Potentially Toxic Element Pollution Levels and Risk Assessment of Soils and Sediments in the Upstream River, Miyun Reservoir, China

Assessment of heavy metal pollution in soil-parent material relationship across ecosystems

The works of assessing the pollution posed by metals in agricultural areas in developing countries are limited. This study aims to assess metal concentrations and pollution indices of parent materials and soils representing the mantle and oceanic crust units of the ophiolite in the Eastern Mediterranean region, specifically in Kahramanmaraş Province. A total of 88 samples, comprising 44 soil (0-30 cm) and 44 parent material (90 + cm), were collected from the study area. Arsenic (As), mercury (Hg), selenium (Se), uranium (U), molybdenum (Mo), tin (Sn), and cesium (Cs) concentrations were analyzed in these samples, along with the reference metal, iron (Fe). Pollution levels were assessed using enrichment factor (EF) and contamination factor (CF) calculations. Results showed that elemental concentrations (Hg, Se, U, Mo, Sn, and Cs) in soils from the mantle and oceanic crust generally reflected those of the parent material. However, the average As concentration in soils from oceanic crust and mantle units was notably elevated, showing a 3 to fourfold increase compared to the parent material. Based on pollution index values, soils from these units demonstrated a moderate level of enrichment (2 < EF < 5) for As, while other elements (Hg, Se, U, Mo, Sn, and Cs) fell into the low enrichment class (EF < 2). Furthermore, the CF index indicated significant contamination (3 < CF < 6) for As. These findings suggest As contamination in soils from different units of the ophiolite (mantle and oceanic crust), potentially resulting from agricultural chemicals like pesticides and fertilizers.

Plastic Pollution in Paradise: Analyzing Plastic Litter on Malta's Beaches and Assessing the Release of Potentially Toxic Elements

This study investigates plastic litter on two beaches in Malta, Golden Bay and Rivera Beach, with a focus on plastic abundance, characteristics, sources, and the influence of human activity on pollution levels. Conducted in March 2023 during the low-tourist season, 13 sediment samples were collected from a depth of 5 cm using a systematic square sampling method. Plastic litter was quantified and sorted by size, shape, color, and polymer type, and concentrations of potentially toxic elements (PTEs) were measured (Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn, and Fe via ICP-OES). Golden Bay exhibited significantly higher plastic quantities (53.9 ± 4.3 n/m2) compared to Rivera Beach (29.7 ± 4.0 n/m2). Microplastics were dominant on both beaches, with Golden Bay showing a higher proportion (57.0%) than Rivera Beach (50.6%). The plastic litter predominantly consisted of PE (59.6-68.0%) and PP (29.6-38.8%). Golden Bay plastics had PTE concentrations up to 4.9 times higher than those in Rivera Beach, notably for Mn (309.0 μg/g vs. 63.1 μg/g). This research contributes valuable insights into the dynamics of plastic pollution in coastal environments, particularly in areas influenced by tourism.

Evaluation of the Risk from Potentially Toxic Elements (PTEs) in Italy's Most Consumed Processed Fish Products

In a balanced diet, regular fish consumption provides positive outcomes for human health. On the other hand, the seafood supply chain faces a significant food safety risk due to the presence of potentially toxic elements (PTEs). In the present study, to assess the risk for Italian consumers, the concentrations of five PTEs, namely lead, chromium, cadmium, mercury, nickel, and aluminum, were determined in the three most consumed preserved fish in Italy: tuna (Thunnus albacares, Katsuwonus pelamis), mackerel (Scomber scombrus) and anchovy (Engraulis encrasicolus). Samples were collected from the national market, and the instrumental analysis was performed by inductively coupled plasma mass spectrometry (ICP-MS). The analyzed PTEs were found in all the species that were investigated. However, after considering the target hazard quotient (THQ) and the hazard index (HI), it was observed that the three fish preserves did not pose any risk of chronic toxicity for the average consumer, even at the highest concentrations detected. However, for significant consumers, mercury detected in tuna samples represented almost 90% of the tolerable weekly intake (TWI) reported by the European Food Safety Authority (EFSA), representing a matter of concern for consumers, particularly regarding developmental neurotoxicity, whose HI exceeded 111%. The acute toxicity of nickel was also considered for significant consumers at the highest concentration detected, and the margin of exposure (MOE) calculated was above 7000, much higher than the value of 30 indicated by EFSA. Due to the lack of data on non-professional carcinogenicity or human intake through foods with low cancer risk, this toxicity was not considered in the analysis of PTEs.

Human health risk assessment of metals and metalloids in mining areas of the Northeast Andean foothills of the Ecuadorian Amazon

Gold mining (GM) is a major source of metals and metalloids in rivers, causing severe environmental pollution and increasing the exposure risks to the residents of surrounding areas. Mining in Ecuadorian Amazonia has dramatically increased in recent years, but its impacts on Indigenous local populations that make use of rivers are still unknown. The aim of this study was to assess the risks to adults and children caused by the exposure to metals and metalloids in freshwater ecosystems contaminated with tailings released by GM activities in 11 sites of the upper Napo River basin, Ecuador. We selected a carcinogenic and a noncarcinogenic risk assessment method to estimate the hazard index (HI) and total cancer risk (TCR). The concentration of Ag, Al, As, Cd, Cu, Fe, Mn, Pb, Zn, B, and V in water and sediment samples was considered to assess the risks to human health. The calculated HI was 23-352 times greater than the acceptable limits in all sites for both children and adults. Mn and Fe were the main contributors (75% in water and 99% in sediment) to the total calculated risk based on the HI. The calculated TCR for children and adults exceeded approximately one to three times the permissible threshold in all sites. As and Pb contributed up to 93% of the total calculated risk based on TCR for both children and adults. This study demonstrates that the emission and mobilization of metals and metalloids caused by mining activities increase the risk to human health, to which we recommend further monitoring of freshwater contamination in the area and the implementation of preventive health management measures. Integr Environ Assess Manag 2023;19:706-716. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Heavy metal(loid)s contamination in water and sediments in a mining area in Ecuador: a comprehensive assessment for drinking water quality and human health risk

Elevated heavy metal(loid)s concentrations in water lower its quality posing a threat to consumers. This study aims to assess the human health risk caused by heavy metal(loid)s in tap water in Santa Rosa city, Ecuador, and the ecological risk of stream water and sediments in the Santa Rosa River. Concentrations of As, Cd, Cr, Cu, Ni, Pb, and Zn were evaluated in tap waters, stream waters, and sediment samples during the rainy and dry seasons. The Metal Index (MI), Geo-accumulation Index (I_geo), Potential Ecological Risk Index (PERI), and the levels of carcinogenic (CR) and non-carcinogenic risk (HQ) were determined. The results revealed severe pollution levels, mainly in Los Gringos and El Panteon streams, both tributaries of the Santa Rosa River, the primary water source for Santa Rosa inhabitants. More than 20% of the surface water samples showed severe contamination (MI > 6), and 90% of the tap water samples presented a MI value between 1 and 4, which indicates slight to moderate pollution. Drinking water displayed high levels of As, with 83% of the tap water samples collected from households in the dry season above the recommended concentration set by the World Health Organization and Ecuadorian legislation. The I_geo-Cd in the sediment samples was significantly high (I_geo > 3), and the PERI showed very high ecological risk (PERI > 600), with Cd as the main pollutant. HQ and CR were above the safe exposure threshold, suggesting that residents are at risk from tap water consumption, with As being the primary concern.

Metal-mining-induced sediment pollution presents a potential ecological risk and threat to human health across China: A meta-analysis

Aquatic sediment polluted by potentially toxic elements (PTEs) from mining activities represents a potential health "time bomb" for humans and the local ecology, but the integrated analysis of pollution and hazards of PTEs in sediment around typical metal mines in China is limited. Presently, the associated pollution status, spatial distribution, and ecological and health hazards of Cd, Cu, Zn, Pb, Cr, and As were investigated through index evaluation, spatial analysis, health risk assessment models, and Monte Carlo simulation. Overall, the sediment exhibited varying degrees of PTE contamination; notably, the level of Cd was 104.85 times higher than its background value, and it became the most enriched element in the surveyed sediment, followed in descending order by Cu, As, Zn, Pb, and Cr. Nationally, over 64.5% of metal-mining-affected sediment presented a very high ecological risk, contributed mostly by Cd (43.2%-98.7%) followed by As, Pb, and Cu; the risk contributed by both Cr and Zn was found to be negligible. The adverse health risk posed to children by most sediment was 1.72 and 6.46 times higher than that posed to adults for cancerous and noncancerous risks, respectively. The potential noncarcinogenic risks were mainly caused by As, which contributed over 78.9% of the Hazard Index values, then followed by Pb (>9.3%). For both children and adults, the carcinogenic risk of PTEs decreased in the following order: As > Cd > Cr > Pb. The investigated sediment was found seriously affected by nearby metal mines, especially those in regions with long-term and large-scale nonferrous-metal-mining activities. This study could provide a reference for policymakers to develop control strategies for PTE pollution in sediment around mining areas.

Heavy metals contamination in shrimp and crab from southwest regions in Bangladesh: Possible health risk assessment

Shrimp and Crab, important sources of protein, are currently being adversely affected by the rising industrialization, which has led to higher levels of heavy metals. The goal of this study was to evaluate the health risks of contamination associated with nine heavy metals (Cd, Pb, Cu, Cr, Zn, Ni, As, Al, and Fe) in two species of shrimp (Macrobrachium rosenbergii and Metapenaeus monoceros) and one species of crab (Scylla serrata) that were collected from the Khulna, Satkhira, and Bagerhat areas of Bangladesh. Inductively coupled plasma-optical emission spectrometry (ICP-OES) was used for the study. The results showed that all metal concentrations in shrimp and crab samples were below the recommended level, indicating that ingestion of these foods would not pose any substantial health risks to individuals. To evaluate the non-carcinogenic health risks, the target hazard quotient (THQ) and hazard index (HI) were determined, and the target cancer risk (TR) was utilized to evaluate the carcinogenic health risks. From the health point of view, this study showed that crustaceans obtained from the study sites were non - toxic (THQ and HI < 1), and long-term, continuous intake is unlikely to pose any significant health hazards (TR = 10^-7-10^-5) from either carcinogenic or non-carcinogenic effects.

Assessment of Chemical Properties, Heavy Metals, and Metalloid Contamination in Floodplain Soils under the Influence of Copper Mining: A Case Study of Sibay, Southern Urals

The ecotoxicological condition of soils around mining areas is most often unsatisfactory, which affects entire ecosystems and human health. This research sought to analyze the morphological, agrochemical properties, and content of heavy metals (Cd, Cu, Zn) and metalloids (As) of soils located in a floodplain. The study was conducted within the city of Sibay (Republic of Bashkortostan, Russia). The soil samples were collected from the floodplains of the rivers Karagayly and Khudolaz. According to morphological studies, the soil cover was represented by the Lithic Leptosols, Stagnic Phaeozems, and Fluvisols. The results showed that the soils were characterized by high values of organic matter, potassium, and low levels of phosphorus. Soils that were located away from the city in the Karagayly River were not contaminated. However, the floodplain areas pertaining to the urban district and located near the quarries were characterized by severe anthropogenic soil pollution, disrupted integrity of the soil cover, decreased vegetation, and accumulating labile forms of heavy metals and metalloids. The highest degree of pollution was observed in the floodplain soil of the river Khudolaz where all elements exceeded the maximum permissible concentration (MPC) level. Soils in the floodplain of the Karagayly river were marked by an increased degree of contamination of Zn: exceeding MPC by 1.6 times. With the trend toward an arid climate, the ecotoxicological condition of floodplain soils is an important challenge.

The molecular characteristics of DOMs derived from bio-stabilized wastewater activated sludge and its effect on alleviating Cd-stress in rice seedlings (Oryza sativa L.)

To recycle fertilizing contents in wastewater activated sludge (WAS) is attracting increasing interest. Dissolved organic matters (DOMs) in WAS with high content are biologically active. In this work, the molecular composition of DOMs derived from two typical bio-stabilized WAS (DOM_BWS), aerobic composting (DOM_ACS) and anaerobic digestion (DOM_ADS), were analyzed. The mitigative effect and molecular mechanisms of DOM_BWS on rice seedlings (Oryza sativa L.) under Cd-stress were investigated. Our study indicated that DOM_BWS significantly alleviated Cd-stress and facilitated growth recovery of rice seedlings with distinct absorption mechanisms. DOM_ACS, primarily composed of CHO class with low molecular weight rich in carboxyl groups, forming labile Cd-DOM complexes, which promoted Cd-absorption of rice seedlings. While DOM_ADS comprised large molecular weight of CHON class interacted with Cd to produce stable macromolecular complexes in the form of microaggregates, consequently reducing Cd-absorption. At transcriptional level, DOM_BWS restored auxin signal transduction and phenylpropanoid biosynthesis pathways in root cells, and got the expression of glutathione S-transferase well. Besides, DOM_ACS significantly promoted the metabolism of amino acids to alleviate phytotoxicity, while DOM_ADS improved the DNA repair function of rice seedlings. These findings provided novel insights into land-use of bio-stabilized WAS for remediation of heavy metals contaminated soils and food security.

Elements and Pb isotopic composition as evidence for contaminant-metal dispersal in surficial soil and sediment of drinking water source in Beijing, China

Pb pollution in soils and sediments has adverse effects on human health and the environment. Identifying and quantifying the relative contribution of Pb pollution sources are key issues to control Pb pollution. In this study, U, Th and Pb concentration, Pb enrichment coefficient and Pb isotopic composition in the sediment and surface soil samples of the Miyun Reservoir and its upstream Chaohe, Baihe and Tanghe River were analysed to determine the source and relative contribution of Pb pollution. Results show a significant enrichment of Pb in the sediments of the Baihe River (2.7 ± 0.9). The enrichment of Pb in the soils in Baihe (8.0 ± 10.5) and Tanghe (313.3 ± 1139.4) is more obvious, and Pb is unevenly distributed in the soil in the Tanghe Basin. In general, soil is more seriously affected by human activities than sediment. The Pb isotope ratio indicates that mining activities and natural background are the main sources of Pb in soil and sediment. Based on the binary mixture model, the average contribution rate of mining activities to Pb pollution in the sediment is 21.5%, of which the contribution rates in the Miyun Reservoir, Chaohe, Baihe and Tanghe River are 14.86%, 17.20%, 41.03% and 26.32%, respectively. The average contribution rate of mining activities to soil Pb is 43.1%, among which the contribution rates in the Chaohe River Basin, Baihe River Basin and Tanghe River Basin are 58.79%, 60.98% and 36.24%, respectively. In summary, soils and sediments in the basin are affected by mining activities to varying degrees. Nevertheless, natural background is still the main source of Pb in the sediments in the basin and in soil in the Tanghe River. Mining activities are the main sources of Pb in soils in the Chaohe and Baihe River.

Assessment of toxic metal contamination, distribution and risk in the sediments from lagoons used for fish farming in the central region of Peru

Toxic metal contamination, distribution and risk were evaluated in the sediments of three lagoons used for fish farming in the central region of Peru. The distribution of toxic metals in the sediment was in the following descending order of Zn > V > Ni > Cu > Pb > As > Cr > Co > Cd > Sb. Contamination factor (Cf) and geoaccumulation index (I_geo) values for Co, Cr, Cu, Ni, Pb, Sb, V and Zn indicated low contamination and for Cd moderate contamination. The pollution load index (PLI) ranged from 0.3856 to 0.5622; indicating no appreciable contamination and the modified degree of contamination (mCd) corroborated this result. The potential ecological risk (R_i) in the Tranca Grande and Pomacocha lagoons revealed a low potential ecological risk and in Tipicocha a moderate potential ecological risk. HI values < 1 indicated that non-carcinogenic adverse effects were negligible. In adults, the Total carcinogenic risk (TCR) values for As, Cd, Cr, Ni and Pb were less than 1.00E-04, indicating no significant carcinogenic risk. In children, TCR values showed similar behavior with the exception of As. Therefore, considering that fish production for domestic consumption and export is carried out in these lagoons, it is important to continue monitoring toxic metals to protect the health of these ecosystems and human health.

Floodplain soils contamination assessment using the sequential extraction method of heavy metals from past mining activities

Floodplains are among the most precious and threatened ecosystems in the world. The study deals with floodplain soil contamination caused by 8 heavy metals (HMs) (Cd, Co, Cr, Cu, Mo, Ni, Pb, Zn) originating and transported from old mine works along the Štiavnica River in Slovakia. We determined the total HMs content and the HM fractions using BCR sequential extraction method. We selected 12 alluvial sites (AS), two contaminated sites (CS), and one reference site (RS). The sampling points were located within the riparian zones (RZ), arable lands (AL), and grasslands (GL). We confirmed soil contamination by HMs and the related ecological risk by different factors. The contamination by HMs at many AS localities was similar or even higher than at CS localities. The highest contamination factor was calculated for Cu (39.8), followed by Pb (27.4), Zn (18.2), and Cd (7.2). The HMs partitioning in the different fractions at the CS and AS localities revealed that Cd, Zn, and Pb were mainly associated with the exchangeable and reducible fractions, while Cu was mainly associated with the oxidisable fraction. The soil properties were selectively correlated with the HM fractions. Based on the ANOVA results, the effect of different ecosystem types on HM fractions was revealed.

Potentially Toxic Element Contaminations and Lead Isotopic Fingerprinting in Soils and Sediments from a Historical Gold Mining Site

Lead (Pb) isotopes have been widely used to identify and quantify Pb contamination in the environment. Here, the Pb isotopes, as well as the current contamination levels of Cu, Pb, Zn, Cr, Ni, Cd, As, and Hg, were investigated in soil and sediment from the historical gold mining area upstream of Miyun Reservoir, Beijing, China. The sediment had higher ²⁰⁶Pb/²⁰⁷Pb ratios (1.137 ± 0.0111) than unpolluted soil did (1.167 ± 0.0029), while the soil samples inside the mining area were much more variable (1.121 ± 0.0175). The mean concentrations (soil/sediment in mg·kg⁻¹) of Pb (2470/42.5), Zn (181/113), Cu (199/36.7), Cr (117/68.8), Ni (40.4/28.9), Cd (0.791/0.336), As (8.52/5.10), and Hg (0.168/0.000343) characterized the soil/sediment of the studied area with mean I_geo values of the potentially toxic element (PTE) ranging from −4.71 to 9.59 for soil and from −3.39 to 2.43 for sediment. Meanwhile, principal component analysis (PCA) and hierarchical cluster analysis (HCA) coupled with Pearson’s correlation coefficient among PTEs indicated that the major source of the Cu, Zn, Pb, and Cd contamination was likely the mining activities. Evidence from Pb isotopic fingerprinting and a binary mixing model further confirmed that Pb contamination in soil and sediment came from mixed sources that are dominated by mining activity. These results highlight the persistence of PTE contamination in the historical mining site and the usefulness of Pb isotopes combined with multivariate statistical analysis to quantify contamination from mining activities.

Differential Zn and Mn sensitivity of microalgae species from genera Bracteacoccus and Lobosphaera

One of the most common pollutants in natural ecosystems is heavy metals. Algae are sensitive to the action of heavy metals. This allows to use algae to assess the toxicity of heavy metals, bioindication, and during phycoremediation. This study examines the effect of different Zn and Mn concentrations (1.0, 5.0, 25.0, 50.0, 500.0, 1000.0 mg L^-1) on green algae Bracteacoccus minor and Lobosphaera incisa in a chronic bioassay. The results of this study showed that the toxic effect of Zn and Mn on B. minor and L. incisa begins to manifest itself at the lowest of the studied metal concentrations-1 mg L^-1. The critical concentration of Zn, which leads to the complete death of B. minor and L. incisa, is 50.0 and 500.0 mg L^-1, and Mn is 1000.0 mg L^-1 and 500.0 mg L^-1, respectively. It was found that principal component (PC) 1 accounts for 60.47% of the total variance and reflects changes associated with low concentrations of heavy metals (up to 5.0 mg L^-1). PC2 accounts for 27.95% of the total variance. PC2 is mostly associated with high concentrations of ions of heavy metals. Thus, the effect of Zn and Mn concentrations up to 5 mg L^-1and above 50 mg L^-1on B. minor and L. incisa has a different character. At the same time, the response of the studied algae species to the action of Zn and Mn has individual differences. In general, B. minor is more resistant to Mn, while L. incisa is more resistant to Zn.

Ecological Risk Due to Heavy Metal Contamination in Sediment and Water of Natural Wetlands with Tourist Influence in the Central Region of Peru

In this study, the quality of sediment and surface water in two natural wetlands, Paca and Tragadero, in the central region of Peru was evaluated using pollution indices, including the geoaccumulation index, pollutant load index, modified pollution degree, potential ecological risk index, and site rank index, for four heavy metals. Principal component analysis was used to identify potential metal contaminant sources. The determination of Fe, Zn, Pb, and As was performed by flame atomic absorption spectrophotometry. The average concentrations of metals in the sediments of both lagoons decreased in the order Fe > Zn > Pb > As. The analysis of the contamination indices determined that As and Pb are the elements that contribute the most to environmental degradation in both wetlands. There is a strong correlation between the values of potential ecological risk and the modified degree of contamination, revealing that the Paca wetland has a moderate degree of contamination and potential ecological risk, while Tragadero presents a high degree of contamination and considerable potential ecological risk. The application of the site rank index showed that more than 50% of the sampling sites have between high and severe contamination. The principal component analysis presented 79.2% of the total variance. Finally, the results of this study are essential in order to carry out preventive actions for environmental protection in these lake ecosystems of great importance for many activities, such as bird watching.

Accumulation and health implications of metals in topsoil of an urban riparian zone adjacent to different functional areas in a subtropical city

The riparian zone is a river-land ecotone, and its environmental conditions have a significant effect on the river ecosystem and population health. In this study, As, Cu, Cr, Cd, Mn, Fe, Ni, Pb, and Zn in the topsoils of urban riparian zones in a subtropical city in southeast China were quantitatively estimated by inductively coupled plasma-optical emission spectrometry. The geoaccumulation index and health risk evaluation model were adopted to assess the accumulation characteristic and health risk of residents' exposure to metals. Principle component analysis was used to determine the source of metals. The results showed that the mean contents of metals (except Fe) were higher than the soil background value, but none of the metal contents exceeded the mass limit of environmental quality standards. The order of the geoaccumulation index was Cd > Mn > Cu > Cr > Pb > Zn > As > Ni > Fe. The contamination level of Cd was classified as slight, whereas the other metals did not contribute to pollution. The spatial distribution of metals in the riparian zone was compatible with the pattern of functional zones in the adjacent urban areas, where levels of Cr, Cd, Fe, Mn, and Ni were higher in commercial areas, as were Pb and Zn in under-construction land and As in residential and industrial areas. Carcinogenic risks of Cr, As, and Pb were acceptable. The hazard index indicated no significant noncarcinogenic risks from any metals. However, noncarcinogenic risks of metals other than Mn were higher for children than for adults, and the primary exposure route of metal into the human body was ingestion for children and inhalation for adults. Principle component analysis indicated that the primary sources of Cr, Ni, Mn, Cu, and Fe were pedogenic processes and mineral weathering, whereas Zn, As, Pb, and Cd mainly originated from anthropogenic sources, specifically, Zn from transportation emission, Pb from transportation emission and industry waste, As from coal combustion and residential waste, and Cd from pigments/paint used in commercial buildings, urban greening, consumer waste, and transportation emission.

Human Health Risk Assessment for Exposure to Potentially Toxic Elements in Polluted Rivers in the Ecuadorian Amazon

Anthropogenic activities performed in the Ecuadorian Amazon have released potentially toxic elements (PTEs) into the rivers, causing severe environmental pollution and increasing the risk of exposure to the residents of the surrounding areas. This study aims to carry out a human health risk assessment using deterministic and probabilistic methods to estimate the hazard index (HI) and total cancer risk (TCR) related to multi-pathway human exposure to PTEs in polluted rivers. Concentrations of Al, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in surface water and sediment samples from rivers on the Ecuadorian Amazon were considered to assess the potential adverse human health effects. As a result, deterministic and probabilistic estimations of cancer and non-cancer risk through exposure to surface waters and sediments were above the safety limit. A sensitivity analysis identified the concentration of PTEs and the exposure duration (ED) as the two most important variables for probabilistic health risk assessment. The highest risk for receptors was related to exposure to polluted sediments through incidental ingestion and dermal contact routes. According to the deterministic estimation, the human health risk through ingestion of water was above the threshold in specific locations. This study reveals the potential health risk to which the population is exposed. This information can be used as a baseline to develop public strategies to reduce anthropogenic pollution and exposure to PTEs in Ecuadorian Amazon rivers.

The impact of increased flooding occurrence on the mobility of potentially toxic elements in floodplain soil - A review

The frequency and duration of flooding events is increasing due to land-use changes increasing run-off of precipitation, and climate change causing more intense rainfall events. Floodplain soils situated downstream of urban or industrial catchments, which were traditionally considered a sink of potentially toxic elements (PTEs) arriving from the river reach, may now become a source of legacy pollution to the surrounding environment, if PTEs are mobilised by unprecedented flooding events. When a soil floods, the mobility of PTEs can increase or decrease due to the net effect of five key processes; (i) the soil redox potential decreases which can directly alter the speciation, and hence mobility, of redox sensitive PTEs (e.g. Cr, As), (ii) pH increases which usually decreases the mobility of metal cations (e.g. Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺, Zn²⁺), (iii) dissolved organic matter (DOM) increases, which chelates and mobilises PTEs, (iv) Fe and Mn hydroxides undergo reductive dissolution, releasing adsorbed and co-precipitated PTEs, and (v) sulphate is reduced and PTEs are immobilised due to precipitation of metal sulphides. These factors may be independent mechanisms, but they interact with one another to affect the mobility of PTEs, meaning the effect of flooding on PTE mobility is not easy to predict. Many of the processes involved in mobilising PTEs are microbially mediated, temperature dependent and the kinetics are poorly understood. Soil mineralogy and texture are properties that change spatially and will affect how the mobility of PTEs in a specific soil may be impacted by flooding. As a result, knowledge based on one river catchment may not be particularly useful for predicting the impacts of flooding at another site. This review provides a critical discussion of the mechanisms controlling the mobility of PTEs in floodplain soils. It summarises current understanding, identifies limitations to existing knowledge, and highlights requirements for further research.

Soil contamination by potentially toxic elements and the associated human health risk in geo- and anthropogenic contaminated soils: A case study from the temperate region (Germany) and the arid region (Egypt)

The aim of this study was to assess the soil contamination caused by potentially toxic elements (Al, As, Co, Cr, Cu, Fe, Mn, Mo, Ni, Se, V, and Zn) using various indices and the associated risk of human health for adults and children in selected soils from Germany (Calcic Luvisols, Tidalic Fluvisols, Haplic Gleysols, and Eutric Fluvisols) and Egypt (Haplic Calcisols, Sodic Fluvisols, and Eutric Fluvisols). Soil contamination degree has been assessed using indices such as contamination factor (CF), pollution load index (PLI), geo-accumulation index (I_geo), and enrichment factor. We also assessed the health risk for children and for male and female adults. Chromium, Cu, As, Mo, Ni, Se, and Zn in the German Fluvisols had high CF of >6, while in the Egyptian Fluvisols Se, Mo, As, and Al revealed a high CF. The PLI (1.1-5.2) was higher than unity in most soils (except for Tidalic Fluvisols), while the most important contributor was Se, followed by Mo and As in the Egyptian Fluvisols, and by Cr, Cu, and Zn in the German Fluvisols. The median value of hazard index (HI) for children in the studied soils indicated an elevated health risk (higher than one), especially in the German Fluvisols (HI = 4.0-29.0) and in the Egyptian Fluvisols (HI = 2.2-5.2). For adults, median HIs in all soils were lower than unity for both males and females. The key contributor to HI was As in the whole soil profiles, accounting for about 59% of the total HIs in all three person groupings. Our findings show that in the studied multi-element contaminated soils the risk for children's health is higher than for adults; while mainly As (and Al, Cr, Cu, and Fe) contributed significantly to soil-derived health risk.

Systematic Assessment of Health Risk from Metals in Surface Sediment of the Xiangjiang River, China

The common empirical screening method is limited to a preliminary screen target from vast elements for human health risk assessments. Here, an element screening procedure was developed for assessing the human health risk of the elements in the sediment of the Xiangjiang River. Ninety-six surface sediment samples from eight sampling stations were collected and 27 elements of each sample were investigated. Thirteen of the 27 elements were screened for human health risk assessments through the three-run selections by calculating anthropogenic factors, building element maps, and the removal of unnecessary elements. Pb posed the greatest health risk and exhibited a potential noncarcinogenic risk for adults at the stations S4 and S5, although no visible noncarcinogenic and carcinogenic risk for adults and children in the Xiangjiang River. Our study also suggested that the chalcophile elements were associated with greater health risk, compared to the lithophile and siderophile ones.

Evaluating the effect of dam construction on the phosphorus fractions in sediments in a reservoir of drinking water source, China

It is widely acknowledged that dams affect sediment transport and water quality. To support water management of reservoirs, it is useful to explore how the fractions of phosphorus (P) in sediments were changed after the dam was built. The aim of this study was to assess the spatial and temporal trends of the P fractions in sediments from the Miyun Reservoir, a pivotal drinking water supply for Beijing City, the capital of China. Nine surface sediment samples, together with a sediment core, were collected. The concentrations of total P (TP) and their fractions were then determined by using a sequential extraction method. The results showed that the reservoir was classified into three areas spatially based on the TP concentrations, i.e., high (Baihe area), medium (transitional area), and low (Chaohe area) concentrations. The concentrations of iron-bound P (BD-P) and metal oxide-bound P (NaOH-P) were higher in the Baihe and Chaohe regions than those in the transitional area and tended to increase with water depth. Dam construction can lead to the concentrations of P increased in sediments and further increase the potential of internal P loadings. This study revealed the effect of dam construction on sedimentary P accumulation. The results will be helpful in better understanding the mobility and bioavailability of P in the aquatic ecosystem, which aim to achieve a more highly targeted environmental management for this important region.