Groundwater Quality Monitoring Research Articles

Assessing data variability in groundwater quality monitoring of contaminated sites through factor analysis and multiple linear regression models

Monitoring of long-term contaminant concentrations trends is essential to verify that attenuation processes are effectively occurring at a site. However, monitoring data are often affected by extreme variability which prevents the identification of clear concentration trends. The variability is higher in long-screened monitoring wells, which are currently used at many contaminated sites, although it has been known since the 1980s that monitoring data from long-screened wells can be biased. Understanding the factors that may influence the variability of monitoring data is pivotal. To this end, following hydrochemical conceptual modelling using a multi-method approach, the variability of hydrocarbon concentrations from fully screened monitoring wells was assessed over eleven years at a former oil refinery located in Northern Italy. The proposed methodology combined factor analysis with multiple linear regression models.Results pointed out a higher variability in hydrocarbon concentrations at the plume fringe and a lower variability at the plume source and core. 44–46 % of the total variability in measured hydrocarbon concentrations is due to “intrinsic plume heterogeneity”, related to the three-dimensional structure of a contaminant plume, which becomes thinner at the edge, creating a vertical heterogeneity of redox conditions at the plume fringe. This variability, expressed as increasing concentrations of sulfate and decreasing concentrations of methane, represents a background variability that cannot be reduced by improving sampling procedures. The remaining 56–54 % of the total variability may be due to the non-standardization of some purging and sampling operations, such as pump intake position, purging and sampling time/flow rates and variations in the analytical methods. This finding suggests that monitoring improvements in fully screened wells by standardizing all purging/sampling operations or using sampling techniques that can reduce the actual screen length (e.g., packers or separation/dual pumping techniques) would reduce data variability by more than half.

Assessment of Groundwater Quality and Vulnerability in the Nakivale Sub-Catchment of the Transboundary Lake Victoria Basin, Uganda

This study evaluates the quality and vulnerability of groundwater within the Nakivale Sub-catchment of the transboundary Lake Victoria Basin in Southwestern Uganda. Groundwater quality assessment focuses on its suitability for both drinking and agricultural uses. Hydrochemical analysis of 19 groundwater samples revealed that 90% comply with World Health Organization drinking water standards, although localized contamination was noted, particularly in terms of total iron, nitrate, potassium, magnesium, and sulfates. The drinking groundwater quality index shows that over 90% of the samples fall within the good-to-excellent quality categories. Elevated nitrate levels and chloride–bromide ratios indicate human impacts, likely due to agricultural runoff and wastewater disposal. For irrigation, Sodium Adsorption Ratio analysis revealed medium-to-high salinity hazards in the region, while Sodium Percentage and other parameters indicated low-to-moderate risks of soil degradation. DRASTIC vulnerability assessments identified low contamination risks due to impermeable geological layers, steep terrain, slow groundwater recharge, deep aquifer depth, and clayey soil cover. These findings emphasize the need for conjunctive water resource management, including improved groundwater quality monitoring, public education on sustainable practices, and protective measures for recharge zones and areas highly susceptible to contamination. By addressing these issues, this study aims to preserve groundwater resources for domestic and agricultural use, ensuring long-term sustainability in the region.

Monitoring groundwater vulnerability for sustainable water resource management: A DRASTIC-based comparative assessment in a newly township area of Bangladesh

Groundwater is a vital source of freshwater in our daily lives. Global and local groundwater quality are degrading due to rapid urbanization, human interference, and policy variations, which is prominent in developing nations like Bangladesh. The major purpose of this research is to analyze aquifer vulnerability in Bangladesh's north-central area (Mymensingh) using conventional and modified DRASTIC modeling. Seven influencing hydrogeological factors were employed to develop and integrate conventional DRASTIC modeling: soil media, net recharge, aquifer depth, aquifer media, topography, hydraulic conductivity, and influence of vadose zone, while land use and lineament density were used with them for modified DRASTIC modeling. The findings from four vulnerability analysis detected 29.56% (93.35 sq.km), 22.24% (83.12 sq. km), 28.52 (106.93 sq. km), and 37.6% (140.55 sq.km) of the study area as high to very high vulnerable zones for groundwater pollution. Lower groundwater depth, higher hydraulic conductivity, moderate to high groundwater recharge, dense lineaments, dense settlement, agricultural land, and inland waterbodies together might indicate a high vulnerability in the research area. The validation results based on EC and nitrate levels show that conventional (r = 0.884, p ≤ 0.01; r = 0.951, p ≤ 0.01) and modified DRASTIC models (r = 0.868, p ≤ 0.01; r = 0.840, p ≤ 0.01) have a stronger association with unconfined aquifers, than confined aquifers. Modification with both additional parameters showed more accuracy compared to the conventional one. Frequent monitoring of groundwater quality in high and moderately vulnerable zones is recommended for earlier detection and prevention of potential aquifer degradation.

Determination of the Quality of Groundwater in Mankweng, Limpopo Province, South Africa, Using the Water Quality Index.

There is a lack of groundwater quality monitoring, especially in developing countries like South Africa. This study aimed to evaluate borehole water quality. Groundwater was analysed for pH, dissolved oxygen (DO), temperature, electrical conductivity (EC), total dissolved solids (TDSs), turbidity, chemical oxygen demand (COD), nitrogen (N), sulphate (SO42-), fluoride (F-), chloride (Cl-), calcium (Ca2+), magnesium (Mg2+), potassium (K+), and sodium (Na+) using a multi-parameter device, spectrophotometer, turbidity meter, and inductively coupled plasma optical emission spectrophotometer. Total coliforms and Escherichia coli were quantified using the Colilert system. The water quality index (WQI) was calculated using the arithmetic weighting method. The parameters ranged as follows: pH (6.71-7.94), DO (2.19-7.79 mg/L), EC (379.67-1317.33 µS/cm), TDSs (190-659 mg/L), temperature (16.75-22.31 °C), turbidity (0.17-3.21 NTU), COD (9-50 mg/L), F- (0.17-2.09 mg/L), Cl- (36.1-184.55 mg/L), N (0.64-28.56 mg/L), SO42- (27.18-112.13 mg/L), K+ (1.71-21.77 mg/L), Ca2+ (29.59-134.59 mg/L), Mg2+ (16.72-110.78 mg/L), and Na+ (38.52-170.63 mg/L). One borehole was polluted with E. coli (9 MPN/100 mL) and 25% were contaminated with coliforms beyond 10 MPN/100 mL. The WQI ranged from 50.430 to 190.220. The results underscore the importance of regular monitoring of groundwater.

Analysis of groundwater and surface water quality using modelled water index and multivariate statistics in Kampala and Mbarara Districts, Uganda

The demand for domestic, public and industrial use of water increases with population growth. However, activities from humans and natural environment have resulted into decline in water quality. The aim of this study was to evaluate the quality of groundwater and surface water collected from Kampala and Mbarara districts of Uganda using water quality index and multivariate statistics. A total of 10 physicochemical parameters (pH, water temperature, chloride, sulphate, nitrate, electrical conductivity, total dissolved solids, total suspended solids, total solids, and phosphate) were measured monthly to evaluate the quality of water in the study districts. Results showed that sulphate, electrical conductivity and total dissolved solids were observed with significantly high values in surface water than the groundwater for both seasons. Among all the parameters measured, electrical conductivity was observed with the highest value (2129.67 ± 1.41 µS/cm) while nitrate concentration (0.57 ± 0.02 mg/L) was observed with the lowest during the wet season in surface water. In addition, the mean values of nitrate, electrical conductivity, total dissolved solids and sulphate detected in the groundwater and surface water were within the recommended limits, while phosphate and chloride were observed with mean concentrations above the regulatory limits in 50% of the samples. The correlation analysis revealed strong and positive association between electrical conductivity and total dissolved solids in groundwater and surface water for both seasons. Also, the chemical make-up of groundwater and surface water within the study districts revealed that the determination of water quality rests on two major indices (conductivity and anthropogenic-pollutants) based on the factor analysis. The two indices accounted for 0.619% in groundwater and over 0.70% in surface water, indicating more pollution in surface water. Moreover, the water quality index (WQI) values obtained ranged from 14.81 to 115.73 in dry season and 7.77 to 108.24 during the wet season. According to WQI classification, 42% of the samples collected fell within the “excellent” and “good” categories while others fell within “poor” and “unfit” categories (58%) during the dry season. Based on these findings, appropriate treatment methods, proper sanitation and waste management should be implemented in locations with critical water conditions. Also, frequent monitoring of groundwater and surface water quality by environmental protection agency is highly recommended.

Isotopic study for evaluating complex groundwater circulation patterns, hydrogeological zoning, and water-rock interaction in a Mediterranean coastal karst environment

In this study groundwater provenance, circulation, and rock interaction processes have been assessed by cross processing the spatial distribution of chemical and isotopic signatures in freshwater with the hydrogeological features of the coastal karst carbonate aquifer of Murgia, located in the southeastern end of Italy, along the Adriatic Sea. Thanks to widespread groundwater quality monitoring (major, minor, and trace-element analyses) and multi-isotopic measures of O, H, Sr, and B, some assumptions about complex groundwater circulation patterns, hydrogeological zoning, and water-rock interaction have been drawn. Three sectors have been distinguished into the Adriatic side of the Murgia aquifer all fed by two main recharge areas located on the most elevated, inner side of the aquifer. Each sector is characterized by different groundwater circulation patterns, residence time, and hydrogeochemical features. The water samples collected into the western sector evidence a certain degree of water-rock interaction, which allows us to assume long groundwater flow paths and residence time. On the contrary, the eastern sector of Murgia has been proven to be characterized by short residence times and a possible direct freshwater contribution even in the downstream course due to the massive presence of karst forms. Herein, the isotopic analysis of the water samples does not provide evidence of water-rock interaction. Finally, in the third, central sector, water infiltrated at different locations mixes flowing through relatively long paths even though not sufficient to allow groundwater to gain the rock's isotopic signature.

Establishing a Groundwater Quality and Quantity Monitoring System as a Prerequisite for the Determination of Protection Zones in Lipjan, Kosovo

Establishing a Groundwater Quality and Quantity Monitoring System as a Prerequisite for the Determination of Protection Zones in Lipjan, Kosovo

A robust decision-making approach for designing coastal groundwater quality monitoring networks.

This paper presents a new approach to the spatiotemporal design of groundwater quality monitoring networks for coastal aquifers. A fusion model combines the outputs of several developed simulation models to make estimates more accurate. A modified GALDIT method is used to incorporate the aquifer vulnerability to saltwater intrusion. The value of information (VOI) theory is applied to determine sufficient monitoring wells. The groundwater quality monitoring network is designed by employing a robust decision-making (RDM) approach under different management strategies and economic considerations. This approach incorporates the deep uncertainties of some critical variables, including water level and total dissolved solids (TDS) concentration at the coastline and pumping flow rates of agricultural wells. The new methodology is implemented in the coastal Qom-Kahak aquifer, Iran. The results illustrate that the combination model has significantly improved evaluation criteria compared to individual prediction models. The fusion model results indicate that thirty monitoring wells would be ideal. The RDM-based analyses in the Qom-Kahak aquifer showed that an optimal network with 30 monitoring wells outperforms the current network regarding various criteria, such as VOI and variance of estimation error. The new well configuration also demonstrates a suitable spatial distribution. Given that the current sampling frequencies are unsuitable for areas with varying vulnerabilities, we recommend sampling every 3months in areas with moderate vulnerabilities and once every three seasons in areas with low vulnerabilities, based on the information transfer index. Finally, a management strategy in which the pumping rate should be less than 60% of the current rate is suggested to prevent saltwater intrusion into the aquifer.

Mobility and persistence of pesticides and emerging contaminants in age-dated and redox-classified groundwater under a range of land use types

Understanding groundwater contamination patterns is hampered by the heterogeneous groundwater age and redox status over the depth range typically sampled for identifying pesticides and emerging contaminants threats. This study explores depth patterns of groundwater age and redox status across various land use types, unraveling spatial and temporal trends of pesticides and emerging contaminants using data from groundwater quality monitoring in the south of the Netherlands. The Netherlands is an ideal testing ground due to its high population density and widespread groundwater contamination from multiple sources. 146 multi-level observation wells were age-dated using 3H/3He, and contaminant concentrations were analyzed based on recharge year, land use type, and redox conditions, mitigating uncertainties from spatial and depth-dependent variations in both groundwater age and redox status. Redox-recharge year diagrams were developed to visually evaluate contaminant patterns in relation to these factors and to assess concentration patterns in relation to contamination history. Most detections of pesticides, metabolites, and emerging contaminants occurred in the youngest recharge periods (2000–2010 and 2010–2020) and in agricultural areas. However, certain contaminants, including BAM, desphenyl-chloridazon, short-chain PFCAs, PFOA, and EDTA, were consistently found in older water and Fe- or SO4-reduced conditions, indicating their mobility and persistence in the regional groundwater system. Comparing the presence of contaminants in specific redox classes and recharge periods with known application or leaching history provides insights into retardation (e.g., PFOS) and degradation (e.g., 2-hydroxy-atrazine, benzotriazole), explaining lower detection frequencies in earlier recharge periods. Identifying recharge years from age-dated groundwater helps relate contaminants to farmland application or river water recharge periods, revealing leaching history and contamination origins. The presented framework has the potential to enhance the interpretation of large groundwater datasets from dedicated, short-screened observation wells, such as those from the Danish GRUMO network, the Dutch monitoring networks, and parts of the US National Water Quality Program.

Distributed wireless IoT based sensing and quality monitoring system in protection of wetlands groundwater areas

Abstract This paper presents the development and implementation of a sensor network based on the Internet of Things (IoT) to monitor key groundwater quality parameters with the goal of minimizing potential risks in the protection of biodiversity. These parameters include the water level, water temperature, pH, conductivity, and dissolved oxygen. The system prioritizes scalability, ease of use, real-time data acquisition and minimal power consumption, resulting in efficient and dependable water quality monitoring with the convenience of remote applications. The continuous measurement system was set up to be a single source of information for monitoring groundwater quality in protected wetland areas across international borders, including Tompojevacki Ritovi (Municipality of Tompojevci, Croatia) and Lake Zobnatica (Municipality of Backa Topola, Serbia). The findings of two years of Wireless Sensor Network (WSN) monitoring were compared to standard laboratory methods to demonstrate the accuracy and precision of WSN readings. Appropriate calibration and installation of the WSN give a larger volume of data and thus grow the database, allowing for a more accurate identification of water contamination and a quick response in the event of pollution. Smart IoT-based sensors help to protect water quality and, as a result, the well-being of ecosystems and human communities, which is especially important in protected areas like wetlands.

The GIS framework is used to assess Lucknow City's groundwater quality using the water quality index [WQI

Monitoring groundwater quality continuously is essential to reducing the dangers of geochemical pollutants through suitable treatment techniques and guaranteeing safe drinking and irrigation. Thus, this study's main goal was to evaluate the appropriateness of the groundwater that was collected, from India's Lucknow for irrigation as well as drinking. To assess the quality of the groundwater in the research area, ten samples were taken from various locations. Analysis was done on some parameters, including pH, total dissolved solids (TDS), electrical conductivity (EC), total hardness, total alkalinity, BOD, COD, nitrate, total nitrogen, E. Coli, and ammonia. The water quality index (WQI) has arithmetical weights. Using a critical grading system that shows overall quality, the water's quality was evaluated and categorized as very good, good, moderate, bad, and unfit for consumption. Increasing public understanding and decision-making to make informed choices about efficient care, management, and long-term, sustainable social growth is greatly aided by this classification. To find relationships between the different parameter values, a correlation matrix was created and examined. As a result, the results imply that the groundwater in the investigated region is secure and appropriate for irrigation and consumption.

Deciphering geochemical fingerprints and health implications of groundwater fluoride contamination in mica mining regions using machine learning tactics.

The contribution of mica mining activities to fluoride (F-) contamination in groundwater has been chased in this study. For the purpose, groundwater samples (n = 40, replicated thrice) were collected during the post-monsoons (September-October) from a mica mining area in the Tisri block of Giridih district, Jharkhand. The study has employed a synergy of classical aquifer chemistry, statistical approaches, different indices, Self-Organising Maps (SOM), and Sobol sensitivity index (SSI) to unveil the underlying aquifer chemistry, identify the impacts of mining activities on groundwater quality and its associated health hazard. Fluoride levels varied from 0.34 to 2.8ppm, with 40% of samples exceeding the World Health Organization's permissible limit (1.5ppm). Physicochemical analysis revealed significant differences in electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH) and major ion concentrations (Na+, HCO3-, Ca2+) between fluoride-contaminated (FC) and fluoride-uncontaminated (FU) groups. Higher Na+ and HCO3- associated with F- contaminated samples, were indicative of silicate weathering and carbonate dissolution as primary geogenic sources for this ion. Health risk assessment (HRA) revealed hazard quotient (HQ) values exceeding unity, indicating non-carcinogenic risks, particularly for children in most samples from group FC. The mean Water Quality Index (WQI) of FC group (156.76 ± 7.30) was significantly higher (p < 0.05) than group FU indicating of its unsuitability. SOM could accurately (80%) predict presence of fluoride in water samples based on other major ions. Sobol sensitivity analysis successfully identified fluoride concentration and body weight as most impactful parameters affecting human health. The integration of advanced modelling techniques and geospatial analysis as Inverse Distance Weightage (IDW) maps has provided a robust framework for ongoing groundwater quality monitoring in mining-affected regions and can help proactive intervention in risk-prone areas. Overall, this comprehensive study takes us a step ahead towards ensuring safe drinking water access for the global community.

Assessment of a groundwater quality monitoring network for Disi-Aquifer in southern Jordan using Water Quality Index (WQI)

Assessment of a groundwater quality monitoring network for Disi-Aquifer in southern Jordan using Water Quality Index (WQI)

Assessing the Suitability of CCME WQI as a Groundwater Quality Monitoring Tool: An Environmental Ergonomics Case Analysis

This study was conducted with the aim of protecting groundwater, which plays a crucial role in ensuring food quality in the market, preserving public health, and safeguarding the ecosystem, as many regions rely on clean natural groundwater for their population’s survival. The objective of this study was to use the Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) for groundwater at 12 stations in the Okhla Industrial Area, Nangloi, and Karol Bagh in the Delhi Region. CCME WQI is an effective tool for assessing groundwater quality and communicating water conditions to various users. The research methodology involved fieldwork from June to October 2020 for three different periods in the year: pre-monsoon, monsoon, and post-monsoon, to observe variations in water quality and differences in various physicochemical properties of water. The CCME WQI was applied using sixteen water quality parameters, fourteen of which were physicochemical parameters and two of which were microbiological parameters. Among the physicochemical parameters were color, odor, pH, turbidity, nitrate, total hardness, iron, chloride, fluoride, total dissolved solids, calcium, magnesium, sulfate, and alkalinity, while the microbiological parameters included the total coliform and Escherichia coli counts. Based on the results obtained from the water quality index, station A9 scored between 0 and 44, indicating the lowest water quality index due to wastewater discharges and industrial contamination. The water quality at other stations also requires attention to achieve excellent ratings. The study concludes that serious measures should be taken for proper management of the area to protect the population from hazardous diseases. The research results show that stations 1, 2, and 10 were rated as excellent, station 12 as good, stations 4, 5, and 8 as moderate, stations 3, 6, and 11 as marginal, and station 9 as the poorest in terms of water quality in the year 2020 during the pre-monsoon, monsoon, and post-monsoon periods. To improve the parameters and groundwater quality, it would be necessary to reduce the impact of industry, anthropogenic–geogenic activities, and domestic activities.

Research on Real-Time Groundwater Quality Monitoring System Using Sensors around Livestock Burial Sites

Research on Real-Time Groundwater Quality Monitoring System Using Sensors around Livestock Burial Sites

Assessment of groundwater quality and suitability for irrigation purpose using irrigation indices, remote sensing and GIS approach

Assessing both the quantitative and qualitative aspects of groundwater is essential for evaluating its suitability for irrigation and drinking purpose. Consequently, this current study showcases its importance by determining groundwater quality in Sundargarh district of, India, where groundwater serves as vital water resources. 360 groundwater samples were collected from various dug wells during pre-monsoon season of 2014–21 and analyzed for major ions, some important irrigation water quality indices along with pH, EC and TDS. Statistical evaluation of groundwater quality parameters was performed by physiochemical analysis with association of ArcGIS 10.4 for developing the spatial mapping. Furthermore, statistical and hydrochemical analysis was executed by exhibiting box plot generation, correlation study and hierarchical cluster analysis followed by categorization of water facies in , 1920; CGWB, 2013; Gad and Hattab, 2019’ has/have not been found in the reference list. Please add the corresponding reference(s) to the reference list.>Xlstat 2023, SPSS 23 and Diagrammes 6.1. Groundwater is mostly characterized as Na+-SO42- and deep meteoric percolation (DMP) type based on Base Exchange Indices with the dominance of Ca2+ and HCO3− as the major cation and anion respectively. Besides that, groundwater from 92%, 96%, 84%, 100%, 99%, 98%, 57%, 64%, 100%, 77%, 98% and 89% dug wells are found to be highly suitable for cultivation of major crops of this district depending on spatial variation of EC, TDS. Cl−, SAR, RSC, KR, PI, %Na, ESP, MAR, SSP and PS respectively. Groundwater facies are mostly categorized as Ca–HCO3 (60.8%) and C2–S1 (65.5%) type based on Piper and Wilcox diagram respectively. The dominant geochemical controlling factors are evaporation, reverse ion exchange and silicate weathering. Therefore, the objectives of this present research may provide necessary information to the regulatory boards and policy makers for efficient monitoring of groundwater quality and contaminated aquifers in Sundargarh district to make fit this crucial water resources for agricultural purpose.

Evaluation of groundwater quality for drinking and irrigation purposes, ionic sources and land use/land cover impacts in the Kathua region of Jammu and Kashmir, India

Kathua is one of the fast-growing industrial districts of the Union Territory of Jammu and Kashmir, northern India. The primary source of water in Kathua is groundwater, which is widely used for industrial, agricultural, drinking, and building purposes. The groundwater system is changing significantly both in terms of quantity and quality in the study area due to recent industrial and infrastructural developments. Thus, 40 groundwater samples were collected from different wells in the pre-monsoon season, May 2022, and analyzed for physicochemical variables to determine the impact of geogenic and anthropogenic activities on the groundwater. The drinking groundwater quality appears to be excellent to good. Of the variables that were examined, two—TH and HCO3—had concentrations higher than the recommended limits of the BIS and WHO guidelines. Groundwater contains alkaline earth metals and weak acids, and its hydrochemistry is controlled by rock‒water interactions (silicate weathering or cation exchange and reverse-ion exchange processes). Several parameters (electrical conductivity, sodium percentage, sodium adsorption ratio, permeability index, magnesium adsorption ratio, residual sodium carbonate, and the Kelly’s ratio) were used to evaluate groundwater suitability for irrigation. The permeability index, magnesium adsorption ratio, and residual sodium carbonate indicate that the groundwater of a few samples is unsuitable for irrigation purposes. Land use/land cover (LULC) change analysis was used to determine the potential impacts of LULC changes on groundwater. Anthropogenic interventions are a major cause of LULC changes that are considerably reducing groundwater recharge zones, increasing surface runoff, and artificially polluting groundwater through domestic and industrial wastes, according to the LULC analysis conducted using satellite data for the year 2017 and 2022. Therefore, to minimize the effects of LULC on groundwater, prompt action must be taken, requiring regular monitoring of groundwater quality and LULC changes. The results of the study may be useful to the general public, farmers, and policy makers in the sustainable development and management of groundwater.

A risk assessment framework utilizing bivariate copula for contaminate monitoring in groundwater.

Regular groundwater quality monitoring in resource-constrained regions present formidable challenges in terms of funding, testing facilities and manpower; necessitating the development of easily implementable monitoring techniques. This study proposes a copula-based risk assessment model utilizing easily measurable indicators (e.g., turbidity, alkalinity, pH, total dissolved solids (TDS), conductivity), to monitor the contaminates in groundwater which are otherwise difficult to measure (i.e., iron, nitrate, sulfate, fluoride, etc.). Preliminary correlation between the indicators and the target contaminates were identified using Pearson coefficient. Best representative univariate distributions for these pairs were selected using the Akaike Information Criterion (AIC), which were used in the formulation of the copula model. Validation against observed data showcased the model's high accuracy, supported by consistent Kendall Tau correlation coefficients. Through this model, conditional probabilities of the contaminants not exceeding the permissible limits set by the Bureau of Indian Standards (BIS) were calculated using indicator concentration. Notably, an inverse correlation between iron concentration and conductivity was noted, with the likelihood of iron exceeding BIS limits decreasing from 90 to 50% as conductivity rose from 500 to 2000 micromhos/cm. TDS emerged as a pivotal indicator for nitrate and sulfate concentrations, with the probability of sulfate surpassing 10mg/l decreasing from 75 to 25% as TDS increased from 250 to 750mg/l. Likewise, the probability of nitrate exceeding 1mg/l decreased from 90 to 60% with TDS levels reaching 1500mg/l. Furthermore, a 63% probability of fluoride concentrations remaining below 1mg/l was observed at turbidity levels of 0-10 NTU. These findings hold significant implications for policymakers and researchers since the model can provide crucial insights into the risks associated with the contaminates exceeding the permissible limit, facilitating the development of an efficient monitoring and management strategies to ensure safe drinking water access for vulnerable populations.

Impact of ionic strength on goethite colloids co-transported with arsenite (As3+) through a saturated sand column under anoxic condition: Experiment and mathematical modeling

The knowledge about co-transport of goethite and As3+ to investigate the effect of goethite colloids on As3+ transport under various degrees of seawater intrusion, particular extremely conditions, in groundwater environment is still limited. The main objective is to investigate the influence of seawater intrusion on the sorption, migration, and reaction of As3+and goethite colloids into sand aquifer media under anoxic conditions by using the bench-scale and reactive geochemical modeling. The research consisted of two parts as follows: 1) column transport experiments consisting of 8 columns, which were packed by using synthesis groundwater at IS of 0.5, 50, 200, and 400 mM referring to the saline of seawater system in the study area, and 2) reactive transport modeling, the mathematical model (HYDRUS-1D) was applied to describe the co-transport of As3+ and goethite. Finally, to explain the interaction of goethite and As3+, the Derjaguin-Landau-Verwey-Overbeek (DLVO) calculation was considered to support the experimental results and HYDRUS-1D model. The results of column experiments showed goethite colloids can significantly inhibit the mobility of As3+ under high IS conditions (>200 mM). The Rf of As3+ bound to goethite grows to higher sizes (47.5 and 65.0 μm for 200 and 400 mM, respectively) of goethite colloid, inhibiting As3+ migration through the sand columns. In contrast, based on Rf value, goethite colloids transport As3+ more rapidly than a solution with a lower IS (0.5 and 50 mM). The knowledge gained from this study would help to better understand the mechanisms of As3+ contamination in urbanized coastal groundwater aquifers and to assess the transport of As3+ in groundwater, which is useful for groundwater management, including the optimum pumping rate and long-term monitoring of groundwater quality.

Investigation of Heavy Metal Composition and Associated Health Risks from Selected Groundwater Wells in Temeke, Dar-es-Salaam

Water quality continues to be the challenge to residents in Dar es Salaam due to various anthropogenic activities in the city. This study was conducted to assess groundwater quality by determining concentrations of heavy metals. Both probability and Nonprobability sampling techniques were used to collect samples from 40 groundwater wells in 24 wards of Temeke municipal and analysed using Microwave Plasma Atomic Emission Spectrometer (Agilent 4210 MP-AES) at the Geochemistry Laboratory of the University of Dar es Salaam. Results indicated varying heavy metal concentrations ranging from 0.71 ± 0.08 to 6.64 ± 0.21 mg/l for As, 0.02 ± 0.01 to 0.07 ± 0.01 mg/l for Co and 0.16 ± 0.01 to 0.02 ± 0.01 mg/l for Pb. The As, Co and Pb concentrations exceeded (P &amp;lt; 0.05) the recommended TBS standards of 0.05 mg/l, 0.003 mg/l and 0.01 mg/l respectively. Other concentrations ranged from 0.01 ± 0.01 to 0.88 ± 0.01 mg/l for Cu, 0.02 ± 0.01 to 3.55 ± 0.02 mg/l for Fe, 0.00 ± 0.00 to 4.63 ± 0.03 mg/l for Mn and 0.01 ± 0.01 to 3.00 ± 0.01 mg/l for Zn. The Cu, Fe, Mn and Zn concentrations were below (P &amp;gt; 0.05) the allowable TBS limits of 0.05 mg/l, 0.3 mg/l, 0.1 mg/l and 3 mg/l respectively. Health risk analysis revealed potential adverse health effects from long term consumption of As, Mn and Pb with Hazard Quotient exceeding 1 (HQ &amp;gt; 1). The Hazard Index (HI) for all groundwater samples was also above 1 (HI &amp;gt; 1) indicating a higher likelihood of adverse health effects. The study concluded that groundwater wells in Temeke Municipal are affected through natural and anthropogenic activities leading to high levels of heavy metal concentrations. Also, this study provides valuable information on risk associated by continued usage of groundwater in Temeke region and hence informs respective stakeholders on groundwater quality and potential risks thereby emphasizing the need for remedial measures and stricter regulations to safeguard public health. The study recommends the need for regular groundwater quality and safety monitoring to assess the levels of heavy metals concentrations and implement sustainable groundwater management strategies to address the increasing water demand in Temeke municipal, Dar es Salaam.