Water Quality Research Articles

Application of selected indicators to assess contamination of municipal landfill leachate and its impact on groundwater

Leachate formation is one of the most important factors taken into account during the operation and long-term management of municipal waste landfills. Systematic assessment of groundwater and leachate contamination may be useful in selecting the appropriate method of leachate management or treatment processes. The use of indicators to quantify the contamination potential of leachate and groundwater in the vicinity of MSW could help landfill managers assess their quality. Therefore, the aim of the study was to assess the representativeness of selected indicator methods for analyzing the temporal variability of leachate and groundwater properties in the vicinity of two municipal waste landfills in a Central European country (Poland). The leachate pollution index (LPI), sub-LPI and adjusted leachate pollution index (r-LPI) were used to assess the quality of leachate water, while the landfill water pollution index (LWPI) was used to assess the variability of groundwater quality. The results confirmed that LWPI is an effective method for assessing the quality of groundwater in the vicinity of municipal waste landfills. The obtained results confirm the negative impact of landfills, despite the insulation used. LWPI showed poor quality of groundwater and visible impact of the landfill (landfill W, average LWPI - 2.34) and moderately polluted waters and minor impact of the landfill (landfill S, average LWPI - 1.37). In most cases, it was observed that two parameters, EC and TOC, are the main factors contributing to the deterioration of groundwater quality. The sub-LPI analysis showed that leachates from both landfills have a very low content of heavy metals, so they should not have a negative impact on the biological treatment process. The obtained r-LPI values were in all cases higher than the calculated LPI values. For landfill S, the average r-LPI was 26.3 (Z-1) and 25.7 (Z-2). However, the average LPI was 13.5 (Z-1) and 13.2 (Z-2). For landfill W, the average r-LPI was 14.6 and the average LPI was 11.4. Analysis conducted on multi-year leachate and groundwater data using specific indicators can help managers better understand the impact of MSW on surrounding areas and help avoid potential operational problems in the future.

Hydrogeological studies of the Sepidan basin to supply required water from exploiting water wells of the Chadormalu mine utilizing reverse osmosis (RO) method

Due to the lack of rainfall potential in Central Iran, the water scarcity is still the main problem of production in the country. Accordingly, the use of unconventional waters will be inevitable. This study presents the amount of water required by the Chadormalu mine from the water wells of the Sepidan Plain, as well as the deficit or excess for exploiting the complex and the water treatment plant by reverse osmosis (RO) method. These studies were carried out to manage the groundwater resources of the Sepidan and Saghand basins and include the water level variations of piezometers, the water consumption of exploitive wells, aqueducts, and the Sepidan River every month. Furthermore, a sample of complete chemical analysis of the aqueducts' Saghand basin and the water entering the RO and leaving it for environmental evaluations have been carried out each season. The average discharges of water wells in the Sepidan Plain were 86.45 and 82.28l/s in 2221 and 2023, respectively. Moreover, the amount of water exploitation has been lower than the renewable (dynamic) reserves, which in the heart of the water intake has a uniform increase in the monthly hydrograph's water level. At the same time, the reduction of total dissolved solids (TDS) entering from exploitation water intakes to the amount of 580mg/l indicates the principled exploitation of dynamic reserves. The RO unit's output had no effect on the quality of the Saghand Playa's water but improved it qualitatively.

From thaw till fall: Interacting hydrology, carbon cycle, and greenhouse gas dynamics in a subarctic stream-lake continuum.

Carbon-water interaction studies between aquatic and terrestrial ecosystems are especially needed today in Arctic and Boreal regions, as they are facing drastic warming and precipitation shifts. Despite the importance of streams in the carbon cycle, northern stream-based studies are scarce, owing to a lack of measurements throughout the north, and possibly skewing global greenhouse gas estimates. We used a combination of multiscale measurements to quantify water sources (H2O isotope proxies), carbon availability (dissolved in/organic carbon concentrations) and quality (water absorbance, SUVA254 -index), microbial community structure (16S rRNA sequencing), and carbon dioxide (CO2) and methane (CH4) fluxes and concentrations. Our study site comprises a groundwater-influenced and peatland-dominated second-order stream, along with its adjacent lake inlet located in Northern Finland. Sampling was conducted three times during the summer of 2019 at 21 locations along the stream-lake continuum. Temporal and spatial shifts in water sources altered carbon characteristics, with CH4 concentrations being the key environmental factor shaping the microbial communities, overriding the influence of dissolved organic carbon amount and quality. The prevalence of methanotrophic bacteria highlighted the importance of CH4 as a carbon source and the methanotrophic groups as drivers of the CH4/CO2 source-sink attributes of subarctic stream systems. Our results highlight the value of integrated hydrological, biogeochemical, and microbiological measures to resolve the biocomplexity of carbon-water interactions in northern headwater catchments.

Refining submarine groundwater discharge analysis through nonlinear quantile regression of geochemical time series

A reliable quantification of fresh submarine groundwater discharge (SGD) is key to understanding and managing water quality and habitat of coastal ecosystems. However, current radon tracer-based SGD quantifications suffer greatly from uncertainty and subjectivity in tracer signal processing and the indirect estimation of non-SGD related tracer sources and sinks. This study provides a new procedure and models SGD rates as upper envelopes in radon and inverted salinity vs water depth regressions over tidal cycles. We use non-linear quantile regression to model these envelopes and account for signal lag correction and noise suppression via optimization towards matched radon and inverted salinity envelope data, and a monotonic (i.e., non-oscillating) trend for the water depth. We then quantify the SGD rate based on the temporal change of the modeled radon envelope inventory and define the radon signature of the fresh groundwater endmember (which is critically important for the calculation of volumetric discharge rates) as the zero-salinity intercept in the envelope regression. Our results indicate that the traditional radon mass balance, if applied at a data aggregation interval of < 1 h and if based on a subjective mixing loss estimation, may lead to a substantial overestimate of SGD. This limitation should be carefully considered in the calibration of lager scale, model-based SGD analyses.

Influence mechanisms of dissolved organic matter and iron minerals on naphthalene attenuation during river infiltration

Natural attenuation of naphthalene (NAP) in riverbank filtration zones is vital for maintaining water quality and is affected by dissolved organic matter (DOM) and iron minerals. However, the effects of DOM and iron minerals on the attenuation of NAP remain unclear. In this study, the attenuation mechanisms of NAP under the influence of DOM and iron minerals were explored in a riverside source area. Field dynamic monitoring data revealed that the NAP concentration in groundwater is mainly influenced by DOM, effective bound‑iron, and the intensity of river water infiltration recharge. Column experiments indicated that DOM with α-Fe2O3 or α-FeO(OH) reduced medium permeability by 8.16 % or 6.85 %, respectively, increasing water retention time. However, they had different effects on the attenuation of NAP. The coexistence of α-Fe2O3 and DOM enhanced NAP attenuation capacity by 9.13 %–45.91 %, while α-FeO(OH) and DOM reduced it by −13.25 % to −24.13 %. These effects were attributed to changes in the medium permeability, particle size, secondary mineral formation, and microbial community structure. Specifically, α-Fe2O3 and DOM reduced medium permeability, increasing the adsorption and biodegradation reaction time of NAP, and promoted secondary mineral (FeCO3) formation, increasing the adsorption capacity of medium for NAP, while α-FeO(OH) and DOM underwent cementation, resulting in larger particles and reduced adsorption capacity for NAP. Additionally, α-FeO(OH) and DOM promoted Shewanlla growth, inhibiting NAP attenuation by competing with NAP-degrading bacteria. These findings improve the understanding of the natural attenuation of polycyclic aromatic hydrocarbons (PAHs) in riverbank filtration, offering a basis for evaluating and controlling PAH pollution risks.

Optimizing aquatic weed management in Lake Ossa, Cameroon: Harnessing the power of biological control and real-time satellite monitoring

Salvinia, Salvinia molesta Mitchell (Salviniaceae) is a free-floating aquatic fern native to Brazil and considered one of the worst weeds in the world. When left unchecked, salvinia forms dense mats on the water surface, limiting sunlight penetration and altering water quality that disrupt ecosystem processes. In 2016, salvinia was first reported in Lake Ossa, Cameroon, and by summer 2021, had expanded to cover almost 49 % of the lake’s 4,000-hectare surface. A multinational team initiated a biological control and monitoring program, importing the salvinia weevil, Cyrtobagous salviniae Calder & Sands (Coleoptera: Curculionidae) from Louisiana, USA, in summer 2021. The objectives of this study were to: quantify the changes in salvinia cover and other floating vegetation, document the establishment and impact of the biological control program, and deliver a tool for near-real time monitoring of floating vegetation. We developed a satellite-based remote sensing application to document in near real-time the changes in coverage of floating vegetation. Using this tool, we quantified the reduction in the salvinia coverage by 80 % within three years of the release of the weevil. Field surveys in 2022 and 2023, demonstrated weevil establishment in the lake and widespread salvinia browning that was associated with weevil damage. Linear regressions of the percent cover of floating vegetation over time, demonstrated that after the weevil release, the rate of change decreased to −1.7 % per 60 days. Field monitoring and satellite imagery showed the establishment of a sedge (Oxycaryum sp., Cyperaceae) within the salvinia mat in late 2021. This secondary invasion slowed the reduction in coverage of floating vegetation from −1.7 % to −0.6 % per 60 days, and warrants further research. By late 2023, the revitalization of Lake Ossa restored fishing and transportation opportunities for the community, and also the comeback the emblematic African manatee. The success of the biological control of salvinia in Lake Ossa is not surprising due to its tropical conditions. However, it highlights the importance of early intervention and continuous monitoring. We propose that the integration of biological control and remote sensing technology is becoming more accessible and can be automated; therefore, a replicable model for future invasive weed programs around the world.

Impact of residential hot water heater type and water stagnation on drinking water quality within a full-scale premise plumbing system

Impact of residential hot water heater type and water stagnation on drinking water quality within a full-scale premise plumbing system

Occurrence and characteristics of microplastics across the watershed of the world’s third-largest river

While rivers as primary conduits for land-based plastic particles transferring to their "ultimate" destination, the ocean, have garnered increasing attention, research on microplastic pollution at the scale of whole large river basins remains limited. Here we conducted a large-scale investigation of microplastic contamination in water and sediment of the world’s third-largest river, the Yangtze River. We found concentrations of microplastics in water and sediment to be 5.13 items/L and 113.9 items/kg (dry weight), respectively. Moreover, microplastic pollution levels exhibited a clear decreasing trend from upstream to downstream. The detected microplastics were predominantly transparent in color, with fibrous shapes predominating, sizes mainly concentrated below 1mm and composed primarily of PP and PE polymers. Our analysis results indicated that compared to geographical and water quality parameters, anthropogenic factors primarily determined the spatial distribution pattern of microplastics. Moreover, the microplastic abundance in sediment upstream of the dam was significantly higher than that in the downstream sediment, while the trend of microplastic concentrations in water was opposite. Therefore, more effort is needed to monitor microplastic contamination and their ecological environmental effects of sediment before dams in future research.

Retrofitting agricultural detention systems can economically enhance nitrogen treatment with payment for services approach

Despite their global presence and multiple services including water storage and treatment, limited field studies have focused on quantifying water quality effectiveness of agricultural stormwater detention areas (SDAs; farm ponds). Limited information that does exist stems from unverified modeling studies. Economics is another neglected aspect of SDAs. An SDA in the Everglades basin of Florida was monitored to quantify its baseline nitrogen (N) treatment. Design flaws of underutilized surface storage in variably ponded areas and short-circuiting were rectified by retrofitting the SDA through compartmentalization, increase in outflow structure control elevation, and installing channel plugs. Post-retrofit total N retentions doubled (7500 from 3700 kg), a similar trend was also observed in surface water volume indicating that water retention drives N retention. Targeting enhanced water retention through retrofits can achieve reductions in downstream nutrient flows. The cost of additional N treatment from retrofits was $12/kg, an order of magnitude less than the published costs for other detention systems including newly constructed wetlands ($180/kg) and tailwater recovery systems ($214/kg). A scale-up showed that retrofitting SDAs could reduce the N discharge to an estuary in the Everglades by more than 50 %. A win-win payoff to farmers for SDA retrofits through a payment for environmental services program can achieve nutrient treatment economically and facilitate large-scale adoption.

Research on intelligent river water quality management system using blockchain-internet of things

Research on intelligent river water quality management system using blockchain-internet of things

Water quality assessment of groundwater resources in rural areas of Karachi, Pakistan

Water quality assessment of groundwater resources in rural areas of Karachi, Pakistan

Effect of irrigation water quality on chemical and physical properties of soils

Effect of irrigation water quality on chemical and physical properties of soils

A common framework for the development of spring water contamination early warning system in western Mediterranean karst areas: Spanish and French sites

Karst water resources, traditionally used worldwide for drinking purposes, are highly vulnerable to contamination. Scientific-technical efforts must therefore be done to ensure sufficient water quality for human consumption. Early-Warning-Systems emerge as an effective spring scale protection strategy for real-time identification of contamination episodes at drinking water capture points. With this ambition, the proposed stepwise procedure for the implementation of site-specific Early-Warning-Systems (EWS), focuses on three critical features: identification of groundwater contamination proxy parameters, warning dissemination and system validation. It was tested at three karst springs affected by temporary faecal contamination and intended for supplying drinking water to populations in Spain (Ubrique) and France (Montpellier). The applied statistical techniques, coupled to the analysis of individual flood events at karst springs, allowed to identify the optimal combination of groundwater and contamination proxy parameters at each study site according to the main contaminants and recharge mechanisms. The decision tree-like workflow, used to evaluate groundwater quality at hourly time step and set up the EWS, was then constructed considering a specific combination of hydroclimatic, hydrodynamic and physical variables together with national regulations for drinking water. Hence, warning thresholds were adapted to the behaviour of each karst system, and used to trigger the alarm when specific parameters and proxies exceeded the defined limits. The performance of the EWS was assessed by implementing 4 specific Key Performance Indicators (KPIs) dedicated to appreciate the effectiveness of the workflows in identifying contamination events and verifying estimated warning thresholds. The performed analysis demonstrated an overall successful functioning of the EWS for the three case studies, with mean anticipation times ranging between 12 and 45 h and <3 % of failure rate.

Looking beyond the surface: Understanding the role of multiple stressors on the eutrophication status of the Albufera Lake (Valencia, Spain)

Aquatic ecosystems face significant impacts from human-related stressors, demanding a deep understanding of their dynamics and interactions for effective management and restoration. The Albufera Lake (Valencia, Spain) presents a complex scenario of multiple interacting stressors affecting its eutrophic status. In this study, we compiled a 50-year dataset and used Generalized Additive Models (GAMs) to analyse the dynamics of the main stressors affecting the ecological status of the Albufera Lake. Then, we assessed their individual and combined effects on eutrophication using chlorophyll-a concentration as a proxy and provided recommendations to enhance water quality. Overall, we found a decrease in annual water inflow and a clear effect of rice cultivation on the seasonal patterns of the Lake's residence time. Our analysis also shows an increase of average water temperature of 2 °C for the last 50 years, and an increase in the frequency and severity of heat waves. In contrast, we found a slightly negative long-term trend in conductivity, despite the occurrence of seasonal peaks in summer. Regarding nutrients, we identified a clear reduction of total phosphorus (from 1.08 mg/L in 1987 to 0.20 mg/L in 2022), while nitrate concentrations have been rather stable. Our results also point at an increase of toxic pressure exerted by organic and inorganic contaminants during the last years, with seasonal toxicity peaks occurring during rice field drainage periods. The main stressors affecting the chlorophyll-a levels were found to be temperature, water scarcity, and nitrate concentration as well as the interactions between temperature and conductivity, conductivity and nitrate, conductivity and water scarcity, and nitrate and total phosphorus. We found that stressor interactions are highly dynamic and result in synergistic and antagonistic effects that vary according to different stressor levels. Finally, our GAM framework points to two potential scenarios: increasing freshwater inflows or deregulating hydrology to allow seawater exchange, which are key for improving the ecological status of the Albufera Lake in the short-term.

Aqua-stream: an IoT based smart water management system for sustainable living

&lt;p class="03IJISAEAbstract"&gt;Aqua-stream, an innovative internet of things (IoT) enabled water management system, utilizes the power of long short-term memory (LSTM) networks, a sophisticated time-series forecasting machine learning technique with Kafka. Aqua-stream seamlessly integrates LSTM within the Kafka streaming architecture for efficient real-time data processing, ensuring quick responses to emerging water management needs. LSTM is employed for real-time anomaly detection, dynamically analyzing streaming data to prevent leaks through automated shut-off valves. The system’s comprehensive dashboard utilizes LSTM insights for live water quality analysis; adaptive scheduling based on individual preferences and personalized recommendations, enhancing cost-effective water management. This streamlined approach extends to the smart gardening system, where LSTM guides automation for optimal plant care incorporating sensors to monitor soil moisture, temperature, and sunlight levels. This system automatically adjusts watering and lighting to ensure optimal conditions for plant growth. Users can control and monitor their garden remotely via a smartphone, facilitating plant care while saving water and energy. Aqua-stream redefines home water management, offering a holistic solution that combines intelligent water conservation with smart gardening for a sustainable and connected living experience. Aqua-stream represents a seamless integration of LSTM-based machine learning and IoT technologies, offering an intelligent, yet simplified, solution for sustainable and connected living.&lt;/p&gt;

Assessment of groundwater quality for agricultural purposes in Qazvin Province, northwestern Iran: A fuzzy inference and indicator Kriging approach

This study addresses the challenge of assessing groundwater quality for agriculture in Qazvin Province, northwestern Iran. In this region, over-extraction has led to significant degradation of groundwater resources. Traditional assessment methods often overlook uncertainties and spatial variability in groundwater quality. To address this, our study aimed to integrate fuzzy inference and geostatistical methods to assess groundwater quality under uncertain conditions. The research was conducted in two stages. First, a fuzzy inference system classified six key water quality parameters: Electrical Conductivity (EC), Sodium Adsorption Ratio (SAR), Residual Sodium Carbonate (RSC), Total Hardness (TH), sodium ion concentration (Na⁺), and chloride concentration (Cl⁻), into three categories: "desirable," "acceptable," and "unacceptable," using 54 fuzzy rules. In the second stage, we applied ordinary Kriging and indicator Kriging to spatially interpolate these classifications and produce probabilistic maps of groundwater quality risk across the study area. In ordinary Kriging, the average Root Mean Square Error (RMSE) values for EC, SAR, RSC, TH, Na⁺, and Cl⁻ were 0.94 dS/m, 1.54, 1.42 meq/L, 3.13 mg/L, 3.03 mg/L, and 2.62 mg/L, respectively, indicating reliable assessments of groundwater quality parameters. Results also suggest that by 2023, areas classified as "unacceptable" increased by 142.0% since 2009, with an additional 25.2% of the region facing a 40 to 80% probability of further degradation. These findings highlight important trends in groundwater quality, assisting local authorities in prioritizing areas for preventive interventions. This supports sustainable agricultural practices and aligns with the United Nations Sustainable Development Goal 6 for water resource management.

Long-term water quality dynamics and trend assessment reveal the effectiveness of ecological compensation: Insights from China’s first cross-provincial compensation watershed

Long-term water quality dynamics and trend assessment reveal the effectiveness of ecological compensation: Insights from China’s first cross-provincial compensation watershed

Environmental and Hydrological Synergies Shaping Phytoplankton Diversity in the Hetao Irrigation District

Phytoplankton are crucial primary producers in freshwater ecosystems, driving matter and energy flow across trophic levels, essential for biodiversity and ecological balance. Most research emphasizes environmental factors shaping their diversity, while the role of hydrological connectivity remains poorly understood. This study collected 81 phytoplankton samples from the Hetao Irrigation District along a gradient from upstream to downstream and utilized high-throughput sequencing to evaluate the spatial distribution patterns of phytoplankton diversity. The study analyzed the impacts of environmental factors, hydrological connectivity (water surface ratio, Wp), and human activities (land-use intensity, LUI) on phytoplankton diversity. The results revealed that the phytoplankton community comprised 9 phyla, 158 families, 378 genera, and 1189 species. There were significant differences in phytoplankton diversity among different water bodies, with a gradual increase in phytoplankton diversity from west to east across the five major irrigation areas. Lake Ulansuhai had relatively low phytoplankton diversity. The ASV number, Chao1 index, and ACE index showed significant positive correlations with dissolved oxygen (DO), pH, and water temperature (WT). The Shannon index and Pielou’e evenness (Pielou_e) index showed significant positive correlations with the water surface ratio (Wp). The partial least squares model indicated that environmental factors directly influenced phytoplankton diversity. Hydrological connectivity indirectly affected phytoplankton diversity by altering environmental factors. We emphasize that hydrological connectivity is as important as environmental factors in driving phytoplankton diversity in the Hetao Irrigation District. This study provides key insights for water quality assessment and biodiversity conservation in the region.

Phosphorus cycle in shallow lakes affected by crucian carp (Carassius auratus): Effects of fish density and size

Crucian carp (Carassius auratus) is an omni-benthivorous fish common in many shallow lakes in China. The presence of crucian carp can contribute to the nutrient cycles in lakes and thus affect water quality. In this work, a two-by-two factorial mesocosm experiment was performed with crucian carp of different sizes and densities, to investigate their effects on the cycle of phosphorus (P). Results showed that nutrients in particulate form increased in overlying water due to crucian carp disturbance, especially for treatments with higher fish densities and larger individuals. Smaller individuals at high density have a greater ability to promote P release from sediment, due to a stronger combined effects of physical disturbance and excretion. Accumulation of feces led to sediment anaerobiosis and the reductive dissolution of iron oxide-hydroxide, which were the main factors affecting the desorption of P. Our results quantify the endogenous P diffusion fluxes across the sediment-water interface attributed to different densities and sizes of crucian carp disturbance, and suggest controlling crucian carp at low density and small size to minimize their impact on sediment P flux.

Trace analysis of taste and odour compounds in drinking water by stir bar sorptive extraction followed by thermal desorption - gas chromatography - mass spectrometry (SBSE-TD-GC-MS)

Because of negative tap water quality perception, people often prefer bottled water over tap water despite the higher energy consumption and production of plastic waste. Taste and odour (T&O) deviations in tap water are an important aspect of this issue and should be avoided. However, T&O compounds typically occur at low concentrations (≤ ng.L−1) and are numerous, originating from various sources, ranging from source water to kitchen taps. Consequently, unravelling T&O events is challenging and causing compounds may remain unknown. Therefore, a multi-compound method (SBSE-TD-GC–MS) was developed, optimised and validated for the simultaneous trace analysis of 45 T&O compounds in drinking water. It covers key compounds of different odour categories with a wide range of physical-chemical properties and originating from the different steps of production and distribution. The intra- and interday precision of the method was shown by relative standard deviations (RSD) lower than 15 % and 23 %, respectively, for 75 % of the measured concentrations. For most of the compounds (>75 %), the detection capability (CCβ) was below 1/3rd of their lowest reported odour threshold concentration (OTC), while for the other 6 compounds, the CCβ was within the reported OTC range. Additionally, the CCβs were comparable to or lower than those in literature. As a proof of concept, the method was used to investigate the occurrence and concentrations of T&O compounds before (surface water) and after drinking water production. The results show a clear removal of compounds related to microbial activity (e.g. geosmin, 2-methylisoborneol, 2,4,6-tribromoanisole) after treatment and an increase of compounds related to disinfection. Although rarely investigated, 3-methylbutanal showed concentrations similar to its OTC in treated drinking water, emphasizing the necessity of a broad ultra-trace analysis to ultimately prevent the occurrence of T&O compounds and guarantee tap water quality.