Assessment of groundwater quality based on principal component analysis and pollution source-based examination: a case study in Ho Chi Minh City, Vietnam

Potential usage of boron modified carbon nanodots as a marker candidate for coronavirus disease (COVID-19) antibody detection

The global outbreak of COVID-19 in December 2019 has highlighted rapid and accurate diagnostic tools for effective intervention. While the RT-PCR test offers 86 % sensitivity, uncertainties often require supplementary screening. This research investigates how carbon dots (CDs) can be utilized as markers for COVID-19 antibodies, taking advantage of their biocompatibility and low toxicity. CDs were synthesized using citric acid (CA) and APBA with boronic acid, enabling the detection of COVID-19 IgG antibodies with increased absorbance and fluorescence. Comprehensive analyses confirmed the successful synthesis of APBA-CDs, prompting further exploration of their impact on SARS-CoV-2 RNA. Increased absorbance levels were observed in categories K1, K2, and K3, attributed to the introduction of CDs into plasma, indicating effective binding of APBA-CDs to COVID-19 antibodies. In addition, the fluorescence tests consistently showed heightened levels across all categories, emphasizing the effective binding of APBA-CDs with COVID-19 antibodies, particularly in positive plasma samples. As a part of our analysis, we conducted a PCA test to validate the data, which revealed that APBA-CDs are specific to IgG+ antibodies. The results showed a sensitivity rate of 74 % and a specificity rate of 53 %, while, when tested for IgM antibodies, the sensitivity and specificity rates were 63 % and 27 %, respectively. These findings highlight the potential of APBA-CDs as a sensitive and specific marker for COVID-19 antibody detection, offering potential for diagnostic tool development.

Groundwater quality evaluation of the weathering mantle in crystalline basement aquifer system, southern Brazil

Groundwater is the main source of water for more than 2 billion people worldwide. In southern Brazil, the Crystalline Basement Aquifer System is composed of strategic groundwater reservoirs. Groundwater is mostly taken from shallow wells, and it is often used without any treatment, which poses a risk to public health. The present study aims to evaluate shallow groundwater quality and the geochemistry of shallow and deep groundwater located in the municipality of Canguçu, southern Brazil. The physicochemical and microbiological parameters of groundwater samples collected from shallow wells were monitored and analyzed using ANOVA variance analysis and water quality index (CCME WQI) approaches. Also, the results were compared with secondary data from deep wells. The monitored shallow wells had thermotolerant coliforms, Escherichia coli, pH, potassium, manganese, iron, and nitrate in disagreement with the guidelines of the World Health Organization. Moreover, variance analysis showed that the parameters temperature, dissolved oxygen, pH, chloride, and magnesium were the most influenced by seasonal variations. According to the CCME WQI, most samples had good quality (60%), 28% had fair quality, and 12% had poor quality. In addition, the field campaigns with higher precipitation rates also presented fair quality. Therefore, most of the shallow groundwater quality is affected by surface pollutants from the urban area, aggravated in rainy periods. Whereas deep groundwater is influenced by geochemistry mechanisms. The results revealed the risk of water consumption for public health and the urgent need for better maintenance of these wells and water treatment implementation.

Evaluation of potential human health risks arising from nitrate and fluoride in the groundwater of Aurangabad, Bihar using GIS and chemometric analysis

This study employed the groundwater pollution index to assess the appropriateness of groundwater for human consumption. Additionally, the hazard index was utilized to evaluate the potential non-carcinogenic risks associated with fluoride and nitrate exposure among children, women, and men in the study region. A total of 103 samples were collected from the Aurangabad district of Bihar. The analyzed samples were assessed using several physicochemical parameters. Major cations in the groundwater are Ca2+ > Mg2+ and major anions are HCO3- > Cl- > SO42- > NO3- > F- > PO43-. Around 17% of the collected groundwater samples surpassed the allowable BIS concentration limits for Nitrate, while approximately 11% surpassed the allowed limits for fluoride concentration. Principal component analysis was utilized for its efficacy and efficiency in the analytical procedure. Four principal components were recovered that explained 69.06% of the total variance. The Hazard Quotient (HQ) of nitrate varies between 0.03-1.74, 0.02-1.47, and 0.03-1.99 for females, males, and children, respectively. The HQ of fluoride varies between 0.04-1.59, 0.04-1.34, and 0.05-1.82 for females, males, and children, respectively. The central part of the district was at high risk according to the spatial distribution maps of the total hazard index (THI). Noncarcinogenic risks due to THI are 47%, 37%, and 28% for children, females, and males, respectively. According to the human health risk assessment, children are more prone to getting affected by polluted water than adults. The groundwater pollution index (GPI) value ranges from 0.46 to 2.27 in the study area. Seventy-five percent of the samples fell under minor pollution and only one fell under high pollution. The spatial distribution of GPI in the research area shows that the central region is highly affected, which means that this water is unsuitable for drinking purposes.

An integrated approach based on HFE-D, GIS techniques, GQISWI, and statistical analysis for the assessment of potential seawater intrusion: coastal multilayered aquifer of Ghaemshahr-Juybar (Mazandaran, Iran)

The overexploitation of coastal aquifers is one of the important reasons for the salinity of groundwater due to seawater intrusion (SWI). This study assesses the hydrochemical changes of the Ghaemshahr-Juybar (GH.-J.) plain. For this purpose, specific statistical methods, modified Piper diagram groundwater quality indicators ([Formula: see text] and [Formula: see text]), groundwater quality index specific to seawater intrusion ([Formula: see text]), and hydrochemical facies evolution diagram (HFE-D) along with GIS (Geographic Information System) techniques were applied to identify the spatiotemporal changes of salinity in coastal multilayer alluvial aquifer. The results show that the chemical composition in the GH.-J. aquifer is basically controlled by three main factors: (1) Caspian SWI and fossil saltwater penetration from an underlying layer, (2) reverse cation exchange process, and (3) feeding by domestic sewage, agricultural activities, and use of nitrate chemical fertilizers. The investigation of the hydrogeochemical facies evolution process shows that due to the reduction of extraction from wells, saltwater infiltration has significantly decreased. Therefore, according to the geological and lithological conditions of the aquifer and exposure to seawater, it is possible to prevent the entry of saltwater from the confined aquifer into the unconfined aquifer and the saltwater intrusion by developing well optimal operation policies in order to control withdrawal from semi-deep wells and the elimination of deep wells. This practical approach to managing the salinity of coastal aquifers is suitable for the allocating groundwater resources and for use in the development of aquifer simulation models.

MLR index-based principal component analysis to investigate and monitor probable sources of groundwater pollution and quality in coastal areas: a case study in East India

Identifying groundwater contamination sources and supervising groundwater quality conditions are urgently needed to protect the groundwater resources of coastal areas like Contai of India, as communities here are heavily relying on groundwater which deteriorates progressively. So current research aims to address in detail about origins and influencing factors of groundwater contamination, status, and monitoring water quality by employing extremely useful leading technologies like principal component and factor analyses (PCA/FA), groundwater quality index (GWQI), and multiple linear regression (MLR) that helps to simplify complicated works instead of the conventional methods. Eight groundwater quality parameters were evaluated here, such as pH, TH (total hardness), Tur (turbidity), EC (electrical conductivity), TDS (total dissolved solids), Mn (manganese), Fe (iron), and Cl (chloride) for 38 sites. Three principal components with ~ 81% of the total variance were extracted from the PCA/FA analysis. The origin of maximum loadings of each factor is identified as a result of saline water, disintegration and leaching process, organic or else biogenic activities, and lithogenic or otherwise non-lithogenic links through percolating water. GWQI results show that ~ 87% of the samples fall into the good category and ~ 13% of the samples fall into the poor to very poor category. A model consisting of Tur, Fe, EC, Mn, TH, and Cl as independent parameters is more feasible and is proposed to predict GWQI obtained from MLR analysis. This MLR model also suggests that turbidity with the highest beta coefficient (0.820) is a key contributor relative to the entire groundwater class in this affected area. The findings relating to this research may support the designer and officials in monitoring and protecting coastal groundwater resources like selected areas.

Human exposures to multiple water sources in the southwestern coastal region of Bangladesh: water quality, pollution sources, and preliminary health risks appraisals

The coastal areas of Bangladesh have poor accessibility to fresh drinking water and the groundwater is not suitable for drinking, cooking, and other domestic uses due to high levels of salinity and potentially toxic elements. The current study focuses on understanding of the distribution of some physicochemical parameters (temperature, pH, EC, TDS, and salinity) and chemical elements (Fe, Mn, Zn, Ca, Mg, Na, K, Cu, Co, Pb, As, Cr, Cd, and Ni) with health perspective in drinking water from the southwestern coastal area of Bangladesh. The physicochemical properties of the water samples were examined with a multiparameter meter, while the elemental concentrations were analyzed using atomic absorption spectrometer. Water quality index (WQI) and irrigation indices were utilized to determine the drinking water quality and irrigation feasibility, respectively, whereas hazard quotients (HQs) and hazard index (HI) were used to assess the probable pathways and the associated potential risks to human health. The concentrations of some toxic elements in measured samples were relatively higher compared to drinking water guidelines, indicating that ground and surface water are not apt for drinking and/or domestic uses. The multivariate statistical approaches linked the source of the pollutants in the studied water body mostly to the geogenic origin including saline water intrusion. WQI values ranged from 18 to 430, reflecting excellent to unsuitable categories of water quality. The assessment of human health risks due to exposure to contaminated water demonstrated both carcinogenic and non-carcinogenic health risks in the exposed residents of the study area. Therefore, appropriate long-term coastal area management strategies should be adopted in the study region for environmental sustainability. The findings of this research will be supportive in understanding the actual situation of fresh drinking water in the area for policymakers, planners, and environmentalists to take effective necessary measures to ensure safe drinking water in the study area.

Metal(loid)s in tap-water from schools in central Bangladesh (Mirpur): Source apportionment, water quality, and health risks appraisals

Considering the health risks originating from the exposure of metal(loid)s in tap-water and the concomitant vulnerability of school-going students, 25 composite tap water samples from different schools and colleges of central Bangladesh (Mirpur, Dhaka) were analyzed by atomic absorption spectroscopic technique. Elemental abundances of Na, Mg, K, Ca, Cr, Mn, Fe, Co, Ni, Zn, As, Cd, and Pb in the studied tap water samples varied from 4520 to 62250, 2760-29580, 210-3000, 15780-78130, 1.54-5.32, 7.00-196, 2.00-450, 0.04-1.45, 8.23-24.4, 0.10-813, 0.10-10.5, 0.002-0.212, and 1.55-15.8 μgL^-1, respectively. Dissolved metal(loid)s' concentrations were mostly within the national and international threshold values with few exceptions which were also consistent with the entropy-based water quality assessment. Multivariate statistical approaches demonstrated that hydro-geochemical processes like water-rock interactions mostly govern the major elemental (Na, Mg, K, Ca) compositions in tap water. However, anthropogenic processes typically control the trace elemental compositions where supply pipeline scaling was identified as the major source. Cluster analysis on sampling sites separated two groups of schools and colleges depending on their establishment years where tap water from older schools and colleges possesses relatively higher levels of metal(loid)s. Hence, gradual pipeline scaling on a temporal scale augmented the metal(loid)s' concentrations in tap-water. In terms of non-carcinogenic health risks estimation, studied tap-water seems to be safe, whereas elemental abundances of Pb and As can cause carcinogenic risks to school-going people. However, progressive deterioration of water quality by pipeline scaling will be supposed to cause significant health risks in the future, for which preventative measures should be adopted.

Hydrogeochemical characterization and natural background level determination of selected inorganic substances in groundwater from a semi-confined aquifer in Midwestern Burkina Faso, West Africa

Hydrogeochemical processes that govern selected inorganic substances distribution in a semi-confined aquifer were characterized using traditional hydrogeochemical approaches and natural background levels (NBLs). Saturation indices and bivariate plots were used to investigate the effects of water-rock interactions on natural evolution of the groundwater chemistry, whereas Q-mode hierarchical cluster analysis and one-way analysis of variance classified the groundwater samples into three distinct groups. To highlight the groundwater status, NBLs and threshold values (TVs) of the substances were calculated using pre-selection method. Piper's diagram showed that the Ca-Mg-HCO₃ water type was the only hydrochemical facies of the groundwaters. Although all samples, except a borewell with a high NO₃^- concentration, had major ion and transition metal concentrations within the World Health Organization's recommended guideline values for drinking water, Cl^-, NO₃^- and PO₄^3- exhibited scattered distribution patterns, reflecting their nonpoint anthropogenic sources in the groundwater system. The bivariate and saturation indices revealed that silicate weathering and possible gypsum and anhydrite dissolution contributed to the groundwater chemistry. In contrast, NH₄⁺, Fe_T and Mn abundance appeared to be influenced by redox conditions. Strong positive spatial correlations between pH, Fe_T, Mn and Zn suggested that mobility of these metals was controlled by pH. The relative high F^- concentrations in lowland areas may imply the impact of evaporation on this ion's abundance. Contrary to TVs of HCO₃^-, those of Cl^-, NO₃^-, SO₄^2-, F^- and NH₄⁺ were below the guideline values, confirming the influence of chemical weathering on the groundwater chemistry. Based on the present findings, further studies that take into account more inorganic substances are required for NBLs and TVs determination in the area, thereby setting up a robust sustainable management plan for the regional groundwater resources.

Site prioritization and performance assessment of groundwater monitoring network by using information-based methodology

The arbitrary distribution of groundwater monitoring sites and the redundancy of observation data restrict the ability of monitoring network to provide reliable and effective data information. The purpose of this study is aimed at finding a quantitative method to screen ideal monitoring locations and evaluate the efficiency of the monitoring network. In terms of site selection, we use hydrogeological information, monitoring density and monitoring location to select the suitable site to monitor groundwater quality, understand the temporal trends and identify the abnormal signals of pollution sources. To evaluate the efficiency of monitoring network we used the groundwater quality data for consecutive years to evaluate the groundwater monitoring network based on information entropy and principal component analysis (PCA). The results show that the optimized groundwater monitoring network is comprised of 10 monitoring wells. The efficiency evaluation results of information entropy and PCA are basically consistent. The maximum mutual information (T) and comprehensive index of monitoring site (Laiguangying) were 1.29 and 3.25 respectively, while the minimum T and comprehensive index of monitoring site (Jinzhan) were 1.05 and -0.36 respectively, and the data efficiency was low. This study provides a good example for optimizing a groundwater pollution monitoring network.

Influencing factors and mechanism by which DOM in groundwater releases Fe from sediment

The groundwater in many aquifers contains elevated concentrations of iron (Fe). Although much of this Fe is from its release from water-bearing sediments under natural environmental conditions, sufficient evidence is lacking to clarify whether anthropogenic pollutants, such as dissolved organic matter (DOM), can increase this natural release. In this time series and comparative analysis study, an Fe increasing effect was verified through laboratory leaching tests. The influences of the aqueous environmental conditions, such as pH, were also investigated. DOM can promote the release of Fe from sediments and increase the concentration of Fe in groundwater. In addition, lower or higher pH and temperature can enhance the release of Fe to some extent. Higher concentrations of DOM provided a more thorough release of Fe from the sediment; additional ions such as Cu also affected Fe release. It is possible that complexation between DOM and Fe occurs through ligand dissolution and reduction, thus promoting the release of Fe. The findings indicate that DOM imported through anthropogenic activities can increase the release of Fe from aquifer sediments into groundwater, thus worsening Fe pollution in groundwater. This study explored the mechanism by which different types of DOM release Fe from aquifer sediments and investigated the factors that influence this process. The findings provide insights into the geochemical processes of Fe in the groundwater.

Environmental and Socioeconomic Factors for Gastric Cancer in 14 Counties of the Huai River Basin from 2014 to 2018

To explore the potential relationship between environmental and socioeconomic factors and the risk of gastric cancer (GC) in the Huai River Basin, the GC incidence rate (GIR) and GC mortality rate (GMR) data from 2014 to 2018 in 14 counties of the Huai River Basin were collected from the Chinese Cancer Registration Annual Report. Environmental and socioeconomic parameters were collected through the Statistical Yearbook. The 14 counties were classified into three groups with low, moderate, and high risk of GC according to the point density of environmental factors (PDF) and index of socioeconomic factors (ISF). Significant differences in GIR and GMR were found among the counties with PDF (χ² = 21.36, p < 0.01) and ISF (χ² = 11.37, p < 0.05) levels. Meanwhile, significant differences in mortality rate were observed among counties with different PDF (χ² = 11.25, p < 0.01) and ISF (χ² = 18.74, p < 0.01), and the results showed that the ISF and PDF were increased while the GIR and GMR were decreased. Meanwhile, there was a lag effect between them, and we used two models to explore the lag effects between ISF, PDF and GIR and GMR; the coefficient influence between the ISF lag phase and GIR was −2.9768, and the coefficient influence between PDF and the lag phase on the GIR was −0.9332, and there were both significant impact when there was a probability of more than 95%. The results showed that the higher the ISF and PDF that lags in one stage, the more GIR was reduced, while the impact of the ISF and PDF on lag stage on mortality was not obvious. We used differential GMM to test the results, and also research results were relatively robust. Overall, GIR and GMR decreased with increasing point density of environmental factors and index of socioeconomic factors.

The effects of terrain factors on the drainage area threshold: comparison of principal component analysis and correlation analysis

How and to which extent terrain factors affecting the drainage area threshold (DAT) are disputable. This paper uses principal component analysis (PCA) and correlation analysis to study the influence degree of terrain factors on DAT. Firstly, 22 watersheds, locating in the severe soil erosion region (SSER) of Loess Plateau of China, are picked out as the example areas. The purpose of the mean change point method (MCP) to detect the relationship between DAT and gully density (GD) is to get a reasonable DAT. Secondly, nine terrain factors are calculated, and their statistical values are compared and put in the matrix to clear the different effects on DAT. Finally, the effects of statistical eigenvalues of terrain factors on DAT are compared with PCA and the correlation analysis. According to the PCA, the nine terrain factors are summarized into three principal components, which are slope, height variation, and relief factor. By calculating the score weighted by each factor coefficient matrix and eigenvalue, the result states that slope (S), terrain curvatures (K), and surface roughness (SR) are the factors that have great influence on DAT. Meanwhile, the results of correlation analysis indicate that S, SR, and K have exerted a great influence on the DAT, and the significance level was above 0.05. Both the results of PCA and correlation analysis make clear that the slope is the most direct and influential factor affecting DAT, while other factors are more or less related to slope directly and indirectly. The result implies that the vertical variation of terrain has a strong correlation with the slope, and also has a great influence on DAT. This research not only would be of great significance to recognize the mechanism of gully development, but also able to provide a scientific reference for soil and water conservation in the Loess Plateau.

A comprehensive physico-chemical quality and heavy metal health risk assessment study for phreatic water sources in Narora Atomic Power Station region, Narora, India

An investigation of water quality and heavy metal distribution in the groundwater samples collected from the vicinity of Narora Atomic Power Station (NAPS), Narora, India, was conducted for the metals including Cu, Zn, Ni, Co, Cd, Pb, and Fe. A total of 16 water quality parameters were measured for all the groundwater samples, and TDS, TH, Mg²⁺, Ca²⁺, F^-, and turbidity were found to be on the higher side in comparison to the prescribed limits of Indian standards. Geometrical mean concentrations for these heavy metals were found to be 0.049, 0.213, 0.23, 0.135, 0.017, 0.061, and BDL for Cu, Fe, Zn, Pb, Cd, Co, and Ni, respectively. Pb and Cd were more than the permissible limits (0.01 mg/L for Pb and 0.003 for Cd) prescribed for safe drinking water while Cu and Fe were exceeding the permissible limits of 0.05 mg/L and 0.3 mg/L in 32% and 36% samples, respectively. Health risk assessment was done by calculating total hazard quotient (THQ), and the values for all the metals were below the threshold value of 1.0 beyond which they may pose a significant risk.

Source analysis and health risk assessment of groundwater pollution based on multivariate statistical techniques in Kashgar Delta Area, Xinjiang, China

In this study, 63 groundwater samples were collected in the Kashgar Delta Area in Xinjiang in 2016, and then, the samples were tested and the test results were analyzed. Multivariate statistical techniques were used to determine the sources of pollution, and the USEPA (United States Environmental Protection Agency) model was used to assess the long-term health risk of groundwater to adults and children in the study area. The concentrations of groundwater chemical Na⁺, Cl^-, SO₄^2-, NH₄⁺-N, TDS, F^-, I^-, As, Fe, Mn, Pb, Hg, pH, TH, and COD_Mn, which exceed the permissible level in the study based on groundwater quality index and possibly pose a potential threat to the health of the residents in the area, which are mainly influenced by geological conditions. The source of the pollutants is the dissolution of minerals in the aquifer medium, which is greatly affected by the high-salinity groundwater environment, pH conditions, redox conditions, and evaporation and concentration effect. The values of the noncarcinogenic health risk index HQ_n follow the descending order of Cl^- > F^- > As > Fe > Mn > Pb > Hg > NH₄⁺-N; There are eight nonarcinogens and one carcinogen in groundwater of which Cl^- is the dominant noncarcinogenic factor, while As is the main carcinogenic pollutant in the study area. The health risk ratio results show that Cl^- and As are the main pollutants that pose the greatest threat to both adults' and children's health, and they should be considered as the primary indicators for health risk management and control.

Simulating contaminant transport in unsaturated and saturated groundwater zones

The demand for clean and adequate water is rising rapidly with increasing population. This growing demand for water necessitates the measurement of the quantity and quality of water. Simulation modeling has become increasingly popular in the last two decades largely because of their predictive ability. This paper reviews the approaches for simulation modeling in groundwater resources management, focusing on models that have been used to simulate contaminant transport through the aquifer system. Recent research papers that have integrated the models for unsaturated and saturated zones have also been studied and described. Integrated models require assessment of the complex interactions between the groundwater zones and the movement of water and solute through them. Due to this, integrated models provide a more accurate modeling approach than models that have been independently developed for saturated and unsaturated zones. Application of such models is encouraged at the regional level to arrive at the best groundwater management decisions. PRACTITIONER POINTS: In the past few decades, modeling of contaminant transport in groundwater systems has seen tremendous applications. A number of models exist that independently simulate flow and solute transport in unsaturated and saturated zones. Recently, focus has been given on developing advanced coupled modeling approaches that require less inputs and run times.

Assessment of surface and groundwater quality for irrigation purposes in the Danube-Tisa-Danube hydrosystem area (Serbia)

The study evaluates irrigation water quality in the Danube-Tisa-Danube hydrosystem area (Vojvodina, northern Serbia). The area is dominantly a plain with about 75% arable land, suitable for agricultural production and irrigation. Use of water of inadequate quality can have long-term effects on irrigated land and affect the yield of cultivated crops. The analyses included data from 40 surface water and 23 groundwater quality monitoring locations, observed during the period 2013-2018. The average annual values of the concentrations of major cations and anions and of electrical conductivity in surface and groundwater were comparatively analyzed. These values were statistically significantly higher (by p < 0.05) in groundwater bodies with most of the analyzed parameters. Hydrochemical classification of water types shows that 95% of surface and 87% of groundwater locations belong to the Ca·Mg-HCO₃ water type. Water suitability for irrigation was assessed using specific parameters and indices (sodium adsorption ratio, Na%, residual sodium carbonate, magnesium hazard, permeability index, and Kelly's index). The results showed that surface and groundwater resources are generally of good quality and suitable for irrigation, with sporadic deviations at several locations. The principal component analysis (PCA) was used to identify the most important variables affecting the chemical composition of the analyzed waters and group the monitoring locations by their chemical characteristics. The spatial variation of the analyzed water quality indices was shown on thematic maps.

Anthropogenic Organic Pollutants in Groundwater Increase Releases of Fe and Mn from Aquifer Sediments: Impacts of Pollution Degree, Mineral Content, and pH

In many aquifers around the world, there exists the issue of abnormal concentrations of Fe and Mn in groundwater. Although it has been recognized that the main source of this issue is the release of Fe and Mn from aquifer sediments into groundwater under natural environmental conditions, there lacks enough reliable scientific evidence to illustrate whether the pollutants imported from anthropogenic activities, such as organics, can increase this natural release. On the basis of time series analysis and comparative analysis, the existence of an increasing effect was verified through laboratorial leaching test, and the impacts of aquatic chemical environment conditions, such as pH, on the effect were also identified. The results showed that the increase of organics in groundwater made the release of Fe and Mn more thorough, which was favorable for the increase of groundwater concentrations of Fe and Mn. The higher the contents of Fe- and Mn-bearing minerals in aquifer sediments, the higher the concentrations of Fe and Mn in groundwater after the release reaches kinetic equilibrium. Lower pH can make the leaching more thorough, but the neutral environment also increases the amount of Mn. It can be deduced that the pollutants such as organics imported by anthropogenic activities can indeed increase the releases of Fe and Mn from aquifer sediments into groundwater, thus worsening the issue of groundwater Fe and Mn pollution. The findings provide a deeper insight into the geochemical effects of Fe and Mn in the natural environment, especially in the groundwater system.