Toxic Elements In Water Research Articles

Adsorption of As nano-clusters on different graphene environments

We investigate the adsorption of As nano-clusters on graphene sheets in various environments, including vacancies and anchors with Fe and/or O impurities. To achieve this, we conducted Density-Functional Theoretical (DFT) calculations using the freely distributed SIESTA code. Our findings reveal a direct correlation between the number of vacancies and the adsorption energy, indicating that a higher number of vacancies result in higher adsorption of As-clusters. Additionally, as the Asn-cluster size increases, the adsorption energy decreases. Furthermore, our results suggest that transition metal impurities (such as Fe) serve as effective elements for functionalizing graphene facilitating the adsorption of metallic clusters in this way, making it suitable for applications in wastewater filtration or the purification of toxic elements in water. Finally, we address finite size effects on the adsorption of graphene sheets by perform calculations on graphene flakes of different sizes saturated in different ways.

Identifying toxic elements in water, sediments, and roots of mangrove forest (Avicennia marina) in Chabahar Bay, Sea of Oman

Mangroves play a crucial role in filtering pollutants from water and sediments. However, excessive accumulation of potentially toxic elements (PTEs) has harmful effects on marine organisms. This article investigates the concentration and distribution of PTEs in water, sediment, and the roots of endangered mangrove species in Chabahar Bay, a subtropical coastal wetland. The relationship between PTE absorption and accumulation rates with flow rate, mangrove extent, and sedimentation was also explored. Water, sediments, and aerial roots samples were taken at four stations along the wetland from upstream fresh water toward outfall. According to the results, Cd had more distribution in sediment and water samples and plants did not play as adsorbent in the study area. The lowest and highest PTEs concentrations were detected in water and sediment media, respectively. The average concentrations of PTEs in the sediments in the Chabahar Bay were Fe > Cr > Zn > Ni > Cu > Pb > Co > As > Cd while in aerial roots of the mangroves were Fe > Zn > Ni > Cr > Cu > Co > As > Pb > Cd. Except Zn, As, and Cd, there was a good correlation between increasing PTEs content in the sediments with decreasing flow velocity and increasing vegetation density along stations 3 to 4. In addition, the amount of PTEs uptake by the mangroves was less than that of global wetlands. The results also demonstrated a greater uptake in aerial roots in saline water for Cr, Ni and Co. Since the absorption rate of PTEs by the aerial roots of pneumatophores is slower than that in sediments, elevated concentrations of PTEs in the sediment can disrupt the entire ecosystem, leading to a potential decline in biodiversity. These toxins can enter the food chain, affecting not only organisms directly interacting with the sediment but also higher trophic levels, such as fish and birds.

Source apportionment, ecological and health risk assessment of potentially toxic elements in water, sediment and blackchin tilapia {Sarotherodon melanotheron (Rüppell 1852)} from Lagos and Ologe Lagoons, Lagos State, Nigeria

BackgroundLagos and Ologe Lagoons are parts of the Lagos Lagoon Complex, which provide fish as an animal protein source to the locals. However, these fish species have a high propensity to accumulate pollutants including Potentially Toxic Elements (PTEs) from their environment. This potentially constitutes a health risk to fish consumers. Therefore, this study investigated concentrations of some PTEs (As, Cd, Cr, Cu, Fe, Pb, Ni, and Zn) in water, sediment, and fish (Sarotherodon melanotheron) from Lagos and Ologe Lagoons, the ecological and health risks associated with the consumption of the fish as well as the likely sources of the PTEs. MethodsWater, sediment, and fish (S. melanotheron) samples were collected monthly for ten months (June 2022 - March 2023) from three sites: Badore and Baiyeku in Lagos Lagoon and Ologe Lagoon. The concentration of PTEs was determined in the environmental matrices {water, sediment, and three organs (gill, muscle, liver)}. The range of values for method detection limits (MDL), limits of detection (LOD), limits of quantitation (LOQ), and recovery rates were 0.01 – 0.025 mg kg−1, 0.00002 – 0.002 mg L−1, 0.0001 – 0.0067 mg L−1 and 97.19±2.45 - 99.85±1.16% respectively. The ecological risk of PTE in water and sediment was assessed by various indices. Estimated dietary intake (EDI), health risk index (HRI), and target hazard quotient (THQ) were the human health risk assessment indices employed. The distribution and source of the PTEs were analyzed using the coefficient of variation, Pearson's correlation matrix, principal components analysis, and hierarchical cluster analysis. ResultsThe water and sediment quality assessment indices indicated that the water and sediment from the lagoons had low contamination with respect to the eight PTEs studied. EDI values were generally less than 1 except for Fe and Zn. THQ for all PTEs in the three sampling stations and across the different population groups was less than 1 except for Fe. PCA revealed two major sources of PTE pollution which are natural and anthropogenic. As, Cd, Cr, Cu, and Pb were probably due to anthropogenic inputs like agricultural operations and industrial activities while Fe, Ni, and Zn may have occurred due to lithological sources like rock weathering and volcanic events. ConclusionBased on the result of the study, the waters from the lagoons are still suitable for agricultural usage. The sediments are also largely uncontaminated with respect to the eight PTEs studied. The EDI and THQ show that consumption of S. melanotheron from the sites may not constitute any significant health risk to humans and the sources of the PTEs are lithologic and anthropogenic.

An Assessment of Ph, Toxic and Essential Chemical Elements in Water by Analytical Techniques.

Water quality and safety assessment has become essential in water resource studies. Water is an important substance in all aspects of life. Therefore, it must have beneficial compositions and ensure sustainable purity. Water quality monitoring is essential for the protection of public health. Sediments and pollutants in water could harm the organisms in the water body. Polluted water is a complex global problem affecting human and animal health, agriculture, and industry. Water could be affected and contaminated by toxic elements. Toxic element pollution is a serious environmental problem and a hazard that can be monitored in water. Technologies were developed to assess the essential and toxic elements in water. Inductively coupled plasma atomic emission spectrophotometry (ICP-AES) has been used to analyze water and determine water quality. The results show the total concentration of all elements: 0.001-0.0042, 0.0095-0.004, 0.0066-0.0042, and 0.0923-0.078 mg/L for mercury, arsenic, cadmium, and lead, respectively. Physical and chemical properties of water samples, such as pH, salinity, TDS, EC, turbidity, and DO, were measured.

Risk assessment and pollution loads of potentially toxic elements in water of four rivers flowing into the Mediterranean Sea

One of the main sources of metal accumulation in the marine environment is transport by rivers. Using data from 2014 to 2017 for various stations, this study analysed the distribution of potential toxic element (PTE) concentrations in surface waters, the pollution loads and the water quality index of the large rivers flowing into the Mediterranean Sea (Manavgat, Göksu, Seyhan and Ceyhan). 13 different elements (As, Cd, Cr, Co, Cu, Fe,Pb, Li, Mn, Ni, Se, Zn, Al) were determined within the scope of the study. While the estimation of risk assessments for both adults and children via dermal and ingestion pathways using the United States Environmental Agency (USEPA) formulas. Pollution indexes such as Chronic daily intake (CDI), hazard quotient (HQ), hazard index (HI) and carcinogenic risk (CR) were calculated. Additionally, water quality index (WQI), pollution load ındex (PLI) and contamination factors (CF) were also determined. Since it is a detailed monitoring study of three years, all findings are evaluated using average values for each river. The highest mean PTE concentrations across all rivers were found at stations S4 (Seyhan), S1 and M1 (Manavgat) with Ni (0.1895) > Se (0.0618) > Al (0.0598), respectively. The values of PLI were found to be generally high (3−6) and very high (>6) in all studied rivers. Additionally, these rivers are subject to significant contamination with Pb, as CF>5, indicating very high levels of contamination, was found as a minimum of 166 for Pb in all rivers. Considering all risk assessments, it is concluded that children are more sensitive to ingestion and dermal exposure pathways than adults, and their carcinogenic risk is 4.5 times greater than adults. Besides, according to the statistical analysis, the strong and weak correlation of Al with other elements indicates that the source of the pollution is natural and anthropogenic processes, respectively.

Utilizing sustainable hemp biomass as an eco-friendly for potentially toxic elements removal from water

Potentially toxic elements in water is one of the important environmental problems. In this study, it was aimed to produce an environmentally friendly and cost-effective biosorbent using sustainable hemp biomass. The chemical composition of hemp biosorbents was characterized by FTIR, SEM, and XRD, and the results showed that the biosorbent could be a good alternative. A batch system was used to investigate the effects of initial concentration, pH, contact time, and temperature on the removal performance of Cu (II) and Zn (II) ions. The statistical analysis was performed, and the amount of adsorbed substance, kinetic values, and experiment results were evaluated for suitability. Kinetic data determined the best fit to pseudo-second-order kinetics for Cu (II) and Zn (II) ions. Adsorption determined the Langmuir model for Cu (II) ions and the Freundlich model for Zn (II) ions. The maximum adsorption capacity in the batch system was determined as 25.59 mg/g for Cu (II) and 12.97 mg/g for Zn (II) ions. The obtained thermodynamic data confirmed the endothermic nature of the adsorption. In desorption studies, after three cycles, the adsorption efficiency decreased from 83.3% to 52.8% for Cu (II) and from 82.1% to 49.7% for Zn (II). Study results showed that hemp biosorbent may be an alternative adsorbent that can be used to remove PTEs from wastewater.

Assessment of Essential and Potentially Toxic Elements in Water and Sediment and the Tissues of Sciaena deliciosa (Tschudi, 1846) from the Coast of Callao Bay, Peru.

The lorna drum Sciaena deliciosa is a coastal demersal species and one of the underlying artisanal fisheries in some areas of Peru, and is also a source of protein for Peruvian coastal dwellers. The investigation addresses concern about the environmental impact on this fish species and the potential risks to human health through the consumption of contaminated seafood. This research endeavors to assess the concentration of potentially toxic and essential elements in the muscle and liver tissues of S. deliciosa, in addition to the presence thereof in water and sediment capture areas on the coast of Callao, Peru. The study revealed that, in water samples, Ag, Ni, and Zn exceed Peruvian standards, but were below international standards, and Ba, P, Se, and Sn exceed international standards. In the sediments, As, Cd, Pb, Fe, and Zn were above international standards. In the fish, S. delicious muscle demonstrated As, Hg, and Pb exceeding at least one international standard. In the liver, As, Hg, Pb, and Cu exceed international standards. The study approach increased accuracy in risk assessments, offering crucial insights into the interplay between heavy metal pollution, water quality, and animal health, informing risk management strategies. Future studies can explore the long-term effects of heavy metal exposure on different organisms and consider their cumulative impact on health.

Environmental Radioactivity, Ecotoxicology (238U, 232Th and 40K) and Potentially Toxic Elements in Water and Sediments from North Africa Dams

The natural radioactivity of 238U, 232Th and 40K was measured in water and sediment samples collected from Sidi Salem dam (Tunisia) and Aïn Dalia dam (Algeria) in the Tuniso-Algerian transboundary basin. The samples were measured using a TERRA detector of gamma, beta, and alpha rays, and atomic absorption and gamma-ray spectrometry were used to analyze the levels of radionuclides and toxic elements, respectively. Potentially toxic elements (Fe, Pb, Zn, Ni, Cr, Cu and Cd) and associated health risks in surface water and sediment of dams were investigated in this present study. The concentrations of Fe, Pb, Zn, Ni, Cr, Cu and Cd in surface water ranged from 5.430 to 9.700 mg·L−1, 0.022 to 0.168, 0.018 to 0.142, 0.065 to 0.366, BDL to 0.0351, BDL to 0.071 and BDL to 0.048 mg·L−1, respectively. In the sediments, the concentrations of Fe, Pb, Zn, Cu, Ni, Cd and Cr were of the order of 136.7, 3.41, 3.22, 0.213, 0.182, 0.15 mg·L−1 and BDL, respectively. The mean radioactivity rates in the water samples were 1.72, 0.068 and 94.6 Bq·L−1 for 238U, 232Th and 40K, respectively (Tunisia dam), and were 1.9, 0.09 and 131.43 Bq·L−1 for 238U, 232Th and 40K, respectively (Algeria dam). The mean 238U, 232Th and 40K radioactivity concentrations measured in the sediment samples were 2.67, 0.18 and 197.87 Bq·kg−1, respectively (Tunisian dam), and were 4.34, 0.27 and 287.61 Bq·kg−1, respectively (Algeria dam). The activity concentration of 40K was higher than that of 238U and 232Th for the water and sediment samples. The activity concentrations follow the order 40K > 238U > 232Th. The cumulative impact of these radio-geochemical elements can cause immediate serious problems in the ecosystem due to their high potential toxicity to the environment and human health in this study area and can be transposable to any other similar region. A good knowledge of monitoring quality and quantity for transboundary water resources and international collaborations are essential to safeguard human health (women’s breast cancer, thyroid cancer, neurological impact) and avoid conflicts, especially during climatic upheavals of drought.

Potentially Toxic Elements in Water, Soil, and Plants from an Agroecosystem with Hydrothermal Mud Pools

Potentially Toxic Elements in Water, Soil, and Plants from an Agroecosystem with Hydrothermal Mud Pools

Ecological and human health risk assessment of potentially toxic elements in water and soils within a crude oil waste management facility, Southwestern Ghana.

Crude oil waste management is challenging due to the diverse constituents of the waste and its consequent impact on valued environmental receptors (water and soil). Characterization of the potentially toxic elements (PTEs) in soils and water within the surroundings of crude oil waste management facility is imperative, to aid evaluation of potential risks. The study assessed the potential environmental and human health risks posed by PTEs in soil and water from surroundings and adjoining settlement communities. A total of forty-four (44) samples were analyzed for PTEs (Cr, Pb, Zn, Co, Mn, Ni, Hg, Fe, As, Cu, Hg, and Cd) and physicochemical properties in both matrices. The total carcinogenic risk (TCR) for adults and children in the neighbouring community was 4.73 × 10-6 and 1.2 × 10-4, respectively, which was due to the high carcinogenic slope factor of arsenic. A strong correlation was observed between the PTEs and physicochemical properties, and their health risk was attributed to both geogenic and anthropogenic factors. The study indicated that the human health and ecological risk values obtained were within acceptable limits, with the waste management facility posing a higher risk in comparison to the nearby community. These risks may be attributed to the specific nature and intensity of the activities conducted at the facility. Hence, there is the need for continuous promotion of occupational and public awareness on the health and environmental impact of crude oil waste management.

Water quality and health risk assessment of potentially toxic elements in water of Samsun Rivers of the Mid-Black Sea, Turkey

Water quality and health risk assessment of potentially toxic elements in water of Samsun Rivers of the Mid-Black Sea, Turkey

Potentially Toxic Elements in Water, Sediments and Fish from the Karstic River (Raša River, Croatia) Located in the Former Coal-Mining Area.

The assessment of the environmental quality of a sensitive karst aquatic system under the centuries-long anthropogenic influence of the coal mining industry is important for both improving the quality of water resources and protecting aquatic wildlife and human health. In this study, we investigated the anthropogenic impact on the aquatic environment of the upper and middle course of the Raša River through the analysis of a suite of metal(loid)s in three aquatic compartments (water, sediment, fish) using inductively coupled plasma mass spectrometry (ICP-MS). Concentrations of inorganic constituents in water were low, while the chemical composition of stream sediments mainly reflected the geological background of the area, indicating the origin of metal(loid)s from predominantly natural sources. Although comparison with PEC-Q values indicated that existing sediment quality conditions could pose a threat to benthic organisms with regard to Cr and Ni, the constant vertical profiles of these elements suggested their natural origin from the weathering of flysch. Element levels in the muscle of targeted fish species were in accordance with the values typical for low-contaminated freshwater systems, while levels of Cd, Pb and Hg were mostly below the European regulatory limits for toxic elements in foods, indicating that the low concentrations of most contaminants in muscles of fish from the Raša River do not present a risk to humans or other consumers. The obtained data indicated a generally low contamination status of the western part of the Raša River basin with regard to the analyzed inorganic elements.

Assessment of potentially toxic elements in water and sediments in the drainage network of Lake Mariout, Egypt

The present work investigated the distribution and assessment of potentially toxic elements (PTEs) in the water and surface sediments of both Qalaa and Umum Drains. The water samples were taken from eighteen sampling sites covering the downstream part of the two drains before reaching Lake Mariout Main Basin (LMMB) and Lake Mariout Fishery Basin (LMFB) during the summer period. The samples collected were analyzed for Cu, Cd, Zn, Co, Ni, Mn, Fe and Al. Pollution loading index (PLI), enrichment factor (EF), contamination factor (CF), Geo accumulation index (Igeo) and sediment quality guidelines (SQGs) were calculated as a criterion of possible contamination. Qalaa Drain is characterized by a low pH value of 6.93 compared to the other waters in the studied areas. The lowest Cl was always recorded in the water of Qalaa Drain with an average of 0.65 g Cl/L. The water of Umum Drain, LMMB and LMFB are continually aerated with O2 concentration, compared to the Qalaa drain, which constantly carries H2S. The outcomes revealed that the concentrations of the dissolved metals are at suitable levels according to U.S. Environmental Protection Agency (USEPA). Fe and Al are the two abundant metals in the sediment of the four studied areas. The order of abundance of the metals in the sediments of the present study areas was Fe > Al > Zn > Mn > Cu > Ni > Co > Cd. For the sediments, only cadmium and zinc concentrations in all sites during the study period exceeded the average shale rock concentration. According to the examined indices, the level of contamination in Qalaa Drain ranges from considerable to extremely high. Additionally, the four examined regions have higher Cu and Zn contents than SQGs.

Mercury and Arsenic Discharge from Circumneutral Waters Associated with the Former Mining Area of Abbadia San Salvatore (Tuscany, Central Italy).

Dissolved and suspended toxic elements in water discharged from abandoned and active mining areas pose several critical issues, since they represent a threat to the environment. In this work, we investigated the water, suspended particulates, and stream sediments of a 2.1 km long creek (Fosso della Chiusa) that is fed by waters draining the galleries of the abandoned Hg mining area of Abbadia San Salvatore (Mt. Amiata, Tuscany, central Italy). The geochemical results show evidence that the studied matrices are characterized by relatively high concentrations of Hg and As, whereas those of Sb are generally close to or below the instrumental detection limit. Independent of the matrices, the concentration of As decreases from the emergence point to the confluence with the Pagliola creek. In contrast, Hg concentrations display more complex behavior, as water and sediment are mainly characterized by concentrations that significantly increase along the water course. According to the geoaccumulation index (Igeo), sediments belong to Class 6 (extremely contaminated) for Hg. The Igeo of As varies from Class 6, close to the emergence, to Class 2 (moderately contaminated), dropping to Class 0 (uncontaminated) at the confluence with the Pagliola creek. Finally, the total mass load of Hg and As entering the Pagliola creek was computed to be 1.3 and 0.5 kg/year, respectively, when a mean flow rate of 40 L/s was considered. The calculated loads are relatively low, but, when the Fosso della Chiusa drainage basin is taken into account, the specific load is comparable to, or even higher than, those of other mining areas.

Solubility, toxicity, and accumulation of metals from biotite schist rock in Danio rerio fish

Abstract The objective of this work was to determine the solubility of biotite schist rock powder by different methods, as well as the potential toxicity/accumulation of its metals in Danio rerio freshwater fish. Solubility was tested in ultrapure water and in CaCl2 solution (10 mmol L-1). Metal contents were analyzed by inductively coupled plasma optical emission spectroscopy. Fish were separated into different groups and then exposed to biotite schist powder. The solubility of toxic elements in water is not lethal, and, 30 days after the end of exposure, there is no accumulation of metals in the fish.

Sustainable and eco-friendly approach for controlling industrial wastewater quality imparting succour in water-energy nexus system

Water pollution has become the biggest threat for the present as well as the next generation of flora and fauna. The increase in number of industries for nation's technological developments are also the producer of tons of wastewater with toxic elements posing high risk to the lives of living entities in/above water. The step towards development is nowadays becoming a threat to the natural environment which eventually affects the living organisms. This problem is advancing exponentially and needs an urgent solution which is sustainable and eco-friendly in nature. The deteriorating water quality has captivated the attention of the social workers, individuals and the government. Numerous steps have been taken by the municipal authorities in the terms of schemes and policies. These policies govern the quality of water, sets the permissible limits of toxic elements in the industrial effluents, create awareness among people, and restore the water bodies. The need arose as the presence of chemicals and toxic elements in water changes its composition beyond the safe limits assigned by the healthcare organization. The paper frames the statistical status of industrial effluents, major contributors of water pollution, permissible limits of discharge in water bodies, framed policies, discussed previous research carried out for elimination of contaminants, their experimental work considering various plant species and eventually the utilization of this approach in the water-energy nexus system. This research article proposes a biological technique named as “Rhizo-filtration” as a mode to control the water quality. Its long term process is capable of eliminating toxins using the plant species. After successful completion of removal of toxic element from water, the plant species can be harvested and further utilized as biofuel briquette replacing woods and other fuel. Later on, the remaining ashes can be further used as fertilizers for maintaining the fertility of the soil. This research article defines a cost effective and eco-friendly approach for controlling the water contamination due to industrial effluents and saving the lives of aquatic animals and human beings. Though this technique dates back to 1980s but its implementation is highly the need of hour in the growing technological environment. In today's time the technological environment has to go hand in hand with the natural environment for the well-being of the living organisms and successfully accomplish the restoration process of the already deteriorated natural resources.

Pollution and biodiversity: a case study of the Argun River Basin

We analyzed the studies on the hydrochemical composition in the Argun basin and evaluated the level of pollution. We found that the water of the Argun River was contaminated by organic substances and toxic elements. We distinguished 9 major types of the ecosystems based on the prior findings. The prevalent species of Cladophora fracta was chosen as an indicator for the monitoring of the Argun drainage basin pollution by toxic elements. The concentrations of toxic elements in algae remained unchanged for a long term and they appeared to be more informative for the assessment of pollution than the rapidly changing water quality. It is necessary to determine indicator hydrobionts for each type of the ecosystems within such a vast territory as the Argun basin. Our findings showed that current mining production produces a negative ecological impact on the quality of the water ecosystems which should be considered during further developments. It is necessary to conduct a research on the regional background concentrations for toxic elements in water and hydrobionts, and to enlarge the list of indicator hydrobionts for water quality assessment.

Spatial distribution, partitioning, ecological risk and source apportionment of potential toxic elements in water and sediments of the Hoor Al-Azim wetland and their bioaccumulation in selected commercial fish species

The potentially toxic elements (PTEs) concentrations in water and sediments were measured in the Hoor Al-Azim wetland to evaluate the spatial distribution, pollution rate, fate, partitioning, and ecological risk and also to recognize the PTEs sources in sediments using MLR-APCs (multiple linear regression-absolute principal component scores) receptor model. The human health risk was investigated based on the seven fish species consumed in the study area. Based on the results, water and sediment contamination was observed at some stations in the southern part of the wetland where agricultural water drains. Also, the sediments of oil well drilling disposal site was polluted by PTEs. Based on the MLR-APCs model, 80.8% of Mo and 81.5% of Se originated from agricultural source. Total target hazard quotients (TTHQ) values suggested that the children could experience adverse health effects due to consumption of Coptodon zillii, Aspius vorax, Carassius auratus and Carasobarbus luteus.

Simultaneous quantitative speciation of selected toxic elements in water using high performance liquid chromatography coupled to inductively coupled plasma-mass spectrometry (HPLC-ICP-MS)

The aim of this study was to conduct multi-elemental speciation of As(III), dimethylarsinic acid (DMA), monomethylarsenic acid (MMA), As(V) and Cr(VI) in water samples using high performance liquid chromatography coupled to inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) in a single analytical run. Chromatographic parameters, spectral interference identification, and elimination and the performance characteristics of the method were successfully optimized for quantification of As(III), DMA, MMA, As(V), Cr(VI) and Cr(III) in water samples. The percentage errors of 6.93–43.2% for identified potential interferences were eliminated by applying the inter-element mathematical correction method. The limit of detection (LOD) and limit of quantification (LOQ) of As species and Cr(VI) were varied from 0.040-0.298 μg L−1 and 0.133–2.98 μg L−1, respectively. The LOD and LOQ of total As, Cr and Pb determined using ICP-MS were ranged from 0.013-0.203 μg L−1 and 0.045–0.675 μg L−1, respectively. The accuracy of the method was confirmed by achieving the percentage recovery of 83.4% for As species, 90.2% for Cr(VI) and 110–118% for total concentrations of As, Cr and Pb using standard reference material for trace elements in water (SRM 1643f). Furthermore, the accuracy of the speciation analysis method was checked using the spiking and recovery studies and yielded percentage recoveries in the range of 78.3–95.4% for the analyte species. The quantities of species determined in water samples were in the range of 0.314–0.402 μg L−1 for As(III), 0.168–0.533 μg L−1 for DMA, 0.226–0.312 μg L−1 for MMA, 0.191–0.459 μg L−1 for As(V), 0.500–3.28 μg L−1 for Cr(VI) and 0.390–12.6 μg L−1 for Cr(III) in high-flow seasonal state of the river. In the low-flow seasonal state, concentrations varied from 0.314-0.391 μg L−1 for As(III), <0.094 μg L−1 for DMA, 0.315–26.7 μg L−1 for MMA, 0.290–0.744 μg L−1 for As(V), 0.426–5.42 μg L−1 for Cr(VI) and 0.424–96.8 μg L−1 Cr(III). Total concentrations of As, Cr and Pb in water samples of high-flow seasonal state ranged from 0.949-1.88 μg L−1, 1.08–14.9 μg L−1 and 0.190–33.8 μg L−1, respectively. In low-flow seasonal state, the total concentrations of As, Cr and Pb in water samples varied from 1.13-26.5 μg L−1, 3.28–97.5 μg L−1 and 0.455–0.610 μg L−1, respectively. The variations between analytes species and total As, Cr and Pb in seasonal states of the river were statistically insignificant (p > 0.05) at a 95% confidence level except for DMA. The nonpoint sources pollution such as atmospheric deposition of dust released from coal mining, power stations, sewage effluents discharge and agricultural activities are presumably the sources of potentially toxic elements in the Mokolo River.

Evaluation and risks assessment of potentially toxic elements in water and sediment of the Dor River and its tributaries, Northern Pakistan

The present study investigated the concentrations of potentially toxic elements in water and sediments of the Dor River and its tributaries. The physicochemical parameters of water and sediment samples were investigated, including potentially toxic elements (PTEs), such as Fe, Ni, Co, Zn, Cd, Pb, Mn, and Cr. Among the PTEs tested, the highest concentration in water was observed for Fe 787 μg/L upstream and the lowest was observed for Cd 1.98 μg/L downstream. The human risk posed by the PTE concentrations in water was evaluated. The maximum CDI value was observed for Fe 48.3 μg/kg-day and the maximum HQ value was observed for Co 2.73 for children downstream owing to their water consumption. The PTE concentrations in sediments were evaluated for the quantification of pollution and the ecological risk index (ERI). The Dor River and its tributaries were classified according to the contamination factor (CF): Cr, Co, and Zn had low CF, Pb indicated a moderate CF and Cd had a considerable CF. The pollution level index values attributed to sediment concentrations were slightly higher than 1, suggesting pollution in the river. The highest and lowest ERI values in sediments were calculated for Cd of 168 and Zn 0.45, respectively. The downstream sediment of the study area posed a moderate ecological risk level to aquatic systems due to Cd.