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The Cairngorms in north-east Scotland is remote from pollutant sources although it currently receives ca. 10 kg ha1 yr1 S and ca. 11 kg ha1 yr1 N deposition from the atmosphere. In 1955, 15 lochs (lakes) at a range of altitudes were sampled and analysed for major ion concentrations. A new survey of these and an additional 23 lochs and their catchment soils was conducted in 1999 to determine the impact of acid deposition, and the changes in loch chemistry since the 1955 survey. The bedrock geology of this region has a strong influence on the loch chemistry. Surface waters were generally more acidic in high altitude areas due to predominantly poorly buffered, thin alpine soils developed on granitic parent material (mean acid neutralising capacity (ANC) for 23 lochs = 30 μeq L1). At lower altitudes where the geology is dominated by Dalradian metamorphic rocks surface waters are comparatively base rich and have higher ANC (mean ANC for 15 lochs = 157 μeq L1). Surface water nitrate concentrations show a negative relationship with soil C:N status, in that higher nitrate only occurs at low soil C:N ratios. A comparison of data for 1955 and 1999 shows that sulphate concentrations are significantly lower (67.8 and 47.5 μeq L1, respectively), and pH has improved (pH 5.6 and 5.9) in response to decreased S deposition since the mid 1970s. However, mean nitrate concentrations were found to increase from 2.48 μ>eq L1 in 1955 to 5.65 μeq L1 in 1999. Differences in the sampling and laboratory methods from 1955 and 1999 are acknowledged in the interpretation of data. [ABSTRACT FROM AUTHOR]

Starolesnianske pleso is a small and shallow acid lake in the High Tatra Mountains, situated at 2000 m above sea level, on granitic bedrock, with sparse and thin soil cover. When detailed measurements began in the 1980s Starolesnianske pleso had pH below 5 and only one species of cladoceran zooplankton, the ubiquitous Chydorus sphaericus Palaeolimnological investigations show changes in cladoceran zooplankton and chironomid zoobenthic assemblages since about 1920 and a major change in 1970–1980. The dynamic acidification model MAGIC was used to reconstruct changes in water chemistry over the past 150 years. The results from MAGIC agree well with the sediment record; pH levels gradually decreased from 6.5 in the mid-1800s to about 5.6 in 1920 (first response in biota) to below 5.0 by 1970, and concentrations of inorganic aluminium rose dramatically beginning about 1960. In the 1990s the lake water chemistry showed clear signs of reversal in acidification brought about by a major decline in S deposition. [ABSTRACT FROM AUTHOR]

The NITREX project, which encompasses seven ecosystem-scale experiments in coniferous forests at the plot or catchment level in northwestern Europe, investigates the effect of atmospheric nitrogen (N) deposition in coniferous forests. The common factor in all of the experiments is the experimentally controlled change in N input over a period of 4–5 years. Results indicate that the status and dynamics of the forest floor are key components in determining the response of forests to altered N inputs. An empirical relationship between the carbon–nitrogen (C/N) ratio of the forest floor and retention of incoming N provides a simply measured tool through which the likely timing and consequences of changes in atmospheric N deposition for fresh waters may be predicted. In the terrestrial ecosystem, a 50% increase in tree growth is observed following the experimental reduction of N and sulfur inputs in a highly N-saturated site, illustrating the damaging effects of acidifying pollutants to tree health in some locations. Few biotic responses to the experimental treatments were observed in other NITREX sites, but the rapid response of water quality to changes in N deposition, and the link to acidification in sensitive areas, highlight the need for N-emission controls, irrespective of the long-term effects on tree health. The observed changes in ecosystem function in response to the experimental treatments have been considered within the framework of the current critical-load approach and thus contribute to the formulation of environmental policy. [ABSTRACT FROM AUTHOR]

Lakes in mountainous areas are of special interest in environmentalstudies because such takes are generally particularly sensitive to inputs of atmospheric pollution and to changes in climate. Mountain lakes provide, therefore, an early warning of more widespread environmental changes. Surveys of lake-water chemistry in mountain areas in Norway, and mountain areas elsewhere in Europe which have crystalline bedrock, clearly show that such lakes are generally very dilute with low concentrations of base cations, alkalinity and SO42-. Mountain lakes also have low concentrations of total-P and TOC. The low concentrations of inorganic and organic ions are due to several factors of which low weathering rates, thin soils, high water fluxes and sparse vegetation in the catchment are of major importance. N03- concentrations on the other hand, are often higher in mountain lakes relative to low elevation lakes in the same area, due to the lower retention capacity of atmosphericallydeposited N in mountain catchments. [ABSTRACT FROM AUTHOR]

In June 1983 a whole-catchment liming experiment was conducted at Tjonnstrond, southernmost Norway, to test the utility of terrestrial liming as a technique to restore fish populations in remote lakes with short water-retention times. Tjonnstrond consists of 2 small ponds of3.0 and 1.5 ha in area which drain a 25-ha catchment. The area is located at about 650--700 meters above sea-level in sparse and unproductive forests of spruce, pine and birch with abundant peatlands. A dose of 3 ton/ha of powdered limestone were spread by helicopter to the terrestrial area. No limestone was added to the ponds themselves. Theponds were subsequently stocked with brown and brook trout. Liming caused large and immediate changes in surface water chemistry; pH increased from 4.5 to 7.0, Ca increased from 40 to 200 mu eq/L, ANC increased from -30 to +70 mu eq/L, and reactive-Al decreased from about 10to 3 mu mol/L. During the subsequent 11 years the chemical composition of runoff has decreased gradually back towards the acidic pre-treatment situation. The major trends in concentrations of runoff Ca, ANC, pH, Al and NO{sub}3{end} in runoff are all well simulated by the acidification model MAGIC. Neither the measured data nor the MAGIC simulations indicate significant changes in any other major ion as a result of liming. The soils at Tjonnstrond in 1992 contained significantly higher amounts of exchangeable Ca relative to those at the untreated reference catchment Storgama. In 1992 about 75% of the added Ca remains in the soil as exchangeable Ca, 15% has been lost in runoff, and10% is unaccounted for. The whole-catchment liming experiment at Tjonnstrond clearly demonstrates that this liming technique produces a long-term stable and favourable water quality for fish. Brown trout inboth ponds in 1994 have good condition, factors, which indicate thatthe fish are not stressed by marginal water quality due to re-acidification. The water quality is still adequate after 11 years and >20 water r [ABSTRACT FROM AUTHOR]