Hydrogeochemsitry of montane springs and their influence on streams in the Cairngorm mountains, Scotland

International audienceSprings are important groundwater discharge points on the high altitude (>800m) plateaux of the Cairngorm mountains, Scotland and form important wetland habitats within what is often a dry, sub-arctic landscape. The hydrogeochemistry of a typical spring in the Allt a'Mharcaidh catchment was examined between 1995-98 in order to characterise its chemical composition, identify the dominant controls on its chemical evolution and estimate groundwater residence time using 18O isotopes. Spring water, sustained by groundwater flow in shallow drift deposits and fractured bedrock, was moderately acidic (mean pH 5.89), with a very low alkalinity (mean 18 ?eq l-1) and the ionic composition was dominated by sea-salts derived from atmospheric sources. Geochemical modelling using NETPATH, predicted that the dissolution of plagioclase mainly controls the release of Si, non-marine Na, Ca, K and Al into spring water. Hydrological conditions influenced seasonal variations in spring chemistry, with snowmelt associated with more rapid groundwater flows and lower weathering rates than summer discharges. Downstream of the spring, the chemistry of surface water was fundamentally different as a result of drainage from larger catchment areas, with increased soil and drift cover, and higher evaporation rates. Thus, the hydrogeochemical influence of springs on surface waters appears to be localized. Mean ?18O values in spring water were lower and more damped than those in precipitation. Nevertheless, a sinusoidal seasonal pattern was observed and used to estimate mean residence times of groundwater of around 2 years. Thus, in the high altitude plateau of the Cairngorms, shallow, coarse drift deposits from significant aquifers. At lower altitudes, deeper drift deposits, combined with larger catchment areas, increase mean groundwater residence times to >5 years. At high altitudes, the shallow, permeable nature of the drifts dictates that groundwater is vulnerable to impacts of environmental changes that could be usefully monitored at spring sites

Assessing recovery from acidification of European surface waters in the year 2010: Evaluation of projections made with the MAGIC Model in 1995

In 1999 we used the MAGIC (Model of Acidification of Groundwater In Catchments) model to project acidification of acid-sensitive European surface waters in the year 2010, given implementation of the Gothenburg Protocol to the Convention on Long-Range Transboundary Air Pollution (LRTAP). A total of 202 sites in 10 regions in Europe were studied. These forecasts can now be compared with measurements for the year 2010, to give a "ground truth" evaluation of the model. The prerequisite for this test is that the actual sulfur and nitrogen deposition decreased from 1995 to 2010 by the same amount as that used to drive the model forecasts; this was largely the case for sulfur, but less so for nitrogen, and the simulated surface water [NO3-] reflected this difference. For most of the sites, predicted surface water recovery from acidification for the year 2010 is very close to the actual recovery observed from measured data, as recovery is predominantly driven by reductions in sulfur deposition. Overall these results show that MAGIC successfully predicts future water chemistry given known changes in acid deposition

Anthropogenic Space Weather

Anthropogenic effects on the space environment started in the late 19th century and reached their peak in the 1960s when high-altitude nuclear explosions were carried out by the USA and the Soviet Union. These explosions created artificial radiation belts near Earth that resulted in major damages to several satellites. Another, unexpected impact of the high-altitude nuclear tests was the electromagnetic pulse (EMP) that can have devastating effects over a large geographic area (as large as the continental United States). Other anthropogenic impacts on the space environment include chemical release ex- periments, high-frequency wave heating of the ionosphere and the interaction of VLF waves with the radiation belts. This paper reviews the fundamental physical process behind these phenomena and discusses the observations of their impacts.Comment: 71 pages, 35 figure

Modelling the effects of changing climate and nitrogen deposition on nitrate dynamics in a Scottish mountain catchment

The effect of changing climate and N deposition on montane ecosystems is a topic of considerable importance. Mountains are vulnerable environments and their ecosystems are often in a delicate balance. An application of the INCA-N model is presented to simulate current-day nitrate dynamics in a Scottish mountain lake and to project the possible future effects of climate change and reductions in N deposition on lake nitrate concentration ([NO3-]). The INCA-N model is calibrated using data from 1996–2006 in an attempt to determine the controls on [NO3-] in Lochnagar and process sensitivities to changing climate. Predictions were sensitive to hydrologic, vegetation-related and in-soil processes. Over the longer term, surface water [NO3-] in this mountain ecosystem is expected to increase. From 2020 to 2100, when N deposition is modelled at a constant rate, warmer temperature exerts a stronger effect on N losses to the lake surface than the N deposition. While the effects of a warming climate are projected to lead to increased surface water [NO3-], concentrations are not projected to either return to, or exceed, historical levels

Effects of future N deposition scenarios on the Galloway region of SW Scotland using a coupled sulphur and nitrogen model (MAGIC-Wand).

The Galloway region of Southwest Scotland has been subject to decades of acidic deposition which has resulted in damage to soils, surface waters and aquatic biota. A survey of lochs was conducted in 1979, 1988, and 1993, over which time there have been dramatic changes in total sulphur and nitrogen deposition. The MAGIC model successfully reproduced the major chemical changes in water chemistry from 1979 to 1988 during which time there was a rapid decline in sulphur deposition. A new coupled sulphur and nitrogen model (MAGIC-WAND) has been used to evaluate the regional hydrochemical response to changing patterns of N & S deposition from the period 1988 to 1993. Details of the model structure and parameterisation are discussed. The model under-predicts the response of non-marine sulphate in the region suggesting that there has been a slight increase in deposition over this period. Future hydrochemical responses to different nitrogen deposition scenarios are presented, indicating that the potential increase of nitrogen in surface waters is closely linked to the age and extent of different mosaics of commercial afforestation within the individual catchments

Past acidification and recovery of surface waters, soils and ecology in the United Kingdom: prospects for the future under current deposition and land use protocols

The dynamic hydrogeochemical model MAGIC has been applied extensively throughout Europe and North America and has proven to be a valuable tool for predicting the chemical response of catchment soils and surface waters to future changes in atmospheric pollution and land use. Here we present an application of MAGIC to 22 sites in the UK Acid Waters Monitoring Network (UKAWMN) that incorporated uncertainty in model calibration (using 20 years of surface water observations) to evaluate past acidification and prospects for future recovery in surface waters, soils and key ecological indicators. Simulated ANC in 1860 indicated that prior to industrialisation, all UKAWMN surface waters were above the critical acid neutralising capacity (ANC) limit of 20 μeq l–1, with the exception of a naturally acid site, underlain by granite with large expanses of bare rock, scree and eroded peat in Northern Ireland (Blue Lough); this site had a baseline ANC value <20 μeq l–1. The significant increase in acidic deposition from 1860 to its peak during the 1970s resulted in surface water acidification at 14 of the study sites (ANC < 20 μeq l–1). The rate and magnitude of chemical recovery in soil is highly variable among sites owing to differences in factors such as soil mineral weathering and base saturation. Despite the significant reductions in sulphur and to a lesser extent nitrogen deposition since 1970, the simulated soil base saturation at all study sites either continued to decline or remained stable until the late 1980s, with marginal recovery detected at some sites in the past decade. Predictions were based on an emission reduction scenario (Gothenburg protocol) to 2020, and land use scenarios to 2050 based on approved Forestry Commission plans at the five afforested sites. Model predictions indicated that, in general, surface water acid status will continue to improve during the next decade and beyond under the Gothenburg protocol. Surface water recovery was primarily attributed to the significant decline in sulphate concentrations from a present day mean of 58.5 μeq l–1–43.8 μeq l–1 in 2020. The contribution of nitrate (NO3–) leaching to the total acid status of surface water was small and predicted to decrease from 10.9 μeq l–1 in 2007 to 9.6 μeq l–1 in 2020. By 2100, NO3– concentrations increased slightly to 11.8 μeq l–1 having a small confounding influence on the rate of chemical recovery at most sites in the network. The future response of soil base saturation to reductions in acid deposition and land use change was mixed and the difference in behaviour between sites is unclear. Whilst recent studies (Malcolm et al., 2014a, Malcolm et al., 2014b and Monteith et al., 2014) have demonstrated that forest practices have contributed to the acidification of surface waters, in this study, there was no evidence from the model predictions that forested sites will follow a different recovery trajectory to moorland sites. Planned reductions in coniferous forest cover amounting to approximately 13% across the five afforested sites resulted in a slight increase in ANC and pH. Ecological predictions highlighted the sensitivity of three indicator species (Baetis Rhodani, Achnanthes minutissima and salmonids) to changes in the acid status of surface water in the past and into the future. There was clear evidence of biological recovery by 2015 with some sites returning close to their pre-industrial biological status (Allt a’Mharcaidh) while at others (including Loch Grannoch and River Etherow) predicted recovery was incomplete for one or more of the studied indicator species