly by urban influences; those at St. Margaret's Bay (25 km west of the city) appear to be affected by both urban and regional influences. The urban effect appears to have diminished somewhat during the 5 yr, possibly because the urban emissions have decreased by 35% since 1980.     

Interpretation of Mercury Concentrations in Eight Headwater Lakes in Kejimkujik National Park, (Nova Scotia, Canada) by Use of a Geographic Information System and Statistical Techniques

The concentration of mercury in eight headwater lakes in Kejimkujik National Park correlated positively with total organic carbon, total nitrogens, aluminum, iron and sodium andnegatively with pH and alkalinity (Gran). Annual average mercuryyield of the lakes correlated positively with basin area to lakesurface area ratio, and watershed areas underlain by granite bedrock and glacial deposits and negatively with greywacke bedrock. Principal component analysis indicated that first threecomponents account for 80% of the total variance in the data.The components were related to physiography and geology of the watershed, hardness of water, and atmospheric washouts of longrange transported acidic pollutants and dust particles. Mercuryin the lake waters was associated with the physiography and geology of the watershed. Total organic carbon, aluminum and iron were good predictors of mercury concentration in the lakewaters as were the basin area to lake surface area ratio, and basin areas underlain by granite bedrock, and Halifax slate forthe lake mercury yield. The results showed that transport of mercury from the watershed is a major source of mercury in thestudy lakes.     

The zinc status of some Nova Scotia soils and crops

Abstract

Ranges for total, 0.1N HCl and EDTA‐(NH₄)₂CO₃ extractable Zn in 69 samples of surface soil (0–15 cm), representing nine soil series, were 14–108, 0.9–10.5 and 0.5–8.0 ppm respectively. Total Zn in barley (Hordeum vulgare), carrot (Daucus carata sativa), corn (Zea mays L), grape (Vitis spp.), onion (Allium cepa), pea (Pisum sativum, strawberry (Fragaria spp.), and wheat (Triticum spp.) leaves and in barley and wheat grain ranged from 13.5 to 80.6 ppm.

The results suggest that, with the possible exception of corn leaf samples from one location, Zn levels in plant tissue were adequate. However, the results also indicate that liming strongly acid sandy soils reduces Zn availability and may induce a deficiency in Zn sensitive crops.     

Sulphur isotope tests of seasalt correction factors in precipitation: Nova Scotia,Canada

Sulphate in precipitation is an index of atmospheric pollution but natural sources also contribute to its concentration. One of the dominant natural sources of sulphate is seasalt and reseachers have routinely calculated its proportion using reference species such as Cl^?, Na⁺ and Mg²⁺. Such a method of estimation assumes conservatism of, and a purely marine origin for, the reference species. The stable isotopes of sulphur were utilized to assess the validity of these assumptions for a coastal area in Canada by taking advantage of the sulphur isotopic signature of seasalt sulphate (+20‰). The seaspray component (PSS) was calculated for 39 coastal rain events using Cl^?, Na⁺ and Mg²⁺ as reference species and these parameters were plotted against the sulphur isotopic composition of sulphate in the sample. All three regression lines yielded a value of ≈ +4‰ for a sample containing no seasalt. The regression lines extrapolated to δ ³⁴S≈+20, +17 and +16‰ using Cl^?, Na⁺ and Mg²⁺ respectively for a theoretical sample whose sulphate was derived totally from seasalt. This observation confirms that for this locality, the marine component of precipitation sulphate utilizing Cl^? is isotopically equivalent to sea spray sulphate, suggesting that Cl^? is a suitable reference species. It also supports the use of δ ³⁴S_SO4 as a constraint on the selection of the correct reference species for estimation of the seasalt component in a particular study area.     

Meteorological analyses of acidic precipitation in Ontario

Meteorological analyses of precipitation and air quality data for the period 1976 to 1983 have been undertaken to infer potential source regions of acidity in Ontario. Techniques such as air parcel trajectory modelling and synoptic weather classification have been utilized. A meteorological data acquisition system has been implemented to provide historical and real-time trajectory statistics. This paper provides an overview of these studies. For areas of South and Central Ontario, precipitation events most commonly occur with pre-warm front and cyclonic situations, and trajectories from the south and southwest octants. Furthermore, most of the reported wet deposition of S and N is associated with trajectories from these octants, the direction of the Ohio Valley industrial source region and industrialized SW Ontario. High air concentrations of S and N are also associated with trajectories from these octants.     

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.     

A Scandinavian model used to predict the reacidification of limed lakes in Nova Scotia and Ontario,Canada

A Scandinavian reacidification model was used to predict the reacidification of three limed lakes in the Sudbury area, Ontario, and Sandy Lake in Nova Scotia. A prediction was made also for the future reacidification of Bowland Lake, 70 km north of Sudbury, limed in 1983. The reacidification of a neutralized lake is dependent on the continuing dilution of the dissolved calcium carbonate, and for a limited period of time, the dissolution of calcite from the bottom. The test of the model on the Canadian laked shows that the model may be a useful tool for lake liming design and planning.     

Acidification of Nova Scotia lakes I: Response of diatom assemblages in the Halifax area

A comparison is made of diatom remains in surficial lake sediments collected in 1971 and 1980. Changes of similar magnitude towards more acid tolerant assemblages are observed in four lakes studied in detail despite widely differing aquatic environments. No attempt is made to reconstruct past chemistry, the significant point being that at the most fundamental level, local lacustrine biological systems are being stressed to the point of alteration. The pattern of that alteration with emphasis on ‘simplification’ is discussed with the suggestion that rates of acidification may be as important as net changes.     

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.