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The MAGIC model was used to evaluate the relative sensitivity of several possible climate-induced effects on the recovery of soil and surface water from acidification. A common protocol was used at 14 intensively studied sites in Europe and eastern North America. The results show that several of the factors are of only minor importance (increase in pCO2 in soil air and runoff, for example), several are important at only a few sites (seasalts at near-coastal sites, for example) and several are important at nearly all sites (increased concentrations of organic acids in soil solution and runoff, for example). In addition changes in forest growth and decomposition of soil organic matter are important at forested sites and sites at risk of nitrogen saturation. The trials suggest that in future modelling of recovery from acidification should take into account possible concurrent climate changes and focus specially on the climate-induced changes in organic acids and nitrogen retention.

High mountain lakes are sensitive to environmental change and the effects of air pollution and lake acidification have been recorded in many countries. The EU funded EMERGE programme included a pan-European assessment of the extent of acidification in mountain lakes located above the tree-line. A static critical loads model, the First-order Acidity Balance (FAB) model, was used to assess (1) the extent of critical load exceedance in 300 lakes in nine European lake districts and (2) the relative importance of sulphur and nitrogen deposition in contributing to acidification. The regional sensitivity of FAB to the choice of critical acid neutralising capacity (ANC: 0 or 20 meq L–1) was explored. With a critical ANC value of 0 meq L–1 only four lake districts had sites showing exceedance of critical loads; Piedmont Aquat. Sci. 67 (2005) 237–251 1015-1621/05/030237-15 DOI 10.1007/s00027-005-0742-0 © EAWAG, Dübendorf, 2005 Aquatic Sciences Ticino, the Pyrenees, the Retezat Mountains and the Tatras. When a more stringent critical ANC of 20 meq L–1 was used, all nine lake districts showed critical load exceedance in one or more lakes. For two lake districts, the Retezat Mountains of Romania and the Rila Mountains of Bulgaria, critical load exceedance is recorded here for the first time. Nitrogen is a more important agent of acidification in some areas such as the Pyrenees and Piedmont Ticino, and its relative importance is likely to increase elsewhere as pan-European measures to reduce sulphur deposition continue to take effect. Given the coarse scale deposition data used and potentially underestimated loads at high altitudes, the extent of the acidification problem may be under-represented here.

The process-oriented catchment-scale model MAGIC was used to simulate water chemistry at Lake Redó, a high mountain lake in the Central Pyrenees, Spain. Data on lakewater and atmospheric deposition chemistry for the period 1984-1998 were used to calibrate the model, which was then used to reconstruct past and to provide forecasts for three hypothetical future scenarios of deposition. Forecast scenarios considered several combinations of changes in S and N deposition due to abatement strategies, and in base cation deposition due to climate-induced changes in air-mass trajectories from northern Africa. Scenario 1 assumed constant deposition of base cations at the present level plus the expected decrease in S and N deposition resulting from reduced emissions; scenario 2 (best case) assumed an increase in base cation deposition plus the same decrease in S and N deposition as in scenario 1; scenario 3 (worst case) assumed a decrease in base cation deposition plus no decrease in S and N deposition. The hindcast indicated that during the past 140-year period changes in lake water chemistry have been significant for a remote mountain catchment, although no substantial acidification has occurred. In this regard Lake Redó can be described as a "non-sensitive lake" maintaining a reference condition. The forecasts indicated changes that do not affect this status, but the trends, even if slight, were different between scenarios. A slight decline in the surface water ANC is predicted by Scenario 3. The N budget indicates an unusually low retention in the catchment, which may result in enhanced sensitivity to further increased N deposition. Some of the discrepancy between modelled and measured Ca2+ in lake water during 1984-98 could be explained by changes in rainfall amounts and by increased weathering rates due to increases in air temperature.

The increase in emission of sulphur oxides and nitrogen (both oxidised and reduced forms) since the mid-1800s caused a severe decline in pH and ANC in acid-sensitive surface waters across Europe. Since c.1980, these emissions have declined and trends towards recovery from acidification have been widely observed in time-series of water chemistry data. In this paper, the MAGIC model was applied to 10 regions (the SMART model to one) in Europe to address the question of future recovery under the most recently agreed emission protocols (the 1999 Gothenburg Protocol). The models were calibrated using best available data and driven using S and N deposition sequences for Europe derived from EMEP data. The wide extent and the severity of water acidification in 1980 in many regions were illustrated by model simulations which showed significant deterioration in ANC away from the pre-acidification conditions. The simulations also captured the recovery to 2000 in response to the existing emission reductions. Predictions to 2016 indicated further significant recovery towards pre-acidification chemistry in all regions except Central England (S Pennines), S Alps, S Norway and S Sweden. In these areas it is clear that further emission reductions will be required and that the recovery of surface waters will take several decades as soils slowly replenish their depleted base cation pools. Chemical recovery may not, however, ensure biological recovery and further reductions may also be required to enable these waters to achieve the "good ecological status" as required by the EU Water Framework Directive.

We present results from a study that used a non-intrusive diagnostic for mixing, species concentration, optical gain, and spatial beam profile for HF chemical lasers. The instrument is based on hyperspectral imaging using a low order Fabry-Perot interferometer. The basic theory behind this technology is described and several applications to a chemically reacting flow field are presented. We also discuss application of this device to a subsonic HF chemical laser., Presented at the Proceedings of the AIAA Plasmadynamics and Lasers Conference (33rd), Maui, HI, May 2002.