Human Exposure Risk Assessment Due to Heavy Metals in Groundwater by Pollution Index and Multivariate Statistical Methods: A Case Study from South Africa

Removal of Pb(II) ions from aqueous solutions using natural and HDTMA-modified bentonite and kaolin clays

This work focused on the removal of Pb(II) from aqueous solution using kaolin and bentonite clays modified with hexadecyl trimethyl ammonium bromide (HDTMA). The clays were characterized using a zetasizer, scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Brunauer-Emmet-Teller (BET), Fourier-transform infrared (FTIR) spectroscopy and thermal gravimetric analysis (TGA). Factors that influence the adsorption of Pb(II) from aqueous solution, namely pH, contact time, adsorbent mass, ionic strength, temperature and initial Pb(II) concentration were investigated. The results show that HDTMA was successfully incorporated into the kaolin and bentonite clay structures. The most favorable parameters for the adsorption of Pb(II) ions onto all adsorbents was pH of 6.0, temperature of 25 °C and adsorbent mass of 200 mg. Adsorption isotherms and kinetic studies showed that the adsorption of Pb(II) onto kaolin, bentonite and organobentonite clays followed the Langmuir isotherm and pseudo-first order kinetic model, while the adsorption onto organobentonite was better explained by the Freundlich isotherm and pseudo-second order kinetic model. Maximum monolayer adsorption capacity of organobentonite, calculated from the Langmuir model was 18.75 mg/g, which is higher than that obtained for the unmodified bentonite (14.71 mg/g); while for organokaolin it was 2.26 mg/g, which is less than that of the unmodified kaolin (4.19 mg/g). Thermodynamic studies showed that the reactions were exothermic and unfavoured at high temperatures. The adsorbents also showed good removal efficiency for up to four regeneration cycles.

Exploring and exploiting the rice phytobiome to tackle climate change challenges

The future of agriculture is uncertain under the current climate change scenario. Climate change directly and indirectly affects the biotic and abiotic elements that control agroecosystems, jeopardizing the safety of the world's food supply. A new area that focuses on characterizing the phytobiome is emerging. The phytobiome comprises plants and their immediate surroundings, involving numerous interdependent microscopic and macroscopic organisms that affect the health and productivity of plants. Phytobiome studies primarily focus on the microbial communities associated with plants, which are referred to as the plant microbiome. The development of high-throughput sequencing technologies over the past 10 years has dramatically advanced our understanding of the structure, functionality, and dynamics of the phytobiome; however, comprehensive methods for using this knowledge are lacking, particularly for major crops such as rice. Considering the impact of rice production on world food security, gaining fresh perspectives on the interdependent and interrelated components of the rice phytobiome could enhance rice production and crop health, sustain rice ecosystem function, and combat the effects of climate change. Our review re-conceptualizes the complex dynamics of the microscopic and macroscopic components in the rice phytobiome as influenced by human interventions and changing environmental conditions driven by climate change. We also discuss interdisciplinary and systematic approaches to decipher and reprogram the sophisticated interactions in the rice phytobiome using novel strategies and cutting-edge technology. Merging the gigantic datasets and complex information on the rice phytobiome and their application in the context of regenerative agriculture could lead to sustainable rice farming practices that are resilient to the impacts of climate change.

Concentration, spatial distribution, and non-carcinogenic risk assessment of arsenic, cadmium, chromium, and lead in drinking water in rural areas of eight cities of West Azarbaijan province, Iran

Exposure to heavy metals through drinking water can cause significant adverse health effects. The aim of the present study was to investigate the concentration, spatial distribution, and assessment of non-carcinogenic risk attributed to exposure to arsenic (As), chromium (Cr), cadmium (Cd), and lead (Pb) in rural areas of eight cities of the West Azerbaijan province of Iran. Eighty-five water samples were taken from randomly selected drinking water wells in the rural areas, and the concentration of the heavy metals was measured by using standard methods. The concentration distribution maps were drawn, and the non-carcinogenic health risks for ingestion and dermal exposure pathways were calculated in four age groups (including infants, children, teenagers, and adults). According to the obtained results, arsenic is considered as the most worrying pollutant among the investigated heavy metals. The maximum measured concentration for arsenic was 371.9 μg/L, which is 37 times the maximum permissible limit. The results of the health risk assessment illustrate that exposure to heavy metals via dermal contact do not pose significant non-carcinogenic risks. However, the calculated non-carcinogenic risks for oral exposure to arsenic were very high and concerning. The highest hazard quotient for oral exposure to arsenic was related to rural of city G (82.64). It is recommended to take the necessary measures as soon as possible regarding the supply of safe drinking water in the studied areas.

Minimizing the exposure risk from groundwater pollution by optimizing the temporal extraction patterns

Optimization models for minimizing pollutant exposure from groundwater resources require time and resources that many communities might not have ready access to due to their economic conditions. In such cases, it might be useful to develop a "rule of thumb" approach for suggestions in case of uncertainties and inadequate means to address these uncertainties. Monte Carlo analysis was performed for a simplified groundwater system, and the effects of temporal extraction patterns, distance to the pollution source, dispersivity, pollutant pulse period, pore water velocity, and decay were examined for minimizing the high pollutant exposure risk from the extracted groundwater. Results indicate that, in a high uncertainty scenario, the best bet for minimizing the risk of high pollutant exposure would be to adopt a frequent temporal extraction pattern and supply the water as a mixture of extractions from multiple wells spread over an area. These findings can be used as a "rule of thumb" wherever time and resources might be the limiting factors.

Distribution of Essential and Toxic Elements in Pelecus cultratus Tissues and Risk Assessment for Consumer Health

Nowadays, the problem of inland water pollution is acute. It is caused by vast industrial growth and agricultural intensification. Concentrations of Cd, Pb, Zn, Cu, Mn, Fe, Mg, and Kwere determined in the muscles, liver, and gonads sabrefish from Rybinsk Reservoir areas with different anthropogenic loads. The tissue samples were analyzed by atomic absorption spectrometry. Heavy metals accumulated more intensively in the body of fish from more polluted areas of the reservoir. Among the analyzed elements, the maximum accumulation levels were found for K, Zn, and Fe and the minimum levels were observed for Cd and Pb. The gonads contained the largest concentration of Cd and Mn, the muscles contained the highest concentrations of Mg, and the other elements mainly accumulated in the liver of sabrefish. The THQ and HI values for all elements did not exceed 1, which suggests that there is no potential non-carcinogenic risk to human health. The target values of carcinogenic risk (TR) for cadmium ranged from 8.32 × 10-6 to 1.22 × 10-4 in the muscles. The increased content of cadmium in the gonads of sabrefish not only poses a risk to human health, but also to the reproduction of this species in the Rybinsk Reservoir.

Impact of acid mine drainage on groundwater hydrogeochemistry at a pyrite mine (South China): a study using stable isotopes and multivariate statistical analyses

Combining environmental isotope analysis with principal component analysis can be an effective method to discriminate the inflows and sources of contamination in mining-affected watersheds. This paper presents a field-scale study conducted at an acid mine drainage (AMD)-contaminated site adjacent to a pyrite mine in South China. Samples of surface water and groundwater were collected to investigate transport in the vadose zone using stable isotopes of oxygen (δ¹⁸O) and hydrogen (δD) as environmental tracers. Principal component analysis of hydrogeochemical data was used to identify the probable sources of heavy metals in the AMD. The heavy metal pollution index (HPI) was applied to evaluate the pollution status of heavy metals in the groundwater. The groundwater associated with the Datai reservoir was recharged by atmospheric precipitation and surface water. On the side near the AMD pond, the groundwater was significantly affected by the soluble metals produced by pyrite oxidation. The concentrations of some metals (Al, Mn, and Pb) in all of the samples exceed the desirable limits prescribed by the World Health Organization (Guidelines for drinking-water quality, 4th edn. World Health Organization, Geneva, 2011). Among them, the concentration of Al is more than 30,000 times higher than the desirable limits prescribed by the World Health Organization (2011), and the concentration of Mn is more than 3000 times higher. The HPI values based on these heavy metal concentrations were found to be 10-1000 times higher than the critical pollution index value of 100. These findings provide a reference and guidance for research on the migration and evolution of heavy metals in vadose zone water in AMD-contaminated areas.

Geochemical evolution and the processes controlling groundwater chemistry using ionic ratios, geochemical modelling and chemometric analysis in uMhlathuze catchment, KwaZulu-Natal, South Africa

The sources of chemical constituents of groundwater and its associated hydrogeochemical processes in the part of Mhlathuze catchment was identified. Groundwater of the area is classified into soft to very hard and the nature is identified as acidic to alkaline. The overall electrical conductivity is < 3000 μS/cm except in three wells. The predominant water type is NaCl (69% of samples) and CaMgCl facies. Gibbs plots, mCa/Mg ratio, mNa/Cl ratio, Ca + Mg vs HCO₃+SO₄ plot, Na + K vs HCO₃ plot, Ca/Na vs HCO₃/Na, Chloroalkaline indices (CAI 1, CAI 2) and Ca + Mg-HCO₃-SO₄ vs Na + K-Cl plots confirm the impact of silicate, carbonate mineral weathering and ion exchange reaction in this aquifer. However, few wells are influenced by the evaporation process. Groundwater is highly undersaturated with sulphate, chloride minerals and saturated with carbonate minerals. CA revealed that Cl and SO₄ are derived from anthropogenic sources and a significant positive correlation between HCO₃ and Cl reveals that wastewater recharge has most likely simulated the mineral weathering in the vadose zone, which could have further enhanced HCO₃ and Cl in the aquifer. PCA resulted in three factors. Factor 1 defines the influence of geogenic and anthropogenic processes while Factors 2 and 3 imply the mineral weathering and nitrification processes. Hierarchical cluster analysis defines that evaporation, anthropogenic input, silicate and carbonate weathering and nitrification process are the sources of chemical constituents of groundwater in this aquifer.

Human Health Risk Assessment Is Associated with the Consumption of Metal-Contaminated Groundwater around the Marituba Landfill, Amazonia, Brazil

Groundwater is present in its purest form beneath the earth's surface. However, metal contamination is potentially a problem faced by many countries. For this reason, the present study aims to make an assessment of the risks associated with groundwater consumption around the Marituba landfill in an Amazon region. The present study was characterized as transversal with the use of primary data. The sampling occurred in a stratified random way, performed in two radii of action being the 1st radius of 2.5 km away from the landfill and the 2nd radius of 3.5 km away from the landfill to the neighborhoods. A total of 184 points were collected. In all communities the average daily dose (ADD) was higher than the reference oral dose (Rfd), for the metals As, Pb and Mn the risk quotient (HQ) was greater than 1 (one) in all neighborhoods, the concentration of Mn in the least exposed neighborhood was greater than 10 µg.L^-1, even at a distance of 3.5 km from the landfill. The average concentrations for As and Pb did not exceed the recommended, however, they were more significant for the Beira Rio neighborhood, respectively 1.47 µg.L^-1 and 1.9 µg.L^-1. And the average concentration for Cu was more significant for the Uriboca neighborhood 18.20 µg.L^-1, but within the recommended. The average of the general concentration of Heavy Metals Pollution Index (HPI) of the water consumed was 80.03, indicating that the water consumed by the population is contaminated by metals.

Human health risk assessment of heavy metal and pathogenic contamination in surface water of the Punnakayal estuary, South India

Variation in levels of toxic heavy metals in river system during the COVID-19 pandemic lockdown might potentially assist in development of a public health risk mitigation system associated with the water consumption. The water quality of Punnakayal estuary in the Thamirabarani River system from the south India, a vital source of water for drinking and domestic purposes, industrial usage, and irrigation was assessed here. A comparitive assessment of physico-chemical variables (pH, EC, TDS, DO, BOD, turbidity and NO₃), microbiological parameters (total coliform bacteria, fecal coliform bacteria, fecal streptococci and escherichia coli) and toxic metals (As, Cr, Fe, Cu, Zn, Cd, and Pb) suggested a decrease of 20% in the contaminant ratio during the lockdown period in comparison to the pre-lockdown period. The Health risk assessment models (HQ, HI, and TCR) highlighted carcinogenic and non-carcinogenic hazards for both children and adults through the ingestion and dermal adsorption exposures. The HI values for both As and Cr exceeded the acceptable limit (>1) during the lockdown period, but the potential risk for children and adults remained low in compaisio with the pre-lockdown period. Our results suggested that the Thamirabarani River system remained hostile to human health even during the lockdown period, and it requires regular monitoring through a volunteer water quality committee with private and government participations.

Bibliometric Analysis of Groundwater’s Life Cycle Assessment Research

Groundwater is an important water resource that accounts for 30% of the world’s freshwater. 97% of this extracted groundwater is for drinking and human use. Due to anthropogenic activities, this resource is affected and, consequently, its life cycle is modified, changing its natural state. This paper aims to analyse the scientific production that deals with the study of groundwater’s Life Cycle Assessment (LCA), using bibliometric methods. Thus, it contributes to the evolution of knowledge of this resource in terms of its use (environmental, economic and social). The methodological process includes: (i) selection and analysis of search topics in the Scopus and Web of Science (WoS) databases; (ii) application of Bibliometrix and Visualisation of Similarity Viewer (VOSviewer) software to the data collected; (iii) scientific structure of the relation of the topics groundwater and life cycle, considering programme lines and relations in their sub-themes; (iv) literature review of Author keywords. A total of 780 papers were selected, 306 being from Scopus, 158 from WoS and 316 published in both databases. The time evolution of the analysed data (publications) indicates that groundwater LCA studies have seen exponential growth (between 1983 and 2021). In addition, it has three development periods: introduction (years between 1983 and 2001), growth (between 2002 and 2011) and maturation (between 2012 and 2021). At the country level (origin of contributions authors), the USA dominates the total scientific production with 24.7%, followed by Denmark with 12.8% and 10.3% for China. Among the main topics of study associated with LCA are those focused on: the proposal of remediation methods, the application and development of technologies and the use of water resources by the urban community. This study allows establishing new trends in agricultural development issues about irrigation efficiency, wastewater reuse, mining and treatment, climate change in a circular economy scheme related to sustainability and life cycle assessment.

COVID-19 lockdown impacts on heavy metals and microbes in shallow groundwater and expected health risks in an industrial city of South India

In this investigation, the positive impact of COVID-19 lockdown on heavy metals concentration and biological parameters in the shallow groundwater samples of Coimbatore city of South India was ascertained. The groundwater samples (n=15) were obtained from shallow open wells during before lockdown (24-25 February 2020) and after lockdown (2-3 June 2020) periods. These samples were analysed for heavy metals (Fe, Mn, Ni, Cr and Pb) and biological parameters (E. coli, Fecal coliforms, Fecal streptococci and Total coliforms). Fe concentration was within the permissible limit but, the concentrations of Mn, Ni, Cr and Pb were above the allowable limits for drinking uses as per the WHO. However, after lockdown the number of samples crossing the cutoff limit had considerably decreased (Mn: from 2 to 0 mg/L; Ni: from 13 to 10 mg/L; Cr: 7 to 5 mg/L and Pb: from 13 to 8 mg/L). The heavy metal pollution index (HPI) revealed that 176.75 km² (67.4%) and 85.35 km² (32.6%) areas fell under unsuitable and very poor categories, respectively, during the pre-lockdown period, whereas 138.23 km² (52.6%), 118.98 km² (45.3%) and 4.89 km² (2.1%) areas fell under very poor, poor and good categories, respectively, during the post-lockdown period. Similarly, Total coliform, Fecal coliform and E. coli had decreased distinctly due to the pandemic lockdown. Therefore, the shutdown of small and large-scale industries during the lockdown period had improved the groundwater quality. The health risk assessment showed that 93%, 87% and 80% of pre-lockdown samples, and 87%, 80% and 73% of post-lockdown samples possessed non-carcinogenic risks (HI > 1) for children, female and male categories, respectively.

Engineered Whole-Cell-Based Biosensors: Sensing Environmental Heavy Metal Pollutants in Water-a Review

The frequent exposure and accumulation of heavy metals in organisms cause serious health issues affecting a range of organs such as the brain, liver, and reproductive organs in adults, infants, and children. Several parts of the world have high levels of heavy metals affecting millions of people, costing millions of dollars for improving the potability of water and medical treatment of the affected. Hence, water quality assessment is required to monitor the degree of heavy metal contamination in potable water. In nature, organisms respond to various environmental pollutants such as heavy metals, allowing their survival in a diverse environmental niche. With the advent of recombinant DNA technology, it is now possible to manipulate these natural bioreporters into controlled systems which either turn on or off gene expression or activity of enzymes in the presence of specific heavy metals (compound-specific biosensors) otherwise termed as whole-cell biosensors (WCBs). WCBs provide an upper hand compared to other immunosensors, enzyme-based sensors, and DNA-based sensors since microbes can be relatively easily manipulated, scaled up with relative ease, and can detect only the bioavailable heavy metals. In this review, we summarize the current knowledge of the various mechanisms of toxicity elicited by various heavy metals, thence emphasizing the need to develop heavy metal sensing platforms. Following this, the biosensor-based platforms including WCBs for detecting heavy metals developed thus far have been briefly elaborated upon, emphasizing the challenges and solutions associated with WCBs.

Adsorption and Release Characteristics of Purified and Non-Purified Clinoptilolite Tuffs towards Health-Relevant Heavy Metals

The occurrence of health-relevant contaminants in water has become a severe global problem. For treating heavy-metal-polluted water, the use of zeolite materials has been extended over the last decades, due to their excellent features of high ion exchange capacity and absorbency. The aim of this study was to assess the effect of heavy metal uptake of one purified (PCT) and two non-purified clinoptilolite tuffs (NPCT1 and NPCT2) in aqueous solutions on monovalent ions Ni+, Cd+, Cs+, Ba+, Tl+, and Pb+. Experiments were furthermore carried out in artificial gastric and intestinal fluids to mimic human digestion and compare removal efficiencies of the adsorbent materials as well as release characteristics in synthetic gastric (SGF) and intestinal fluids (SIF). Batch experiments show low sorption capacities for Ni+ and Cd+ for all studied materials; highest affinities were found for Ba+ (99–100%), Pb+ (98–100%), Cs+ (97–98%), and Tl+ (96%), depending on the experimental setup for the PCT. For the adsorption experiments with SGF, highest adsorption was observed for the PCT for Pb+, with an uptake of 99% of the lead content. During artificial digestion, it was proven that the PCT did not release Ba+ cations into solution, whereas 13,574 ng·g−1 and 4839 ng·g−1 of Ba+ were measured in the solutions with NPCT1 and NPCT2, respectively. It was demonstrated that the purified clinoptilolite tuff is most effective in remediating heavy-metal-polluted water, particularly during artificial digestion (99% of Pb+, 95% of Tl+, 93% of Ba+). In addition, it was shown that the released amount of bound heavy metal ions (e.g., barium) from the non-purified clinoptilolite tuffs into the intestinal fluids was significantly higher compared to the purified product.

Various Natural and Anthropogenic Factors Responsible for Water Quality Degradation: A Review

Recognition of sustainability issues around water resource consumption is gaining traction under global warming and land utilization complexities. These concerns increase the challenge of gaining an appropriate comprehension of the anthropogenic activities and natural processes, as well as how they influence the quality of surface water and groundwater systems. The characteristics of water resources cause difficulties in the comprehensive assessment regarding the source types, pathways, and pollutants behaviors. As the behavior and prediction of widely known contaminants in the water resources remain challenging, some new issues have developed regarding heavy metal pollutants. The main aim of this review is to focus on certain essential pollutants’ discharge from anthropogenic activities categorized based on land-use sectors such as industrial applications (solid/liquid wastes, chemical compounds, mining activities, spills, and leaks), urban development (municipal wastes, land use practices, and others), and agricultural practices (pesticides and fertilizers). Further, important pollutants released from natural processes classified based on climate change, natural disasters, geological factors, soil/matrix, and hyporheic exchange in the aquatic environment, are also discussed. Moreover, this study addresses the major inorganic substances (nitrogen, fluoride, and heavy metals concentrations). This study also emphasizes the necessity of transdisciplinary research and cross-border communication to achieve sustainable water quality using sound science, adaptable legislation, and management systems.

Exposure and health risk assessment from consumption of Pb contaminated water in Addis Ababa, Ethiopia

Exposure to lead (Pb) through drinking water has been linked to adverse health outcomes. Children are particularly susceptible. This study was designed to measure Pb contamination level in drinking water of the Ethiopian city Addis Ababa and assess the associated health risks. Eighty-eight fully-flushed drinking water samples were collected from all ten sub-cities of Addis Ababa. Pb concentration was measured using an Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The chronic daily intake (CDI), the hazard quotient (HQ), and the cancer risk (CR) of Pb were determined to assess exposure levels and health effects. Blood lead level (B-Pb) for children was modelled using the integrated exposure uptake biokinetic model (IEUBK). The mean concentration of Pb in the drinking water was 17.8 μg/l, where >50% of the samples exceeded WHO's 10 μg/l guideline. Significant spatial variation of Pb was noticed among sub-cities. The mean CDI was 1.43 and 0.59 μg/kg/day for children and adults, respectively. The HQ showed that 8% of children and 2.3% of adults exceeded the safe limit. The predicted geometric mean of B-Pb ranged from 3.23 to 14.65 μg/dl. The risk of a child having a B-Pb level >5 μg/dl at the median water Pb concentration (10.5 μg/l) was estimated at 13.4%. Based on the 95^th percentile Pb concentration (75.1 μg/l), 89.6% of children would have B-Pb levels above the 5 μg/dl threshold. The estimated CR was found in the range of 1 × 10^-7 to 9.9 × 10^-5; hence cancer risks are not a concern. The study concluded that Addis Ababa's drinking water is likely to be a source of lead exposure where consumers at specific city locations are at risk of numerous non-cancer health effects. The impacts are expected to be severe in the Ethiopian context; hence further investigations and coordinated interventions are required.

Using multivariate statistical analysis in assessment of surface water quality and identification of heavy metal pollution sources in Sarough watershed, NW of Iran

The Sarough watershed in NW Iran hosts a large amount of mineral occurrences and ore deposits which may be considered as the source of heavy metals in the region. The area has been studied previously; however, the methodology of this paper was less focused on previous studies. This study aimed to assess water quality, determine the spatial distribution pattern, and identify the sources of heavy metals in the main tributaries of Sarough watershed using pollution indexes, multivariate statistical methods, and processing data by geographic information system. Totally, 51 water samples were collected along the main rivers to determine the concentrations of heavy metals by ICP-MS. Regarding the drinking water, agriculture, and freshwater aquatic life guidelines, the rivers were assumed unsafe considering most of toxic elements' content, especially As. The mean values for heavy metal pollution indexes (HPI: 237.32) and metal indexes (MI: 25.37) indicated the intensive heavy metal pollution. The cluster analysis categorized the 51 sampling sites into four clusters with respect to pollution level. The results obtained from the Kruskal-Wallis and multiple comparison tests had the harmony with the results of CA in introducing the most impacted sampling sites and the parameters responsible for water quality degradation. The results of PCA showed the maximum similarity between As, Sb, Se, Fe, and Mn as well as base metals which was attributed to anthropogenic input from mining and mineral processing wastes. Association of Cr and Ni may suggest a lithology source (weathering of metamorphosed ultramafic outcrops). The maps prepared in the GIS system showed the spatial distribution pattern of toxic elements with maximum values nearby mining sites which decreases gradually toward downstream areas. Finally, the results showed that the Sarough River and its tributaries are influenced by high concentrations of heavy metals from the drainages of mining and ore processing sites and naturally occurring metal loadings as well as the geogenic sources such as weathering of geologic formations and hot springs.

Causes of heavy metal contamination in groundwater of Tuticorin industrial block, Tamil Nadu, India

Groundwater is the major freshwater resource in urban and rural areas of India that provides potable water. The quality evaluation of existing groundwater resources is vital and it's quantity for the optimal utilization and maintenance. The bounding coordinates of the selected study area of Tuticorin industrial area is between 8°38'24" and 8°51'0" latitude and between 77°54'36" and 78°12'36" longitude. Groundwater samples were collected as grid form at 40 locations during the pre- and postmonsoon seasons in the year 2017. Fe, Zn, Co, Pb, Mn, Ni, Cr, and Cu metal concentrations were determined using AAS (Atomic Absorption Spectrophotometer)-Perkin Elmer makes the model AAnalyst 200. Most of the groundwater samples were exceeded by the WHO 2008; USEPA 2009; and BIS 2012 guideline for drinking water standards. Further to assess the groundwater pollution status based on the heavy metal indices such as heavy metal pollution index (HPI), heavy metal evaluation index (HEI), degree of contamination (DOC), hazard quotient (HQ), hazard index (HI). Statistical analyses to found the appropriateness of groundwater for consumption and factors of contamination. The evaluation results indicate that groundwater is highly deteriorated and unsuitable for drinking in premonsoon period. While evaporation of water which increases the heavy metal concentration in premonsoon and dilution factor was affected in postmonsoon season. The increased concentration of heavy metals in groundwater might have been caused by evaporation, anthropogenic activities, and dissolution of rock formations which poses risk to human health. If this kind of growing contamination in the groundwater is unattended, it may lead to various health issues to the people from this region. Therefore, a consistent and sustainable water management should be carried out in this region in order to improve the groundwater quality.

Oceanic karma? Eco-ethical gaps in African EEE metal cycle may hit back through seafood contamination

The increasing global demand for electric and electronic equipment (EEE) such as smartphones, tablets and electric car batteries has resulted in an increase in heavy metal releases to the environment at different steps during its manufacture (e.g. mining, extraction, production and e-waste). Some critical raw materials (CRMs) that supply the worldwide demand of technology are mainly sourced from Africa, but their resulting heavy metal pollution can reach citizens from other regions of the world through seafood caught in African waters, which would act as a vector. In this study, we review heavy metal contents in African fish and, as proof of concept, we analyse heavy metal content in three tuna species (Thunnus alalunga, T. albacares and T. obesus) caught in different regions inside the Sustainable Fisheries Partnership Agreements (SFPAs) by Spanish fleets and commercialised in Spain. Thunnus alalunga and T. albacares from African waters had higher concentrations of heavy metals (especially Hg but also As and Pb) in muscle than samples of the same species caught in other waters. Metal profiles in tunas from African waters were significantly correlated with those of continental and coastal fish from nearby areas impacted by mines and e-waste, as found in the literature review. Based on these results we identify research priorities that should be addressed in order to improve the social and environmental sustainability of EEE metal manufacture in Africa.

Toxic heavy metals and nutrient concentration in the milk of goat herds in two Iranian industrial and non-industrial zones

This work aimed to explore the concentration of nickel, manganese, iron, copper, chromium, and lead in the milk of goat herds in the industrial area of Asaluyeh (southern Iran) and the non-industrial area of Kaki. The milk of 16 goat herds (each herd had at least ten goats) was collected in several villages in each area, and at the same time, the drinking water and forage of goats were sampled. The concentration of elements in the samples was determined by ICP-OES. The mean concentrations of chromium, copper, iron, manganese, lead, and nickel in milk samples of the Asaluyeh area were 16.423 ± 0.349, 0.146 ± 0.118, 6.111 ± 0.501, 0.239 ± 0.016, 0.141 ± 0.030, and 1.447 ± 0.101 mg/kg, respectively. Concentrations of heavy metals (except for copper) in the milk of goats in the industrialized area of Asaluyeh were significantly higher than that of Kaki (P < 0.05). Also, the content of heavy metals was significantly correlated with lactose levels (P < 0.05). The hazard index for drinking the goat milk was computed to be 0.444 and 0.386 for the Asaluyeh and Kaki area, respectively, which shows a minimal effect of this exposure pathway.

Health Risk Assessment of Heavy Metals in Groundwater of Industrial Township Virudhunagar, Tamil Nadu, India

The present investigation deals with the health risk assessment due to the heavy metals (Cd, Cr, Cu, Co, Mn, Pb, Ni, and Zn) in groundwater in the industrial township of Virudhunagar district. Twenty groundwater samples were collected, and the measured concentration of the heavy metals follows the order Pb > Ni > Zn > Co > Cr > Cd > Cu > Mn. The metal pollution indices (heavy metal evaluation index, Heavy metal pollution index, degree of contamination) were calculated using the measured heavy metal concentrations. The samples collected nearer to the industrial zone have elevated concentrations of Pb, Cd, and Ni. The carcinogenic and noncarcinogenic risks were calculated based on the measured heavy metals concentration and average daily intake of water. The calculated carcinogenic risk values (5.66 × 10^-3-1.56 × 10^-2) (Pb, Cd, and Ni) exceed the acceptable limit of 10^-6-10^-4. The noncarcinogenic risk exceeds the acceptable limit of one for the heavy metals Pb and Cr. The higher carcinogenic and noncarcinogenic risk values reveal that the study area has health risks due to Pb, Cd, Ni, and Cr metals. Furthermore, factor analysis and cluster analysis showed that the industrial impact and wastage dumpsites are the prime sources for heavy metal contamination in groundwater of the study area.

Removal of Cadmium from Contaminated Groundwater Using a Novel Silicon/Aluminum Nanomaterial: An Experimental Study

Cadmium (Cd) is a harmful element to human health and biodiversity. The removal of Cd from groundwater is of great significance to maintain the environmental sustainability and biodiversity. In this work, a novel low-temperature roasting associated with alkali was applied to synthesize an eco-friendly adsorbent using coal fly ash. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray fluorescence, and X-ray photoelectron spectroscopy were applied to analyze the physical and chemical characteristics of the adsorbent. The experiments show that a significant improvement in specific surface area and activity of adsorbent was observed in this study. The functional groups of Na-O and Fe-O were verified to be beneficial in the removal of Cd²⁺. The material capacity to adsorb Cd²⁺ was considerably improved, and the maximum uptake capacity was 61.8 mg g^-1 for Cd²⁺ at 25 °C. Furthermore, pH and ionic strength play critical roles in the adsorption process. The Langmuir and pseudo-second-order models can appropriately describe the adsorption behavior, and the enhanced adsorption ability of Cd²⁺ by modified coal fly ash was attributed to ion-exchange, co-precipitation, and complexation. Higher sorption efficiency was maintained after two regeneration cycles. These results offer valuable insights to develop high-performance adsorbent for Cd²⁺ removal.

Heavy Metals in Wastewater and Sewage Sludge from Selected Municipal Treatment Plants in Eastern Cape Province, South Africa

This study assessed the distribution of five heavy metals (Cd, Pb, Cu, Zn, and Fe) across the various stages of treatment in three selected sewage treatment facilities and their receiving waterbodies in the Eastern Cape Province, South Africa. Aqueous and solid (sludge) samples were collected monthly from September 2015 to February 2016. Quantitation was achieved by atomic absorption spectrometry after necessary sample preparations. Concentrations of heavy metal cations in the sludge generally varied from <DL (below detection limit) to 1.17 mg kg−1, <DL to 0.14 mg kg−1, 27.588 to 69.789 mg kg−1, and <DL to 0.099 mg kg−1 for Cu, Cd, Fe and Pb; while Zn was below detection all through. Similarly, the levels of Cu, Cd, and Fe in the influents, effluents, upstream and downstream across the three plants ranged from <DL–6.588 mg L−1, <DL–0.636 mg L−1, <DL–0.878 mg L−1 and <DL–0.711 mg L−1, respectively; Zn and Pb were less than DL in all the matrices and study locations. All the contaminants were below hazardous levels in all the sludge and aqueous samples except Cd which was higher in effluents and surface waters across the board. Wastewater Treatment Plant (WWTP)-A exhibited better removal capacity for Fe (86.6%), compared to WWTP-B (34.7%) and WWTP-C (56.9%). However, the removal of Cu and Zn was very poor in all the treatment facilities studied. Carcinogenic and non-carcinogenic risks evaluated were sufficiently low. This suggests that the levels of contamination, even with respect to Cd, was minimal. Nevertheless, efforts should be made to keep the concentrations of these contaminants at levels safe for humans and aquatic organisms. Furthermore, the use of the effluents from these facilities for irrigation should be discouraged to prevent unnecessary build-up of metals in the soil and plants grown with such, as well as subsequent bioaccumulation and biomagnification in the food chain.

Rare earth elements (REE) in the urban wastewater of Cotonou (Benin, West Africa)

The rare earth element (REE) contamination of urban wastewater, which was collected from open sewers and the inlet of a wastewater treatment plant in Cotonou (Benin), was assessed. The drinking water distributed to the inhabitants of Cotonou and water samples from private wells were also analyzed. The sampling occurred between October and December 2016 and the samples were analyzed by ICP-MS. Although the only magnetic resonance imaging facility in Cotonou opened in November 2016, pollution by anthropogenic gadolinium (Gd), which is included in phase contrast agents, was observed: there was 30-620 times more Gd in wastewater samples than in drinking and well water samples. Europium was another REE presenting positive anomalies. It is hypothetized than the europium came from the leachates of solid waste piles in the street. In the absence of any wastewater treatment, the REEs found in the wastewater are spread to the aquatic environment. It would be interesting to monitor the wastewater REEs over the long term. So far, the aquifers used for water provision have not been polluted by the anthropogenic REEs.

Spatial Distribution and Health Risk Assessment of Dissolved Trace Elements in Groundwater in southern China

To understand the groundwater environmental quality and the impact of trace elements in the construction of urban agglomeration in China, this study collected 58 groundwater samples from the core area of the Chang-Zhu-Tan urban agglomeration (Changsha, Zhuzhou, Xiangtan) and quantitatively analyzed the content of 13 dissolved trace element and their spatial distribution characteristics. The health risk assessment model was further used to evaluate the human health risk caused by trace element pollution in groundwater. It was observed that Ba had the highest average concentration (0.28 mg·L⁻¹), whereas Cd had the lowest (2.1 × 10⁻⁵ mg·L⁻¹). Compared with China’s groundwater environmental quality standard, the exceeding rates of Se, Mn, Zn, and Ni concentrations were 37.93%, 17.24%, 1.72% and 1.72%, respectively. Ba, Cd, Co, Cr, Cu, Fe, Mo, and Pb did not exceed the corresponding standards. The 13 trace elements were distributed in a scattered pattern in space and the trace elements in both banks of the Xiang River, Zhuzhou, Weishui River and surrounding areas were relatively high. Health risk assessments showed that the carcinogenic risk values of Cd, Cr, and Pb and the health risk values of 10 non-carcinogenic elements were less than the corresponding maximum acceptable risk level. The health risks associated with non-carcinogenic substances through ingestion were higher than those associated with dermal absorption. Among the non-carcinogenic substances, Ba and Mn posed the greatest health risks. With respect to drinking water exposure, Cr had the highest carcinogenic risk, followed by Pb. Furthermore, Cd had the lowest carcinogenic risk. This study recommended that continuous monitoring of Ba, Mn, and Cr in groundwater should be practiced by assessing the risk of these elements in the Chang-Zhu-Tan urban agglomeration.

Environmentally Sensitive Elements in Groundwater of an Industrial Town in India: Spatial Distribution and Human Health Risk

This paper presents the results of a study to assess the groundwater quality in an industrial town located in Punjab, India. A total of 99 samples of groundwater were analyzed during the premonsoon and postmonsoon periods of 2018, which revealed the presence of numerous environmentally sensitive elements (ESEs), namely, arsenic (As), aluminum (Al), chromium (Cr), iron (Fe), mercury (Hg), nickel (Ni), selenium (Se), and lead (Pb). Geographic information system (GIS)-based spatial interpolation showed higher contamination levels around the industrial areas and the drainage channel where industrial effluent is generally discharged. Further, groundwater quality was assessed using the heavy metal pollution index (HPI) and the metal index (MI), which indicated poor drinkability of the groundwater. Human exposure to groundwater contaminated with ESEs can pose serious health risks; therefore, noncarcinogenic and carcinogenic health risks due to presence of these elements were also evaluated. Reported health risks to humans from exposure to contaminated groundwater indicate the importance of regular monitoring of groundwater for ESEs vis-a-vis industrial effluent disposal practices.

Sources and behavior of trace elements in groundwater in the South Eastern Desert, Egypt

Due to water scarcity, the groundwater will represent an essential source of water in many communities worldwide. This study was carried out to investigate the main hydrogeochemical characteristic of trace elements composition, their sources, and its vulnerability in groundwater to the human population. Fifteen groundwater samples were collected from boreholes and hand dug wells from the South Eastern Desert, Egypt, and analyzed for Al, As, B, Fe, Mn, Cd, Co, Cr, Cu, Hg, Ni, Pb, Rb, Sb, Sr, Th, U, V, and Zn using inductively coupled plasma mass spectrometry. Multivariate analyses were applied to identify the distribution and potential source of trace elements. The groundwater is tapped from the Miocene and the fractured basement rock aquifers. The mean concentrations of trace elements exceed the guideline values of all organizations, except in some wells for Zn, Cu, and Co. Cationic trace elements declined in the order of Mn > Fe > Zn > Al > V > Ni > Rb > Sr > U > Cu > Cr > Co > Cd > Pb > Th > Sb > Hg. Oxyanions As (mean 15.48 mg/L) and B (mean 1.24 mg/L) showed very high concentrations and higher than the average WHO concentrations in water suggesting potential adverse toxicity to all aquatic organisms. Five factor analyses indicated that different geochemical contributions are involved in the chemical characteristics of groundwater in the study area. Water-rock interaction and dissolution processes in bed rocks from different coastal Miocene deposits, meta-volcanics, basic-ultrabasic rocks, granitic and meta-sediments, seawater intrusion, residential wastes, and mining activities, in addition to the pH/Eh conditions, adsorption, and surface complexation during the chemical weathering are the main factors influence the trace elements distribution in groundwater. Results from this study for the six different groundwater aquifers are a unique insight into the sources and mobility of the observed trace elements in the groundwater and can be used in the assessment of contamination for drinking water wells. The association of trace elements from different aquifers might be useful in tracers studies of water-rock interaction. Due to the enrichment of trace elements in nearshore and crystalline groundwater aquifers in the study area and in similar areas worldwide, treatment technologies, and sustainable water management processes should be applied to prevent severe risks to the communities.

Public Water Supply and Sanitation Authorities for Strategic Sustainable Domestic Water Management. A Case of Iringa Region In Tanzania

Water supply is a mandatory service for the majority from respective legal public water utilities, and its sustainability reflects implementations of best management strategies at a local level. The objectives of this study were (i) to assess current approaches used in water quality and quantity management and (ii) propose a sustainable domestic water management strategy. This was achieved through secondary water data trends, on-site water quality assessments, visits of water supply and sanitation authorities, and assessment of their performances. It was observed that water supplied in rural-based authorities was quite different from that supplied in an urban setting as far as quality and quantity are concerned; urban-based supplies are more affordable to users than rural ones. A new strategy on water management is presented for sustainable water supply; it is based on controlling groundwater abstractions and preference of surface water in public water supplies. Rural water supply management must learn several practices realized in urban supplies for the betterment of services for the majority of the users.

A critical assay of heavy metal pollution index for the groundwaters of Peenya Industrial Area, Bangalore, India

Heavy metals, due to their non-biodegradability and tendency to cause detrimental effects in human beings, are considered as the most hazardous and toxic pollutants. The present investigation was taken up to evaluate the heavy metal concentrations in the groundwaters of Peenya Industrial Area in Bangalore. The concentration of six eco-toxic metals such as chromium, copper, cadmium, iron, nickel, and lead were analyzed for 30 groundwater sampling stations in the study area using atomic absorption spectrometer. The concentration of heavy metals followed the order Cr> Fe >Pb>Cu> Ni> Cd. The analysis results have been used to compute two pollution indices in the groundwater, namely heavy metal pollution index and metal index. Heavy metal pollution index is an effective method of rating and ascertaining the water quality with respect to heavy metals. An index value of 100 is considered to be critical, and on the basis of mean concentration, this value in the study area was observed to be 146.32, which is considerably higher than the stipulated critical index value. 63.33% of the groundwater samples are seen to be having an index far above the critical figure of 100. The mean concentration of metal index was 10.36 and it was seen that 46.67% of the groundwater samples fell under the seriously affected category (metal index values above 6). The results not only show that groundwater of the present study is unacceptable for drinking but also clearly indicate the influence of urban, industrial, and agricultural activities on the groundwaters of the said area. This study has massive relevance in designing control measures and action plans for reducing the pollutant influx into the groundwaters. Prompt enforcement of environmental protection laws is needed to prevent continuous pollution of the area. Further, an immediate and sustainable collective action by all stakeholders to control the pollution level is highly recommended, as this issue poses a severe public health threat.

Soil Enzymatic Activities as Influenced by Lead and Nickel Concentrations in a Vertisol of Central India

A pot-culture was conducted in Completely Randomized Design with three replicates to study the effect of Pb and Ni on enzymatic activities in a Vertisols. Results indicated that increasing in the levels of Pb from 0, 100, 150 and 300 mg kg^-1 soil significantly reduced the dehydrogenase activity (DHA) 38.9, 32.1, 30.9, 18.1 µg triphenylformazan g^-1 soil 24 h^-1; acid phosphatase activities 73, 61, 58, 55 µg PNP g^-1 soil h^-1 and alkaline phosphatase activities 80.7, 69.4, 66.2 and 64.0 µg PNP g^-1 soil h^-1, respectively. Application of Ni up to 100 mg kg^-1 had significantly improved the soil enzymatic activities and thereafter there was no such change up to the highest level (300 mg Ni kg^-1). Among soil enzymatic activities, DHA was more sensitive to Pb application. The findings generated through this study can be useful for managing waste water for safe disposal as well as sustainable crop production.

The reach of human health risks associated with metals/metalloids in water and vegetables along a contaminated river catchment: South Africa and Mozambique

BACKGROUND

Anthropogenic pollution was identified as an environmental problem of concern when, in 2008, dozens of crocodiles died in the Olifants River catchment near the border of South Africa and Mozambique. Given the close proximity of households to the river and their making use of river water, we aimed to determine to what extent water pollution has an impact on health of indigent communities in South Africa and Mozambique in the catchment area.

METHODS

Water and vegetable samples were collected from the study areas. Biota samples were washed with double de-ionized Milli-Q water and freeze-dried. Heavy metal analyses in water and vegetables were done by means of Inductively Coupled Plasma Optical Emission Spectroscopy. Metal concentrations were applied in a human health risk assessment to estimate health risks.

RESULTS

Mean concentrations of antimony, arsenic, cadmium, chromium, mercury, molybdenum, nickel and selenium in water samples from South Africa exceeded the World Health Organization guidelines for safe levels of intake. Only iron exceeded the recommended guidelines in water samples from Mozambique. Metals/metalloids were found in lower concentrations at Mozambique sites downstream of South African sites. In vegetables, uranium was between 10 and 20 times above safe guidelines in South Africa and between 3 and 6 times in Mozambique. Arsenic in water samples posed the highest cancer risk.

CONCLUSIONS

Even with a reduction in the metal concentrations in river water from South Africa to Mozambique, the potential to cause adverse human health impacts from direct use of polluted river water is evident in both countries.

Human Health Risk Assessment of Trace Metals in Surface Water Due to Leachate from the Municipal Dumpsite by Pollution Index: A Case Study from Ndawuse River, Abuja, Nigeria

The study assessed the level of heavy metals in surface water across Ndawuse River near the dumpsite at Phase 1 District of the Federal Capital Territory (FCT), Abuja, Nigeria. The results indicated that oxygen demand, turbidity and heavy metals were above the standard limits set for drinking water. Multivariate analysis using principal component analysis and hierarchical cluster analysis revealed natural and anthropogenic activities as sources of heavy metal contamination. The estimated non-carcinogenic effects using hazard quotient toxicity potential, cumulative hazard index and daily human exposure dose of surface water through ingestion pathway were less than a unity. The estimated carcinogenic risks (CRing) exceeded the suggested potential risk limits, with lead (Pb) having the highest CRing value for all age groups. However, children were found to be more susceptible to heavy metals over a period of time according to the estimated values. The concentration of heavy metals in the investigated river could pose an adverse health risk to several communities that rely on this receiving water bodies for domestic purposes. Therefore, there is need for strict enforcement of environmental laws to protect aquatic ecosystem and to avoid long term cumulative exposure risk that heavy metals may pose on human health.

Geospatial distribution of metal(loid)s and human health risk assessment due to intake of contaminated groundwater around an industrial hub of northern India

The study focused on analyzing concentrations of metal(loid)s, their geospatial distribution in groundwater around an industrial hub of northern India. Human health risk posed due to the intake of contaminated groundwater was also evaluated. For this, 240 samples were assayed using inductively coupled plasma emission spectrophotometer. For risk assessment, the methodology proposed by US Environmental Protection Agency was adopted. Geometric mean of Al, As, Mo, Cd, Co, Cr, Fe, Mn, Ni, Pb, Se, and Zn was 193.13, 27.35, 4.22, 2.85, 92.81, 14.97, 271.78, 25.76, 54.75, 19.50, 16.94, and 1830.27 μg/l, respectively. Levels of Al (84%), As (63%), Ni (63%), Pb (49%), and Se (41%) exceeded the Bureau of Indian Standards (BIS). Principal component analysis is accounted for ~ 88% of the total variance and reflected pollution loads of Al, As, Mo, Cr, Fe, Se, and Pb in the groundwater. Based on it, four sources of metal(loid)s, namely geogenic (34.55%), mixed (industrial and agricultural, 26.76%), waste dumping (15.31%), and industrial (11.25%) were identified. Semi-variogram mapping model demonstrated significant geospatial variations of the metal(loid)s. Hazard index (HI) suggested potential non-carcinogenic risks to the inhabitants due to As, Al, Ni, Se, and Pb, which were the largest contributors. Based on maximum concentrations of metal(loid)s, HI for child and adult was above unity. Arsenic was identified as the most hazardous pollutant that may have chronic carcinogenic health implications. At western side of study area, carcinogenic health risks exceeded critical threshold of 1 × 10^-4, indicating that As posed health risks to residents by intake of groundwater.

Evaluation of water quality and human risk assessment due to heavy metals in groundwater around Muledane area of Vhembe District, Limpopo Province, South Africa

Groundwater is considered as good alternative to potable water because of its low turbidity and perceived low contamination. The study assessed the physio-chemical and heavy metals concentrations in eight randomly selected boreholes water at Muledane village in Limpopo Province of South Africa and the results were compared with South African National standard permissible limit. The impacts of heavy metals on human health was further determined by performing quantitative risk assessment through ingestion and dermal adsorption of heavy metals separately for adults and children in order to estimate the magnitude of heavy metals in the borehole samples. Parameters such as turbidity, nitrate, iron, manganese and chromium in some investigated boreholes did not comply with standard limits sets for domestic water use. Multivariate analyses using principal component analysis and hierarchical cluster analysis revealed natural and anthropogenic activities as sources of heavy metal contamination in the borehole water samples. The calculated non-carcinogenic effects using hazard quotient toxicity potential, cumulative hazard index and chronic daily intake of groundwater through ingestion and dermal adsorption pathways were less than a unity, which showed that consumption of the water could pose little or no significant health risk. However, maximum estimated values for an individual exceeded the risk limit of 10^-6 and 10^-4 with the highest estimated carcinogenic exposure risk (CR_ing) for Cr and Pb in the groundwater. This could pose potential health risk to both adults and children in the investigated area. Therefore, precaution needs to be taken to avoid potential CR_ing of people in Muledane area especially, children using the borehole water.