Deposition of nutrients and major ions by precipitation in south-central Ontario

As part of a study of the substance budgets of lakes in south-central Ontario, a network of precipitation collectors (8 bulk, 7 wet only) was operated to measure the deposition of nutrients and major ions. Results are reported for total P, total Kjeldahl N, NO ₃ ^? ?N, NH ₄ ⁺ ?N, total N, Fe, H⁺, Ca⁺⁺, Mg⁺⁺, Na⁺, K⁺, SO ₄ ⁼ and CL^? for a two year period (August 1976–July 1978). On an equivalent basis the dominant anion in both bulk and wet precipitation was SO ₄ ⁼ , with H⁺ the dominant cation. Precipitation in the study area is more acidic than that analyzed at any other location on the Canadian Shield to date. Concentrations of ions varied by 1 to 3 orders of magnitude between individual precipitation events and annual deposition varied by as much as 2-fold in the two years of study. Annual wet deposition contributed >60% of bulk deposition for all substances except total P. Seasonal trends in deposition with summer maxima were noted for most ions. For Harp Lake, a small Precambrian Lake with a lake area of 12.6% of its total drainage area, precipitation input directly to the lake surface was an important source of nutrients and major ions. This was especially the case for P, N and H⁺ because these substances were retained by the terrestrial drainage basin.     

Geochemistry of aquatic and terrestrial sediments,precambrian shield of Southeastern Ontario

Lake water and sediment samples from approximately 2200 lakes and glacial sediment (sub-solum) samples from about 1800 sites were collected throughout a 38000 km² rectangular area extending from Georgian Bay east to the Ottawa and St. Lawrence Rivers, Ontario, Canada. Lake water alkalinity and pH patterns are similar to the distribution of carbonate components in glacial drift. Carbonate-rich drift derived from the Paleozoic limestone terrain on the northeast flank of the Precambrian Frontenac Arch has been dispersed in a southwestward direction across a variety of non-calcareous metasedimentary and igneous rocks of the Canadian Shield, providing a buffering capacity to lakes situated in granitic terrain. The distribution patterns of mobile trace and minor elements are influenced by geochemical processes associated with subaerial weathering, ground and surface water transport, and the geochemical environment within the lakes themselves. Although composition of the drift is generally reflected by lake geochemistry, these post depositional processes can cause significant variations between patterns derived from the two sample types. Anions and cations such as S0₄ , Cl^?, Na⁺, and F^? exhibit concentration patterns thought to reflect both anthropogenic inputs and natural variations due to differences in the geology. All regional geochemical patterns may show evidence of local enhancement caused by high concentrations of chemically distinctive minerals in drift or nearby bedrock.     

Biology and chemistry of three Pennsylvania lakes: Responses to acid precipitation

The biology and chemistry of three northeastern Pennsylvania lakes was studied from summer 1981 through summer 1983 to evaluate lakes with different sensitivities to acidification. At the acidified lake (total alkalinity ≤ 0.0 μeq L^?1) there were fewer phytoplankton and zooplankton species than at the moderately sensitive lakes. The most numerous plankton species in all three lakes are reportedly acid tolerant. Among the benthic macro- invertebrates (BMI) there were more acid tolerant Chironomidae at the acidified lake, but more acid intolerant Ephemeroptera and Mollusca and a higher wet weight at the least sensitive lake. There were no differences among the lakes' BMI mean total numbers or mean number of taxa. The fish community at the acidified lake was dominated by stunted Lepomis gibbosus, but L. machrochirous were most abundant in the other lakes. Principal component analysis suggested a shift in all three lakes over the sampling period toward combined lower pH, alkalinity, specific conductance, Ca and Mg and higher Al and Mn. Such chemical changes have been associated with acidification. The rate and extent of acidification appeared to be controlled by geological and hydrological characteristics of the drainage basins.     

The significance of in-lake production of alkalinity

Alkalinity production in terrestrial and aquatic ecosystems of Canada, the U.S.A., Norway and Sweden is calculated from either strong acid titrations or budgets for base cations and strong acid anions, using mass-balance budgets. Where alkalinity budgets for lakes and their catchments are calculated in acid-vulnerable geological settings, in-lake processes often contribute more to lake alkalinity than yield from terrestrial catchments. Nitrate and sulfate removal, and Ca exchange with sediments are the predominant alkalinity generating mechanisms in lakes. Nitrate and sulfte removal rates increase as the concentrations of NO^? ₃ and SO₄ ^2? in lake water increase, so that in-lake acid neutralizing capacity increases as acid deposition increases. Both processes occur in sediments overlain by oxic waters, at rates which seem to be controlled primarily by diffusion.     

Patterns of water chemistry among twenty-seven oligotrophic lakes in Kejimkujik National Park,Nova Scotia

A cluster analysis was used to apportion 27 oligotrophic lakes in southwestern Nova Scotia into five multivariate groups on the basis of patterns of covariation of 11 chemical variables (Cl, SO₄, Gran alkalinity, organic anions, Ca, Mg, K, Na, H⁺, and color). These groups are described in terms of the average values of the chemical variables. The relationships among the groups were investigated by an ordination by detrended correspondence analysis. The first, and by far the strongest axis of the ordination separated lakes with relatively large concentrations of alkalinity, from strongly colored lakes with large concentrations of H⁺ and organic anions. Axis 2 separated acidic lakes, from lakes with large concentrations of Ca and alkalinity.     

Ion mass budgets for small forested catchments in Finland

Ion mass and H⁺ budgets were calculated for three pristine forested catchments using bulk deposition, throughfall and runoff data. The catchments have different soil and forest type characteristics. A forest canopy filtering factor for each catchment was estimated for base cations, H⁺, Cl^? and SO ₄ ^2? by taking into account the specific filtering abilities of different stands based on the throughfall quality and the distribution of forest types. Output fluxes from the catchments were calculated from the quality and quantity of the runoff water. Deposition, weathering, ion exchange, retention and biological accumulation processes were taken into account to calculate catchment H⁺ budgets, and the ratio between external (anthropogenic) and internal H⁺ sources. In general, output exceeded input for Na⁺, K⁺, Ca²⁺, Mg²⁺, HCO ₃ ^? (if present) and A^? (organic anions), whereas retention was observed in the case of H⁺, NH ₄ ⁺ , NO ₃ ^? and SO ₄ ^2? . The range in the annual input of H⁺ was 22.8–26.3 meq m^?2 yr^?1, and in the annual output, 0.3–3.9 meq m^?2 yr^?1. Compared with some forested sites located in high acid deposition areas in southern Scandinavia, Scotland and Canada, the catchments receive rather moderate loads of acidic deposition. The consumption of H⁺ was dominated by base cation exchange plus weathering reactions (41–79 %), and by the retention of SO ₄ ^2? (17–49 %). The maximum net retention of SO ₄ ^2? was 87% in the HietajÄrvi 2 catchment, having the highest proportion of peatlands. Nitrogen transformations played a rather minor role in the H⁺ budgets. The ratio between external and internal H⁺ sources (excluding net base cation uptake by forests) varied between 0.74 and 2.62, depending on catchment characteristics and acidic deposition loads. The impact of the acidic deposition was most evident for the southern Valkeakotinen catchment, where the anthropogenic acidification has been documented also by palaeolimnological methods.     

The use of calibrated lakes and watersheds for estimating atmospheric deposition near a large point source

We have measured the input and output rates of substances to and from both lakes and watersheds in the Sudbury and Muskoka-Haliburton areas of Ontario. At the former location, we have conducted mass balance studies on 5 lakes and their watersheds for 2½ yrs. At the latter site, we have measured mass balances for 6 lakes and about 30 individual watersheds for the past 5 yrs. Substances studied included SO₄ ^2?, NO₃ ^?, NH₄ ⁺, H⁺, major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺) and HCO₃ ^?. During the course of the investigation at Sudbury we have made several observations that indicate that the inputs of some substances, specifically SO₄ ^2? or SO₄ ^2?-precursors and strong acids, to lakes and watersheds are underestimated when measured as bulk deposition (i.e. by collection in a continuously open container): (a) The output of SO₄ ^2? from the calibrated watersheds was substantially greater than the input measured as bulk deposition. (b) The SO₄ ^2? concentrations of the lakes could not be explained on the basis of the measured inputs. An additional input directly to the lake surface was needed to obtain a mass balance. (c) The net input of acids measured as bulk deposition to the watersheds was much less than the acid consumed, which was estimated by the net output of Ca²⁺, Mg²⁺, Na⁺, K⁺, Al³⁺, and the net retention of NO₃ ^?. (d) The major cation content of the study lakes could be explained on the basis of weathering reactions in the lakes' watersheds only if the input of strong acid had been underestimated. When these observations were quantified, they indicated a major portion of the total input of SO₄ ^2?-precursors and of strong acid was not included in our bulk deposition measurements. Deposition of SO₂ is the most likely explanation for these observations.     

Headwater lake chemistry during the spring freshet in North-Central Ontario

From data on 30 headwater lakes in north-central Ontario we found that, during the spring snow melt of 1981, all lakes underwent serious declines in alkalinity. Generally, SO₄ ^2?, alkalinity, Ca⁺ and Mg²⁺ concentrations were reduced by runoff and rain then recovered to intermediate levels after the major inputs declined. As expected, a range in responses was evident with lower alkalinity systems showing the greatest changes. The observed changes, however, were consistent with acid loading having depleted alkalinity. In calculating an input-output budget for each lake, we found that changes in Cl^?, Na⁺, and K⁺ were consistent with atmospheric inputs being the major source as the difference between the expected input and the actual contribution from rain and snow had a mean near zero. There appears to be a significant, ? 45%, watershed source of sulphate that we hypothesize is from dry deposition occurring prior to snowfall and is eluted with the melting process. With refinements to a mass balance approach explaining the watershed source of SO₄ ^2? and Al, we feel it is possible to predict springtime lake changes given a few chemical and simple morphometric variables.     

Changes in water quality in the Laflamme Lake Watershed Area,Canada

The Laflamme Lake Watershed Area is located in a sensitive region on the Canadian Shield and is subjected to wet atmospheric loading between 17 and 25 kg ha^?1 yr^?1. From 1981 to 1988, the level and fluctuations of the atmospheric deposition of acidifying substances has led to various responses in the water chemistry of headwater lakes in the area. The general trend in atmospheric inputs is a gradual increase of acidifying substances from 1981 to 1985 followed by a 2 yr decrease then a return to previous values. In the two lakes with almost no alkalinity acidification has occured throughout the 1983 to 1988 period. In the four lakes with slightly higher alkalinity values, a reversal in acidification is seen when atmospheric loading decreased in 1986. Along with the interannual trends, seasonal variability to acidification occurs with sensitivity of surface waters being highest during spring melt. Sensitivity to acidification can also be altered by watershed processes and in the Laflamme Lake Watershed, soil processes are effective in altering the acidity of precipitation before it reached the lake. In this watershed, wet atmospheric inputs of H⁺ and NO₃ ^? are larger than surface water outputs while the reverse occurs for Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^? and SO₄ ^2?.     

Alkalinity production in epilimnetic sediments: Acidic and non-acidic lakes

Interstitial water profiles in epilimnetic sediments of lakes with varying water column alkalinities were collected to assess the origin and importance of sedimentary alkalinity in freshwater lakes. Release of Ca²⁺ and NH₄ ⁺, and consumption of SO₄ ^? are the most important contributors to alkalinity production m sediments of non-acidic lakes. In acidic lakes, Fe²⁺ and Mn²⁺ replace Ca²⁺ as the dominant cation contributors to alkalinity production. The sedimentary alkalinity flux is an important component of the acid neutralizing capacity of freshwater lakes. However, the presence of large alkalinity gradients in sediment porewaters does not necessarily indicate a large source of alkalinity for the lake, as a significant portion of the alkalinity iu associated with the formation of Fe²⁺, Mn²⁺ and NH₄ ⁺ Oxidation of Fe²⁺ and Mn²⁺ at the anoxic-oxic interface and biological removal of NH₄ ⁺ in the overlying water column results in consumption of the co-diffusing alkalinity.     

Watershed vs in-lake alkalinity generation: A comparison of rates using input-output studies

As a means of assessing the relative contributions of watershed (terrestrial) and in-lake processes to overall lake/watershed alkalinity budgets, alkalinity production rates for watersheds and low alkalinity lakes were compiled from the literature and compared. Based on net alkalinity production data, derived using wet or bulk deposition data, mean and median alkalinity production for 20 watersheds in North America and Europe were 89 and 69 meq m^?2 yr^?1 (range 20 to 235 meq m^?2 yr^?1). For a subset of 10 watersheds with dry deposition data, terrestrial alkalinity production neutralized an additional 35 meq m^?2 yr^?1 of acidic deposition. For 11 lakes, mean and median in-lake alkalinity generation were 99 and 88 meq m^?2 yr^?1 (range 22 to 240 meq m^?2 yr^?1). Analysis of data indicates that for the low alkalinity systems described here, areal alkalinity production rates for watersheds and lakes are approximately equal. This relationship suggests that watershed area to lake area ratio can be used as a convenient estimator of the relative importance of watershed and in-lake sources of alkalinity for drainage lake systems. For precipitation-dominated seepage lakes and other systems where hydrology limits soil-water contact, hydrologic flow paths and residence times can be of overriding importance in determining alkalinity sources. For regions dominated by drainage lakes with high watershed area to lake area ratios (such as the Northeastern U.S.), however, alkalinity budgets are dominated by watershed processes. Omission of in-lake alkalinity consideration for most lakes in such regions would have little impact on computed alkalinity budgets or on predicted response to changes in acidic deposition loadings.     

Mid-term trends in acid precipitation,streamwater chemistry and element budgets in the strengbach catchment (Vosges Mountains,France)

In the Vosges Mountains (NE of France), integrated plot-catchment studies have been carried out since 1985 in the Strengbach basin to study the influence of acid atmospheric inputs on surface water quality and element budgets. In this paper, available mid-term time series (1985–1991) have been considered to detect obvious trends, if any, in surface water chemistry and element budgets. Air quality data showed a slight decline for SO₂, whereas NO₂ slightly increased over the period, but these trends are not very significant. This is in agreement with increased N concentration (mainly as NH ₄ ⁺ ) and with the stability of SO ₄ ^2? in open field precipitation. Because of a significant decrease in rainfall amount over the period, only inputs of NH ₄ ⁺ increased significantly whereas H⁺ and SO ₄ ²⁺ inputs declined. In spring and streamwaters, pH and dissolved Si concentration increased mainly as a result of a reduced flow. Na⁺, K⁺, Cl^? and HCO-3~^? concentrations remained stable whereas Ca²⁺, Mg²⁺ and SO ₄ ²⁺ concentrations declined significantly. Only NO ₃ ^? concentration increased significantly in springwaters. The catchment budgets revealed significant losses of base cations, Si and SO ₄ ^2? . These losses decreased over the period. Nitrogen was retained in the ecosystem. However, a longer record is needed to determine whether or not changes in surface water chemistry have resulted from short-term flow reductions or long-term changes in input-output ion budgets. This is specially true with N because the decline in SO ₄ ^2? output was accompanied by N accumulation.     

Influence of wetlands and coal mining on stream water chemistry

Comparisons of stream water chemistry over a 2 yr period in East Fork, which drains an entirely forested watershed, and Big Run, which drains a forested watershed 8 % of which is occupied by Big Run Bog, indicated that Big Run Bog had no effect on stream water H⁺ or Cl^? concentrations, but with increasing stream discharge the wetland was a source of Ca⁺⁺ Mg⁺⁺, K⁺, Na⁺, NO₃ ^?, and SO₄ ^?, and a sink for Fe^{+ +}. Further comparisons with Tub Run, which drains a forested watershed, 13 and 12% of which is occupied by Tub Run Bog and an abandoned, unreclaimed coal surface mine, respectively, suggested that Tub Run Bog removes H⁺, Ca ++, Mg⁺⁺, Fe⁺⁺, and 50₄ ^? from inputs of acid mine drainage. Wetland areas on the landscape contribute to the regulation of stream water chemistry in ways that are different from upland areas, and wetlands may have considerable applied potential for minimizing the impact of the mine drainage on stream water quality.     

Simulation of flow patterns and ion-exchange in soil percolation experiments

An increased understanding of ion-exchange processes in raw-humus was obtained by simulations using quantitative mathematical models. The work is based on a series of percolation experiments with a water flow of about 1 mm min^?1 through raw-humus samples of 4 cm thickness. For the input solutions consisting of 10^?3 N H₂SO₄, HNO₃, HCl and NaCl the results indicate that cation-exchange reactions are the most important processes for the chemical composition of the run-off. Since a large part of the water flows quickly through the soil, both the water residence time and the ion-exchange kinetics must be taken into account. As a basis for the chemical model, a hydrologic sub-model reproducing the residence time distribution of the flow in the soil is used. Considering the ions H⁺, M⁺ (monovalent metal ions) and M²⁺ (divalent metal ions), four different chemical models were tried but only one of them gave satisfactory agreement with the experimental results. This model has 5 independent parameters and consists of first and second order chemical processes.     

In-lake alkalinity generation by sulfate reduction: A paleolimnological assessment

The generation of alkalinity by SO₄ reduction and net storage of reduced S in lake sediments has been estimated from an analysis of sediment cores from 16 lakes in ME, VT, NY, MI, MN, and WY. The cores have been dated by ²¹⁰Pb. The rate of pre-1850 (background) storage of S in lake sediments suggests that alkalinity contribution to lake water from this process ranged from 0.2 to 9.3 geq L^?1, with an average of 4 geq L^?1, Background values are similar for all lakes and remain low in the WY lakes up to the present. Maximum alkalinity contributions recorded in sediment, from upper mid-west and eastern lakes, dated between 1850 and 1985 are between 0.4 and 33 geq L^?1, with a lake mean maximum of 9.9 geq L^?1, Significant increases in recent S storage only occur in eastern lakes. Average values for net S accumulation in the sediment of most lakes for post-1850 sediment are typically less than half of maximum values.     

Effects of acidic meltwater on chemical conditions at nearshore spawning sites

Chemical conditions at lake charr (Salvelinus namaycush) spawning sites were monitored during snowmelt in low alkalinity lakes in Ontario, Canada. Embryos within the interstitial water of the spawning substrate were exposed to abrupt and potentially toxic levels of H⁺ and inorganic Al as acidic runoff water inundated the shallow nearshore sites. Early runoff events, those that occurred while the lake ice was still snow-covered and under-ice water temperatures were <2°C, appeared to be most threatening, because of deep penetration of the runoff water. These highly site-specific events exhibit wide temporal and spatial variability.     

The effects of acid perturbation on a controlled ecosystem

Duplicate, 8-compartment, continuous-flow microcosms were used to study the effects of acid addition on community function, algal community structure, and degradation of a plasticizer, diethyl phthalate. Inputs of HCl decreased the alkalinity (measured as CaC0₃) from 25 to 8 mg 1^?1, creating diurnal H⁺ activity curves that indicated that the ecosystem was being severely stressed. Removal of excess acid was accompanied by a return to a normal diurnal pH cycle. Nutrient concentrations and O₂ production did not give a definite indication of stress resulting from the addition of acid. Algal community structure and total biomass were not affected by acid inputs. Also, degradation rates of diethyl phtalate by the aquatic bacteria were similar for the control and the acid-stressed systems. These studies indicate that acid inputs can significantly disrupt normal ecosystem function, such as diurnal pH cycling, without having a measurable impact on other parameters usually monitored in aquatic ecosystems.     

Element mass balances for South Carolina Coastal Plain watersheds

Element mass balance estimates for South Carolina Coastal Plain watersheds indicate that fertilizers and liming materials are the major sources for inputs of Ca, Mg, K, Cl, and HCO₃ whereas precipitation is the major input for Na and SO₄. Stream flow is the chief mode of output for all of these elements. A balance between input and output is evident only for Cl. Retentions of 50% or more are shown by Ca, Mg, K, HCO₃ and SO₄ whereas Na shows an apparent net loss. The retention of Ca, Mg and HCO₃ suggests that less than 25% of the dolomitic liming materials applied to the landscape actually dissolve and that the carbonate chemistry of Lower Coastal Plain streams is therefore probably largely controlled by seepage of groundwaters from underlying calcareous aquifers. The retention of K and the loss of Na may be due to cation exchange reactions on soil clays whereas the apparent retention of SO₄ is probably due to reduction to H₂S in floodplain environments and soil adsorption.     

Estimating the atmospheric input of pollutants into a watershed

Estimating the atmospheric input of ions to a watershed has traditionally been accomplished through either the extrapolation of point measurements of deposition or the integration of model estimated deposition. This paper examines the characteristics of precipitation chemistry on the eastern seaboard of the United States where precipitation quality could conceivably affect fish habitats in estuaries. The measured values presented here have been extracted from the data base of the Utility Acid Precipitation Sampling Program (UAPSP) precipitation chemistry network. These data illustrate the nature of ionic deposition at four points on the eastern seabord. The deposition of H' (acidity) is shown to be dependent upon the amount of sulfate and, to a lesser degree, nitrate in the precipitation. It is also shown that the quantity of ionic deposition on a storm-by-storm basis was influenced by the amount of water deposition but the relationship was not very strong. Thus the use of water deposition as a surrogate for ionic deposition is not justified in these watersheds. Finally, it is shown that the deposition of H⁺, SO₄ ^2?, NO₃ ^?, and NH₄ ⁺ were not clearly seasonal. While a large percentage of total ionic deposition occurred in a small number of precipitation events, these exceptional events were not confined to a particular season.