Biological indicators of lake acidification

Indicator taxa are identified, based on both synoptic surveys and whole lake acidification experiments, for lake acidification in the pH 6.0 to 5.0 range. Acidobiontic diatoms (e.g Asterionella ralfsii, Fragillaria acidobiontica, etc.), periphyton (Mougeotia and related species), macroinvertebrates (e.g. Hyalella azteca, Orconectes sp., etc.), leeches, and cyprinid fishes (e.g. Pimephales promelas, Notropis cornutus, etc.) are identified as target organisms during early phases of lake acidification.     

Liming and reacidification reactions of a forest lake ecosystem,lake Lysevatten,in SW Sweden

Long-term monitoring, 1973 to 1987, of reactions to liming and reacidification of a forest lake ecosystem near the Swedish west coast is reported in this study. Treatment of Lake Lysevatten with a slag product of limestone in 1974 resulted in neutralization and a positive alkalinity. Prolonged dissolution proceeded for about 7 yr whereby 86% dissolved. During 1984–86 Lake Lysevatten approached maximum reacidification with high Al concentrations and an affected biota. Asellus aquaticus L. decreased and dominance within chironomid groups approached preliming conditions. However, the most obvious biological change was the development of the filamentous algal genus Mougeotia and increased growth of Sphagnum. Populations of both plants increased notably when pH declined to about 5. Our study suggests that extensive reacidification (pH < 6.0) of limed lakes should be avoided by successive treatments to prevent development of destabilized lake ecosystems.     

Regional monitoring of lake acidification in Finland

The primary objective of this monitoring is to detect long-term Long-Range Transboundary Air Pollution (LRTAP) induced changes in the water quality of small lakes, throughout Finland, with low conductivity. The monitored lakes (n=171, sampled every autumn since 1990 and in 1987) have a smaller watershed (usually headwater or seepage lakes), a larger lake/catchment ratio, and lower base cation concentrations, alkalinity and pH than Finnish lakes on average. The monitoring network provides background data for air pollution dose/response studies, critical load calculations and for the modelling of acidification scenarios. The declining sulphate deposition seems to be reflected in small headwater lakes all over southern and central Finland as a lowering of the sulphate concentration in the waters. Nitrate concentrations in these lakes have been typically low in the autumn. The base cation concentration is not generally declining, as it is in deposition in many areas. The sulphate concentration in lakes has declined more than base cations. Hydrologically, the recent years have been quite variable because of varying annual precipitation. The variation in alkalinity and pH in typical Finnish lakes is dependent on the content of humic material derived from catchments. The monitoring period is too short to reveal consistent trends in major ion chemistry. However, signs of improvement in recent years can be seen; in comparing 1993 to 1987, years with similar organic acidity and base cations, it seems that the sulphate decline in lakes monitored is compensated by a significant rise in both alkalinity and pH.     

Factors influencing pH in lake water

Using an improved titration technique, Lee and Brosset (1978) have established the presence in a number of lake waters of an acid withk _a = 3 × 10^?4. It is shown that higher concentrations of this acid, which seems to correspond to a functional group of humus, may under certain conditions drastically contribute to the lowering of pH of lake water.     

An overview of lake neutralization experiments in Ontario

In 1981, an experimental neutralization program was initiated in Ontario to investigate the feasibility of using neutralization as an interim measure for the protection of acid-sensitive lakes and the restoration of acidified lakes. Aerial applications of powdered limestone (CaC0₃) to two lakes were used to increase whole-lake pH and alkalinity, and experiments were initiated to investigate the neutralization of lake trout (Salvelinus namaycush) spawning shoals with crushed limestone. Intensive studies are continuing to assess temporal patterns in water chemistry and to evaluate the long-term responses of zooplankton, phytoplankton, zoobenthos and fish communities.     

Methods of selecting lake shorelines as nature reserves

Botanical evaluations often tend to over-emphasise the importance of high species diversity and rarity. It is doubtful whether a regional selection of reserves based primarily on such evaluations attains the intended goal of nature conservation, which should be to preserve every main type of habitat and every species. A new method is presented for the selection of lake shorelines as nature reserves, based on a classification of the composition of the plant communities. The primary aim is to achieve a representation in these reserves of all the major plant communities found on lake shorelines in the region. The results of this selection method are then compared with those based on evaluations of diversity, area, rarity, naturalness and representativeness.     

Diatoms as indicators of the rate of lake acidification

Autecological studies of diatoms as pH indicators have opened the way to estimating a lake's past pH on the basis of its diatom species composition and relative abundance. Estimating the rate of lake acidification from its sediment subfossil diatoms is possible when these subfossils can be identified and accurately enumerated in the surface sediments of 20 to 30 lakes. Once this is done the diatoms down the length of the sediment core of one or more of these lakes can be enumerated and the pH inferred at each depth. This technique holds considerable promise in assessing the temporal impact of acid precipitation for acid-sensitive lakes. When loga values were regressed against observed pH for 28 lakes located north of Lake Superior, a significant (P < 0.01) correlation (r = 0.89) resulted. Downcore diatom stratigraphy for one of these lakes indicated that its pH had dropped from 6.2 to 5.2 over the last 20 yr while a second lake had dropped from a pH of 7.1 to 5.2 over the last 30 yr.     

Sulphate deposition by precipitation into lake Ontario

Measurements of sulphate concentration in precipitation from individual snow storms of several hours duration in the Western Lake Ontario region indicate that approximately 9–66 mg M^?2 of SO is being deposited into the Lake per storm. This amount is up to several times more than daily average values over long periods found by other workers. Using a mean sulphate concentration of 4 mg l^?1 and an annual accumulation of precipitation of 760 mm, the yearly sulphate deposition by precipitation is about 0.1 % of the total mass of sulphate in the Lake; however, more significantly, it is of the same order of magnitude as that discharged directly into the Lake by industry.     

Primary production in a eutrophic acid lake

Total P concentrations, chlorophyll concentrations, and phytoplankton production were investigated bi-weekly in Tibbs Run Lake, Monongalia County, West Virginia, from March 1977 to March 1978. Mean H⁺ concentration in the lake was 25.1 μeq 1^?1 (pH 4.6). The acidic condition of the lake is attributed to inputs of acid via precipitation (mean H⁺ concentration of the bulk precipitation was 79 μeq 1^?1, pH 4.1), and the low buffering capacity of the watershed (bedrock composition of sandstone). Effect of the watershed is shown by the net retention of imput of P (ca. 26%) and H⁺ (ca. 68%). Total P loading to the lake was 0.495 g P m^?2 yr^?1. The single inflow accounted for 95% of the total loading while bulk precipitation accounted for the remainder. Mean summer chlorophyll concentration was 22.2 mg m^?2. Phytoplankton production expressed volumetrically as aP-vol-x value was 9.78 mg C m^?3 h^?1. Regression analysis indicated that H⁺ do not affect chlorophyll concentrations or phytoplankton production but rather that P limits algal biomass. Trophic status of Tibbs Run Lake based on a P budget model, chlorophyll concentration, and volumetric production all indicate that the lake is meso-eutrophic.     

A protocol for determining lake acidification pathways

The chemistry of 282 sampled low pH (<6.0) lakes in the U.S. E.P.A. Eastern Lake Survey (ELS) was evaluated in an attempt to assess why these systems have low pH. Evaluations were made using a decision protocol for classifying lakes according to several hypothesized acidifying mechanisms: acidic deposition, presence of wetlands and organic soils, acid mine drainage, watershed S sources, salt driven acidification, and changes in land use. The algorithm evaluates lakes in three steps: (1) initial exclusion criteria exclude from consideration lakes with pH greater than 6.0 or subject to strong confounding influences (e.g., road salt); (2) a general classification discriminates between lakes according to anion dominance; and (3) a secondary classification of lakes within each anion dominant class determines the most likely acidification pathway, using preliminary quantitative criteria designed to discriminate among competing hypotheses. Results computed for sampled lakes were scaled-up to produce regional population estimates, using the statistical framework of the ELS. Acidic deposition appears to be the most likely cause of low pH conditions in about two-thirds of the non-excluded lakes in the ELS low pH target population. Organic acidity arising from wetlands or land use changes appears to be primarily responsible for the low pH status of one quarter of these lakes. Watershed S sources and acid mine drainage appear to be of negligible importance, though further information on dry deposition rates and/or watershed soils is required to confirm this.     

Numerical simulation model of fatty acids in lake sediments

The finite element model was successfully applied to predict the Pb-210 and total extractable fatty acid concentrations at different depths in two sediment cores from Lake Ontario by using different transport parameters. The transport parameters were computed from Pb-210 data. These parameters were used to simulate the total extractable fatty acid concentrations at different depths. The computed results were compared with observed data and results were compared by statistical methods. Good agreement was achieved though improved results were observed in a two layer model accounting for bioturbation in the upper 4–6 cm of sediment. By modifying this model is useful to apply the contaminant transport in lake sediments, industrial waste disposal ponds, and fish ponds with different geological, physical, chemical and biological parameters at different depths.     

Characterization and neutralization requirements of two acidic lake sediments

Preparations for neutralization of two acidic lakes in the southwest Adirondacks included determination of base neutralization capacity for sediments as well as the water column. For sediments this involved assessing vertical and horizontal gradients in sediment properties related to sediment-bound acidity. The analyses showed significant variance vertically (depth within the sediment profile) and horizontally (due mainly to depth of overlying water) in both lakes. Base requirements, equivalent to the acidity present 3in 2 cm of sediments ranged between 0.011 and 0.022 kg CaCO₃ m^?3 for the two lakes. Preliminary observations indicate pH³ values and Ca content increased in the surficial sediments of both lakes after treatment.     

Environmental chemistry of copper in torch lake,Michigan

A study of Keweenaw Peninsula and adjacent Lake Superior waters was undertaken to evaluate the significance of Cu tailings deposits as a potential source of Cu and the controlling Cu concentrations in these waters. Metal concentrations were determined by atomic absorption techniques. Copper concentrations, especially in areas affected by discharge of large quantities of Cu mine tailings for over 100 yr, were relatively high. Concentrations of apparently dissolved Cu of up to 100 μg 1^?1 were found in Torch Lake in the summer of 1972. These high Cu levels may be partially explained by industrial spills of copper wastes that occurred around that time. However, relatively high concentrations appeared to persist in Torch Lake waters throughout the annual cycle. The vast quantities of crushed Cu-bearing ore that comprise the bottom sediments and line the shores show a Cu content ranging from 1300 to 3800 mg 1^?1. These materials act as a reservoir of Cu providing a continual supply of Cu to these waters. Laboratory leaching studies of these materials demonstrate that they can release potentially significant amounts of Cu when suspended in lake water. Although the Cu levels found in Torch Lake exceed US EPA-recommended maximum allowable levels for these waters, there are reports of substantial fish and algal populations. Equilibrium calculations indicate the predominance of various soluble Cu species in the following order of abundance: Cu(OH)⁺ > Cu⁺⁺ > CuCO₃. However, Cu in these waters may not be controlled by solubility relationships of Cu compounds but rather by sorption onto surfaces of Fe and Mg hydrous oxides resulting in the occurrence of Cu in relatively non-toxic forms. Any additional mining or reclamation operations pose a potential hazard to aquatic ecosystems because of the wide-spread Cu contamination that already exists in the waters of this area.     

Complexing properties of nitrilotriacetic acid in the lake environment

At concentrations above 1 ppm NTA can react with sparingly soluble compounds to release the metal and associated anions through complexation. It also interacts with sediment to release certain metals depending on the abundance of the metals in the sediment. In situ and laboratory experiments have been carried out to study such interactions and also to follow the fate of these released metals after NTA has degraded. Degradation of certain NTA-metal complexes in lake water medium has also been studied. It was found that certain NTA complexes (Cu, Ni, Cd, Hg) are very resistent to degradation.     

Copper profiles in the sediments of a mining-impacted lake

Purpose  

The sediments of Torch Lake, located in Houghton County, MI, USA, have been impacted by copper mining activity. Remediation of the site has focused on immobilizing shoreline tailing deposits. However, a large amount of copper remains in the mining-sourced sediment, and high copper concentrations persist in surface sediments. This study analyzes sediment core and sediment trap data to determine the source of copper in the surface sediments.     

The spreading of crude oil spills across a lake

Water, Air, & Soil Pollution - The spreading of two different crude oils on the surface of lakes in the Mackenzie River delta region near Inuvik, N.W.T., Canada was examined. The crude oils...     

Base neutralizing capacity of sediments from an acidic lake

The base neutralizing capacity (BNC), or alkalinity consumption, of acidic lake sediments may influence the amount of neutralizing agent required to neutralize a lake if the sediment BNC is large relative to the BNC of overlying waters. The extent ofin situ sediment BNC in acidic Bowland Lake (pH 5.0) was inferred by (1) measuring the loss of Ca-45 to acidic sediments from labeled lake water neutralized with CaCO₃, and (2) measuring exchangeable Ca in sediments collected prior to and following neutralization of Bowland Lake with calcite (CaCO₃). The sediment BNC derived from the Ca-45 radiolabeling experiment was 0.01 mg CaCO₃ g^?1 w wt. The mean losses of Ca-45 from the aqueous phase of neutralized and untreated sediment/water mixtures were not significantly different. The mean pH of both neutralized and untreated mixtures decreased to 4.0 during the incubation, possibly because of oxidation of reduced sediments. Sediment BNC estimates derived from literature data for several lakes may be overestimated because of the inclusion of anoxic sediments containing significant amounts of reduced Fe. There was no significant difference in exchangeable Ca between sediments from untreated Bowland Lake and sediments collected 10 m after whole-lake neutralization indicating that little of the supplied alkalinity had been lost to the sediments. Hence,in situ sediment BNC was probably small in Bowland Lake.     

Specific rates of net methylmercury production in lake sediments

Specific rates of Hg (²⁰³HgCl₂) methylation and McHg (¹⁴CH₃HgI) demethylation in aerobic and anaerobic conditions were determined in samples of surface sediments (0 to 2 cm) taken from five small headwater lakes in Southern Finland. The highest rates of methylation were measured in anaerobic conditions. However, the importance of aerobic methylation increased with increasing Fe and Mn content in sediment. There was little difference between aerobic and anaerobic demethylation. The results demonstrate that the net McHg production in lake sediments depends on the individual characteristics of the lake, particularly pH and and sediment properties. These characteristics seem to affect demethylation in anaerobic conditions and methylation in aerobic conditions.