Vertical distribution, pollution pattern, ecological risks, and geochemical fractionation of potentially toxic metals in riverine core sediments

This study investigates toxic metal contamination in the sediments of the Değirmendere River Basin (riverbed and estuary) in Türkiye, with the aim of assessing pollution levels, ecological risks, and the seasonal variability of metal concentrations. Sediment samples were collected from 20 stations during the summer and winter of 2022 and analyzed using geochemical and statistical methods. The metals evaluated include Cu, Pb, Zn, Ni, As, Co, V, and La. The findings reveal that Cu (79.46 ± 20.17 μg g-1) and Pb (63.83 ± 15.11 μg g-1) exceeded pollution thresholds, with the highest concentrations observed in winter, particularly in estuarine areas affected by industrial and urban activities. Seasonal variations were significant for As, Pb, V, and Zn (Mann-Whitney U, p < 0.05), with higher concentrations of As, Pb, and Zn in winter, likely due to increased runoff and erosion. The Geoaccumulation Index (Igeo) and Sediment Enrichment Factor (SEF) indicated moderate to significant contamination for Cu, Pb, and As. The ecological risk index (RI) categorized the estuary as a moderate to considerable ecological risk area, with RI values ranging from 150 to 319.2. These findings highlight significant anthropogenic impacts on sediment quality in the Değirmendere River Basin, emphasizing the urgent need for continuous monitoring and targeted mitigation measures.

Rapid urbanization and industrialization have aggravated heavy metal contamination in river sediments of the riverine ecosystem in developing countries like Bangladesh owing to their toxicity and persistence. Sediments are dynamic components and useful indicators to understand the level of contamination and their associated ecological risks in the aquatic environment. The study was conducted to investigate the heavy metal contamination in sediments for assessing the ecological risks of an urban river of Bangladesh using principal component analysis (PCA), Pearson’s correlation matrix, geo-accumulation index (Igeo), contamination factor (CF), contamination degree (CD), pollution load index (PLI), enrichment factors (EF), and potential ecological risk factor (RI). The ranges of Zn, Cr, Cu, Pb, and Cd in sediments were 42.22–99.55, 11.12–57.83, 7.98–53.31, 6.76–22.41, and 0.38–0.87 mg/kg, respectively. In the present study, heavy metal concentration in sediments followed the descending order of Zn > Cr > Cu > Pb > Cd, while the concentrations of Cu, Cr, and Cd were higher and the concentrations of Pb and Zn were lower than the toxicity reference value (TRV). Geoaccumulation index (Igeo) demonstrated that most of the sediment samples were unpolluted to moderately polluted. The PLI ranged from 0.334 to 1.209 that stated that sediments were moderately polluted by studied metals. The multivariate statistical analysis revealed that heavy metal contamination was influenced by multiple pollution sources. The extent of heavy metal pollution in the Shitalakhya River implies that the condition is much frightening to both the aquatic biota and inhabitants in the vicinity of the river.

This study assessed heavy metal contamination in sediments within the Anambra drainage basin in Southern Benue Trough, Nigeria. Twelve river sediments were collected from the basin upstream and downstream in two seasons—rainy and dry seasons. The control was collected from the basin source. Samples were analyzed using X-ray fluorescence (XRF) spectroscopy for common major Potential Toxic Metals (PTMs). Concentration of zinc (Zn), nickel (Ni), manganese (Mn), iron (Fe), chromium (Cr), lead (Pb), vanadium (V), molybdenum (Mo), scandium (Sc) and europium (Eu) were detected in trend: Fe > Mn > Zn > Pb >>> Cr > Ni > Mo > Eu > Sc. Contamination trend in rivers shows Adada > Oji > Ezu > Obele > Mamu > Ankpa. The rainy season and the upstream sediments had lower concentrations than the dry season and downstream, respectively. Sediments had higher PTMs concentrations than the background sediments, though most PTMs concentrations were within the recommended standards- USEPA, WHO and Consensus-Based Sediment Quality Guidelines (CBSQGs). Contamination factor (Cf), enrichment factor (Ef), and geo-accumulation index (Igeo) recorded range from 0 to 15, 0 to 6.69 and − 8.43 to 3.32 respectively, signifying significant accumulation and enrichment of PTMs. Pollution load index (PLI) of the heavy metals ranges between 0.24 and 1.34, which suggest that at the different seasons, the basin was enriched with PTMs to a pollution level through anthropogenic activities. In the Anambra drainage basin, concentration and distribution of heavy metals may have been influenced by both non-anthropogenic and anthropogenic processes such as geology of the area, weathering and erosion as well as mining and agricultural activities.

Potentially toxic metals (PTMs) contamination in the soil poses a serious danger to people's health by direct or indirect exposure, and generally it occurs by consuming food grown in these soils. The present study assessed the pollution levels and risk to human health upon sustained exposure to PTM concentrations in the area's centuries-old glass industry clusters of the city of Firozabad, Uttar Pradesh, India. Soil sampling (0-15cm) was done in farmers' fields within a 1km radius of six industrial clusters. Various environmental (geo-accumulation index, contamination factor, pollution load index, enrichment factor, and ecological risk index) and health risk indices (hazard quotient, carcinogenic risk) were computed to assess the extent of damage caused to the environment and the threat to human health. Results show that the mean concentrations of Cu (33mgkg-1), Zn (82.5mgkg-1), and Cr (15.3mgkg-1) were at safe levels, whereas the levels of Pb, Ni, and Cd exceeded their respective threshold limits. A majority of samples (88%) showed considerable ecological risk due to the co-contamination of these six PTMs. Health risk assessment indicated tolerable cancer and non-cancer risk in both adults and children for all PTMs, except Ni, where adults were exposed to potential threat of cancer. Pearson's correlation study revealed a significant positive correlation between all six metal pairs and conducting principal component analysis (PCA) confirmed the common source of metal pollution. The PC score ranked different sites from highest to lowest according to PTM loads that help to establish the location of the source. Hierarchical cluster analysis grouped different sites into the same cluster based on similarity in PTMs load, i.e., low, medium, and high.

The present study aimed to investigate the concentrations of potentially toxic metals (PTMs) in the drainages, rivers, and coast of Malacca in Peninsular Malaysia. The ranges of total PTM concentrations (mg/kg dry weight) were 1.88–7.01 for Cd, 18.9–1689 for Cu, 26.0–850 for Ni, 56.5–307 for Pb, and 75.4–312 for Zn. Based on an ecological risk assessment and geochemical fractions, it was concluded that heavy metals pollute the drainages and the Malacca River. The potential ecological risk index (PERI) categorised the drainage and river sites as a “very high ecological risk”. Therefore, it was shown that elevated levels of PTMs in the drainages near Malacca Industrial Area and in the Malacca River sediment were most probably attributed to untreated (or incomplete treatment of) industrial effluents. The drainage sediments were found to have higher hazard quotient (HQ) values for the three pathways of the PTMs for children and adults. Although in general, the non-carcinogenic risks of the PTMs for children and adults indicated no significant detrimental health effects, the hazard index (HI) for Pb in children at drainage locations surpassed 1.0, suggesting a non-carcinogenic risk (NCR), which is a cause for worry. Consequently, the ecological health risk assessments offered critical information for PTM pollution reduction and environmental management in future sustainable development initiatives in Peninsular Malaysia’s drainages and rivers. The present findings on the ecological health risks of PTMs based on 2006 samples can serve as an important baseline for future reference and comparison. This work should encourage future investigations on the direct impact of the risks to the residents during floods in Malaysia, as part of mitigation and risk assessments of the contaminated drainage and river sediments in an attempt to lower the hazards for the surrounding residents.

The Valsequillo reservoir is a Ramsar wetland due to its importance as a point of convergence of migratory waterfowl. It is located in Central Mexico and is currently endangered by the constant spill of municipal and industrial discharges from Puebla city. On this context, we evaluated thirteen potential toxic metals (PTMs) in water, Water hyacinth (E. crassipes) plants and sediments at this site. A combined number of 31 samples were collected from the study area. The degree/extent of metal contamination in sediments was assessed through different geochemical indexes, namely: Geoaccumulation index (Igeo), Enrichment Factor (EF) and Potential Ecological Risk Index (PERI). The ability of Water hyacinth plants residues as a phytodepurator in the Ramsar site was tested in terms of the bioaccumulation factor (BF) and the translocation factor (TF). The results concerning sediments showed that Pb, Cu and Hg pose a threat to the aquatic environment since Igeo and EF indicate sediments ranging from moderately contaminated to contaminated. Moreover, PERI pointed out Hg as the main contributor to the ecological risk in sediments, especially in the part of the reservoir covered by E. crassipes. Water hyacinth plants displayed good capacity to absorb PTMs from the water, since the content of Co, Zn, As, Ni, Cu, Pb, Ti, Cr, Ba, Mo and V in the total plant was (all values in mg/kg of dry weight) 21 ± 9, 408 ± 300, 12 ± 6, 93 ± 21, 93 ± 69, 53 ± 29, 1067 ± 643, 78 ± 55, 362 ± 39, 14 ± 0.6 and 96 ± 35, respectively. Metal content in sediments resembles to that of E. crassipes; especially in the roots, suggesting a constant deposition of plants at the bottom of the reservoir, which contributes to the eutrophication of the water. The present work encourages the need for a sustainable management of Water hyacinth plants in the Ramsar site, since they represent a plague and a natural phyto-depurator at the same time.

Abstract: In this study we have worked on the evaluation of heavy metal contamination in the sediments taken from the Jiangsu lagoon and thereby used the Enrichment factor (EF), Pollution load index (PLI), Geoaccumulation index (Igeo), Potential ecological risk index (PERI), Potential ecological risk index (PERI), Potential toxicity response index (PTRI) and Risk assessment code (RAC) and the methods of statistical analysis. The average EF of Zn is found to be less than 2, and the average EF of Cu, Cr, Cd, Pb and Ni are found to be greater than 2 in Jiangsu lagoon.The EF for Pb, Cd and Cr are higher along the Jiangsu lagoon and harbor, which reveals the anthropogenic contribution to the increased content of the surface sediments of the Jiangsu coast. PLI values calculated for Yancheng suggest that this zone is appreciably less impacted by metal pollutants than Nantong. Zn (Igeo(mean)&lt;0), as unpolluted to moderately polluted with Cu (0&lt;Igeo(mean)&lt;1), moderately polluted with Ni (1&lt;Igeo(mean)&lt;2), moderate to strongly polluted with Cd (2&lt;Igeo(mean)&lt;3), and strongly polluted with Cr and Pb (3&lt;Igeo(mean)&lt;4). The potential ecological risk indices of Cu, Zn and Ni in 9 stations in Lianyungang coast were lower than 40, which indicated slight potential ecological risk of three metals in 9 stations.Potential ecological risk indices of Cu, Zn and Cd in 9 stations in Yancheng lagoon were lower than 40, which indicated slight potential ecological risk of two metals in 9 stations. The sediments show a medium risk for Cu with PERI value greater than 40 indicating a moderate risk from sediments across the entire Nantong region. The amount of Cu and Ni with low risk, while Cd with moderate, with high risk in Lianyungang coast. Cu, Zn and Cd with low risk, while Cr and Ni with moderate risk, but, the Pb with very high risk in Yancheng coast. Cu and Zn with low risk, Cr and Ni with medium risk, Pb,Cd with high risk in Nantong coast.

This study aimed to assess the impact of the reopening of the Grand-Bassam inlet on the seasonal metal contamination of the superficial sediments of the area II of the Ébrié system by thirteen trace metals (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, and Zn) and the associated ecological and human health risks. This study was conducted from May 2023 to April 2024. US-EPA sediment quality guidelines and four metal contamination indices (Contamination Factor, Geoaccumulation Index, Contamination Degree, and Mean Contamination Degree) were used to assess the metal contamination of these substrates. Their ecological risks were assessed using two sediment quality guidelines (SEQ-Eau V2 and CB-SQGs) and four indices (mHQ, PERI, mPEC-Q, and mERM-Q). Human health risks, primarily through dermal contact, were assessed using the non-carcinogenic dermal hazard index and lifetime carcinogenic risks index. The findings indicated that metal seasonal contamination of these substrates by trace metals ranged from low to moderate. Overall seasonal metal contamination of these sediments varied from moderate to considerable. Ecological risks were significant during some seasons. Generally, metal contamination and ecological risks were lower during the study period compared to before the reopening of this inlet. Short-term carcinogenic risks for humans were low, while lifetime carcinogenic risks were very high.

Understanding pollution levels, ecological health risks, and sources of potentially toxic metals (PTMs) in the soil from university campuses is critical for assessing environmental safety. Soil samples were collected from 12 locations across urban parks and green areas at Sohag University in Egypt. The samples were processed and analysed for heavy metals, including iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), chromium (Cr), lead (Pb), zinc (Zn), copper (Cu), and cadmium (Cd). Pollution levels were evaluated using indices such as the pollution index (PI), pollution load index (PLI), geo-accumulation index (Igeo), and enrichment factors (EFs). Among the pollution indices, the EFs showed the highest sensitivity in detecting anthropogenic contributions, particularly for Cd, Pb, and Cr. Spatial distribution maps and multivariate statistical analyses, including correlation matrix (CM), principal component analysis (PCA), and cluster analysis (CA), were applied to identify the relationships between PTMs and soil properties, and source apportionment was performed using positive matrix factorisation (PMF). The results indicated that Mn, Ni, and Co were primarily geogenic, whereas Pb, Zn, Cr, and Cd showed higher concentrations, suggesting moderate-to-significant anthropogenic pollution. Pb and Cd pose considerable ecological risks, whereas other metals such as Cr and Cu exhibit moderate ecological threats. The non-carcinogenic and carcinogenic risks to the students were within safe limits, as defined by United States Environmental Protection Agency (USEPA) threshold values. Source apportionment using PMF identified five main sources of PTMs: industrial and anthropogenic activities (30.0%), traffic emissions (25.0%), natural soil processes (20.0%), agricultural practices (15.0%), and mixed industrial traffic sources (10.0%). These findings emphasise the importance of controlling anthropogenic activities to ensure a safer campus environment.

Bangladesh Fisheries Research Institute conducted a study to evaluate heavy metal contamination in the sediment of the Halda river. Data were collected from four locations: Khondokia Khal, Katakhali, Madari Khal, and Madarsha. Concentrations of eight heavy metals (Cd, Cr, Ni, Cu, Fe, Mn, Pb, and Zn) were measured, with Cd ranging from 0.04 to 0.96 mg kg-¹, Cr from 18.20 to 48.14 mg kg-¹, Ni from 0.70 to 9.10 mg kg-¹, Cu from 6.70 to 9.10 mg kg-¹, Fe from 14501.00 to 20323.00 mg kg-¹, Mn from 270.00 to 430.00 mg kg-¹, Pb from 1.83 to 8.12 mg kg-¹, and Zn from 29.00 to 43.00 mg kg-¹, respectively. The geoaccumulation index (Igeo) indicated Mn contamination (0.37 ± 0.02), supported by Improved Nemerow Index (IN) showing moderate contamination of heavy metals in the river Halda. The pollution load index (PLI) (0.31 ± 0.04) indicated no significant pollution, and the contamination factor (CF) also demonstrated low pollution levels. Katakhali Khal exhibited the highest degree of contamination and the modified degree of contamination was (mCd) 4.22 ± 0.45. Enrichment factor (EF) ranged from 0.43 ± 0.10 to 4.14 ± 3.33, indicating minimal to moderate enrichment. Ecological risk factor (Eir) (12.75 ± 0.68 to 49513.56 ± 39.23) and risk index (RI) (467.70 ± 4.53 to 641.92 ± 27.72) demonstrated varying degrees of ecological risk. The modified hazard quotient (mHQ) indicated very low to low contamination severity. Principal Component Analysis (PCA) and Cluster Analysis (CA) revealed correlations among heavy metals, suggesting similar sources. These findings emphasize the need for immediate action to address heavy metal contamination in the Halda river sediment.

• Soil processes affect metal chemical speciation and their biogeochemical activity. • The current study predicted chemical speciation of eight metals in two soil layers. • Divalent forms of metals predominated in both soil layers (79.9%). • Chromium showed a chemical speciation that varied from that of the other metals (95.8% as CrOH+). • Mean percentage ages of all metal ions were similar for all 15 field locations investigated. From soil contamination and risk assessment perspectives, it is imperative to understand the ecological processes occurring in soils. Certain soil processes greatly affect chemical speciation of potentially toxic metals (PTMs), and thus also influence their biogeochemical activity. The current study analyzed chemical speciation of eight PTMs (Cd, Cr, Fe, Cu, Mn, Ni, Zn, and Pb) in upper and lower soil layers for 15 agronomic fields of Vehari-Pakistan using Visual Minteq software. The divalent forms of most PTMs (PTM2+) generally predominated in both soil layers (79.9% overall occurrence). However, chromium revealed a different pattern of chemical speciation (95.8% as CrOH+) compared to other PTMs. The mean percentage of all the PTMs2+ was slightly higher for the lower soil layer (81.3%) than in the upper layer (78.4%), the trend being same for all the PTMs, except Cr. This higher PTMs2+ percentage in lower soil layers than upper layers was due to lower content of organic matter and other anions such as Cl− and HCO 3 − . The mean percentage ages of all the PTMs2+ was similar among all the 15 agronomic fields, which was confirmed by strong Pearson correlation values (R2 > 0.95). The PCA graph grouped all the agronomic fields and PTM2+ closely, except Cr2+ and Cu2+. This grouping confirmed the similar chemical speciation of PTMs, except Cu and Cr in studied fields.

The present study aimed to evaluate the potential toxic heavy metal (PTHM) concentrations and associated ecological and health risk of nearby inhabitants (child and adult populations) of the Bokaro thermal power station (BTPS), Jharkhand, India. The fly ash containing PTHMs is released from the thermal power plant and contaminates the soil of the nearby agricultural area, roadside area and residential area. Furthermore, PTHMs cause ecological risk as well as carcinogenic health effects in adults. Inhabitants are exposed to PTHMs through exposure pathways (for instance, direct ingestion, dermal contact and air inhalation), and PTHMs were examined in this study by calculating the estimated daily intake (EDI). The contamination factor (Cf) of Cd exceeded the threshold value throughout the study area, whereas the Cf of Hg was observed higher only in roadside soil (RSS). The geoaccumulation index (Igeo) of Cd was higher in the top soil of agricultural soil (AS) (7.39) and RSS (9.38). The level of PTHMs was monitored slightly higher in the topsoil of RSS. The ecological risk index (Eri) was detected to be the highest in RSS (1628.9). The permissible limit of Cd (0.05mgkg-1) and Pb (0.1mgkg-1) for all sampled vegetables and grain crops was surpassed. The transfer factor (TF) of the studied vegetables and grain crops was in the order of Cd > Cr > Pb > Hg > As. The results of the present study concluded that the hazard quotient (HQ) values for all PTHMs analysed in soil throughout the study area were < 1, which indicates that the child population was within the safe limit. However, the adult population was at a high risk of non-carcinogenic health effects due to increased permissible limits of Cd, Pb and Cr in vegetables and grain crops whereas the target carcinogenic risk (TCR) of Pb and Cr was higher and indicated that there may be a health risk of cancer in adults.

This study presents the first comprehensive assessment of heavy metal contamination, ecological risk, and potential human health implications in alluvial sediments from the Mbam and Noun Rivers in Central Cameroon. Eighty-two sediment samples were collected and analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) to determine the concentrations of Cr, V, Ni, Cu, Zn, Pb, Sn, U, and Th. The results were compared with upper continental crust (UCC) background values and ecotoxicological benchmarks, including threshold effect level (TEL), probable effect level (PEL), effect range-low (ERL), and effect range-median (ERM). Several contamination and ecological indices are as follows: contamination factor (CF), enrichment factor (EF), geo-accumulation index (Igeo), pollution load index (PLI), and ecological risk indices (Er, RI) were used to evaluate pollution intensity and its environmental implications. In the Mbam River, metal concentrations generally decreased upstream, following the order V > Cr > Zn > Ni > Cu > Pb > Th > Sn > U, with moderate contamination (CF = 1.2-3.5) and PLI values between 1.3 and 1.5, indicating diffuse anthropogenic influence. In contrast, the Noun River displayed extremely high uranium and vanadium enrichment (CF₍U₎ > 5; EF₍U₎≈3.8), resulting in RI values up to 240, which denote considerable to very high ecological risk. Human health indices revealed hazard index (HI) values below 1 for all sites, indicating no immediate non-carcinogenic risk, though children showed higher exposure (HI_child = 0.19-0.34) than adults. Total carcinogenic risk (TCR) values (10-⁶-10-4) remained within the acceptable range but were highest at downstream Mbam sites, reflecting cumulative exposure to Cr (VI), Ni, and U. These findings indicate that metal enrichment in both rivers stems from the weathering of uranium-bearing lithologies combined with localized anthropogenic activities, including artisanal mining and agricultural runoff. Continuous monitoring and integrated watershed management are recommended to mitigate ecological degradation and long-term health risks in the Mbam-Noun River system.

Freshwater lakes in central India like Pandharabodi Lake (PBL), face escalating environmental pressures due to anthropogenic activities, threatening their ecological conditions. Despite growing concerns, systematic investigations on trace metal pollution in the PBL sediments are so far not done, hindering effective conservation strategies. The present study aims to evaluate temporal distribution, enrichment, and potential eco-environmental risks of 14 trace metals (Al, Fe, Mn, Zn, Cu, Cr, Ni, Pb, Co, U, V, Rb, Th, and Sc) in the PBL core sediments. A sediment core from the deepest part of the PBL along with 06 soil samples around the lake was collected and analyzed for trace metal concentrations using X-ray fluorescence (XRF) technique. The metal pollution was assessed using enrichment factor (EF), Index of geo-accumulation (Igeo), contamination factor (CF), ecological risk factor (Er), potential ecological risk index (PERI), and multivariate statistical analyses. The geochemical study of trace metals in the vertical profile, pollution indices, and statistical assessment revealed low to moderate pollution in the core sediments of the lake. The highest contamination factor (CF) values were observed at 8cm core depth for Cu indicating "considerable pollution", while Fe, Mn, Al, Co, Cr, V, Zn, Ni, and Sc show "moderate pollution". The maximum enrichment factor (EF) values were recorded at 32cm core depth for Rb and at 24cm for U indicating "moderate enrichment". The mean geo-accummulation index (Igeo) values for Cu show that the PBL core sediments had "low level of pollution" by Cu, while remaining metals show the unpolluted nature of sediments. The estimated potential ecological risk index (PERI) showed "low potential risk" for aquatic organisms and plants due to its low value (< 150), i.e., < 66.80 in 100% of samples in consideration of eco-environmental risk. The principal component analysis (PCA)/factor analysis (FA), correlation coefficients, and hierarchical cluster analysis (HCA) showed that Cu had considerable contamination in the PBL core sediments due to anthropogenic activities like particulate matters released from adjoining iron and steel plant and opencast coal mine in addition to its origin from the geogenic (natural) sources like weathering and erosion of basalts and soils present in the catchment area. The present findings provide valuable insights for policymakers, contributing to the development of effective conservation strategies for freshwater lakes in central India and other tropical regions.

This study aimed to assess heavy metals in the surface sediments of the Bharalu river, India. Metal concentrations ranged from 6.65−54.6 mg/kg for Ni, 25.2−250.0 mg/kg for Zn, 83.3−139.1 mg/kg for Pb, and 11940.0−31250.0 mg/kg for Fe. The level of metal contamination was assessed using sediment quality guidelines, geo-accumulation index (Igeo), enrichment factor (EF), pollution Load Index (PLI),Nemerow’s pollution index (PIN), and potential ecological risk index. Pb exceeded the sediment quality guidelines at all sites indicating a potential threat to the river ecosystem. (Igeo) and EF also showed moderate to severe enrichment for Pb. Potential ecological risk (RI) showed low risk in the sediments, and Pb is the major contributor to ecological risk. Overall, pollution indices revealed comparably higher contamination of the sediments in the downstream sites than in the upstream site. PCA and correlation matrix analysis indicated both anthropogenic and natural origins for metals. Among anthropogenic sources, urban discharges and waste dumping could be mainly attributed to metal contamination in the river sediments. These findings may aid in developing future river management methods explicitly aimed at tackling heavy metal pollution to prevent further damage to the river ecosystem.