Concentration and pollution assessment of heavy metals within surface sediments of the Raohe Basin, China

Potential risk assessment and occurrence characteristic of heavy metals based on artificial neural network model along the Yangtze River Estuary, China

Pollution from heavy metals in estuaries poses potential risks to the aquatic environment and public health. The complexity of the estuarine water environment limits the accurate understanding of its pollution prediction. Field observations were conducted at seven sampling sites along the Yangtze River Estuary (YRE) during summer, autumn, and winter 2021 to analyze the concentrations of seven heavy metals (As, Cd, Cr, Pb, Cu, Ni, Zn) in water and surface sediments. The order of heavy metal concentrations in water samples from highest to lowest was Zn > As > Cu > Ni > Cr > Pb > Cd, while that in surface sediments samples was Zn > Cr > As > Ni > Pb > Cu > Cd. Human health risk assessment of the heavy metals in water samples indicated a chronic and carcinogenic risk associated with As. The risks of heavy metals in surface sediments were evaluated using the geo-accumulation index (Igeo) and potential ecological risk index (RI). Among the seven heavy metals, As and Cd were highly polluted, with Cd being the main contributor to potential ecological risks. Principal component analysis (PCA) was employed to identify the sources of the different heavy metals, revealing that As originated primarily from anthropogenic emissions, while Cd was primarily from atmospheric deposition. To further analyze the influence of water quality indicators on heavy metal pollution, an artificial neural network (ANN) model was utilized. A modified model was proposed, incorporating biochemical parameters to predict the level of heavy metal pollution, achieving an accuracy of 95.1%. This accuracy was 22.5% higher than that of the traditional model and particularly effective in predicting the maximum 20% of values. Results in this paper highlight the pollution of As and Cd along the YRE, and the proposed model provides valuable information for estimating heavy metal pollution in estuarine water environments, facilitating pollution prevention efforts.

Nanotechnology Approaches for the Remediation of Agricultural Polluted Soils

Soil pollution from various anthropogenic and natural activities poses a significant threat to the environment and human health. This study explored the sources and types of soil pollution and emphasized the need for innovative remediation approaches. Nanotechnology, including the use of nanoparticles, is a promising approach for remediation. Diverse types of nanomaterials, including nanobiosorbents and nanobiosurfactants, have shown great potential in soil remediation processes. Nanotechnology approaches to soil pollution remediation are multifaceted. Reduction reactions and immobilization techniques demonstrate the versatility of nanomaterials in mitigating soil pollution. Nanomicrobial-based bioremediation further enhances the efficiency of pollutant degradation in agricultural soils. A literature-based screening was conducted using different search engines, including PubMed, Web of Science, and Google Scholar, from 2010 to 2023. Keywords such as "soil pollution, nanotechnology, nanoremediation, heavy metal remediation, soil remediation" and combinations of these were used. The remediation of heavy metals using nanotechnology has demonstrated promising results and offers an eco-friendly and sustainable solution to address this critical issue. Nanobioremediation is a robust strategy for combatting organic contamination in soils, including pesticides and herbicides. The use of nanophytoremediation, in which nanomaterials assist plants in extracting and detoxifying pollutants, represents a cutting-edge and environmentally friendly approach for tackling soil pollution.

Metal contamination, their ecological risk, and relationship with other variables in surface sediments of urban rivers in a big city in Asia: case study of Hanoi, Vietnam

Urban rivers are significantly impacted by anthropogenic pressure. This study presents the updated assessment of the concentrations of 11 metals and other variables (pH, total organic carbon (TOC) and nutrients (total nitrogen, total phosphorus, and total silica)) in the sediments of four urban rivers in inner Hanoi city, Vietnam, during the period 2020-2022. The mean concentrations of Fe, Zn, As, and Cr were higher than the permissible values of the Vietnam National technical regulation on the surface sediment quality. Moreover, Zn and Cr were at the severe effect level of the US EPA guidelines for sediment quality. The calculation of pollution indices (Igeo and EF) demonstrated that Mn, Ni, and Fe were from natural sources whereas other metals were from both anthropogenic and natural sources. The ecological risk index revealed that metals in Hanoi riverine sediments were classified at considerable ecological risk. High values of metals, TOC, and nutrients in the sediments of these urban rivers mostly originate from the accumulation of untreated urban wastewater that is enhanced by low river discharge. Our results may provide scientific base for better management decisions to ensure environmental protection and sustainable development of Hanoi city.

Contamination and ecological risk assessment of Cr, As, Cd and Pb in water and sediment of the southeastern Bay of Bengal coast in a developing country

Safe levels of heavy metals in the surface water and sediment of the eastern Bay of Bengal coast have not been universally established. Current study characterized heavy metals such as arsenic (As), chromium (Cr), cadmium (Cd) and lead (Pb) in surface water and sediments of the most important fishing resource at the eastern Bay of Bengal coast, Bangladesh. Both water and sediment samples were analyzed using inductively coupled plasma mass spectrometer. Considering both of the seasons, the mean concentrations of Cr, As, Cd, and Pb in water samples were 33.25, 8.14, 0.48, and 21.14 μg/L, respectively and in sediment were 30.47, 4.48, 0.20, and 19.98 mg/kg, respectively. Heavy metals concentration in water samples surpassed the acceptable limits of usable water quality, indicating that water from this water resource is not safe for drinking, cooking, bathing, and any other uses. Enrichment factors also directed minor enrichment of heavy metals in sediment of the coast. Other indexes for ecological risk assessment such as pollution load index (PLI), contamination factor (CF), geoaccumulation index (Igeo), modified contamination degree (mCd), and potential ecological risk index (PERI) also indicated that sediment of the coastal watershed was low contamination. In-depth inventorying of heavy metals in both water and sediment of the study area are required to determine ecosystem health for holistic risk assessment and management.

Safety of African grown rice: Comparative review of As, Cd, and Pb contamination in African rice and paddy fields

This review aimed to investigate the reported concentrations of arsenic (As), cadmium (Cd), and lead (Pb) in rice cultivated in Africa and African rice paddies compared to other regions. It also aimed to explore the factors influencing these concentrations and evaluate the associated health risks of elevated As, Cd, and Pb exposure. Relevant data were obtained from electronic databases such as PubMed, Scopus, and Google Scholar using specific keywords related to arsenic, cadmium, lead, rice, Africa, paddy, and grain. While the number of studies reporting the concentrations of As, Cd, and Pb in rice and rice paddies in Africa is relatively low compared to other regions, this review revealed that most of the African rice and paddy soils have low concentrations of these metals. However, some studies have reported elevated concentrations of As, Cd, and Pb in paddy fields, which is concerning due to the increased use of agrochemicals containing heavy metals in rice production. Nonetheless, agronomical interventions such as implementing alternate wetting and drying water management, cultivating cultivars with low accumulation of As, Cd, and Pb, amending rice fields with sorbents, and screening irrigation water can limit the bioaccumulation of these carcinogens in paddy fields using phytoremediation techniques. Therefore, we strongly urge African governments and organizations operating in Africa to enhance the capacity of rice farmers and extension officers in adopting approaches and practices that reduce the accumulation of these carcinogenic metals in rice. This is essential to achieve the sustainable development goal of providing safe food for all.

Arbuscular mycorrhizal fungi improve growth and tolerance of Platycladus orientalis under lead stress

Platycladus orientalis is a significant woody plant for phytoremediation in heavy metals contaminated soils. The growth and tolerance of host plants under the lead (Pb) stress were enhanced by arbuscular mycorrhizal fungi (AMF). To evaluate the adjustment by AMF on growth and activity of antioxidant system of P. orientalis under Pb stress. The two-factor pot experiment was conducted with three AM fungal treatments (noninoculated, Rhizophagus irregularis, and Funneliformis mosseae) and four Pb levels (0, 500, 1000, and 2000 mg kg-1). AMF increased dry weight, phosphorus uptake, root vitality, and total chlorophyll content of P. orientalis in spite of Pb stress. Compared with nonmycorrhizal treatments, mycorrhizal P. orientalis had lower H2O2 and malondialdehyde (MDA) contents under Pb stress. AMF increased Pb uptake in roots and decreased the Pb translating to the shoots yet under Pb stress. Total glutathione and ascorbate in roots of P. orientalis were decreased by AMF inoculation. Mycorrhizal P. orientalis had higher superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and glutathione S-transferase (GST) activities in shoots and roots than nonmycorrhizal counterparts. Mycorrhizal P. orientalis under Pb stress showed higher expression of PoGST1 and PoGST2 in roots than that in CK treatments. Future studies will explore the function of induced tolerance genes by AMF of P. orientalis under Pb stress.

Heavy metal stabilization remediation in polluted soils with stabilizing materials: a review

The remediation of soil contaminated by heavy metals has long been a concern of academics. This is due to the fact that heavy metals discharged into the environment as a result of natural and anthropogenic activities may have detrimental consequences for human health, the ecological environment, the economy, and society. Metal stabilization has received considerable attention and has shown to be a promising soil remediation option among the several techniques for the remediation of heavy metal-contaminated soils. This review discusses various stabilizing materials, including inorganic materials like clay minerals, phosphorus-containing materials, calcium silicon materials, metals, and metal oxides, as well as organic materials like manure, municipal solid waste, and biochar, for the remediation of heavy metal-contaminated soils. Through diverse remediation processes such as adsorption, complexation, precipitation, and redox reactions, these additives efficiently limit the biological effectiveness of heavy metals in soils. It should also be emphasized that the effectiveness of metal stabilization is influenced by soil pH, organic matter content, amendment type and dosage, heavy metal species and contamination level, and plant variety. Furthermore, a comprehensive overview of the methods for evaluating the effectiveness of heavy metal stabilization based on soil physicochemical properties, heavy metal morphology, and bioactivity has also been provided. At the same time, it is critical to assess the stability and timeliness of the heavy metals' long-term remedial effect. Finally, the priority should be on developing novel, efficient, environmentally friendly, and economically feasible stabilizing agents, as well as establishing a systematic assessment method and criteria for analyzing their long-term effects.

Effect of crude oil exploration and exploitation activities on soil, water and air in a Nigerian community

The continuous degradation of environmental ecosystems (land, water and soil) resulting from crude oil exploration and exploitation activities continues to gain global attention. This study investigates the effects of crude oil exploration and exploitation activities on soil, water and air in the study area. Soil samples were collected in three replicates at depths of 0-15 and 15-30 cm at sampling distances of 20, 100 and 200 m a from core oil exploitation operation area and a control point. Water samples were also taken from within the study area and analyzed using standard procedures. Major pollutants concentrations of particulate matter (PM_2.5 and PM₁₀) of the air were also measured using Air Quality Index (AQI). The results reveal that the soil, water and air parameters measured mostly at 20 m from the core oil operation area compromise the allowable standards provided for healthy living. In the same manner, some results at 100 and 200 m were slightly higher than the recommended values in some cases of heavy metals and bacteria activities in the soil. The AQI at 20 m was far above the permissible limit provided by the Environmental Protection Agency while others are gradually drawing towards the limit given for each pollutant. To safeguard the health of the residents of the host community and oil field workers, there is a need for proper and frequent environmental monitoring and assessment by authorized regulatory bodies in Nigeria. This will prevent any future exposure which may endanger the lives of the dwellers.

Spatial distribution, ecological risk, and human health assessment of heavy metals in lake surface sections - a case study of Qinghai Lake, China

Qinghai Lake is the largest inland saltwater lake in China, with a drainage area of 29,661 km². This study sought to conduct an ecological and human health risk assessment of metals and heavy metals, including copper, as well as investigate their concentration, distribution, and source distribution. In terms of seasonal variation, the increases in Fe, Cr, As, Pb, and Hg were relatively large, and the spatial distribution of metals presented a three-level stepped distribution trend, gradually increasing from east to west. By further exploring the source and migration path of pollutants, our study found that the source of metals in the sediments of Qinghai Lake is mainly controlled by five rivers entering the lake. Enrichment factor (EF) calculations indicated that the metal accumulation or enrichment capacity of the three central points in Qinghai Lake Basin was strong. Interestingly, the enrichment capacity of Cu and Zn was the strongest among all metals but occurred at low and medium concentration levels, respectively. The Igeo and [Formula: see text] ecological risk assessment results indicated that the individual metals posed little to no ecological risks to the Qinghai Lake Basin. However, the multi-element environmental risk comprehensive index (RI) indicated that Hg (RI = 147.97) represented a slight ecological hazard, Mn (RI = 181.13) posed moderate ecological hazards, and Zn (RI = 386.66) posed strong ecological hazards. The human health risk assessment results showed that the heavy metals in the surface sediments of Qinghai Lake currently do not pose a threat to human health. This information may facilitate the implementation of more stringent monitoring programs in the aquatic ecosystem by the relevant regulatory authorities.

Spatial Distribution, Source Identification, and Potential Ecological Risk Assessment of Heavy Metal in Surface Sediments from River-Reservoir System in the Feiyun River Basin, China

To investigate the pollution characteristics of the surface sediments of the river-reservoir system in the Feiyun River basin, a sediment heavy metal survey was conducted for the first time in the Feiyun River basin. Surface sediments from 21 sampling sites in the Feiyun River basin were collected, and the concentrations and spatial distribution characteristics of 15 heavy metals (Cr, Ni, Cu, Zn, As, Cd, Pb, Mn, V, Co, Mo, Sb, W, Fe, and Se) were analyzed. Three heavy metal ecological risk assessment methods were used to evaluate the potential risks of heavy metals in sediments, and the sources of major heavy metals were traced by correlation analysis and principal component analysis. The results show that (1) the average concentration of heavy metals (As) (212.64 mg/kg) and (Sb) (4.89 mg/kg) in Feiyun River Basin is 33.3 and 6.89 times the background value of Zhejiang Province; the overall spatial distribution of heavy metals is: the mainstream of Feiyun River > Zhaoshandu Reservoir > Shanxi Reservoir, thereby, the pollution is relatively significant; (2) by processing the geo-accumulation index and enrichment index methods, As and Sb are classified as 'severely polluted', 'moderately severely polluted' and 'severely polluted', 'very severe polluted' respectively; (3) the potential ecological index evaluates the surface sediments in the Feiyun River Basin as a very high risk level, the main environmental risk factors are As, Sb, Cd and Mo; (4) the principal component analysis results show that the heavy metals in the sediments of the Feiyun River Basin may be mainly affected by human activities such as sewage from domestic and agricultural activities, mining and smelting, and the others are affected by natural factors.

Heavy metal pollution in Manzala Lake sediments, Egypt: sources, variability, and assessment

The environmental pollution of lake systems due to anthropogenic factors is of growing concern worldwide. Manzala Lake is the largest northern coastal-deltaic lakes of Egypt and has socioeconomic impacts. In this study, the concentrations and origins of seven heavy metals (HMs) and the organic content in the Manzala Lake sediments were explored during the winter and summer. The concentration of the HMs and the organic content were quantified using inductively coupled plasma and loss-on-ignition techniques. Pearson's correlation coefficient (PCC) and principal component analysis (PCA) were applied to evaluate the sources of the metals in the sediments. The HMs and organic matter were enriched during the winter season. The average concentrations of the HMs in the sediments conformed to the following sequence: Fe (14.13) > Mn (0.8) > Cu (0.11) > Zn (0.11) > Ni (0.06) > Pb (0.5) > Cd (0.002) (mg/kg). Sediment quality protocols showed that Mn, Cd, Cu, and Ni pose a significant threat to the aquatic environment in Manzala Lake. The geoaccumulation index (I_geo) values indicated pollution of the sediments with most metals, excluding Fe and Ni. The periodic mean I_geo pollution level followed the sequence Cd > Cu > Zn > Mn > Pb > Ni > Fe. The greatest pollution load index noted during the winter season was principally induced by Cd and Cu. The overall ecological risk index was moderate, with Cd being the most prominent HM. PCA combined with PCC showed that the HM enrichments in the southern (Bahr Al-Baqar Drain [S1], Bashteer [S3], Legan [S5], and Al-Ginka [S8]) and the extreme northeastern (El-Qapouti [S6]) parts of Manzala Lake sediments were mainly due to the discharge from different drains (industrial, agricultural, and municipal wastes) and the industrial region in Port Said, respectively. The lower HM concentrations from the extreme northern parts (Al-Boghaz [S2], Al-Temsah [S4], Al-Hamra [S7], and Al-Kowar [S9]) were due to their isolation from urban areas compared with the other localities. Extensive waste disposal was responsible for the HM pollution in the Manzala Lake sediments. Advanced treatment technologies and monitoring of the pollution in the water and sediments of Manzala Lake are required to decrease the accumulation of the heavy metals.

Distribution and ecological risk assessment of heavy metals using geochemical normalization factors in the aquatic sediments

Thamirabharani river acquires a noticeable quantity of sewage and agriculture waste from local inhabitants. The distribution of heavy metals in the surface sediments of the Thamirabharani river was analyzed using Inductively Coupled Plasma- Mass Spectrometry (ICP-MS) to study the ecological risks. The heavy metal concentrations in the sediments ranged from 0.098 ± 0.03(Cd) to 159.181 ± 13.36 mg kg^-1 (Fe). The Cd, Zn, Ni, Fe, and Mn concentrations in the sediments were above the US Environmental Protection Agency-Sediment Quality Guidelines. The fact that Cd, Co, and Cu concentrations at sites 4 and 5 exceeded the background values (BGVs) of 0.2, 13, and 32 mg kg^-1 suggests anthropogenic activity, notably in the downstream of the river. The sediment contaminated with Cd is more evident, particularly in the estuarine region. The potential ecological risk index (150<PERI≤300) and ecological risk co-efficient (40 < Er < 80) revealed moderate ecological risk at the estuarine region (S5). There was a moderate level of pollution in the downstream region (S4 and S5) based on a geo-accumulation index (Igeo), contamination factor (CF), pollution load index (PLI), and the moderate degree of contamination (mCd) values. According to the geochemical normalization factors, the downstream region (sites 4 and 5) was moderately polluted than the upstream region (S1 and S2), which may affect the estuarine/marine ecosystem. This information may facilitate the relevant regulatory authorities to implement the requisite stringent monitoring program in the aquatic ecosystem.

Nanomaterials for the Treatment of Heavy Metal Contaminated Water

Nanotechnology finds its application almost in every field of science and technology. At the same time, it also helps to find the solution to various environment-related problems, especially water contamination. Nanomaterials have many advantages over conventional materials, such as high surface area, both polar and non-polar chemistries, controlled and size-tunable, easier biodegradation, which made them ideal candidates for water and environmental remediation as well. Herein, applications of non-carbon nanomaterials, such as layered double hydroxides, iron oxide magnetite nanoparticles, nano-polymer composites, metal oxide nanomaterials and nanomembranes/fibers in heavy metal contaminated water and environmental remediation are reviewed. These non-carbon nanomaterials, due to their tunable unique chemistry and small size have greater potentials for water and environmental remediation applications.

Ecological-Health Risks of Potentially Toxic Metals in Mangrove Sediments near Estuaries after Years of Piggery Farming Bans in Peninsular Malaysia

The Sepang Besar River (SBR) was reported to be highly contaminated with Cu and Zn due to piggery farming wastes before 1998. Following the piggery farming ban (PFB) in 1998 in Bukit Pelanduk, the present study aimed to assess the ecological-health risks of potentially toxic metals (PTMs) (Cu, Pb, and Zn) in the mangrove surface sediments from SBR. Two adjacent rivers, namely the Sepang Kecil River and Lukut River, were also included for comparison purposes. The PTMs of present sediment samples collected in 2007 and 2010 were compared with those reported before and after PFB. The PTMs levels were lower than those of established sediment quality guidelines. Results of bioavailable fractions, individual contamination factor, risk assessment code, potentially ecological risk index (PERI), and non-carcinogenic risk (with HI < 1.0 based on the pathways of Cu, Pb, and Zn and the order: ingestion > dermal contact > inhalation), the present findings indicated that the three rivers had caused no ecological-health risks of Cu, Pb, and Zn. In particular, SBR estuary had drastic lower levels of Zn (7.48–9.40 times lower between 1998 and 2010) and Cu (8.30–36.9 times lower between 1998 and 2010), after 12 years of PFB. Based on the exponential decay model, the PERI values showed that the estuary of SBR has been improved from a “considerable ecological risk” to a “minimal ecological risk” after 12 years of PFB. This is the first paper on the ecological-health risks of Cu, Pb, and Zn in the estuary of SBR. Future monitoring is still necessary for effective risk management of the mangrove ecosystem at SBR.

Does aquatic sediment pollution result in contaminated food sources?

The sediment pollution of the aquatic environment by waste due to anthropogenic activity is of an increasing concern. The contaminants coming from the aquatic environment can enter the aquatic food chain and accumulate in the tissues of fish and shellfish used for human consumption. The aim of this study was to sum up the current level of knowledge concerning the pollution of aquatic sediments and its transfer to aquatic foods as well as to indicate whether such contamination has the potential to affect the health and welfare of aquatic organisms as well as the quality and safety of the species intended for human consumption. Based on the results of scientific studies, the European Food Safety Authority, and the Rapid Alert System for Food and Feed, contamination of fish and seafood occurs predominantly through their diet and the levels of bioaccumulative contaminants are higher in fish which rank higher in the food chain. Contamination of aquatic habitats can not only significantly affect behavior, development, and welfare of aquatic organisms, but it can also affect the safety of fish and seafood for human consumption.

Environmental Impacts and Immobilization Mechanisms of Cadmium, Lead and Zinc in Geotechnical Composites Made from Contaminated Soil and Paper-Ash

Paper-ash is used for remediation of heavily contaminated soils with metals, but remediation efficiency after longer periods has not been reported. To gain insights into the mechanisms of immobilization of cadmium (Cd), lead (Pb), and znic (Zn), a study was performed in the laboratory experiment in uncontaminated, artificially contaminated, and remediated soils, and these soils treated with sulfate, to mimic conditions in contaminated soil from zinc smelter site. Remediation was performed by mixing contaminated soil with paper-ash to immobilize Cd, Pb, and Zn in the geotechnical composite. Partitioning of Cd, Pb, and Zn was studied over one year in seven-time intervals applying the sequential extraction procedure and complementary X-ray diffraction analyses. This methodological approach enabled us to follow the redistribution of Cd, Pb, and Zn over time, thus, to studying immobilization mechanisms and assessing the remediation efficiency and stability of newly formed mineral phases. Cd, Pb, and Zn were effectively immobilized by precipitation of insoluble hydroxides after the addition of paper-ash and by the carbonization process in insoluble carbonate minerals. After remediation, Cd, Pb, and Zn concentrations in the water-soluble fraction were well below the limiting values for inertness: Cd by 100 times, Pb by 125 times, and Zn by 10 times. Sulfate treatment did not influence the remediation efficiency. Experimental data confirmed the high remediation efficiency and stability of insoluble Cd, Pb, and Zn mineral phases in geotechnical composites.

The thermodynamic stability, potential toxicity, and speciation of metals and metalloids in Tehran runoff, Iran

Surface runoff is the most significant source of water in dry cities like Tehran. The surface runoff is polluted by heavy metals, which their risk level is a function of their speciation. Herein, Tehran runoff quality and the speciation of metals and metalloids were investigated. The results of quality showed that oxidation-reduction potential (Eh) and pH ranged from + 186 to + 230 mV and from 7.31 to 10.29, respectively. Cluster analysis indicated that Cr, Si, Mn, Fe, Pb, Se, Th, Ba, Ni, Li, and Sr had similar behaviors and origins, and salinity played an active role in restricting their concentrations. Eh and dissolved oxygen (DO) negatively affected the concentrations of all the studied elements. The speciation model (according to HSC Chemistry program) exhibited that all the studied elements are stable; however, in two cases, they would become unstable (pH < 7, Eh <  - 480 mV or Eh > 1100 mV) and (pH > 10, Eh <  - 570 mV or Eh > 970 mV). Also, Ba, Cd, Li, Mn, Al, As, Sr, Cr, Si, and Se are present in bioavailable species and As and Cd in the runoff exist in high toxic oxidation states of + 3 and + 2, respectively. The linear regression of Cu, Co, Cd, Zn, and As with Eh provided a good fit, and all of these metals were significant at levels 1 and 5%. Finally, it is recommended to continuously monitor the Eh-pH changes for investigating the potential toxicity of metals and predicting the metal pollution by regression equations in any other stations.

Environmental sustainability and prevention of heavy metal pollution of some geo-materials within a city in southwestern Nigeria

Increased anthropogenic activities may cause the release of potentially hazardous metals into the environment. This is a major public health concern. The study was aimed at accessing ways by which pollution can be prevented with enhanced environmental sustainability in Ibadan, Southwestern, Nigeria. Geo-materials (groundwater, soil and stream sediment) were collected, analyzed for heavy metals using inductively coupled plasma-mass spectrometry. Results of acidity (pH), electrical conductivity (EC), total dissolved solid (TDS) and heavy metals (Zn, As, and Cd) obtained in water were compared with WHO permissible limits. All parameters were found within WHO permissible limits except TDS (624.35 mg/L). Risk index showed dangerous to extremely dangerous. High TDS can be attributed to weathering while high Cd, Zn and Pb in stream sediment and soil are due to anthropogenic effect. Provision of adequate disposal facilities should be created by private and government agencies and the use of it must be enforced.

Relationship of arsenic and chromium availability with carbon functional groups, aluminum and iron in Little Washita River Experimental Watershed Reservoirs, Oklahoma, USA

Sediment from three reservoirs located in the Little Washita River Experimental Watershed (LWREW) in Oklahoma, USA with contrasting dominant land uses were analyzed for total and extractable concentrations of arsenic (As) and chromium (Cr), and the potential ecologic risk to benthic organisms. Extractable As ranged from 0.24 to 1.21 mg kg^-1, in the order grazing>cropland>forest and 0.13-0.58 mg kg^-1 for extractable Cr, in the order of forest>grazing>cropland. However, only approximately < 1.5% of total As and < 4% of total Cr were extractable. Total As ranged from 16.2 to 141 mg kg^-1 and total Cr ranged from 5.06 to 40.1 mg kg^-1 both in the order of cropland>grazing>forest. The sediment exhibited an alkaline pH (8.0-8.7). As sorption exhibited a positive relationship with Al (r = 0.9995; P = 0.0001), Fe (r = 0.9829; P = 0.0001), and C (r = 0.4090; P = 0.0017) and Cr correlated positively with Al (r = 0.9676 P = 0.0001), Fe (r = 0.9818; P = 0.0001), and C (r = 0.3368; P = 0.0111). In addition, both As and Cr exhibited positive relationships with carbon (C) functional groups in the order of O-alkyl C> methoxyl C> alkyl C> aromatic C> carboxyl C> phenolic C. The sediment concentration analysis results illustrated that As in all reservoirs exceeded their respective Threshold Effect Level (TEL) and/or Probable Effect Level (PEL) indicating that existing concentrations of metals in these sediments were sufficiently high to cause adverse effects. However, Cr concentrations in all reservoirs evaluated was lower compared to the TEL and PEL.

Pollution Caused by Potentially Toxic Elements Present in Road Dust from Industrial Areas in Korea

We examined the pollution characteristics of potentially toxic elements (PTEs) in road dust (RD) from nine industrial areas in South Korea to assess PTE pollution levels and their environmental risks for devising better strategies for managing RD. The median concentrations (mg/kg) were in the order Zn (1407) > Cr (380) > Cu (276) > Pb (260) > Ni (112) > As (15) > Cd (2) > Hg (0.1). The concentration of PTEs was the highest at the Onsan Industrial Complex, where many smelting facilities are located. Our results show that Onsan, Noksan, Changwon, Ulsan, Pohang, and Shihwa industrial areas are heavily polluted with Cu, Zn, Cd, and Pb. The presence of these toxic elements in RD from the impervious layer in industrial areas may have a moderate to severe effect on the health of the biota present in these areas. The potential ecological risk index (Eri) for PTEs was in the decreasing order of Cd > Pb > Hg > Cu > As > Zn > Ni > Cr, indicating that the dominant PTE causing ecological hazards is Cd owing to its high toxicity. Our research suggests the necessity for the urgent introduction of an efficient management strategy to reduce RD, which adds to coastal pollution and affects human health.

Assessment the Seasonal Variability and Enrichment of Toxic Trace Metals Pollution in Sediments of Damietta Branch, Nile River, Egypt

This work appraises the extent of toxic trace metals and seasonal pollution degree in Damietta branch sediments of the River Nile of Egypt. The toxic trace metals Fe, Mn, Cd, Co, Cu, Ni, Pb, and Zn were analysed in sediments from six sites during the summer and winter seasons. The metal concentrations and organic matter were determined using inductively-coupled-plasma mass spectrometry and loss-on-ignition, respectively. Multivariate statistical methods were used in order to allocate the possible metals sources and their relationships in sediments. The seasonal mean sequence of toxic trace metals was: Fe > Mn > Zn > Pb > Cu > Ni > Co > Cd. The mean Cd, Pb, and Zn values exceeded the sediment quality guidelines and average shale and they represent severe potential toxicity for aquatic organisms. Cu and Co were enriched during winter. The geo-accumulation index stipulated that metal pollution degree in the sequence of: Pb > Zn > Cd > Co > Cu > Mn > Ni > Fe. The highest metal pollution index reported in winter in sites S4/S5 and during summer in sites S4–S6. Different agricultural, wastewater discharge, fisheries, and industrial activities, as well as the effect of dilution/concentration during summer/winter seasons, are the main factors that contributed to metal accumulations in Damietta branch sediments. Continuous monitoring and evaluation of toxic trace metal concentrations of the Damietta sediments and similar localities worldwide can help to protect the ecosystem from harmful metal contaminations.

Comparative analysis of chemical composition of some commercially important fishes with an emphasis on various Malaysian diets

This study compares the chemical composition of cockle (Anadara granosa) and some commercially important marine (Asian seabass Lates calcarifer, grouper Epinephelus bleekeri, hardtail scad Megalaspis cordyla, longtail tuna Thunnus tonggol and Indian mackerel Rastrelliger kanagurta) and freshwater (sutchi catfish Pangasius hypophthalmus, Nile tilapia Oreochromis niloticus and eel Monopterus albus) fishes in Peninsular Malaysia. The results show that the proximate composition and trace metal content were significantly different (P < 0.05) among species investigated. The mean protein content was the highest in eel (19.1%) and the lowest in sutchi catfish (13.0%) and cockle (13.0%). The mean lipid content of Indian mackerel (3.9%) was higher than cockle (2.0%), followed by eel (1.3%) and longtail tuna (0.8%). The mean ash content was the highest in Indian mackerel (1.4%) and the lowest in cockle (0.9%). Zinc and manganese contents in cockle (Zn: 61.2 mg kg−1, Mn: 22.7 mg kg−1) were very high compared to other species investigated. The copper content was minimum in sutchi catfish (1.0 mg kg−1) and a maximum in the hardtail scad (11.7 mg kg−1). Trace metal content in sutchi catfish, Nile tilapia, grouper, longtail tuna, eel and cockle followed an order Zn > Mn > Cu, whereas Asian seabass, hardtail scad and Indian mackerel followed a different order Zn > Cu > Mn. Trace metal content in the tissue of the fishes examined was within safe limits for human consumption except Mn content in the cockle and Cu content in the hardtail scad, which is a matter of concern. When considering the daily fish fat, mineral and trace metal intake, marine fishes and shellfish are better than freshwater fishes.

Role of biochar and Eisenia fetida on metal bioavailability and biochar effects on earthworm fitness

Biochar has gained extensive attention due to its remediation role in soil pollution. However, its hazardous effects on the soil fauna in contaminated soil and its remediation efficiency affected by soil organisms are still obscure. The individual and combined effects of biochar and earthworms (Eisenia fetida) on soil properties, metal bioavailability, and earthworm fitness were investigated in historically heavy metal (HM)-contaminated soil. The results showed that biochar increased the soil pH by 0.31, decreased DTPA-extractable Cd, Cu, Zn and Pb contents by 11.9%, 14.3%, 5.27% and 23.8%, respectively, and immobilized the HMs from a bioavailable fraction to a residual fraction. The co-incubation of biochar and E. fetida decreased soil pH by 0.11 and increased DTPA-extractable Cu, Zn, and Pb contents by 3.75%, 20.9% and 4.43%, respectively. The results of the correlation analysis showed that soil pH was significantly negatively correlated with HM bioavailability, and it was a potential factor contributed to this opposite effect. Furthermore, biochar decreased the biomass growth of E. fetida and inhibited the activities of SOD, CAT and GSH in E. fetida by 31.1%, 51.3% and 29.6% after 28 days of incubation. Overall, biochar and E. fetida showed the opposite effects on the soil remediation, and biochar also led to a negative effect on earthworms. These findings provided insights on verifying the actual remediation effects of biochar and its ecological risk in situ soil remediation.

Ecofriendly Approach for Treatment of Heavy-Metal-Contaminated Water Using Activated Carbon of Kernel Shell of Oil Palm

Heavy metal ion contamination in water poses a significant risk to human health as well as to the environment. Millions of tons of agricultural wastes are produced from oil palm plantations which are challenging to manage. In this study, we converted palm kernel shells (PKS) from a palm oil plantation into activated carbon (AC) having a surface area of 1099 m²/g using phosphoric acid as an activator. The prepared material was characterized using BET, XRD, Raman, FESEM and FTIR analyses. The AC was applied for the treatment of heavy-metal-contaminated water, and different parameters; the pH, adsorbent dosage, contact time and metal ion concentrations were varied to determine the optimal conditions for the metal ion adsorption. Different kinetic models; the zeroth, first-order and second-order, and Freundlich and Langmuir isotherm models were used to determine the mechanism of metal ion adsorption by the AC. Under the optimized conditions, Cr⁶⁺ and Pb²⁺ were removed completely, while Zn²⁺ and Cd²⁺ were more than 80% removed. This is a greener approach in which an agricultural waste, PKS is converted into a useful product, activated carbon and subsequently applied for the treatment of heavy metal-contaminated water.

Soil heavy metal contamination assessment in the Hun-Taizi River watershed, China

The Hun-Taizi River watershed includes the main part of the Liaoning central urban agglomeration, which contains six cities with an 80-year industrial history. A total of 272 samples were collected from different land use areas within the study area to estimate the concentration levels, spatial distributions and potential sources of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn) with a geographic information system (GIS), principal component analysis (PCA) and canonical correspondence analysis (CCA). Only the concentration of Cd was over the national standard value (GB 15618–2018). However, the heavy metal concentrations at 24.54%, 71.43%, 63.37%, 85.71, 70.33%, 53.11%, and 72.16% of the sampling points were higher than the local soil background values for As, Cd, Cr, Cu, Hg, Ni, Pb and Zn, respectively, which were used as standard values in this study. The maximal values of Cd (16.61 times higher than the background value) and Hg (12.18 times higher than the background value) had high concentrations, while Cd was present in the study area at higher values than in some other basins in China. Cd was the primary pollutant in the study area due to its concentration and potential ecological risk contribution. The results of the potential ecological risk index (RI) calculation showed that the overall heavy metal pollution level of the soil was considerably high. Three groups of heavy metals with similar distributions and sources were identified through PCA. The results of the CCA showed that the distribution of mines was the strongest factor affecting the distributions of Ni, As, Zn, Pb, and Cd. However, Cu was strongly influenced by the distance to the nearest river. These findings can provide scientific support for critical planning and strategies for soil pollution control and removal to support the sustainable development of the study area.

Lead-contaminated soils with contrasting texture remediated with phosphate: chemical fractionation and chloropyromorphite stability

Pb can be stabilized in soil as Pb-P mineral. The aims of this study were to access the distribution of Pb in organic and mineral fractions of contrasting texture of soil Pb-contaminated and remediated with P and Cl and to evaluate the stability of chloropyromorphite in these soils. A clay loam Oxisol (sandstone) and a clayey Ultisol (basalt) were used in a factorial experiment, with three replications: two soils, two Pb contamination levels, two soil pH values, and four P doses. The Pb concentrations were determined in seven soil phases. Release kinetics of Pb were performed with 0.1 mol L^-1 pH 2.5 citric acid. The transfer of soil Pb to chloropyromorphite was dependent on the level of contamination in the clay loam Oxisol. In the lowest P dose (molar ratios P:Pb 3:5), the main source was the Pb complexed in the organic matter and in the highest P dose (molar ratios P:Pb 12:5) was the Pb adsorbed by inner sphere in gibbsite and kaolinite. The release of Pb in the citric acid was dependent on the texture and mineralogy of the soils. Pb recovery applied to the clay loam Oxisol was around 100% (biphasic kinetic), while for the clayey Ultisol, the recovery ranged from 43 to 52% (single-phase kinetic). Remediation of Pb-contaminated soils with P and Cl is more efficient in clayey and oxidic soils since chloropyromorphite formation is faster and its solubilization is slower, an important combination in environmental terms.

Application of response surface methodology for optimization of zinc elimination from a polluted soil using tartaric acid

Heavy metal wastes generated from mining activities are a major concern in developing countries such as Iran. Increasing concentrations of these metals in the soil make up a severe health hazard due to their non-degradability and toxicity. In this study, batch washing experiments were conducted in order to investigate the removal efficiency of zinc by biodegradable chelates, tartaric acid. For this purpose, soil samples were collected from the zinc contaminated soil in the region of the Angouran, Zanjan, Iran. Hence, optimization of batch washing conditions followed using a three-level central composite design approach based on the response surface methodology. The results demonstrated that the effects of pH, tartaric acid concentration, and interaction between selective factors on the zinc removal efficiency were all positive and significant (P < 0.05). An optimum zinc removal efficiency of 89.35 ±2.12% was achieved at tartaric acid concentration of 200 mM l−1, pH of 4.46, and incubation time of 120 min as the optimal conditions. Accordingly, response surface methodology is appropriately capable to determine and optimize chemical soil washing process to remediate heavy metal polluted soil.