Aim of this study was to assess quality of the Danube sediment from the water source "Ratno Ostrvo", which is in the vinicity of the Oil Refinery "Novi Sad" (Serbia, Yugoslavia), after bombardment of the refinery in 1999. In the period March-October 2000, sediment samples were analysed for their oil and oil-derivates contents, i.e. mineral oils contents, by quantitative IR-spectrophotometry, and by qualitative and quantitative GC/MS analyses for their polycyclic aromatic hydrocarbons (PAH) contents. Oil pollution was detected in sediment samples.

Drainage of industrial and communal effluents, directly into the water flow, as many hydrotechnical activities, significantly influence the schedule and balance of the processes that take place into water. In this paper, there are represented the results of systematic control of the water quality of the Danube river and DTD (Danube-Tisza-Danube) channel on the parts Vrbas-Bezdan and Becej-Bogojevo, at the control station network of the Republic Weather Bureau (the Republic of Serbia), for the period of 1991-1996. The results show that the most adverse influence of anthropogenic factor is on the part of the flow of the DTD (Danube-Tisza-Danube) channel from Vrbas to the flow into Tisza river.

Nowadays, different profile of experts are present opinion that surface water quality are exchanged. Type and degree of mineralization content exchange are shown by argumentation. The work have carried out taking into consideration suitability of Danube water for irrigation. The results of chemical investigation from three sample locations (Bezdan, Novi Sad and Banatska Palanka), Serbia (Yugoslavia) during the period 1981-1995, were analyzed. The main statistical parameters and tests of homogeneity are used during the work. Results have pointed put more or less concentration decreasing of analyzed parameters. From statistical point of view, exchange of electrical conductivity and potassium are prominent on all three localities.

The results of long standing and systematic monitoring of quality of river Danube's water, done by the net of stations for controllingquality of water of the Republic Hydrometeorological Service of Serbia (Yugoslavia) are given in this paper. The amount of organic matter (HPK, BPK5), concentration of dissolved oxygen, nutritive matters (NH4(+), NO2(-), NO3(-) and total PO4(3-) and conductivity are specially examined. The results are shown depending on seasonal measuring (average values for spring, summer, autumn and winter) during the period 1995-1998, and the changes are analyzed.

Microplastic abundances have been studied intensively in the last years in marine and freshwater environments worldwide. Though several articles have been published about the Mediterranean Sea, only few studies about the Black Sea exist. The Black Sea drains into the Mediterranean Sea and may therefore significantly contribute to the Mediterranean marine pollution. So far, only very few articles have been published about micro-, meso- and macroplastic abundances in the Western Black Sea. In order to fill this knowledge gap and to decipher the number of plastics on the water surface, 12 samples were collected from surface waters with a neustonic net (mesh size 200 μm) in the Black Sea close to the Danube Delta and the Romanian shore. Organic matter was digested and plastic particles were isolated by density separation. The results of visual inspection, pyrolysis GC-MS (for microplastics) and ATR-FTIR (for mesoplastics >5 mm) revealed an average concentration of 7 plastic particles/m³, dominated by fibers (∼76%), followed by foils (∼13%) and fragments (∼11%). Only very few spherules were detected. The polymers polypropylene (PP) and polyethylene (PE) dominated which is in line with other studies analyzing surface waters from rivers in Western Europe as well as in China. Statistical analyses show that the plastic concentration close to the mouth of the Danube River was significantly higher than at four nearshore regions along the Romanian and Bulgarian coastline. This could be explained by plastic inputs from the Danube River into the western part of the Black Sea.

Surface waters are becoming increasingly contaminated by pharmaceutically active compounds (PhACs), which is a potential risk factor for drinking water quality owing to incomplete riverbank filtration. This study examined the efficiency of riverbank filtration with regard to 111 PhACs in a highly urbanized section of the river Danube. One hundred seven samples from the Danube were compared to 90 water samples from relevant drinking water abstraction wells (DWAW) during five sampling periods. The presence of 52 PhACs was detected in the Danube, the quantification of 19 agents in this section of the river was without any precedent, and 10 PhACs were present in >80% of the samples. The most frequent PhACs showed higher concentrations in winter than in summer. In the DWAWs, 32 PhACs were quantified. For the majority of PhACs, the bank filtration efficiency was >95%, and not influenced by concentrations measured in the river. For carbamazepine lidocaine, tramadol, and lamotrigine, low (<50%) filtration efficiency was observed; however, no correlations were observed between the concentrations detected in the Danube and in the wells. These frequently occurring PhACs in surface waters have a relatively even distribution, and their sporadic appearance in wells is a function of both space and time, which may be caused by the constantly changing environment and micro-biological parameters, the dynamic operating schedule of abstraction wells, and the resulting sudden changes in flow rates. Due to the changes in the efficiency of riverbank filtration in space and time, predicting the occurrence and concentrations of these four PhACs poses a further challenge to ensuring a safe drinking water supply.

This research is designed to determine the level and types of pollution in the highly contaminated sediments of the international Begej canal in Timiş district, Romania and north-eastern Serbia. The cross-border canal stretch investigated is currently not navigable, but represents an important waterway between the Danube River in Serbia and the city of Timisoara. Surface sediments were monitored annually from 2008 to 2016 at 36 representative sampling locations, with a wide range of analyses, including eight heavy metals of long-term monitoring concern (Ni, Zn, Cd, Cr, Cu, Pb, As and Hg) and the 16 USEPA PAHs. The purpose of this study was to determine the diversity and impact of anthropogenic and natural sources of pollution at the pollution hot spots on the canal: at the Itebej lock (near the border with Romania) and downstream at the Klek lock.Sediment quality and ecological risk were assessed in order to determine pollutants of concern. Several multi-proxies were applied (e.g. geo-accumulation index (Igₑₒ), ecological risk index (RI) and total benzo[a]pyrene equivalent (B[a]Pₑq)). To determine and predict trends, multivariate statistical methods (factor analysis of principal component analysis (PCA/FA)) were carried out on the organic and inorganic parameters analysed.In the near-border region, acute and significant ecological impacts were observed. The heavy metals Hg, Cr, Pb, Cu and Zn, and the carcinogenic PAH dibenzo[a,h]anthracene, were historically the most frequently detected harmful substances to biota in this and the wider Pannonia region. This is the first long-term study to quantify and derivate the most frequently detected harmful substances of concern for this and similar sites in the wider region, and is additionally supported by significant national and similar environmental data from previous studies in the region.

Novel approaches for estimating the emissions of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) to surface waters are explored. The Danube River catchment is used to investigate emissions contributing to riverine loads of PFOS and PFOA and to verify the accuracy of estimates using a catchment-scale dynamic fugacity-based chemical transport and fate model (STREAM-EU; Spatially and Temporally Resolved Exposure Assessment Model for European basins). Model accuracy evaluation performed by comparing STREAM-EU predicted concentrations and monitoring data for the Danube and its tributaries shows that the best estimates for PFOS and PFOA emissions in the Danube region are obtained by considering the combined contributions of human population, wealth (based on local gross domestic product (GDP)) and wastewater treatment. Human population alone cannot explain the levels of PFOS and PFOA found in the Danube catchment waters. Introducing wealth distribution information in the form of local GDPs improves emission estimates markedly, likely by better representing emissions resulting from consumer trends, industrial and commercial sources. For compounds such as PFOS and PFOA, whose main sink and transport media is the aquatic compartment, a major source to freshwater are wastewater treatment plants. Introducing wastewater treatment information in the emission estimations also further improves emission estimates.

Numerous studies have quantified the amount of plastic litter in aquatic ecosystems and tried to assess its impacts and threats. This reflects a rising awareness of plastic as an environmental problem. As a next logical step, identifying and regulating the sources must be in the focus of scientific efforts. We report on a spillage of industrial microplastic (IMP) from a production plant situated at an Austrian Danube tributary. This is the first identified point source of IMP litter in freshwater systems. However, due to generous thresholds established by the Austrian government substantial amounts of IMP are legally introduced into running waters.

Total concentrations of hydrophobic organic contaminants (HOCs) in sediment present a poor quality assessment parameter for aquatic organism exposure and environmental risk because they do not reflect contaminant bioavailability. The bioavailability issue of HOCs in sediments can be addressed by application of multi-ratio equilibrium passive sampling (EPS). In this study, riverbed sediment samples were collected during the Joint Danube Survey at 9 locations along the Danube River in 2013. Samples were ex-situ equilibrated with silicone passive samplers. Desorption isotherms were constructed, yielding two endpoints: pore water (CW:₀) and accessible (CAS:₀) concentration of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenyl ethers in sediment. CW:₀ concentrations of DDT and its breakdown products exhibited elevated levels in the low Danube, with the maximum in the river delta. Other investigated HOCs did not show any clear spatial trends along the river, and only a moderate CW:₀ variability. CAS:₀ in sediment ranged from 10 to 90% of the total concentration in sediment. CW:₀ was compared with freely dissolved concentration in the overlaying surface water, measured likewise by passive sampling. The comparison indicated potential compound release from sediment to the water phase for PAHs with less than four aromatic rings, and for remaining HOCs either equilibrium between sediment and water, or potential compound deposition in sediment. Sorption partition coefficients of HOC to organic carbon correlated well with octanol-water partition coefficients (KOW), showing stronger sorption of PAHs to sediment than that of PCBs and OCPs having equal logKOW. Comparison of CW:₀ values with European environmental quality standards indicated potential exceedance for hexachlorobenzene, fluoranthene and benzo[a]pyrene at several sites. The study demonstrates the utility of passive sampling as an innovative approach for risk-oriented monitoring of HOCs in river catchments.