Comparative Analysis of Riverine Plastic Pollution Combining Citizen Science, Remote Sensing and Water Quality Monitoring Techniques
Abstract
The Tisza River is the longest tributary of the Danube, draining the eastern part of the Carpathian Basin (Central Europe). Five countries share its catchment with different waste production and management practices. Large amounts of waste, including macroplastics (MaPs), are washed into the river. Some of the litter is trapped by the riparian vegetation forming litter accumulations. The study aimed to map the amount of litter by a citizen science program and remote sensing data and to compare the MaP data to the amount of microplastic fragments in sediments. Volunteers reported 3216 riverine litter accumulations from five countries along the entire length of the Tisza (2016–2022). The results suggest that low flow conditions (e.g., impoundment by dams) support litter and MaP trapping. The volume of large accumulations registered by the citizens showed a good correlation with the area of drifting litter revealed on Sentinel-2 images (2016–2022) using machine learning algorithms. Though the MaPs probably fragmentate during their fluvial transport, no clear connection was found between the volume of litter accumulations and the mean microplastic fragment content of sediments (2019–2022). The “Clean Tisza Map“ reveals the high degree of stranded pollutants along rivers and supports public cleanup activities.
A folyómentés tudománya és technikái – a Riversaver platform bemutatása
Kivonat
A több mint 11 éves PET Kupa kezdeményezés a Tisza és mellékfolyói műanyag szennyezéstől való mentesítése érdekében tett erőfeszítései miatt vált nemzetközi szinten is ismertté. A PET Kupát, mint hulladékszedő versenyt, egy természetfilmes közösség indította útjára, ennek köszönhetően a szervezet történetének minden mérföldköve dokumentálva van. Az elmúlt időszakban még inkább a folyótisztítás és folyómentés került a középpontba, amit az is tükröz, hogy most már az egyesület hivatalos neve is PET Kupa Egyesület és a PET Kupa európai szinten bejegyzett védjeggyé vált.
Ezen átalakulás mögött az a felismerés áll, hogy a PET Kupa birtokában most már olyan ismeretanyag és knowhow, valamint akadémiai és ipari partnerség van a folyók műanyag szennyezése és azok megelőzése, felmérése, felszámolása és a hulladék feldolgozása kapcsán, ami nemzetközi szinten is releváns a folyóink tisztaságának megőrzése érdekében. Ezt a felismerést támasztja alá az is, hogy mára már a PET Kupa számos nemzetközi kutatás-fejlesztési projektben vesz részt, ezek egyike a DALIA projekt, amiben ezt a tudásanyagot dolgozzuk át replikálható protokollokká.
Ez a Folyómentő platform, amin keresztül ezt a tudást elérhetővé tudjuk tenni mások számára is. A tanulmány ezt a tudásmegosztási módszert ismerteti, és példákat mutat be arra nézve, hogy milyen technológiák állnak rendelkezésre a hulladékáradat megismerésére.
DALIA Danube Region Water Lighthouse Action - Proceedings of The 15th & 16th Edition of European Exhibition of Creativity and Innovation EUROINVENT 2023 & 2024
Description of poster publication
Among other R&I Missions, the EU has designated the ‘Restore our Ocean, seas and waters by 2030’ Mission in order to provide a systemic approach for the restoration, protection and preservation of our ocean, seas, and freshwaters. DALIA project is implemented by a consortium of 22 expert organizations (universities, authorities, SMEs, NGOs) from 8 different Danube EU and Associated countries. DALIA innovation actions are supported by the 9 Demonstration Pilot Sites (DPS) in the 6 countries in the Danube River basin area. INCDPM is in charge of DPS 6 dedicated to sturgeon migration by-pass Iron Gates I and II and the proposed activities will provide a technical & scientific solution in order to ensure the connectivity of the migration routes for the ultrasonic tagged sturgeon specimens to by-pass the two Hydropower Stations. The implementing methodology involves four main stages: measurement campaigns in order to determine the exact location for the INCDPM patented monitoring stations (DKMR-01T and DKTB); commissioning ultrasonic tagged sturgeon specimens detection gates (two located downstream the Iron Gates I and II and one downstream Bazias and more in the Serbia and Hungary Danube sectors); developing the best strategy to assist ultrasonic tagged sturgeon specimens to pass upstream and adopting the use of special solutions adapted for each hydropower station; continuous mobile monitoring using boat-mounted VR-100 reception stations for then tagged specimens and recording their behaviour and movements until Baziaș and further upstream for 700 fluvial km until Danube km 1780.
Defining Optimal Location of Constructed Wetlands in Vojvodina, Serbia
Abstract
With the continuous trend of urbanization, increase in industrial capacities, and expansion of agricultural areas, there is also a rise in the amount of wastewater. One of the effective and economical solutions for wastewater treatment has proven to be Constructed Wetlands (CWs). Defining the locations where CWs can be built is not an easy task and there are several criteria that need to be considered. The Geographical Information Systems (GIS) and Multi-Criteria Decision Analysis—Analytic Hierarchy Process (AHP) are combined to select CW locations. AHP is one of the most commonly used methods in many environmental decision making problems, involving various conflicting criteria. In this case, conflicts arise between the evaluation of criteria that influence the selection of CW locations. The evaluation of selected criteria and sub-criteria resulted in a suitability map indicating that the first class represents 44%, the second class 37%, and the third class 16% of the total area. The fourth and fifth classes represent 3% of the total area. The criteria with the highest significance are land use, floodplains and distance of the location from populated places. This study has important implications for sustainable wastewater management in Serbia and provides guidelines for selecting locations for CWs.
Impact of Climate Change on Extreme Rainfall Events and Pluvial Flooding Risk in the Vojvodina Region (North Serbia)
Abstract
Extreme precipitation events, which are common natural hazards, are expected to increase in frequency due to global warming, leading to various types of floods, including pluvial floods. In this study, we investigated the probabilities of maximum 3-day precipitation amount (Rx3day) occurrences during spring in the Vojvodina region, covering both past (1971–2019) and future (2020–2100) periods. We utilized an ensemble of eight downscaled, bias-corrected regional climate models from the EURO-CORDEX project database, selecting the RCP8.5 scenario to examine future Rx3day amounts. The probabilities of occurrences of Rx3day were modeled using the GEV distribution, while the number of events where Rx3day in spring exceeds specific thresholds was modeled using the Poisson distribution. The results indicate that Rx3day with a ten-year return period during the spring months is expected to increase by 19% to 33%. Additionally, the probabilities of having more than one event where Rx3day exceeds thresholds are projected to rise by 105.6% to 200.0% in the future compared to the historical period. The analysis comparing the design values of Rx3day with future projections for the period 2020–2100 revealed that 51 drainage systems are likely to function without difficulties under future climate conditions. However, for the remaining 235 drainage systems, an increased risk of pluvial flooding was identified, as their design precipitation amounts are lower than the future projections. This study reveals that analyzing extreme rainfall events in the context of climate change yields crucial information that facilitates effective planning and policy making in water management, particularly flood protection.
Observed characteristics and projected future changes of extreme consecutive dry days events of the growing season in Serbia
Abstract
One of the frequently used drought metrics in scientific research is the consecutive dry days (CDDs) because it effectively indicates short-term droughts important to ecosystems and agriculture. CDDs are expected to increase in many parts of the world in the future. In Serbia, both the frequency and severity of droughts have increased in recent decades, with most droughts being caused by a lack of precipitation during the warmer months of the year and an increase in evapotranspiration due to higher temperatures. In this study, the frequency and duration of extreme CDDs in the growing season in Serbia were analysed for the past (1950–2019) and the future (2020–2100) period. The Threshold Level Method over precipitation data series was used to analyse CDD events, where extreme CDDs are defined as at least 15 consecutive days without precipitation. In contrast to the original definition of the CDD as the maximum number of consecutive days with precipitation less than 1 mm, here we defined the threshold that is more suitable for agriculture because field crops can experience water stress after 15 days of no rainfall or irrigation. An approach for modelling the stochastic process of extreme CDDs based on the Zelenhasić–Todorović (ZT) method was applied in this research. The ZT method was modified by selecting a different distribution function for modelling the durations of the longest CDD events, enabling a more reliable calculation of probabilities of occurrences. According to the results, future droughts in Serbia are likely to be more frequent and severe than those in the past. The duration of the longest CDDs in a growing season will be extended in the future, lasting up to 62 days with a 10-year return period and up to 94 days with a 100-year return period. Results indicate a worsening of drought conditions, especially in the eastern and northern parts of Serbia. The results can help decision-makers adapt agricultural strategies to climate change by providing information on the expected durations of extreme rainless periods in future growing seasons. Although the analysis was performed in Serbia, it can be applied to any other region.
Hydrodynamic and primary production effects on seasonal DO variability in the Danube River
Abstract
Dissolved oxygen (DO) is a fundamental indicator for water quality and ecosystem health, particularly in the context of anthropogenic impacts and climate change. This study presents the first large-scale dataset of DO concentrations combined with its stable oxygen isotope ratios (expressed as δ18ODO), particulate organic carbon concentrations (POC), and respiration photosynthesis (R P ratios) from five seasonal campaigns along the entire Danube River in 2023 and 2024. Our findings reveal pronounced seasonal DO driven by temperature, biological activity, and hydrodynamic conditions. During spring and summer, enhanced photosynthesis increased DO up to 0.40 mmol L−1, with δ18ODO values down to +12.1 ‰ and POC up to 0.25 mmol L−1 in two highly productive river sections. Low R P ratios of 0.1 further indicated strong net autotrophic conditions. Strong correlations between δ18ODO and POC additionally confirm the influence of primary producers (i.e., photosynthetic organisms) in a river section where a reduced slope led to slower flow and lower turbulence. Notably, δ18ODO values were lower than those expected for atmospheric equilibrium (+24.6 ‰ ± 0.4 ‰), a pattern rarely documented in large river systems. In contrast, tributary inflows from the Tisa and Sava rivers diluted biomass and organic material inputs and led to declines in DO and POC. By late summer, intensified respiration reversed photosynthetic signals, led to the lowest DO concentrations down to 0.16 mmol L−1, and raised δ18ODO up to +23.7 ‰, particularly in the Sava River. In fall, DO levels partially recovered despite continued respiration, as indicated by the highest observed δ18ODO values of +25.9 ‰ and the highest R P ratios of the entire season, reaching 8.9. In winter, oxygen input from the atmosphere became dominant with minimal biological influences. Overall, this study provides new insights into oxygen sources and sinks across the river continuum over several seasons. These new insights underscore the need for continuous DO monitoring, particularly in late summer when oxygen levels can become critically low. Understanding these interactions can help to establish efficient aqueous ecosystem management and conservation strategies in the face of land use and climate change.
Natural abundance δ13C constraints on the detection of microplastic-derived carbon in freshwater environments
Abstract
Microplastics (MPs) are increasingly recognized as emerging pollutants in freshwater systems. Detecting and tracing MP-derived carbon in aquatic food webs, however, remains unresolved, limiting our understanding of ecological impacts. Here, we evaluate the potential and limitations of natural abundance stable carbon isotope measurements (δ13C) as a tool to identify MP signals in freshwater ecosystems. For this purpose, two freshwater algae, Chlorella vulgaris and Chlamydomonas reinhardtii, were exposed under controlled laboratory conditions to one non-biodegradable polymer, low-density polyethylene (LDPE), and two biodegradable polymers, polylactic acid (PLA) and polybutylene adipate-co-terephthalate (PBAT), to assess isotope composition and growth. Laboratory data were complemented by particulate organic carbon (δ13CPOC) measurements from seasonal Danube River campaigns (2023–2024) with modeled predictions based on dissolved organic carbon (δ13CDIC).
MP exposure did not inhibit algae growth, but C. vulgaris exhibited significant (p <0.05) δ13C enrichment (+4 to +5 ‰), whereas C. reinhardtii showed no isotopic response. These shifts were unrelated to polymer isotope values and likely reflect indirect physiological stress rather than assimilation of polymer-derived carbon. Complementary binary mixing experiments further confirmed that measurable isotopic shifts occur only at unrealistically low algae-to-MP ratios (≤10:1), underscoring the limited sensitivity of isotope mass balances. Field surveys revealed pronounced seasonal δ13CPOC variability in the Danube, spanning 7.4 ‰ annually. Yet deviations from modeled expectations were inconsistent with MP inputs and instead reflected natural drivers such as productivity and remineralization. Overall, while natural abundance δ13C can capture subtle algae responses to MP exposure under laboratory conditions, its diagnostic power for tracing MP-derived carbon in complex freshwater systems appears limited.
Irrigation water quality in a framework of sustainable development goal 6: a review of challenges impacts policy alignments
Abstract
This review article aims to consolidate existing classification systems and evaluate the suitability of irrigation water in the context of Sustainable Development Goal 6 (SDG 6), with particular focus on targets 6.3, 6.4, and 6.5. The review explores key physico-chemical parameters of irrigation water quality and their role in determining water usability. Common classification systems such as FAO and US Salinity Laboratory (USSL) frameworks are examined, alongside their application in assessing impacts on soil health, crop productivity, and ecosystem stability. Findings indicate that inadequate irrigation water quality, particularly due to high salinity and sodium content, leads to soil salinization, reduced yields, and degradation of water and soil resources. These effects also extend to environmental and economic systems, through biodiversity loss and increased production costs. Effective management practices, such as improving drainage, using appropriate irrigation water, and applying soil amendments, are useful to mitigate these adverse effects and maintain soil and plant health. Mitigation strategies to address the economic impacts of unsuitable irrigation water quality include infrastructure investment, educational initiatives and policy enforcement. These strategies are closely aligned with European policy initiatives such as the Water Framework Directive, the European Green Deal, and the Blue Deal, all of which aim to promote sustainable irrigation practices and support the successful implementation of SDG 6 targets. The review emphasizes the practical relevance of these findings for policy-makers, water managers, and agricultural stakeholders seeking to implement sustainable irrigation practices and enhance local water resilience under SDG 6 targets.
Investigating currents, flow velocities, and riverbed morphology - An ADCP-Centric approach to understanding hydrodynamics and erosion patterns
Poster Abstract
The sediment movement on a river plays a crucial role in safe navigation and economic activities on navigable channels. Environmental changes over time are given by the morphological characteristics of the riverbed during seasonal water variation on the Danube River. This study presents a comprehensive assessment of the Danube River's velocity and current characteristics based on Acoustic Doppler Current Profiler measurements. The correlation between flow velocities and depths helps to understand the factors that influence sediment patterns and provides insights into the sustainable management of the river system. The study was conducted along a 71-kilometer length of the Sulina Branch from the Danube River, where ADCP measurements were collected at multiple locations and over periods. The data collected included water depth, flow velocity, and current direction. By clustering the column depth cell velocities, it revealed significant spatial and temporal variations in the velocity and current patterns, influenced by factors such as river morphology, discharge, and seasonal changes.
The influence of climate changes on the quality of water and sediments in the Sulina branch of the Danube River
Poster Abstract
The researchers of the REXDAN Research Infrastructure have carried out a series of studies on the state of the aquatic ecosystems in the area of the Sulina branch of the Danube river. In the last 2 years, several sampling campaigns were carried out from the critical points of the study area located on one of the most navigable channels of the Danube. The following physico-chemical parameters were determined for the water samples: pH, temperature, oxygen regime (DO, BOD5 and COD), nutrient regime (N-NH4+, N-NO3-, N-NO2-, N-total, P-total), salinity (SO42-,Cl-) and heavy metals (Fe-total, Zn2+, Cr-total; Cd2+, Ni2+). Sediment samples were analysed to assess the concentration of heavy metals, such as Fe-total, Zn2+, Cr-total; Cd2+, Ni2+. Spectrophotometric method, ion exchange chromatography, electrochemical method and inductively coupled plasma mass spectrometry were used to determine the value of water and sediment parameters. (WFD). With these results, as well as historical data, a number of machine learning prediction algorithms were trained and validated. In this way, an analytical framework based on virtual sensors was developed, the purpose of obtaining them is to increase the sustainability of monitoring activities. In this way, an effective monitoring of the quality of aquatic ecosystems can be carried out, any changes that occur as a result of climate change (especially during periods of extreme drought or flooding) can be noticed and alarm signals can be given to the authorities that manage water resources.
Assessment of suspended sediment concentration and granulometry using AQUASCAT 1000S on the Sulina Branch of the Danube River
Poster Abstract
Suspended particulate matter (SPM) significantly affects water quality, habitat health, and sediment transport. These particles can include pollutants like heavy metals or microplastics, posing risks to aquatic organisms and human consumers. Traditional sampling methods have limitations, especially in stratified or high-energy systems. This study employs the AQUASCAT 1000S, a multi-frequency acoustic profiler, to assess sediment concentration and granulometry along the Sulina branch of the Danube River. The aim is to evaluate the performance of acoustic techniques in detecting suspended sediment dynamics in deltaic riverine systems.
Funded by the European Union
