Chemical Water Quality Research Articles

Evaluation of pilot-scale drinking water treatment trains using a panel of bioassays

ABSTRACT Chemical water quality monitoring is increasingly complemented with bioassays. In this study, the performance of drinking water treatment technologies was evaluated with bioassays. CALUX reporter gene bioassays and the Ames fluctuation bioassay for mutagenicity were used to analyze the responses of raw feed water with and without a spiking mixture of organic contaminants in five different pilot-scale water treatment trains applying advanced oxidation processes, reverse osmosis and filtration with (biological) activated carbon for the preparation of drinking water. In general, CALUX responses in the spiked feed water were in the same range as in the unspiked feed water, indicating that spiking did not significantly elevate the activity measured in the feed water. This observation was in line with a calculation of the combined additive behavior of the spiking mixture using bioactivities of the spiked chemicals in analog bioassays from ToxCast. This calculation gave no indication of a measurable response in the bioassays to be expected by the spiking, except for oxidative stress. Responses in the Ames fluctuation assay in most feed water were in some cases increased by AOP and mostly removed by active concentrations. The bioassay responses demonstrate the removal of emerging chemicals with different mechanisms of action by different water treatment technologies.

Chemical Characteristics and Water Quality Assessment of Groundwater in the Dongjiang-Hanjiang River Basin, China

Groundwater plays an important role in the rapid economic development of the Dongjiang-Hanjiang River Basin. This paper uses the Gibbs model, ionic ratio coefficient analysis, factor analysis, water quality index method and human health risk assessment model to estimate the chemical properties and quality of groundwater in the Dongjiang-Hanjiang Basin. The ion concentration and proportion of SO42- water in the Hanjiang River Basin are higher than those in the Dongjiang River Basin. The groundwater ions come mainly from the dissolution of carbonate rocks, silicate rocks and saline rocks, some of which come from human activities such as industry and mining. Groundwater composition is controlled by rock dissolution, alternating cation adsorption, and human activities. The proportion of rock dissolution is the greatest, but the influence of human activities is obvious. The intensity of human activities such as industry, mining and agriculture is greater in the Hanjiang River Basin than in the Dongjiang River Basin. The overall groundwater quality is poor, and the Dongjiang River Basin is better than the Hanjiang River Basin. The above-standard factors are mainly pH, I−, NO3−, NH4+, As and Pb2+. Nitrate pollution in groundwater is harmful to health and the health risk of children from nitrate is higher than that of adults. The health risk in the Hanjiang River Basin is higher than that in the Dongjiang River Basin. This can serve as a vital reference for similar areas worldwide, offering guidance for groundwater management, pollution prevention and control.

Mining and urbanization affect river chemical water quality and macroinvertebrate communities in the upper Selenga River basin, Mongolia (revised version).

Mongolia is a country with a quickly growing economy mainly based on the mining of gold, copper, coal, and other minerals. Mining, urbanization, and agriculture impact the water quality in the upper Selenga River basin in northern Mongolia, which is the center of the Mongolian economy. Previous measurements of pollution loads were alarming, but restricted to chemical measurements. Here, for the first time, we combine freshwater biomonitoring and laboratory water quality data across a broad gradient of water quality and land use intensity. We track the effects of different types of pollution on aquatic invertebrates and test their use as bioindicators. We collected water samples, environmental parameters, and macroinvertebrates at 36 sampling sites at the rivers of Tuul, Kharaa, and Orkhon and their tributaries Sugnugur, Boroo, Sharyn Gol, Gatsuurt, and Yeröö. PCA of catchment water quality distinguished three groups of pollutants prevalent at the sites, (1) nutrients, (2) salt ions(Cl-, Na+, Mg2+, So42-, Ca2+) and mining by-products (B, Sr, U, Mo), and (3) (heavy) metals, which often exceeded regulatory standards. We recorded a total of 59 macroinvertebrate taxa belonging to 31 families in seven insect orders plus Amphipoda and Gastropoda. Species diversity declined with higher impact. Five environmental factors structured macroinvertebrate community composition in RDA: elevation of sample location, site total nitrogen, dissolved oxygen, electrical conductivity, and water chemistry. We conclude that macroinvertebrate communities are an appropriate and inexpensive tool for monitoring water quality in Mongolia and suggest government action to establish a long-term monitoring program.

Climate variability impact on groundwater quality in Small Island Developing States: Mauritius Island as a case study

This study investigates the impact of climate variability on groundwater quality in Mauritius. This is achieved by analyzing the physical and chemical water quality of the five main aquifers over eleven years. Temporal variations in water quality properties were compared to the Standardised Precipitation Index (SPI), Dry Spells, the Standardised Evapotranspiration Index (SPEI), and other climate variables to gain insights into how precipitation controls groundwater quality. The results reveal that the SPI and the SPEI correlate minimally with water quality indicators. Sulphate is the only water quality indicator that showed correlations above 0.4 in aquifers 2 and 3 against a 12-month SPI. Sulphate, alongside chloride, showed what is termed ”notable correlation,” a concept defined in this paper to accommodate correlations that fall above 0.3 when assessed against global climate modes ENSO and AAO, respectively. These results signify that sulphate is the most sensitive water quality indicator to water quantity changes, notwithstanding the modesty of the correlations. Heavy storms occurring during cyclones impact groundwater quality with respect to conductivity, TDS, salinity, and nitrate, although this could not be statistically tested given the lack of water quality indicators collected on the days surrounding the storm. Therefore, the conclusion is made based on one storm event. The study revealed that individual correlations between climate indices and water quality variables are present but weak. However, the long-term trend in water quality is visible.

Estimation of soil loss using RUSLE model and GIS tools: Case study in the Jucusbamba Micro-Watershed (Amazonas, NW Peru)

Human activities have intensified soil erosion globally, negatively impacting the physical, chemical, and microbiological quality of water and soil. This study estimated soil loss in the Jucusbamba Micro-Watershed (Amazonas, northwestern Peru) using the Revised Universal Soil Loss Equation (RUSLE) integrated with Geographic Information Systems (GIS) and remote sensing (RS) data. Meteorological data, soil maps, digital elevation models, and land cover and use maps were integrated into a GIS environment to predict the spatial distribution of erosion. The results showed five classes of soil loss severity: slight (93.34%), moderate (3.94%), high (1.82%), very high (0.61%), and severe (0.29%). Areas with high, very high, and severe erosion levels were mainly located in the middle and lower parts of the micro-watershed. The average annual soil loss was estimated at 23.24 t/ha/year. The information obtained is crucial for the formulation of soil management plans and programs to address erosion problems in the Jucusbamba River Micro-Watershed. Future research should focus on validating these models through field studies and implementing soil conservation practices based on these findings. Keywords: Amazonas, hydrology, RUSLE model, water erosion map, watershed.

Nutrient Concentration, Water Brightness, Chlorophyll-a, and Phytoplankton Abundance as Indicators for Determining the Trophic Status of Lake Toba, North Sumatera - Indonesia

The purpose of this study was to investigate the water quality and phytoplankton abundance in Lake Toba to determine its trophic status. This research was conducted from January to March 2024 at four stations in Lake Toba. Water samples were taken using a UWITEC water sampler and a plankton net and brought to the laboratory for analysis. The study measured physical and chemical water quality and phytoplankton abundance. The results showed a brightness ranging between 5.8 and 6.3 meters, chlorophyll-a content <10 µg/L, total nitrogen <750 µg/L, and phosphorus ranging from 20 µg/L to 30 µg/L. Based on these parameters, the nutrient quality of Lake Toba was classified as mesotrophic. Phytoplankton abundance ranged from 22,514 to 33,475 individuals/L, with 33 genera identified across nine classes: Bacillariophyceae, Chlorophyceae, Cyanophyceae, Coscinodiscophyceae, Dinophyceae, Euglenida, Fragilariophyceae, Mediophyceae, and Zygnemophyceae. The diversity index (H') was 2.631 - 2.723, the uniformity index (E) was 0.828 - 0.872, and the percentage of blue-green algae was 14.75 - 20.85. Zygnemophyceae was the most dominant phytoplankton class, with Staurastrum sp. being the most prevalent species. In conclusion, Lake Toba's waters are categorized as mesotrophic based on the chemical parameters and as eutrophic based on phytoplankton abundance, indicating potential nutrient enrichment issues that warrant further investigation.

A Tale of Two Tributaries: Source Delineation of Chloride in a Distressed Watershed (Grand Lake St. Marys, Ohio)

Various sources of pollution have been assigned as contributing to the Freshwater Salinization Syndrome (FSS), by which water bodies are undergoing concurrent salinization and alkalinization. In many urban areas that receive substantial snowfall, road salt application has been ascribed as the main source of chloride driving the FSS. In rural areas, however, inorganic (e.g. chemical) and organic (e.g. manure) fertilizer applications have been found to be the most important sources of chloride. Herein, we compared daily mean concentrations of chloride over the past decade of time between Coldwater Creek and Chickasaw Creek, two tributaries of Grand Lake St. Marys, the largest reservoir in Ohio. We also used Weighted Regressions on Time, Discharge, and Season (WRTDS) analyses to visualize trends in chloride data and compared chloride vs. nitrate levels to delineate likely sources of chloride for the two streams. We found that road salt application increased over time in both subwatersheds and that 37% and 25% of the chloride could be apportioned to road salt as a source in Coldwater Creek and Chickasaw Creek, respectively. Additionally, in Coldwater Creek, 37% of the chloride was apportioned to animal or septic sources, while 25% was apportioned to inorganic fertilizers, in comparison with 30% and 42% for Chickasaw Creek. Monitoring and assessing salinized streams for both chemical and biological water quality is important, particularly since the FSS has become increasingly linked to declines in water quality (e.g. harmful algal blooms, including recent upticks in Prymnesium parvum blooms) and is expected to be exacerbated with global climate change (e.g. increased precipitation causing increased runoff of chloride from the land).

Retraction Note: Mining and urbanization affect river chemical water quality and macroinvertebrate communities in the upper Selenga River Basin, Mongolia

Retraction Note: Mining and urbanization affect river chemical water quality and macroinvertebrate communities in the upper Selenga River Basin, Mongolia

20-year water quality analysis reveals spatial variability and long-term changes at North Carolina's Masonboro Island National Estuarine Research Reserve

Urbanization impacts, especially stormwater runoff and pollutant discharge, pose ecological threats to coastal ecosystems globally. Long-term environmental monitoring datasets and assessments are used to quantify anthropogenic impacts on ecosystem health. This study synthesized twenty years (2002–2021) of water quality data from the National Estuarine Research Reserve System-wide Monitoring Program at the understudied Masonboro Island Reserve (North Carolina, United States) and provided an analytical methodology that can be applied to other Reserves and monitoring programs world-wide. Time series and correlation analyses of biological, chemical, and physical water quality parameters were used to identify spatiotemporal trends of nutrient dynamics and phytoplankton biomass at three stations within a 5-km stretch of the Atlantic Intracoastal Waterway. Heterogenous water quality conditions were observed between stations, especially for chlorophyll a, and were influenced by the relative proximity to marine waters, human developments, and urban tidal creeks. Long-term trends indicated significant water quality changes (i.e., increased chlorophyll a, reduced pH and salinity) related to anthropogenic influences. An unexpected and rapid shift in nutrient dynamics occurred around 2007, marked by significantly decreased ammonium and orthophosphate concentrations, which considerably reduced DIN/DIP ratios. This positive change was potentially influenced by sewage infrastructure improvements and stormwater wetland construction, removing waste-derived nutrients that previously entered the ecosystem. Impacts of major storms were also observed with weeks of hypoxia and low salinity following Hurricane Florence. These findings emphasized the value of long-term trend analyses of monitoring program data at multiple sites and provided insights into the significant water quality impacts of urbanization and benefits from wetland protection. This study further encourages the evaluation of long-term water quality monitoring datasets in estuarine environments globally.

Investigation of the chemical and microbial quality of water supplied by treatment stations in Kerman city, Iran

ABSTRACT This study aimed to investigate the quality of water supplied in Kerman city, southeast Iran. Total hardness, nitrite, nitrate, total dissolved solids, electrical conductivity, total coliforms, fecal coliforms, and elements were measured in samples from five stations in four seasons in 2022. The concentration levels of (mg/L) As (0.42 ± 1.83), Cd (0.004 ± 0.01), Cu (2.51 ± 3.38), Ni (1.33 ± 0.86), and Pb (1.50 ± 2.11) were more than the standard. Total coliforms in samples (5.30 ± 7.87) were more than the national standard (0/100 mL) with a significant mean difference in seasons (p-value = 0.04). Fecal coliforms were detected in samples collected in autumn (2.00 ± 0.00/100 mL). The findings showed that water treatment in stations could not remove the toxic heavy metals of As, Pb, and Cd. But the microbial pollution was detected in some samples. Therefore, the use of these waters is generally not recommended. Further studies and comparisons with water quality in the distribution system can provide more useful results.

Coordinated analysis of groundwater spatiotemporal chemical characteristics, water quality, and potential human health risks with sustainable development in semi-arid regions.

The emergence of large-scale time-series data and advancements in computational power have opened new avenues for analyzing the spatiotemporal evolution of groundwater chemistry, water quality, and human health risks. This paper utilizes hydrogeochemical methods to elucidate the controlling factors of water chemical components based on the test results of 124 groundwater samples collected from 31 monitoring wells in Fuxin City, Liaoning Province, China, from 2018 to 2021. By integrating the Random Forest and Enhanced Water Quality Index methods for water quality assessment and employing the Human Health Risk Assessment (HHRA) model to analyze human health risks, our findings indicate that the groundwater is mildly alkaline, with SO4·Cl-Ca·Mg and HCO3-Ca·Mg as the dominant hydrochemical types, primarily derived from the dissolution of carbonate and silicate minerals such as dolomite, limestone, and andesite, and cation exchange reactions. The EI_RF water quality evaluation model reveals that the overall water quality in the study area is poor, with Class I and II water quality zones mainly located in the northeastern and central parts of the study area, showing a gradual transition from Class I and II in the northeast to Classes IV and V in the southwest, significantly influenced by NO3-, TH, TDS, and SO42-. The HHRA model results indicate that the potential non-carcinogenic risk of groundwater nitrates has a severe impact on infants, with the spatial distribution being low in the northeast and high in the southwest. Due to industrial activities, agricultural practices, and population growth, certain areas in developing countries such as China and India exhibit nitrate concentrations significantly higher than those in most international regions, highlighting global environmental and public health challenges. This underscores the importance of enhancing groundwater monitoring and implementing measures to mitigate pollution. These research outcomes hold significant implications for the government in formulating rational protection and management measures to ensure the sustainable utilization of groundwater resources.

Analysis of Residential Well Water Quality Around People's Gold Mines in the Tourist Area of Dusun Selindungan

The Sekotong area has natural charm and potential mining. This area is one of the preferred destinations for visits by local and foreign tourists. However, apart from that, the Sekotong area is also famous as a community gold mining area. Mining activities carried out still use traditional methods, which are very far from environmentally friendly principles, so they can have impacts, including causing a decrease in the quality of residential well water. This research was conducted to determine the water quality of residential wells around community gold mining in the tourist area of Dusun Selindungan Eleven well water samples were taken using a purposive sampling method based on the distance of the well to the source of gold mining waste disposal and are still used by residents to meet their daily needs. Physical, chemical and biological water quality parameters of water samples were investigated in the laboratory, except temperature and pH were measured directly in the field. Data for each water quality variable was analyzed to determine the pollution index. The results show that DO, TDS, content of phosphate, E. Coli bacteria and total coliforms in well water from the study area generally exceed quality standardsWell water in an area that is a different distance from the people's gold mining waste disposal site has each been contaminated with manganese and mercury, although it is still below quality standards.

Wastewater as a nutrient source for hydroponic production of lettuce: Summer and winter growth

Solutions combining soilless cropping systems with wastewater reuse can offer benefits in the agriculture sector, reducing pressure on water resources, promoting sustainable production, and reclaiming wastewater. However, assessing the sanitary risks associated with wastewater reuse is of utmost importance. This study aimed to investigate the hydroponic growth of lettuce (Lactuca sativa var. crispa L.) in wastewater from an urban treatment plant with different levels of treatment and evaluate potential sanitary risks. Crop growth took place in a greenhouse, during summer and winter periods, using wastewater after primary (PTW) or secondary (STW) treatment, and a nutrient solution (NS), as control. Physical and chemical water quality parameters, morphological crop growth parameters, and environmental conditions inside the greenhouse were monitored. Toxicity analyses were carried out through cell viability assays with the Caco-2 cell line and total coliforms and Escherichia coli (E. coli) were determined. Wastewater-grown plants achieved acceptable growth, even though presenting lower fresh weight than NS-plants. STW-plants’ growth was limited essentially by nutrient deficiency, and PTW-plants were affected by nutrient deficiency, pH values, solid load, and N-NO2 concentration. Higher temperatures in summer led to faster crop growth, and lower temperatures in winter allowed better nutrient uptake by the crop. Wastewater-grown plants did not evidence toxicity in leaf extracts up to 1 % w/v. Coliform enumeration data indicated an accumulation in plant roots, with high removal from the wastewater. E. coli was not detected on plants’ leaves and total coliforms were within acceptable limits. Furthermore, the results point to an improvement in the wastewater quality, with minimum removal values of 75.2 % BOD5, 83.1 % COD, 43.4 % P, 44.9 % N, and 90.4 % K. The results demonstrated the viability of wastewater reuse for hydroponic production allowing a better understanding of its processes and contributing to mitigating water scarcity for food production, and the impacts of treated wastewater discharge in freshwater courses, particularly those associated with nutrient delivery to aquatic systems.

Potential deterioration of chemical water quality due to trace metal adsorption onto tire and road wear particles – Environmentally representative experiments

Tire wear particles are an increasing issue in particle emissions to the environment. Germany-wide approximately 100,000 t tire wear particles are emitted every year into the environment which are estimated to be one third of the microplastic emissions. Up to 20% are estimated to reach inland surface waters. Their behavior in the aquatic environment is understudied. Tire wear particles have an overly hydrophobic surface that is capable of adsorbing substances like trace elements. In this study we investigated the adsorption and desorption of trace metals onto and from the particle surface of tire-related samples in water samples of the Freiberger Mulde, a river with naturally elevated concentration of trace elements. The priority trace metals Cr, Ni, Zn, Cd and Pb show a significant adsorption onto the particle surface of tire-related samples. Tire wear particles themselves revealed adsorption of mainly Ni, Cd and Pb. Regarding the German classification for suspended matter in freshwaters, an endangering of the chemical water quality is expected due to the adsorption process and not due to the particles themselves. Upcoming electromobility is expected to increase the Zn (increased tire abrasion) and decrease the Cu amount (reduced brake abrasion) released to freshwaters.

Groundwater health risk assessment and its temporal and spatial evolution based on trapezoidal fuzzy number-Monte Carlo stochastic simulation: A case study in western Jilin province

The United States Environmental Protection Agency (USEPA) Four-step-Method (FSM) is a straightforward and extensively utilized tool for evaluating regional health risks, However, the complex and heterogeneous groundwater environment system causes great uncertainty in the assessment process. Triangular stochastic simulation (TSS) possesses certain advantages in solving uncertainty problems, but its inadequacy with discrete data reveals limitations in this aspect. To solve the above problems, this study proposes to construct trapezoidal fuzzy number-Monte Carlo stochastic simulation (TFN-MCSS) to compensate for the shortcomings of the first two methods. This method adopted trapezoidal fuzzy number (TFN) analysis to comprehensively consider the characteristics of a large dispersion of water quality monitoring data and the uncertainty of the human health risk assessment (HHRA) process. Concurrently, to overcome the subjectivity and uncertainty of artificially determining the interval of TFN in traditional methods, the slope was used to select the most probable interval value (TMPIV) of TFN combined with the α-truncated set technique (α-TST) and MCSS. Based on these, a TFN-MCSS was constructed and applied to groundwater HHRA in western Jilin Province. First, the groundwater chemical characteristic determination and water quality evaluation in western Jilin were performed to identify the main pollution indicators, and the health risk effects of pollutants in groundwater of different aquifers at different time periods on adults and children were evaluated using the TFN-MCSS. The uncertainty and sensitivity were analyzed, and the primary risk control indicators were identified and compared to FSM and TSS. The results reveal that TFN-MCSS was more sensitive to data and could reduce the uncertainty of assessment process. It indicated that over a 10-year period, the health risks associated with unconfined groundwater (UW) and confined water (CW) decreased by greater than 52 %. However, the highest total non-carcinogenic risk index (THI) was 1.3-fold higher than the safety threshold, and this posed a health risk.

Analysis of Drinking Water Quality among Employees of Sulianti Saroso Infectious Disease Hospital

Drinking water is water through or without processing that meets health requirements and can be drunk directly. The aim of the study is to check the quality of drinking water for employees of Sulianti Saroso Infectious Disease Hospital (SSIDH) so that it is suitable or not for consumption in accordance with established quality standards. Drinking water sampling is carried out twice a year with a sampling point of 8 (eight) samples at every 6 (six) months. Based on the results of physical tests, namely smell, turbidity, taste, temperature, total dissolved solids, and color, it shows that the employee's drinking water has met the quality standards according to applicable regulations. Chemical drinking water quality requirements show pH concentrations ranging from 7.22 – 8 and other parameters including organic substances have met the quality standard requirements. Biological test results show the bacteriological quality of drinking water Total Coliform and Escherichia Coli is 0 according the required quality standard of 0 per 100 ml. The quality of drinking water for employees of RSPI Prof. Dr. Sulianti Saroso based on the results of laboratory examinations shows 100% of samples meet the requirements in accordance with the drinking water quality standard.

Water chemical formation mechanism and water quality analysis of Shichuan River under the influence of human activities

ABSTRACT It is necessary to analyze the characteristics of the water environment and factors influencing the basin in order to determine its current ecological status. This study aims to investigate the chemical properties in the Shichuan River Basin using Gibbs diagram, Piper triangle diagram, correlation analysis, factor analysis, and main ion ratio method. The enhanced Nemerow comprehensive index method and fuzzy comprehensive evaluation method are employed for river water quality assessment. The findings reveal that runoff water has a weak alkaline nature with low salinity. The hydrochemical type of river water includes Ca2++Mg2++Na+-SO4 2-, Ca2++Mg2+-SO4 2-+Cl-+HCO3 -, Ca2++Na+-SO4 2-+Cl-+HCO3 -. Silicite and dolomite weathering are identified as primary influencing factors, while evaporite weathering also contributes to variations in chemical composition within the basin's waters. Ca2+, Mg2+, SO4 2- and HCO3 - originate from carbonate rock and silicate rock weathering processes, whereas Na+, K+ and Cl-, are primarily derived from evaporite weathering influenced by domestic sewage and agricultural activities. Agricultural production practices along with discharge of domestic sewage have an impact on Na+, K+, Cl- and NO3 -concentrations in aquatic systems. Water quality at all three monitoring sections falls under level IV classification. Phosphorus emerges as a key limiting factor for eutrophication within this basin's watersheds.

Identifikasi Kualitas Fisik dan Kimia Air Sumur Gali di Wilayah Produksi Terasi di Dusun Jor Desa Jor Kecamatan Jerowaru Kabupaten Lombok Timur

This research aims to determine the physical and chemical quality of dug well water in the area where shrimp paste (terasi) is produced at Jor Hamlet, Jor Village, Jerowaru Subdistrict, East Lombok Regency. The research method used was experimental, focusing on parameters such as temperature, pH, TDS, and hardness based on the Indonesian National Standard (SNI) guidelines. Three sampling points of community dug well water were selected with sampling conducted twice, considering the sampling points based on the distance between the dug wells and the shrimp paste production area being less than 10 meters, and due to the absence of proper wastewater disposal systems at the shrimp paste production site. From the results of the examination of the physical and chemical water quality around the shrimp paste production area in Jor Hamlet, Jor Village, Jerowaru Subdistrict, East Lombok Regency, it was found that several parameters met the requirements according to the Indonesian Ministry of Health Regulation Number 32 of 2017 concerning the Standard of Environmental Health Quality and Health Requirements for Hygiene, Swimming Pools, Solus Per Aqua, and Public Bathing. Parameters such as temperature, pH, and TDS met the standards. However, the examination revealed that the hardness of the dug well water exceeded the standard in one out of the three sampling points. Specifically, samples A and B met the standard for hardness, whereas sample C did not meet the standard because it exceeded the established quality standard of 500 mg/l.

Geophysical contribution based on vertical electrical sounding to hydrogeological evaluation in Ras Jebel coastal aquifer, Tunisia

AbstractThe coastal aquifer of Ras Jebel is located in the northeastern governorate of Bizerte. It is formed by a Mio–Plio‐quaternary geological structure. The region of Ras Jebal is considered an important agricultural centre due to intensive groundwater exploitation. This overexploitation results in a decrease in piezometry and an increase in salinity. The groundwater piezometric study shows a decrease in the piezometric level of approximately −3.34 to −1.79 m in 2015. Our study based on vertical electrical sounding had the aim to monitor the salinity of the water table in 2017, which showed that refill transactions in the aquifer of Ras Jebel caused the improvement of the chemical quality of water. In fact, the salinity in the coastal zone is between 2.53 and 4.14 g/L. As for the resistivity, which reached 2 Ω m near the sea, the geophysical study based on the geoelectric method has provided an electrical image of the basement to clarify the basin structure. The use of an electrical prospection method to study the salinization of the water table of Ras Jebel has highlighted the contribution to the most origin of saltwater: natural origin (sea water intrusion) on the northeastern coast of Ras Jebel. This source is the main origin of the degradation of the quality of underground water resources in Ras Jebel.

An extended novel approach of river health analysis using nonmetric scaling ordination of fish ecological entities and functional identity indices

As river ecosystems continue to face environmental pressures, it is crucial to develop and apply new biologically relevant statistical tools to support river health assessments. This study aimed to test the potential significance of nonmetric ordination scores and multidimensional functional indices of fish communities for analyzing river ecological health linked to variations in environmental factors. We conducted a nonmetric multidimensional scaling (NMDS) to derive ordination scores based on twenty fish ecological entities (FEs) that we newly defined, along with their relative abundance (RA). These FEs were determined through a unique combination of trophic, habitat, and tolerance guilds. Additionally, we calculated the functional diversity and identity (F-Ide) indices using the RA-weighted distances between FEs defined by the guild identities in a multidimensional space. The results showed that these novel analyses were helpful in assessing river ecological health and spatial changes in the environment. The dominant F-Ide in each community was largely responsible for the variation of river health scores, driven by the combined impact of chemical water quality, alterations in substrate composition, land use changes, and the gradient of elevation. These environmental factors significantly influenced the site scores in the first axis of NMDS, F-Ide indices, and river health scores. Therefore, our study highlights the practical value of utilizing nonmetric scaling ordination scores of FEs and F-Ide indices as tools for evaluating the health of river ecosystems. By elucidating fish community variance, these tools can aid in determining the extent of river health degradation attributable to environmental stressors, including chemical water pollution and changes in substrate resulting from changes in land use and at different elevations.