River Environment Research Articles

Effect of sediment erosion on pressure pulsations in a large Pelton turbine

AbstractPelton turbines functioning in sandy river environments often encounter difficulties due to the swift movement of sediment particles, leading to erosion and damage to overflow components. These challenges can result in operational instability, particularly noticeable in large turbines. Pressure pulsation is crucial for turbine stability, and alterations in overflow component profiles caused by sediment erosion can worsen pressure pulsations. This study utilizes numerical simulations to analyze turbine pressure pulsations based on surface profile changes of runner buckets after 2 and 4 years of sediment erosion in a single 500 MW large‐scale Pelton turbine. Our findings reveal that erosion leads to a gradual decrease in pressure pulsation along the bucket's splitting edge from the notch to the root. After 4 years of erosion and wear, the relative pressure pulsation amplitude in the root region increased by more than 530%. Additionally, changes occur in the thickness of the water film in the erosion area on the working surface, disrupting the flow pattern and generating more vortices. This occurrence intensifies the relative pressure pulsation amplitude and reduces bucket stability. The study findings highlight the significant impact of sediment erosion on Pelton turbine pressure pulsation, posing a considerable risk to the unit's operational stability and safety.

Aspects of the ecology of Leporinus striatus Kner 1858 as a support for its conservation in a Federal Conservation Unit

This work describes aspects of the ecology and feeding of Leporinus striatus to fill the gap in information about the species in Brazilian rivers. The study area is in the Ipanema National Forest, Iperó/São Paulo, with the Ipanema River as the place where the specimens were collected in its middle and lower reaches. The size ranged from class 9.0 - 9.5 cm to class 11.5 - 12.0 cm, with females being found in all classes. Class 10 - 10.5 was the one with the highest relative frequency, with males being most abundant in the 9.5-10.0 cm length class and females in the 10-10.5 cm length class. The species' diet was composed of autochthonous species, with the most frequent items being insect fragments and plant material. Based on this information, the species was classified as omnivorous. Underwater observations made it possible to verify that the species is gregarious, inhabiting the water column between midwater and the bottom, preferring stretches with currents and rocky substrate. It performs foraging by leaning its body close to the substrate and biting food on solid surfaces. Small groups made up of at least six individuals shared the areas between rocks and branches. We conclude that, to guarantee the preservation of the species, it is crucial to recognize the significant role played by Conservation Units. However, given the aquatic nature of the species studied, its life cycle is intrinsically linked to stretches that extend beyond the limits of the UC. Additionally, the ecological analyses presented in this study reveal that the species relies on the preservation of a healthy river environment that transcends the boundaries of the conversational unit.

Pollution status and spatial distribution of antibiotic resistance genes in urban surface water and surrounding soil media

The pollution of urban rivers by antibiotic resistance genes (ARGs) is affected by the production of antibiotics and the activities of residents in the regions, posing a threat to the health of the population around the regions. A detailed investigation of the spread of ARGs in urban rivers and the surrounding soil media provides both data support and basic framework for tracking the spread and for the elimination of ARGs. In this study, real-time fluorescence quantitative PCR (qPCR) was used to investigate the contamination status and spatial distribution patterns of ARGs around the entire basin of urban river, namely the Minxin river, and the city ring water system in Shijiazhuang, China. The contamination of ARGs in midstream and downstream of the Minxin river was more severe. No obviously spatial distribution differences were found in the soil samples. Water bodies are more susceptible to human activities than soil. It was identified that sul1, sul2, and blaSHV were the dominant genes of the ARGs. Significant correlations exist between ARGs and int1 and tnpA-IS4. Mobile genetic elements (MGEs) play a key role in the horizontal gene transfer of ARGs, facilitating their spread and dispersal among different species. This work revealed the geospatial characteristics of the distribution of ARGs in urban river basins, concluding that the production and living activities could accelerate the spread and diffusion of ARGs in urban river environments, and that an attention should be given to the use control and discharge of antibiotics.

Using a new fish indicator-based index with scoring and evaluation criteria to assess the ecological status in a disturbed subtropical river of China

Rivers are constantly disturbed by anthropogenic stressors. Developing robust biotic indicators to assess river environments across large spatial scales is important. In the subtropical Liuxi River of China, 34 native fish indicators, including 4 genera and 30 species, were selected from 108 fish species by linear discriminant analysis. These indicators were grouped into 19 ecological items and assigned evaluation scores according to the roles they played in the food web (e.g., keystoneness and trophic level) and their positive feedback on the environment (e.g., requirements for feeding, spawning/nursing, and migrating). Three formulae for calculating the index of fish indicators (IFI) were developed based on the scoring of each indicator and weighted by relative abundance (individual number, i.e., IFIN) and relative biomass (wet weight, i.e., IFIB). Spearman correlation analysis showed that IFIB, which had positive (P< 0.05) correlations with elevation (m), dissolved oxygen (mg/L), flow velocity (cm/s), Shannon-Wiener diversity, benthic index of biotic integrity, exhibited a more powerful explanation of biodiversity and environmental factors than IFIN and unweighted IFI. Therefore, IFIB was most suitable for constructing a scoring system to evaluate ecological status (e.g., water and habitat quality). These results suggested that fish indicator-based scoring and evaluation system was effectively in not only assessing the site- or region-specific ecological status bot also reflecting the fluvial biodiversity and food web integrity. Further application and promotion of this indicator-based evaluation method may improve field investigation efficiency and contribute greatly to the conservation and management of river ecosystems.

Improving Knowledge and Awareness and Contributing to Policy Making on River Pressures through a Citizen Science Approach: Tagus Web Viewer Case (Spain)

Citizen science is considered one of the most appropriate tools to raise public awareness of environmental issues. With the aim of improving knowledge on river environments, this article presents a web application for mobile phones and other portable devices that allows, through the active participation of society, the collection of detailed and systematic information on the main problems facing rivers. The initiative uses a web viewer (Tagus Web Viewer—TagusWV) developed as a pilot project in the Tagus River basin (Spain). This web viewer allows information on river pressures to be collected and the aggregated data to be visualised and extracted for interpretation and analysis. Pressure is defined as any use or activity, legal/illegal, authorised/unauthorised, that has an impact on water quality, morphology, river dynamics or the ecosystem. The data are mainly collected by different groups of citizens. In addition to contributing to the environmental education of citizens involved in a river environment, the data provided in the TagusWV are of particular interest to river managers. The tool is designed to be relevant for any river basin in the world, by simply loading the map, the names of the rivers and the corresponding locations.

Dissemination and persistence of antimicrobial resistance (AMR) along the wastewater-river continuum

Antimicrobial resistance (AMR) is a global health hazard. Although clinical and agricultural environments are well-established contributors to the evolution and dissemination of AMR, research on wastewater treatment works (WwTWs) has highlighted their potential role as disseminators of AMR in freshwater environments. Using metagenomic sequencing and analysis, we investigated the changes in resistomes and associated mobile genetic elements within untreated wastewater influents and treated effluents of five WwTWs, and sediments collected from corresponding river environments in Oxfordshire, UK, across three seasonal periods within a year. Our analysis demonstrated a high diversity and abundance of antimicrobial resistance genes (ARGs) in untreated wastewater influents, reflecting the varied anthropogenic and environmental origins of wastewater. WwTWs effectively reduced AMR in the final effluent, with an average 87 % reduction in normalised ARG abundance and an average 63 % reduction in richness. However, wastewater effluents significantly impacted the antimicrobial resistome of the receiving rivers, with an average 543 % increase in ARG abundance and a 164 % increase in richness from upstream sediments to downstream sediments. The normalised abundance of the human gut-associated bacteriophage crAssphage was highly associated with both ARG abundance and richness. We observed seasonal variation in the resistome of raw influent which was not found in the effluent-receiving sediments. We illustrate the potential of WwTWs as focal points for disseminating ARGs and resistance-selecting chemicals, contributing to the elevation of environmental AMR. Our study emphasises the need for a comprehensive understanding of the anthropogenic impacts on AMR evolution and dissemination in wastewater and river environments, informing efforts to mitigate this growing public health crisis.

Analysis of coastal tourists' environmental attitudes and potential as education for sustainable development

Indonesia has abundant natural resources, including tropical rainforests, biodiversity, mineral mines, waters, and coastal areas. Utilization of these resources must be carried out wisely and sustainably to ensure the welfare of future generations. This research aims to evaluate people's attitudes and behavior towards the environment, especially in river and coastal areas in Central Java, Indonesia. The research methods used are surveys, observations and interviews. The survey was carried out by distributing a questionnaire consisting of 30 questions. This statement includes awareness of protecting the coastal and river environment and real actions or behaviors that care about the surrounding environment. Data collected from the survey was analyzed using descriptive statistical analysis techniques to identify general patterns of respondents' attitudes and behavior. The research results show that people's attitudes toward environmental care are in the high category for 49% of respondents and very high for 51% of respondents. These results do not reflect some of the real actions taken by the community, especially in coastal areas. Several factors influencing environmental awareness were analyzed, including age, gender and education level. Researchers found that educational factors significantly affect attitudes towards environmental care. The results of this analysis can be used to support Education for Sustainable Development (ESD) in increasing pro-environmental awareness and action and supporting sustainable development goals.

Evolution and distribution of antibiotic resistance genes in submerged macrophytes and biofilm systems: From seasonal monitoring to mesocosm experiments

The aquatic ecosystem has been extensively investigated as a hotspot for the spread of antibiotic resistance genes (ARGs); yet, the evolution and distribution of ARGs profiles in submerged macrophytes biofilms and surrounding water remained unclear. In this study, the dynamic distribution and seasonal variations of microbial communities and ARGs profiles were investigated, alongside their assembly processes and mutual interactions. Bacitracin and multidrug resistance genes were predominant, constituting more than 60% of the total ARGs abundance. The deterministic processes (<65%), influenced by the physicochemical properties of the river environment, governed the assembly and composition of ARGs profiles, exhibiting significant seasonal variation. The peak diversity (21 types) and abundance (0.316 copy ratios) of ARGs were detected during the summer. Proteobacteria and Actinobacteria were the dominant bacterial phyla, accounting for 38.41–85.50% and 4.03–27.09% of the microbial community, respectively. Furthermore, Proteobacteria, especially genera such as Acinetobacter, Burkholderia, and Pseudomonas, with various resistance sequences, were the primary carriers of multiple ARGs. Notably, the genetic exchanges between biofilms and surrounding water facilitated the further propagation of high-risk ARGs, posing greater ecological risks. Redundancy analysis indicated that the total nitrogen and temperature in water determined the fate of pathogenic-resistant species. These findings provided theoretical support for the mitigation of ARGs contamination in aquatic environments.

Are parks as favourable habitats for wild bees as wastelands in watercourse valleys of a large city?

Because of the growing population density and rate of urban development, the question of biodiversity conservation in cities and towns is increasingly important. In general, urban environments provide attractive habitats for a diversity of wild bees, but different types of urban habitats can have different effects on these pollinating insects. In this study, we compared the attractiveness of two different urban habitat types – parks (10 sites) and wastelands (10 sites) located in river and canal valleys in Bydgoszcz (northern Poland) – with respect to abundance, species richness, species composition, and functional trait composition of wild bees. We hypothesized that urban wastelands are more attractive to wild bees than urban parks are. Urban wastelands were characterized by higher abundance and species richness of wild bees compared to urban parks. When habitat type was the only predictor, nonlinearity of wild bee abundance and species richness was significant exclusively for wastelands. Overall, both wild bee abundance and species richness depended on the percentage of total bee food plant coverage, regardless of habitat type. Wild bee community composition also responded significantly to the percentage of total bee food plant coverage. Local and landscape features of the green spaces affected the functional traits of the wild bees recorded there. These findings reveal that formal green spaces, such as managed parks, are not sufficient to conserve wild bee resources in urban environments in river and canal valleys. In contrast, high-quality informal urban green spaces, such as urban wastelands, can promote abundant and rich wild bee communities. Thus it is crucial to strive for appreciation and protection of this persistently overlooked category of urban green spaces.

Ecological and Medicinal Importance of Lampreys (Cyclostomata: Petromyzontiformes: Petromyzontidae)

For Pacific lampreys, life is not just about moving from freshwater to saltwater when they reach maturity, these ancient fish have to return to the same river environment where they were born. Going from a saltwater creature to a freshwater creature is not easy, however, and several modifications in appearance and physiology are necessary to survive the dramatic change in salinity. Their return to freshwater is not random, based on chemical signals left by the migration of lamprey larvae to return to rivers They can return to the same place they came from, but, unlike Pacific salmon, this precision is not always guaranteed, however, this transformation and the mapping of rivers require a lot of energy, and the animals resort to parasitization to survive. Lamprey swimming is among the most efficient in the world, as its movements generate zones of low pressure around the body, pulling the body through the water rather than pushing. The objective of this article was to characterize lampreys (Cyclostomata; Petromyzontiformes; Petromyzontidae) regarding their ecological and medicinal importance. The methodological analysis included studies of a particular topic. In its construction process, it is necessary to go through six essential stages: Identification of the theme and selection of the hypothesis or research question; establishment of criteria for inclusion and exclusion of studies/sampling or literature search; definition information to be extracted from selected studies/categorization of studies; evaluation of included studies; interpretation of results; and presentation of knowledge review/synthesis To carry out the study, a search for scientific articles was carried out through Virtual Health Library, in the SCIELO, LILACS, and PUMED databases, using the terminologies registered in the Health Sciences descriptors. Regarding the inclusion criteria, the following were used: Full articles, in Portuguese, and English.

Environmental Communication of the Kapuas River Clean Action by the Pontianak Young Generation

This article aims to increase the perception, experience, and communication of the young generation of Pontianak City in maintaining the cleanliness of the Kapuas River. The most considerable pollution of the river comes from household waste. River hygiene socialization often involves the people of riverside areas, as if they are the ones responsible for river cleanliness. The river cleanup action so far is also considered just ceremonial. This P.K.M. (community service) focuses on two activities: the digital campaign and the collective movement #AksiBersihSungaiKapuas. The digital campaign is carried out ten days ahead of World Environment Day. It contains education and recordings of the actual actions of Pontianak’s Young Generation. 134 digital campaigns are using the hashtag #AksiNyataBersihSungaiKapuas. Meanwhile, the Collective Movement is held on World Environment Day every June 5. A total of 2 tons of garbage was collected in the Kapuas River clean-up action. Plastic waste, water hyacinth, and household waste are the most common. The young generation of Pontianak City is not only a spectator but a subject in education and disseminating the habit of maintaining the cleanliness of the Kapuas River environment.

The significant impact of MPs in the industrial/municipal effluents on the MPs abundance in the Nakdong River, South Korea

Owing to extensive plastic consumption, wastewater from households, business establishments, and industrial activities have been recognised as a significant contributor to microplastics (MPs) in aquatic environments. This case study represents the first investigation of MPs in the Nakdong River, Republic of Korea, that traverses through the largest industrial complex midstream and densely populated cities of Daegu and Busan downstream before flowing into the sea. Monitoring of MP abundance in effluents discharged from three municipal, two industrial, and one livestock wastewater treatment plant (WWTP) into the Nakdong River was conducted over four seasons from August 2022 to April 2023. Identification and quantification of MPs were performed using micro-Fourier transform infrared spectrometry. Seasonal variation in MPs in the Nakdong River was found to be strongly influenced by the nearest upstream WWTPs and rivers, exhibiting a linear relationship that decreased gradually with increasing distance from the WWTPs. The average concentrations of MPs in the six effluent sources ranged from 101 ± 13 to 490 ± 240 particles/L during the yearly monitoring period, while MP concentrations in the river ranged between 79 ± 25 and 120 ± 43 particles/L. Industrial effluents contained higher amounts of discharged MPs (314 ± 78 particles/L) than municipal sources (201 ± 61 particles/L). Notably, two municipal WWTPs, located in the highly densely populated city, discharged the highest total MP amounts per day and released the greatest volumes of effluents. This study provides valuable insights into the monitoring and impact of effluents on MPs in rivers, which could inform MP treatment and management strategies for in river and marine environments.

Temporal changes in the morphological and microbial diversity of biofilms on the surface of a submerged stone in the Danube River

Epilithic biofilms are ubiquitous in large river environments and are crucial for biogeochemical processes, but their community structures and functions remain poorly understood. In this paper, the seasonal succession in the morphological structure and the taxonomic composition of an epilithic bacterial biofilm community at a polluted site of the Danube River were followed using electron microscopy, high-throughput 16S rRNA gene amplicon sequencing and multiplex/taxon-specific PCRs. The biofilm samples were collected from the same submerged stone and carried out bimonthly in the littoral zone of the Danube River, downstream of a large urban area. Scanning electron microscopy showed that the biofilm was composed of diatoms and a variety of bacteria with different morphologies. Based on amplicon sequencing, the bacterial communities were dominated by the phyla Pseudomonadota and Bacteroidota, while the most abundant archaea belonged to the phyla Nitrososphaerota and Nanoarchaeota. The changing environmental factors had an effect on the composition of the epilithic microbial community. Critical levels of faecal pollution in the water were associated with increased relative abundance of Sphaerotilus, a typical indicator of “sewage fungus”, but the composition and diversity of the epilithic biofilms were also influenced by several other environmental factors such as temperature, water discharge and total suspended solids (TSS). The specific PCRs showed opportunistic pathogenic bacteria (e.g. Pseudomonas spp., Legionella spp., P. aeruginosa, L. pneumophila, Stenotrophomonas maltophilia) in some biofilm samples, but extended spectrum β-lactamase (ESBL) genes and macrolide resistance genes could not be detected.

Exploring the Spatiotemporal Evolution Patterns and Determinants of Construction Land in Mianning County on the Eastern Edge of the Qinghai–Tibet Plateau

Studying the spatiotemporal evolution and driving forces behind construction land amidst the intricate ecological and geological setting on the eastern edge of the Qinghai–Tibet Plateau offers invaluable insights for local sustainable development in a landscape transition zone and ecologically fragile area. Using construction land data from four phases, spanning 1990 to 2020, in Mianning County, this study employs methodologies like the Landscape Expansion Index (LEI) and land use transfer matrix to delineate the spatiotemporal evolution characteristics of construction land. A comprehensive set of 12 influencing factors across five categories—geomorphology, geological activity, climate, river and vegetation environment, and social economy—were examined. The Geographically Weighted Regression (GWR) model was then employed to decipher the spatial distribution pattern of construction land in 1990 and 2020, shedding light on the driving mechanisms behind its changes over the three decades. The research reveals distinct patterns of construction land distribution and evolution in Mianning County, shaped by the ecological and geological landscape. Notably, the Anning River wide valley exhibits a concentrated and contiguous development mode, while the Yalong River deep valley showcases a decentralized development pattern, and the Dadu River basin manifests an aggregation development mode centered around high mountain lakes. Over the study period, all three river basins witnessed varying degrees of construction land expansion, transitioning from quantitative expansion to qualitative enhancement. Edge expansion predominantly characterizes the expansion mode, complemented by leapfrog and infilling modes, accompanied by conversions from cropland and forest land to construction land. An analysis of the spatial pattern and drivers of construction land change highlights human-induced factors dominating the Anning River Basin, contrasting with natural factors prevailing in the Yalong River Basin and the Dadu River Basin. Future efforts should prioritize climate change considerations and environmental capacity, aiming for an ecologically resilient spatial pattern of construction land.

Public perception vs ecological quality status: Examining the ecological restoration of the Congost River's Environment

This study examines the public's perceptions of the ecological restoration of the Congost River over the past thirty years, focusing on the period between 2010 and 2022. We conducted a survey of 112 river users across five key zones identified through a pilot study for their high pedestrian density, aiming to analyse how different sociodemographic groups perceive the river's ecological state. A structured questionnaire was distributed along both sides of the river to engage a diverse range of individuals typically utilizing the river environment. The collected data were analysed using regression models and Mann-Whitney U tests to assess differences between groups, with Bonferroni adjustments applied to control for multiple comparisons.The results reveal a broad increase in appreciation for the river since 2010, alongside measurable ecological improvements supported by scientific data. Despite these positive changes, a majority of surveyed users remain sceptical about the river's recovery, with less pronounced scepticism among older respondents, those with higher education, and environmental volunteers. These groups' perceptions align more closely with empirical evidence, highlighting the influence of sociodemographic factors on environmental awareness.Individuals living closer to natural settings and frequent river visitors were found to be more attuned to changes in the river's environment, particularly in aesthetic and sensory aspects. The study underscores the persistence of a perceptual gap between scientific assessments of ecological health and public sentiment, emphasizing the complex relationship between community perceptions and objective environmental indicators. These insights underline the complex relationship between community perceptions and objective environmental indicators, reflecting a broader trend in environmental awareness and the importance of factual communication in ecological issues.

Fine Sediment in Mixed Sand‐Silt Environments Impacts Bedform Geometry by Altering Sediment Mobility

AbstractGeometric characteristics of subaqueous bedforms, such as height, length and leeside angle, are crucial for determining hydraulic form roughness and interpreting sedimentary records. Traditionally, bedform existence and geometry predictors are primarily based on uniform, cohesionless sediments. However, mixtures of sand, silt and clay are common in deltaic, estuarine, and lowland river environments, where bedforms are ubiquitous. Therefore, we investigate the impact of fine sand and silt in sand‐silt mixtures on bedform geometry, based on laboratory experiments conducted in a recirculating flume. We systematically varied the fraction of sand and silt for different discharges, and utilized an acoustic Doppler velocimeter to measure flow velocity profiles. The final bed geometry was captured using a line laser scanner. Our findings reveal that the response of bedforms to an altered fine sediment percentage is ambiguous, and likely depends on, among others, bimodality‐driven bed mobility and sediment cohesiveness. When fine, non‐cohesive material (fine sand or coarse silt) is mixed with the base material (medium sand), an increased dune height and length is observed, possibly caused by the hiding‐exposure effect, resulting in enhanced mobility of the coarser material. However, weakly cohesive fine silt suppresses dune height and length, possibly caused by reduced sediment mobility. Finally, in the transition from dunes to upper stage plane bed, there are indications that the bed becomes unstable and dune heights vary over time. The composition of the bed material does not significantly impact the hydraulic roughness, but mainly affects roughness via the bed morphology, especially the leeside angle.

Raising environmental awareness through community-based efforts to clean and preserve the Karang Mumus river, Samarinda City

River pollution, particularly from littering, has long plagued Samarinda City. The Karang Mumus River exemplifies this challenge, with heavy downstream debris and a lack of upstream catchment areas leading to seasonal flooding. This pollution significantly reduces the community's quality of life and hinders sustainable development efforts. To address this, a community service program was initiated to raise environmental awareness through cleaning and maintaining the Karang Mumus River. The program utilized outreach methods to educate the "Save Karang Mumus" (SKM) community about the river's functions and proper environmental practices in the surrounding area. The activity culminated in a river cleaning initiative. Notably, post-program participants expressed a willingness to actively participate in future river cleaning efforts organized by GMSS-SKM. This positive outcome demonstrates the program's success in raising awareness about the importance of protecting the Karang Mumus River environment.

Influence of sand-gravel quarrying on the river bed and environment (the case of Valvalachay river)

Influence of sand-gravel quarrying on the river bed and environment (the case of Valvalachay river)

Assessing and predicting water quality index with key water parameters by machine learning models in coastal cities, China

The water quality index (WQI) is a widely used tool for comprehensive assessment of river environments. However, its calculation involves numerous water quality parameters, making sample collection and laboratory analysis time-consuming and costly. This study aimed to identify key water parameters and the most reliable prediction models that could provide maximum accuracy using minimal indicators. Water quality from 2020 to 2023 were collected including nine biophysical and chemical indicators in seventeen rivers in Yancheng and Nantong, two coastal cities in Jiangsu Province, China, adjacent to the Yellow Sea. Linear regression and seven machine learning models (Artificial Neural Network (ANN), Self-Organizing Maps (SOM), K-Nearest Neighbor (KNN), Support Vector Machines (SVM), Random Forest (RF), Extreme Gradient Boosting (XGB) and Stochastic Gradient Boosting (SGB)) were developed to predict WQI using different groups of input variables based on correlation analysis. The results indicated that water quality improved from 2020 to 2022 but deteriorated in 2023, with inland stations exhibiting better conditions than coastal ones, particularly in terms of turbidity and nutrients. The water environment was comparatively better in Nantong than in Yancheng, with mean WQI values of approximately 55.3–72.0 and 56.4–67.3, respectively. The classifications "Good" and "Medium" accounted for 80 % of the records, with no instances of "Excellent" and 2 % classified as "Bad". The performance of all prediction models, except for SOM, improved with the addition of input variables, achieving R2 values higher than 0.99 in models such as SVM, RF, XGB, and SGB. The most reliable models were RF and XGB with key parameters of total phosphorus (TP), ammonia nitrogen (AN), and dissolved oxygen (DO) (R2 = 0.98 and 0.91 for training and testing phase) for predicting WQI values, and RF using TP and AN (accuracy higher than 85 %) for WQI grades. The prediction accuracy for "Medium" and "Low" water quality grades was highest at 90 %, followed by the "Good" level at 70 %. The model results could contribute to efficient water quality evaluation by identifying key water parameters and facilitating effective water quality management in river basins.

Uncovering the characteristics of plastic-associated biofilm from the inland river system of Mongolia

The occurrence and characteristics of plastic debris in aquatic and terrestrial environments have been extensively studied. However, limited information exists on the properties and dynamic behavior of plastic-associated biofilms in the environment. In this study, we collected plastic samples from an inland river system in Mongolia and extracted biofilms to uncover their characteristics using spectroscopic, isotopic, and thermogravimetric techniques. Mixtures of organic and mineral particles were detected in the extracted biofilms, revealing plastic as a carrier for exogenous substances, including contaminants, in the river ecosystem. Thermogravimetric analysis (TGA) indicated the predominant contribution of minerals primarily comprising aluminosilicate and calcite, representing approximately 80 wt% of the biofilms. Differential thermal analysis (DTA) coupled with Fourier transform infrared (FTIR) spectrometry operated at 25°C–600 °C enabled the detection of gaseous decomposition products, such as CO2, H2O, CO, and functional groups (O–H, C–H, C–O, CO, CC, and C–C), released from biopolymers in the extracted biofilms. Dehydration, dehydroxylation, and decarboxylation reactions explain the thermal properties of biofilms. The stable carbon (δ13C) and nitrogen (δ15N) isotope ratios of the biofilms demonstrated variable signatures ranging from −24.1‰ to −27.0‰ and 3.1‰–12.3‰, respectively. A significant difference in the δ13C value (p < 0.05) among the upstream, middle, and downstream research sites could be characterized by available organic carbon sources in the river environment, depending on the research sites. This study provides insights into the characteristics and environmental behavior of biofilms which are useful to elucidate the impact of plastic-associated biofilms on organic matter and material cycling in aquatic ecosystems.