Danube River Water Research Articles

Distribution of stable isotopes in surface water along the Danube River in Serbia†

Stable hydrogen and oxygen isotopes were analysed in water samples from the River Danube and its tributaries during a longitudinal survey performed in August 2005 on Serbian territory. Danube river water data ranged from−80‰ to−66‰ for δ2H, and from−11.2‰ to−9.3‰ for δ18O with δ values increasing downstream. The isotopic signatures of the adjacent tributaries (the Tisza, the Sava and the Velika Morava) sampled at the locations close to their confluence with the Danube (Titel, Ostružnica and Ljubičevski most, respectively) just about the time of the campaign were enriched (−67‰ and−63‰ for δ2H, and−9.3‰ and−8.9‰ for δ18O) with respect to the Danube water because of their catchment effects. Hydrogen and oxygen stable isotope values were used in combination with measured physico-chemical and biological parameters to trace hydrological and transport processes in these river systems. The mixing relationships between the Danube main stream and its tributaries were estimated using the mass balance for isotopic composition and electrical conductivity as conservative parameters. Evidence of an incomplete mixing process at the Čenta location, 8 km below the confluence of the Tisza river, with its participation of 88% was shown by its oxygen-18 content. The correlations between river water isotope composition and physico-chemical and biological parameters are discussed. † Revised version of a paper presented at the 9th. Symposium of the European Society for Isotope Research (ESIR), 23 to28 June 2007, Cluj-Napoca, Romania.

In situ influence of coal ash dump on the quality of neighboring surface and ground waters by applying correlation statistic analysis

The aim of this study was to establish the real in situ influence of coal ash and slag transport and storage on the quality of neighboring surface and ground waters by applying correlation statistic analysis. It was found that the waste waters from the coal ash dump do not have any influence on the quality of the Danube river water. The Danube and the waste waters, however, influence the quality of the ground waters of the Petka spring. Changes in the concentrations of elements in the Danube or in the waste waters can have immediate or delayed impact on the quality of the spring waters. The immediate impact has calcium, magnesium, zinc, copper, vanadium, cobalt from Danube; magnesium, vanadium from overflow and drainage waters; copper from drainage water. And the delayed impact has calcium, magnesium, vanadium and silicon from the Danube waters, cobalt from drainage waters, chromium and silicon from overflow waters and magnesium and vanadium from both overflow and drainage waters.

Ecotoxicological Assessment of Sediment, Suspended Matter and Water Samples in the Upper Danube River. A pilot study in search for the causes for the decline of fish catches (12 pp)

Fish populations, especially those of the grayling (Thymallus thymallus), have declined over the last two decades in the upper Danube River between Sigmaringen and Ulm, despite intensive and continuous stocking and improvement of water quality since the 1970s. Similar problems have been reported for other rivers, e.g. in Switzerland, Great Britain, the United States and Canada. In order to assess if ecotoxicological effects might be related to the decline in fish catch at the upper Danube River, sediment, suspended matter and waste water samples from sewage treatment plants were collected at selected locations and analyzed in a bioanalytical approach using a battery of bioassays. The results of this pilot study will be used to decide if a comprehensive weight-of-evidence study is needed. Freeze-dried sediments and suspended particulate matters were extracted with acetone in a Soxhlet apparatus. Organic pollutants from sewage water were concentrated using XAD-resins. In order to investigate the ecotoxicological burden, the following bioassays were used: (1) neutral red assay with RTL-W1 cells (cytotoxicity), (2) comet assay with RTL-W1 cells (genotoxicity), (3) Arthrobacter globiformis dehydrogenase assay (toxicity to bacteria), (4) yeast estrogen screen assay (endocrine disruption), (5) fish egg assay with the zebrafish (Danio rerio; embryo toxicity) and (6) Ames test with TA98 (mutagenicity). The results of the in vitro tests elucidated a considerable genotoxic, cytotoxic, mutagenic, bacteriotoxic, embryotoxic and estrogenic burden in the upper Danube River, although with a very inhomogeneous distribution of effects. The samples taken from Riedlingen, for example, induced low embryo toxicity, but the second highest 17beta-estradiol equivalent concentration (1.8 ng/L). Using the fish egg assay with native sediments, a broad range of embryotoxic effects could be elucidated, with clear-cut dose-response relationships for the embryotoxic effects of contaminated sediments. With native sediments, embryotoxicity was clearly higher than with corresponding pore waters, thus corroborating the view that--at least for fish eggs--the bioavailability of particle-bound lipophilic substances in native sediments is higher than generally assumed. The effect observed most frequently in the fish egg assay was a developmental delay. A comparison of our own results with locations along the rivers Rhine and Neckar demonstrated similar or even higher ranges of ecotoxicological burdens in the Danube River. The complex pattern of ecotoxicological effects caused by environmental samples from the Danube River, when assessed in an in vitro biotest battery using both acute and more specific endpoints, showed that integration of different endpoints is essential for appropriate hazard assessment. Overall, the ecotoxicological hazard potential shown has indeed to be considered as one potential reason for the decline in fish catches at the upper Danube River. However, based on the results of this pilot study, it is not possible to elucidate that chemically induced alterations are responsible for the fish decline. In order to confirm the ecological relevance of the in vitro results for the situation in the field and especially for the decline of the grayling and other fishes, further integrated investigations are required. For linking the weight of evidence obtained by in vitro assays and fish population investigations, the application of additional, more specific biomarkers (e.g. vitellogenin induction, EROD and micronucleus assay) has been initiated in fish taken from the field as well as in situ investigations.

Determination of antidepressants in surface and waste water samples by capillary electrophoresis with electrospray ionization mass spectrometric detection after preconcentration using off‐line solid‐phase extraction

A method for the quantitative determination of seven major antidepressants in surface waters and sewage treatment plant effluents by CE using ESI-MS is presented. Calibration curves for the selected analytes were prepared in Milli-Q purified water and Danube river water extract covering a concentration range of at least one order of magnitude. LODs achieved were between 6 and 13 microg/L for Trazodone and 39 and 53 microg/L for Sertraline in the Milli-Q purified water and Danube river water matrix, respectively. For sample preparation eight different SPE materials were investigated. Best results were obtained for a resin based on hydrophilic divinylbenzene (recoveries from Milli-Q purified water 93-96%; from Danube river water 85-99%). Finally, a series of eight sewage treatment plant effluents were investigated with respect to their content in the selected antidepressants. Six of these samples were tested positive for antidepressants, in particular Venlafaxine, Citalopram and Trazodone in concentrations between 36 and 322 ng/L.

A rapid and sensitive GC–MS method for determination of 1,3-dichloro-2-propanol in water

A rapid analytical method for sensitive determination of 1,3-dichloro-2-propanol (1,3-DCP) in river water has been developed. 1,3-DCP is extracted from water with ethyl acetate. After filtration through sodium sulfate the ethyl acetate phase is analyzed by gas chromatography-mass spectrometry. The method uses 1,3-DCP-d5 as internal standard. Different extraction solvents, concentrations of ammonium sulfate in the water samples, and the effect of humic acid were tested and their influence on the recovery of DCP has been evaluated. The method quantification limit was 0.1 microg L(-1). For spiked water samples (0-5.2 microg L(-1), n=21) a repeatability coefficient of variation of 5.4% was obtained. The average recovery rate of 1,3-DCP was 105+/-3% (n=21). Stability tests, which were carried out with Danube river water, led to an estimated 1,3-DCP degradation rate of 0.008+/-0.0008 day(-1) at 6 degrees C.

Case Study of Petroleum Contaminated Area of Novi Sad After NATO Bombing in Yugoslavia

The 1999 NATO bombing of the oil refinery in Novi Sad (Yugoslavia) has heavily contaminated the Danube River and its sediments, as well as the surrounding soil and groundwater. The destruction of the factories released 73,569 tons of crude oil of which 90% was incinerated, 560 tons reached the Danube River, and the remainder was spilled onto the soil.The contents of oil and oil derivatives in the soil were in the range of 3 to 42,000 mg/kg. The first soil layer contained an average of 67,000 mg/kg of crude oil and oil derivatives. The layers beneath it, above the groundwater table, contained 56 ml/l of free oil derivatives in the drained water.The spreading of this pollution could imperil the groundwater quality in the water supply zone because the refinery is located in the hinterland of the zone. The quality of water and sediment samples was monitored from April 1999 to November 2000 by measuring concentrations of hydrocarbons and polyaromatic hydrocarbons (PAH).The hydrocarbon content in the Danube River water in October 2000 was about 20% of the value measured at the time of the accident. Immediately after the accident the concentration of mineral oil in the surface sediment was in the range of 0.11 to 0.29 g/kg. At the same time PAH concentrations in the river sediment were up to 160 mg/kg, depending on the sampling site location. The values showed a decrease in the course of further monitoring.

Effects of Hydrology and Water Quality on the Fish Communityin Danube Delta Lakes

Man-made changes to the Danube delta include the improvement of the hydrological infrastructure for navigation and fish production purposes and an elevated nutrient load in the inflowing Danube river water. Records from the commercial fishery over the last 40 years indicate a shift from clear water fish (Tinca tinca, Carassius carassius, and Esox lucius) towards species adapted for turbid water. Since the 1970s the most frequently caught species have been Rutilus rutilus, Scardinius erythrophthalmus and the exotic Carassius auratus gibelio. For this study, the fish community in 13 interconnected lakes was sampled in June from 1996 through 1998 using gill-nets and electrofishing. In total 30 species were caught. The fish dominating catches from the different lakes varied from eurytopic/“grey fish” species to limnophilic/“black fish” species. This range corresponds with differences in lake morphometry, substrate type, hydrological distance from the river and presence of aquatic vegetation. The condition of the lakes ranges from pristine to moderately affected, but taken as a whole, the system has maintained its biological diversity with regard to fish communities in floodplains.

Release of cadmium in the Danube estuary: contribution of physical and chemical processes as determined by an experimental approach

The behavior of dissolved cadmium (Cd) in the Danube estuary was investigated through field sampling and mixing experiments using Danube River water and Black Sea water. The experiments were performed by mixing these two end-member waters in various proportions, with the addition of stable or radioactive Cd to the freshwater Danube end-member prior to the mixing. The release of Cd that resulted in maximum concentrations under field conditions was well simulated by mixing experiments. The experimental results were modeled assuming that the release of Cd was the sum of the contribution of physical effects resulting from dilution effects and the contribution of chemical effects resulting from dissolved Cd-complex formation (and isotopic exchange when concerned). In the absence of dissolved Cd-complexing ligands, the release of Cd due to the dilution of the particulate phase during mixing could explain part of the maximum concentrations observed in field conditions. Kinetic effects were established by comparing the theoretical and measured contribution of chemical effects resulting from dissolved Cd-complex formation. The non-equilibrium state observed during the mixing experiment suggested the presence of particulate labile Cd that was not easily mobilized. All these features supported the hypothesis that Cd released in estuaries is controlled both by the dilution of the particulate phase and by kinetic competitive complexation between particulate ligands (covering a large spectrum of nature and strength) and dissolved ligands.

Danube River Water Data Modelling by Multivariate Data Analysis

A data set (48×19) consisting of Danube river water analytical data collected at Galati site, Romania, during a four-year period has been treated by principal components analysis (PCA). The PCA indicated that seven latent factors (“hardness”, “biochemical”, “waste inlets”, “turbidity”, “acidity”, “soil extracts” and “organic wastes”) are responsible for the data structure and explain over 80 % of the total variance of the system. Its complexity is further proved by the application of multiple linear regression analysis on the absolute principal components scores (APCS) where the contribution of each natural or anthropogenic sources in the factor formation is shown. The apportioning makes clear that each variable participates to a different extent to each source and, in this way, no pure natural or pure anthropogenic influence could be determined. No specific seasonality for the variables in consideration is found.

Mixing model for the north-west Black Sea using 90Sr and salinity as tracers

A model to quantify the mixing ratios of Danube and Dnieper river water in the northwestern region of the Black Sea is presented. In this model, mixing ratios are determined from the measured salinity and 90Sr activities of surface water samples. The details of this model and error and sensitivity analyses are presented. Using this approach, mean mixing ratios and hence river transport values can be reliably derived which are of interest to more general questions of pollution transport in this region. Inter-annual variability in the 90Sr input from the Dnieper river and the overall decrease in 90Sr inputs limit the ultimate applicability of this approach.

Reducing conflict over the Danube waters: equitable utilization and sustainable development

This paper develops the idea that the principle of equitable utilization must be applied in concert with sustainable water use not only in the resolution of specific disputes but in the cooperative management of water resources in general. It illustrates this point with two different cases involving the use of the Danube River. The first is the conflict over the Gabcikovo Nagymaros Dam, which now rests before the International Court of Justice. The author argues that a narrow legal ruling that fails to take into account broader issues of equitable utilization as they relate to sustainable development will not satisfactorily address the long‐term questions at stake between the parties. The second involves the situation in the Danube Delta where the potential for conflict exists, but may be minimized through the convention and institutional framework developed to address the environmental degradation and pollution of the Danube River basin, which is based in part on the principle of equitable utilization and the goal of achieving more sustainable water use. The paper provides a brief overview of the geographical features of the Danube River and international water law. It then explores the principle of equitable utilization and sustainable water use in light of the two cases and discusses the implications for the resolution and management of conflicts involving internationally shared water courses.

Ecotoxicological Studies on the Kilian Branch and Delta of the River Danube

Amounts of priority toxicants (heavy metals, petroleum and petroleum products, surfactants, phenols, organochlorine pesticides) in water, bottom sediments, macroinvertebrates, fish, and birds of the Kilian branch and delta of the River Danube were studied from 1978 to 1985. The bottom sediments and larger organisms were shown to be highly polluted by pesticide residues and heavy metals. In the water, organochlorine pesticides were almost completely adsorbed on suspended particles, while metals were found both in solution and in the suspended phase, forming high-molecular-weight complex compounds. Accumulation coefficients for DDT in the higher links of trophic chains (i.e., predatory fish, fish-eating birds) were 105 to 106. Danube river water was found have both acute and chronic toxicity, which was confirmed by biotesting on planktonic crustaceans. Toxicity varied in time and was of a pulsed character.

Changes in the Quality of the Danube River Water in the Section Smederevo-Kladovo in the Conditions of Backwater Effects

The paper describes specific changes in the quality of the Danube river water under the conditions of backwater effects in the Hydropower Plant Djerdap I storage. The results of longterm tests in five profiles of the investigated section, at various discharges give a global view of the intensity of changes in the composition of water mass. The analysis included changes in the contents of: organic matter, oxygen regime, reduction of turbidity and changes in the composition and abundance of plankton. The specific changes in the domain of physico-chemical and biochemical processes and changes in the biological status of the watercourse (composition and structure of plankton) at varying retention times complete the picture of short-term changes in the investigated system. Presentation of some settling effects and processes in the sediment of the storage provides an idea of some long-term changes in the conditions of backwater effects of the Danube in the investigated section.

The Long Term Investigation of the River Danube Water Quality in the Yugoslav Section According to Microbiological Parameters

The results of investigations of Danube river water quality in the Yugoslav section in the period from 1975 to 1988 are presented. The estimation of water quality was based on the numbers of heterotrophs, T/H ratio, and enzymatic activity. In addition, the number of bacteria of some physiological groups was determined. The results indicate that there was a deterioration of water quality in the investigated period. The number of heterotrophs was observably lower in the period from 1975 to 1978 than it has been in recent years. The constant worsening of the water quality is also evident from the the T/H ratio and enzymatic activity measurements.

The Oxygen Monitoring of the Danube River on the Section Oltenita-Black Sea

Danube river basin overlaps great depressions of C entral and SE Europe is the second largest river in Europe and 24 th in the world.The Romanian section represents 29% of the surface area of the whole basin, with 37.7% of the river flowing through its territory. Organic pollution has been increasing in parts of the Danube Basin up till the end of the last century, as industrial production and hous ehold consumption have resulted in increasing loads of wastewater rich in organic matt er.Together with other countries, Romania is part of the transfrrontalier program. The TransN ational Monitoring Network, in short “TNMN” was established to support the implementation of the Danube River Protection Convention in the field of monitoring and assessmen t. In order to monitorize the section Olteni Ńa-Black Sea, in 2008 were taken in study 4 sites, namely: Chiciu, Braila, Tulcea and Sulina. F or this study we have monitored the oxygen represented by: OD, BOD5, CCO-Cr, CCO-Mn, indicators that determine pollution with organic compounds. The methods we used within the European norms and the monitored parameters were analyzed with specialized equipment, like the device for determining the BOD model OxiTop IS 6. In the study the BOD values are higher in the months of spring and summer and indicate the quantity of oxygen required for oxidation the organic materials. Differences between BOD and CCO CCO-Mn-Cr gave us clues on industrial water discharged into emissary. In this study, significan t differences are observed, even two times higher CCO-Cr and CCO-Mn compared to BOD, the water is polluted with organic material from waste water discharged by various industries i n the Danube River tributaries. Dissolved oxygen was determined using Oxigenometrului inoLab730 P, and the values varys depending on atmospheric pressure, water temperature, content of mineral salts, micro-organisms in water. In this case there are no significant differences compared to the maximum allowed. It is recommended the monitoring of the Danube River water quality; the public awareness about the negative effects of anthropogen ic activities on water quality.