Determination of dominant sources of nitrate contamination in transboundary (Russian Federation/Ukraine) catchment with heterogeneous land use.

Nitrate contamination of surface water and shallow groundwater was studied in transboundary (Russia/Ukraine) catchment with heterogeneous land use. Dominant sources of nitrate contamination were determined by applying a dual δ 15N-NO3 and δ 18O-NO3 isotope approach, multivariate statistics, and land use analysis. Nitrate concentration was highly variable from 0.25 to 22 mg L-1 in surface water and from 0.5 to 100 mg L-1 in groundwater. The applied method indicated that sewage to surface water and sewage and manure to groundwater were dominant sources of nitrate contamination. Nitrate/chloride molar ratio was added to support the dual isotope signature and indicated the contribution of fertilizers to the nitrate content in groundwater. Groundwater temperature was found to be an additional indicator of manure and sewerage leaks in the shallow aquifer which has limited protection and is vulnerable to groundwater pollution.

Comparative study of model prediction of diffuse nutrient losses in response to changes in agricultural practices.

This article presents a comparative study of modelled changes in nutrient losses from two European catchments caused by modifications in agricultural practices. The purpose was not to compare the actual models used, but rather to assess the uncertainties a manager may be faced with after receiving decision support from consultants using different models. Seven modelling teams were given the same data about two catchments and their management characteristics and were asked to model the same changes in management practices using the model of their own choice. This can potentially cause accumulated 'errors' due to differences in the modelling teams' interpretation of relevant processes and definitions of boundary conditions (inputs). The study was carried out within the framework of the EUROHARP project, which aimed at harmonising procedures for quantifying diffuse losses of nitrogen and phosphorus from agriculture. Models are important for assessing river basin management plans (RBMPs) as required e.g. under the EC Water Framework Directive and Action Plans under the EC Nitrates Directive. This article illustrates some challenges with respect to interpreting such modelling results. The selected management scenarios include changes in fertiliser application levels, changes in livestock numbers and changes in land-use and crop rotation systems. Seven models were applied for the same scenarios in the Enza catchment in Italy and the Zelivka catchment in the Czech Republic. All models had been calibrated and validated with respect to historical data of climatic conditions, water quality and discharge measurements. The modelling results reveal a variation in predicted effects of the management scenarios, causing different conclusions with respect to choice of best management practice for reducing nutrient losses. The study demonstrates that it is important that care is taken by modellers and involved decision makers throughout the entire modelling process, both with regard to a common understanding of the problem definition, understanding of boundary conditions, and uncertainty of outputs and interpretation of results.

Nitrogen and phosphorus retention in surface waters: an inter-comparison of predictions by catchment models of different complexity.

Nitrogen and phosphorus retention estimates in streams and standing water bodies were compared for four European catchments by a series of catchment-scale modelling tools of different complexity, ranging from a simple, equilibrium input-output type to dynamic, physical-based models: source apportionment, MONERIS, EveNFlow, TRK, SWAT, and NL-CAT. The four catchments represent diverse climate, hydrology, and nutrient loads from diffuse and point sources in Norway, the UK, Italy, and the Czech Republic. The models' retention values varied largely, with tendencies towards higher scatters for phosphorus than for nitrogen, and for catchments with lakes (Vansjø-Hobøl, Zelivka) compared to mostly or entirely lakeless catchments (Ouse or Enza, respectively). A comparison of retention values with the size of nutrient sources showed that the modelled nutrient export from diffuse sources was directly proportional to retention estimates, hence implying that the uncertainty in quantification of diffuse catchment sources of nutrients was also related to the uncertainty in nutrient retention determination. This study demonstrates that realistic modelling of nutrient export from large catchments is very difficult without a certain level of measured data. In particular, even complex process oriented models require information on the retention capabilities of water bodies within the receiving surface water system and on the nutrient export from micro-catchments representing the major types of diffuse sources to surface waters.

Ensemble modelling of nutrient loads and nutrient load partitioning in 17 European catchments.

An ensemble of nutrient models was applied in 17 European catchments to analyse the variation that appears after simulation of net nutrient loads and partitioning of nutrient loads at catchment scale. Eight models for N and five models for P were applied in three core catchments covering European-wide gradients in climate, topography, soil types and land use (Vansjø-Hobøl (Norway), Ouse (Yorkshire, UK) and Enza (Italy)). Moreover, each of the models was applied in 3-14 other EUROHARP catchments in order to inter-compare the outcome of the nutrient load partitioning at a wider European scale. The results of the nutrient load partitioning show a variation in the computed average annual nitrogen and phosphorus loss from agricultural land within the 17 catchments between 19.1-34.6 kg N ha(-1) and 0.12-1.67 kg P ha(-1). All the applied nutrient models show that the catchment specific variation (range and standard deviation) in the model results is lowest when simulating the net nutrient load and becomes increasingly higher for simulation of the gross nutrient loss from agricultural land and highest for the simulations of the gross nutrient loss from other diffuse sources in the core catchments. The average coefficient of variation for the model simulations of gross P loss from agricultural land is nearly twice as high (67%) as for the model simulations of gross N loss from agricultural land (40%). The variation involved in model simulations of net nutrient load and gross nutrient losses in European catchments was due to regional factors and the presence or absence of large lakes within the catchment.

Changes in surface water chemistry caused by natural forest dieback in an unmanaged mountain catchment.

Ionic and nutrient compositions of throughfall, tributaries and lake outlet were analysed in the Plesné catchment-lake system (an unmanaged mountain forest in Central Europe) from 1997 to 2016. The aim was to evaluate changes in surface water chemistry after natural forest dieback. In the 2004-2008, 93% of the Norway spruce trees were killed by bark beetle outbreak, and all dead biomass remained in the catchment. Forest dieback changed the chemistry of all water fluxes, and the magnitude, timing, and duration of these changes differed for individual water constituents. The most pronounced decreases in throughfall concentrations occurred for K+, dissolved organic carbon (DOC), Ca2+ and Mg2+, i.e. elements mostly originating from canopy leaching, while concentrations of NH4+ and soluble reactive phosphorus (SRP) remained almost unaffected. In tributaries, the most rapid changes were increases in NO3-, K+, H+ and ionic aluminium (Ali) concentrations, while terrestrial export of DOC and P forms started more slowly. Immediately after the forest dieback, increase in NO3- concentrations was delayed by elevated DOC availability in soils. NO3- became the dominant anion, with maximum concentrations up to 346µeqL-1 within 5-7years after the bark beetle outbreak, and then started to decrease. Terrestrial exports of Ali, K+, H+, Mg2+, and Ca2+ accompanied NO3- leaching, but their trends differed due to their different sources. Elevated losses of SRP, DOC, and dissolved organic nitrogen continued until the end of the study. In the lake, microbial processes significantly decreased concentrations of NO3-, organic acid anions, H+ and Ali, and confounded the chemical trends observed in tributaries. Our results suggest that terrestrial losses of elements and the deterioration of waters after forest dieback are less pronounced in unmanaged than managed (clear-cut) catchments.

Enriched environment influences brain-derived neurotrophic factor levels in rat forebrain after focal stroke.

Tissue levels of brain-derived neurotrophic factor (BDNF) protein were studied using enzyme immunoassay in different forebrain regions in the ipsi- and contralateral hemispheres of rats housed under enriched or standard conditions after the middle cerebral artery ligation. BDNF levels in the ipsilateral to ligation side was significantly higher only in the frontal cortex of standard as compared to enriched rats. However, BDNF overall was more abundant in standard than in enriched group. In addition, BDNF levels detected in the hippocampus and frontal cortex on the ischemic side of standard rats was higher as compared to contralateral side. The present study shows that housing conditions after permanent middle cerebral artery ligation leads to differential regulation of BDNF protein levels in forebrain regions which might have important implication for post-ischemic recovery.

Changes in the Epilimnetic Bacterial Community Composition, Production, and Protist-Induced Mortality along the Longitudinal Axis of a Highly Eutrophic Reservoir.

We studied changes in the epilimnetic bacterial community composition (BCC), bacterial biomass and production, and protistan succession and bacterivory along the longitudinal axis of the canyon-shaped, highly eutrophic Sau Reservoir (NE Spain) during two sampling campaigns, in April and July 1997. Longitudinal changes in BCC from the river inflow to the dam area of the reservoir were detected by using oligonucleotide probes targeted to the kingdom Bacteria, to the alpha, beta, and gamma subclasses (ALFA, BETA, and GAMA) of the class Proteobacteria, and to the Cytophaga/Flavobacterium (CF) cluster. In general, the inflow of the organically loaded Ter river, with highly abundant allochthonous bacterial populations, induced a clearly distinguishable longitudinal succession of the structure of the microbial food web. The most dynamic changes in microbial parameters occurred at the plunge point, the mixing area of river water and the reservoir epilimnion. Changes within members of BETA and CF were the most important in determining changes in BCC, bacterial abundance and biomass. Much less relevant changes occurred within the less abundant ALFA and GAMA bacteria. From the plunge point downstream, we described a significant shift in BCC in the form of decreased proportions of BETA and CF. This shift spatially coincided with the highest values of heterotrophic nanoflagellate bacterivory (roughly doubled the bacterial production). CF numerically dominated throughout the reservoir without any marked longitudinal changes in their mean cell volume. In contrast, very large cells affiliated to BETA clearly dominated in the allochthonous bacterial biomass brought by the river. BETA showed a marked downstream trend of decreasing mean cell volume. We conclude that the observed BCC shift and the longitudinal shift in food web structure (bacteria-heterotrophic nanoflagellates-ciliates) resulted from highly complex interactions brought about by several major factors: varying hydrology, the high localized allochthonous input of organic matter brought by the river, downstream changing substrate availability, and selective protistan bacterivory.

Natural inactivation of phosphorus by aluminum in atmospherically acidified water bodies.

Atmospheric acidification of catchment-lake ecosystems may provide natural conditions for the in-lake control of P cycling. This process is based on the elevated transport of aluminum from acidified soils and its subsequent precipitation in the water body and is described for strongly acidified forest lakes, acidified and circumneutral reservoirs, and a moderately acidified alpine lake. In water bodies with episodically or permanently acidified inflows a pH gradient develops between lake water and tributaries due to: (i) neutralization of acidic inflows after mixing with waters with undepleted carbonate buffering system, and/or (ii) the in-lake alkalinity generation dominated by biochemical removal of NO3- and SO4(2-). With the pH increasing towards neutrality, ionic Al species hydrolyze and form colloidal Al hydroxides (Al(part)) with large specific surfaces and strong ability to bind orthophosphate from the liquid phase. Moreover, Alpart settles and increases the P sorption capacity of the sediment. The presence of Al(part) on the bottom reduces orthophosphate release from sediments after its liberation from ferric oxyhydroxides during anoxia because Al(part) is not sensitive to redox changes. Consequently, the natural in-lake P inactivation may be expected in any water body with elevated Al input and a pH gradient between its inlet and outlet.

[Influences on radiocesium retention in minipigs]. / Ovlivnení retence radiocesia u miniprasat.

The efficiency of an active substance (AL) prepared in our laboratory as a composite sorbent on the basis of hexacyanoferrates (II) bound on pearl cellulose, in affecting the radiocesium (Cs-137) retention in white miniature pigs was investigated. The function of the composite sorbent in dependence on the way of administration, i.e. its effect on a decrease of primary resorption and its ability to interrupt the enteral cycle was studied, too. The efficiency of stable cesium administration in the form of CsCl in the same process was also determined. It was proved that AL accelerated significantly the excretion through its effect both on primary resorption causing an approx. 11-fold reduction of resorption when administered simultaneously with radiocesium and on the enteral cycle, causing an approx. 3.5-fold increase of excretion of Cs-137 when administered daily. Thus the composite sorbent (AL) administered at long-term along with contaminated feed reduced the equilibrium concentration of radiocesium in meat 30-40 times. This might be of great importance in the time of nuclear emergencies. On the other hand, administration of non-active Cs at a level up to 1 mg Cs/1 kg of liveweight had no significant effect on Cs-137 elimination.