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Nitrogen (N) deposition is globally considered as a major threat to ecosystem functioning with important consequences for biodiversity, carbon sequestration and N retention. Lowered N retention as manifested by elevated concentrations of inorganic N in surface waters indicates ecosystem N saturation. Nitrate (NO3) concentrations in runoff from semi-natural catchments typically show an annual cycle, with low concentrations during the summer and high concentrations during the winter. Process-oriented catchment-scale biogeochemical models provide tools for simulation and testing changes in surface water and soil chemistry in response to changes in sulphur (S) and N deposition and climate. Here we examine the ability of MAGIC to simulate the observed monthly as well as the long-term trends over 10-35 years of inorganic N concentrations in streamwaters from four monitored headwater catchments in Europe: Čertovo Lake in the Czech Republic, Afon Gwy at Plynlimon, UK, Storgama, Norway and G2 NITREX at Gårdsjön, Sweden. The balance between N inputs (mineralization+deposition) and microbial immobilization and plant uptake defined the seasonal pattern of NO3 leaching. N mineralization and N uptake were assumed to be governed by temperature, described by Q10 functions. Seasonality in NO3 concentration and fluxes were satisfactorily reproduced at three sites (R2 of predicted vs. modelled concentrations varied between 0.32 and 0.47 and for fluxes between 0.36 and 0.88). The model was less successful in reproducing the observed NO3 concentrations and fluxes at the experimental N addition site G2 NITREX (R2=0.01 and R2=0.19, respectively). In contrast to the three monitored sites, Gårdsjön is in a state of change from a N-limited to N-rich ecosystem due to 20 years of experimental N addition. At Gårdsjön the measured NO3 seasonal pattern did not follow typical annual cycle for reasons which are not well understood, and thus not simulated by the model.The MAGIC model is able to simulate NO3 leaching on a monthly as well as an annual basis, and thus to reproduce the seasonal and short-term variations in N dynamics.

V důsledku poklesu teploty spalin pod teplotu rosného bodu dochází u řady energetických celků k problémům s korozí vlivem zkondenzovaných kyselin. Dochází tak k značným korozním napadením a poškozením zejména na ohřívácích vzduchu, ekonomizérech, vedeních kouřovodů, ale i v samotném komíně. Ve SVÚM se vyvíjí automatický systém pro kontinuální měření teploty rosného bodu spalin přímo ve spalovacím zařízení. V této práci jsou shrnuty výsledky z dosavadních příprav pilotního provozu v uhelné elektrárně.

Temporal trends in DOC concentration and flux were investigated at two geochemically distinct forested catchments in western Czech Republic. Mean discharge-weighted DOC concentrations averaged 18.8 mg L(-1) at the acidic Lysina catchment, and 20.2 mg L(-1) at base-rich and well-buffered Pluhuv Bor. Between 1993 and 2007 DOC in streamwater increased significantly in both catchments: the mean annual increase was 0.42 mg L(-1) yr(-1) (p < 0.001) at Lysina and 0.43 mg L(-1) yr(-1) (p < 0.001) at Pluhuv Bor, resulting in cumulative increases of 64 and 65%, respectively. These long-term increases in streamwater DOC were correlated with only modest increases in stream pH in both catchments, but large declines in ionic strength (IS), that resulted from declining atmospheric deposition. Neither catchment has undergone changes in soil-water pH, yet DOC concentrations tripled in the soil-water of both catchments. We conclude that changes in ionic strength of soil-water and streamwater, rather than acidity, are the primary drivers of changes in streamwater DOC in this region. Temperature, precipitation and discharge show no statistically significant trends during the study period, suggesting that climate change has played no role in the changes in DOC that we have observed.

Modeling and monitoring of acidification patterns in a limed forest catchment in the Ore Mountains, SE Germany are presented. A lumped-parameter model, MAGIC, satisfactorily reproduced the main parameters of stream water chemistry. Despite repeated whole-catchment liming, between 1993 and 1999 stream water pH increased from 4.3 to only 4.6, while calcium concentrations declined slightly. Stream water sulfate concentration declined from 687 to 396 microeq l(-1), and the pronounced effect of deposition decline during the 1990s was probably more important than liming.

The Lysina catchment in the Czech Republic was studied to investigate the biogeochemical response of Al to high loadings of acidic deposition. The catchment supports Norway spruce plantations and is underlain by granite and podzolic soil. Atmospheric deposition to the site was characterized by high H + and SO 4 2- fluxes in throughfall. The volume-weighted average concentration of total Al (Al t ) was 28 mmol L -1 in the O horizon soil solution. About 50% of Al t in the O horizon was in the form of potentially-toxic inorganic monomeric Al (Al i ). In the E horizon, Al t increased to 71 μmol L -1 , and Al i comprised 80% of Al t . The concentration of Al t (120 μmol L -1 ) and the fraction of Al i (85%) increased in the lower mineral soil due to increases in Al i and decreases in organic monomeric Al (Al o ). Shallow ground water was less acidic and had lower Al t concentration (29 μmol L -1 ). The volume-weighted average concentration of Al t was extremely high in stream water (60 μmol L -1 ) with Al i accounting for about 60% of Al t . The major species of Al i in stream water were fluorocomplexes (Al-F) and aquo Al 3+ . Soil solutions in the root zone were undersaturated with respect to all Al-bearing mineral phases. However, stream water exhibited Al i concentrations close to solubility with jurbanite. Acidic waters and elevated Al concentrations reflected the limited supply of basic cations on the soil exchange complex and slow weathering, which was unable to neutralize atmospheric inputs of strong acids.

Water samples have been collected from two forested catchments in the Slavkovsky les Mountains of western Bohemia, in the Czech Republic. The objective of the study was to compare and contrast elemental fluxes in two catchments with similar conditions of climate, topography, vegetation over and acidic atmospheric deposition, but very different bedrock geology. The Lysina catchment is underlain by slow-weathering leucocratic granite. Soils are podzolized brown earths and peaty gleys with small pools of exchangeable basic cations. Both soils and drainage water at Lysina are acidified by atmospheric deposition. Surface runoff was found to be dominated by sulphate and dissolved silica, accompanied by high concentrations of H+ (volume weighted pH = 3.87). Stream water also displayed extremely high concentrations of total aluminum (volume-weighted mean 66 μmol.l−1). Inorganic monomeric aluminum was the predominant aluminum fraction present, which contained mainly aquo-Al (Al3+ and fluoride complexes.

We present a new formulation of the acidification model MAGIC that uses decomposer dynamics to link nitrogen (N) cycling to carbon (C) turnover in soils. The new model is evaluated by application to 15-30 years of water chemistry data at three coniferous-forested sites in the Czech Republic where deposition of sulphur (S) and N have decreased by >80% and 40%, respectively. Sulphate concentrations in waters have declined commensurately with S deposition, but nitrate concentrations have shown much larger decreases relative to N deposition. This behaviour is inconsistent with most conceptual models of N saturation, and with earlier versions of MAGIC which assume N retention to be a first-order function of N deposition and/or controlled by the soil C/N ratio. In comparison with earlier versions, the new formulation more correctly simulates observed short-term changes in nitrate leaching, as well as long-term retention of N in soils. The model suggests that, despite recent deposition reductions and recovery, progressive N saturation will lead to increased future nitrate leaching, ecosystem eutrophication and re-acidification.

13 páginas, 5 figuras, 1 tabla., 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., This work was supported in part by the Eurolimpacs project (the Commission of European Communities GOCE-CT-2003-505540) and the Research Council of Norway.

The specifie reaction of ketoses with zirconyl chloride was used to develop a method for the determination of fructose in vesicular secretions, seminal plasma, and blood plasma. After deproteinization with 96% ethanol, the samples can be stored at 4°C until further processing. The supernatant is incubated with zirconyl chloride at 100°C for 30 min. Measurements are made of the absorbance and/or fluorescence. The absorbance is measured at 334 nm, and the fluorescence at an excitation wavelength of 355 nm and an emission wavelength of 410 nm. With an aqueous solution containing 40 mmol/liter of zirconyl chloride, the reaction was linear in the fructose concentration range of 0–8 mmol/liter. The reaction product is stable for at least 60 min.