Trends in the Water Chemistry of High Altitude Lakes in Europe (original) (raw)
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Trends in the chemical composition of high altitude lakes selected for the MOLAR project
Here we present the chemical trends of seven high altitude lakes, analysed within the AL:PE and MOLAR Projects of the EU (1999) and selected on the basis of the availability of complete and reliable data for the period 1984-1999. The lakes are representative of the Scandinavian Alps, the Cairngorm Mountains in Scotland, the Alps and the Pyrenees. Significant trends were identified for some indicators of acidification, for instance pH and alkalinity, but not all lakes reacted similarly to decreasing depositions of sulphate and base cations. Differences in lake response are discussed in relation to recent variations of atmospheric deposition chemistry and associated changes in climatic conditions. Beside individual variations of the studied lakes, depending, among other things, on altitude and morphology, catchment characteristics and climate trends play a major role for the reaction of high altitude lakes on changes in atmospheric depositions.
e hydrochemistry of high-altitude lakes in selected mountain ranges of Central and Southern Europe
2006
e results of hydrochemical investigations of 29 high-altitude lakes in two mountain regions of Europe (Carpathian and Rhodope Mountains), diversified genetically and with respect to present morphogenetic processes, are discussed in relation to local geological, climatic, hydrological conditions and anthropopression. e differences in concentration of major ions (Na + , K + , Mg 2+ , Ca 2+ , SO 4 2- and HCO 3 - ) are strongly correlated with the altitude of the lakes, and chemical diversity of their water reflects primarily the differences in intensity of chemical weathering and, to a lesser extent, the difference in mineral composition of bedrock. e characteristics of geological structure of the surroundings of lake basin is reflected in chemistry of the lakes located in the area of occurrence of strongly weathered series of metamorphic rock. e ion ratios in water of the investigated lakes are important indicators of anthropogenic influence.
Regionalisation of chemical variability in European mountain lakes
Freshwater Biology, 2009
1. We carried out a coordinated survey of mountain lakes covering the main ranges across Europe (including Greenland), sampling 379 lakes above the local tree line in 2000. The objectives were to identify the main sources of chemical variability in mountain lakes, define a chemical classification of lakes, and develop tools to extrapolate our results to regional lake populations through an empirical regionalisation or upscaling of chemical properties. 2. We investigated the main causes of chemical variability using factor analysis (FA) and empirical relationships between chemistry and several environmental variables. Weathering, sea salt inputs, atmospheric deposition of N and S, and biological activity in soils of the catchment were identified as the major drivers of lake chemistry. 3. We tested discriminant analysis (DA) to predict the lake chemistry. It was possible to use the lithology of the catchments to predict the range of Ca 2+ and SO 4 2) into which a lake of unknown chemistry will decrease. Lakes with lower SO 4 2) concentrations have little geologically derived S, and better reflect the variations in atmospheric S loading. The influence of marine aerosols on lakewater chemistry could also be predicted from the minimum distance to the sea and altitude of the lakes. 4. The most remarkable result of FA was to reveal a factor correlated to DOC (positively) and NO 3 ) (negatively). This inverse relationship might be the result either of independent processes active in the catchment soils and acting in an opposite sense, or a direct interaction, e.g. limitation of denitrification by DOC availability. Such a relationship has been reported in the recent literature in many sites and at all scales, appearing to be a global pattern that could reflect the link between the C and N cycles. 5. The concentration of NO 3 ) is determined by both atmospheric N deposition and the processing capacity of the catchments (i.e. N uptake by plants and soil microbes). The fraction of the variability in NO 3 ) because of atmospheric deposition is captured by an independent factor in the FA. This is the only factor showing a clear pattern when mapped over Europe, indicating lower N deposition in the northernmost areas. 6. A classification has been derived which takes into account all the major chemical features of the mountain lakes in Europe. FA provided the criteria to establish the most important factors influencing lake water chemistry, define classes within them, and classify the surveyed lakes into each class. DA can be used as a tool to scale up the classification to unsurveyed lakes, regarding sensitivity to acidification, marine influence and sources of S.
Factors affecting water chemistry of alpine lakes
Aquatic Sciences, 1995
During a four-year study (1988-1991), 413 lakes in the Central Alps (Italy, Switzerland and Austria) were investigated to quantify their acidification. The ionic content of the lakes was generally low: 68 % of them had alkalinity values of less than 200 geq 1-1 and were regarded as sensitive to acidification. Moreover, 36 % of the lakes showed alkalinity values of less than 50 geq 1-1. Redundancy Analysis was used to relate the hydrochemistry of 187 lakes to their catchment characteristics. Calcite weathering was the main factor influencing lake chemistry. The same analysis, applied to a subset of 101 lakes lying in watersheds exclusively composed of silicic rocks, showed that lake chemistry was influenced by silicate weathering and nitrogen uptake. These processes were found to be mainly related to lake altitude and the fraction of the watershed not covered by vegetation, i.e. controlled by temperature. The importance of these relations to explain the pH shift produced by climatic variation is also discussed.
Journal of Limnology, 2000
Since 1980, surveys have been performed every three years on about 50 small high-altitude Alpine lakes located in the Swiss part of the Lago Maggiore watershed (Southern Central Alps). Since 1996 one of these lakes, Laghetto Inferiore (LI) has been included in the Mountain Lakes Research (MOLAR) program, an extensive European cooperative research project with 23 partners. Laghetto Inferiore, situated at 2074 m a.s.l., has a watershed mainly composed of crystalline silicic rocks, a maximum depth of 33 m and a theoretical renewal time of 41 days. The watershed includes a second lake, Laghetto Superiore (LS), located at 2128 m a.s.l. The surface water pH of LI is around 6.6, while alkalinity is about 30 µeq l-1 , increasing to 90 µeq l-1 at the maximum depth. Calculated inputs from atmospheric deposition and the main tributary streams were compared with changes in the lake concentration, and outflow fluxes on a monthly basis. Weathering ranged between 90-130 meq m-2 of alkalinity using a mass budget approach, of which 50% was consumed by the actual (H +) and potential (NH 4 +) atmospheric acidity. Chemical trends over the period 1985-1998 show an increase in alkalinity and a decrease in sulphate, due to a reduction in the deposition of atmospheric acidity, and a decrease in nitrate, probably because of increased lake productivity.
Atmospheric deposition and lake chemistry trends at a high mountain site in the eastern Alps
Journal of Limnology, 2000
Records of atmospheric precipitation chemistry starting in 1983 and a series of limnological investigations at two high mountain reference lakes starting in 1988 enable us to describe the response of lake water chemistry to changes in precipitation chemistry and climate. The lakes are located at an altitude well above the timberline in a watershed composed of acidic rocks. Despite the observed reduction in the sulphur atmospheric deposition, the reference lakes showed no corresponding decline in sulphate concentrations, but a marked increase in the acid neutralising capacity was apparent. Changes of the seasonal distribution pattern of the precipitation amounts and a general increase of the air temperature have likely produced an increased weathering which increased the concentration of many inlake solutes and drove the lakes toward more buffered conditions. This phenomenon superimposed to changes like other physical factors (radiation), nutritional conditions and biological factors (enhanced production, competition, predation) has produced in the last years greater modifications than merely those to be expected from the decreased acidic input.
The AL:PE project, involving research institutes from 11 countries, was launched in 1991 to study sediments, diatoms, fish, invertebrates, and water chemistry of 28 lakes in relation to atmospheric pollutant inputs. This paper discusses the chemical results and the analytical quality control used to ensure good comparability of the results. Lake waters show varied chemical characteristics—from very diluted, poorly buffered or acidic waters to lakes with high base cation concentrations—with electric conductivity values ranging from 0.4 to 6 mS m~' at 25°C. Nitrate shows a high range of variability, from values close to zero (Svalbard and Portugal), to 11-25 fieq l"1 (Alps), and up to 50 /xeq l'1 (Tatra Mountains).
Environmental Science and Pollution Research, 2014
Increasing the understanding of high mountain lake dynamics is essential to use these remote aquatic ecosystems as proxies of global environmental changes. With this aim, at Sabocos, a Pyrenean cirque glacial lake or tarn, this study shows the main results of a morphological and catchment characterization, along with statistical analyses of its hydrochemical trends and their concomitant driving factors from 2010 to 2013. Dissolved oxygen, water temperature stratification, and its snow and ice cover composition and dynamics have been also investigated. According to morphological analyses, Sabocos can be classified as a medium-large and deep lake, having a circular contour and a long water retention time as compared to Pyrenean glacial lake average values. Sabocos hydrochemistry is mainly determined by very high alkalinity, pH and conductivity levels, and high Ca 2+ , Mg 2+ , and SO 4 2− content, coming from the easily weatherable limestone-dolomite bedrock. Thus, lake water is well buffered, and therefore, Sabocos tarn is non-sensitive to acidification processes. On the other hand, the main source of K + , Na + , and Cl − (sea salts) and nutrients (NH 4 + , NO 3 − , and phosphorous) to lake water appears to be atmospheric deposition. Primary production is phosphorous limited, and due to the Nsaturation stage of the poorly developed soils of Sabocos catchment, NO 3 − is the chief component in the total nitrogen pool.
The Influence of Catchment Characteristics on the Water Chemistry of Mountain Lakes
Arctic, Antarctic, and Alpine Research, 2001
Forty-four lakes in the Austrian Alps were studied to examine the influence of catchment characteristics on water chemistry. The lakes are located along an altitudinal gradient (1502-2309 m a.s.l.) in a small study area (35.5 km * 15.5 km) without glaciers. Longitude and latitude accounted for 21.4% of the variation in water chemistry. Bedrock mineralogy explained 14.5% of the variation. Vegetation accounted for 13.2% and slope for 5.5% of the variation in water chemistry. No correlations were found between exposure and water chemistry. Water chemistry appeared to be mainly determined by (I) chemical weathering of carbonate minerals and (2) in-lake productivity. Carbonate minerals were assumed to be present in all watersheds. Trees and shrubs enhanced chemical weathering. Concentrations of chemical parameters indicating physical weathering were high in lakes with large, steep catchments. Steep watersheds were correlated with enhanced nitrogen concentrations in the lakes. In-lake productivity obscured relationships between chemical parameters and catchment characteristics. Nonetheless, catchment characteristics explained 45% of the variation in water chemistry, stressing their importance for water chemistry in mountain lakes.
The MOLAR Project: atmospheric deposition and lake water chemistry
Journal of Limnology, 1999
In the framework of the Mountain Lake Research (MOLAR) project, the water chemistry of 23 lakes covering Europe from the Svalbard Islands to the South of Spain were studied. The lakes are located above or beyond the timber line in the most important mountain areas in Europe. Atmospheric deposition was sampled at 11 sites, representative of different lake districts. 24 institutions took part in the activity. The comparability of the analytical results performed in 18 laboratories was assured by strict sampling and analysis protocols and by a detailed programme of Analytical Quality Assessment/Control. The paper summarises the main morphometric and hydrological characteristics of the lakes and their watersheds and discusses the results of the atmospheric deposition and lake water chemistry. An overview on the main processes controlling the composition and ionic ratio of deposition and lake chemistry is given.