Multiple pollution sources unravelled by environmental forensics techniques and multivariate statistics

Source-oriented health risk of heavy metals in sediments: A case study of an industrial city in China

The heavy metals (HMs) pollution caused by accelerated urbanization poses a significant risk to environmental and human health. Sediments, as an important component of aquatic ecosystems, have become a global environmental problem due to their HMs pollution. In this paper, 53 surface water and sediment samples were carried out in the industrial city of Changzhou to analyze and evaluate the pollution characteristics. A comprehensive source risk source allocation and source health risk integrated method based on positive matrix factorization (PMF) and health risk assessment models is applied. We found that the average concentration of most HMs accumulated in sediments greatly exceeds the soil background value in Changzhou, posing a high ecological risk. Pollution sources contribution to the HMs contents ranked as: electronic industry and mechanical manufacturing (29.18 %) > metal smelting industry (20.97 %) > atmospheric deposition and transportation (20.07 %) > natural source (16.32 %) > agricultural source (13.46 %). The hazard index (HI) values and carcinogenic risk (CR) for adults are within an acceptable risk level range. The average HI for children is 1.589, which is an unacceptable risk. Source-oriented health risks indicate that metal mining is the main source of health risks due to the large number of arsenic emissions from metallurgical processes. This study identified pollution levels, sources, and risks of HMs and can provide supporting information for effective source regulation.

Enhanced remediation of organotin compounds and metal(loid)s in polluted sediments: Chemical stabilization with mining-wastes and nZVI versus physical soil washing

Here we describe two innovative approaches for remediating sediments contaminated with organotin compounds (OTCs, mainly TBT) and metal(loid)s. The first involves chemical stabilization through amendments with nanoscale zero-valent iron (nZVI), dunite mining waste, and coal tailings, materials that have not been previously studied for OTC remediation. The second focuses on physical soil washing, using grain-size separation and magnetic separation to isolate the most polluted fractions, thereby reducing the volume of contaminated material destined for landfills. The results for the first approach indicated that OTC degradation occurred mainly through nZVI application, with concurrent immobilization of As and mobilization of Cu. Furthermore, combining nZVI with coal tailings enhanced OTC degradation whereas dunite mining waste effectively immobilized Zn. In turn, in the second approach, grain-size separation efficiently removed coarse material (>500 μm) with low pollutant concentrations. Subsequent magnetic separation selectively concentrated less than 5% of the initial volume of sediment in a magnetic fraction that showed the highest contaminant content. Therefore, 95% of material revealed lower contaminant concentrations than the feed material. These findings highlight the potential of combining physical soil washing, which significantly reduces the volume of contaminated sediments, with chemical stabilization, which can effectively stabilize the polluted fractions isolated in the physical treatment.

Assessment of parent and alkyl -PAHs in surface sediments of Iranian mangroves on the northern coast of the Persian Gulf: Spatial accumulation distribution, influence factors, and ecotoxicological risks

Spatial patterns, potential origins, and ecotoxicological risk of alkylated (APAH) -and parent -(PPAH) polycyclic aromatic hydrocarbons (PAHs) were studied in mangrove surface sediments along the northern coasts of the Persian Gulf, Iran. The mean total concentrations (ngg-1dw) ∑32PAH, ∑PPAHs and ∑APAHs in sediments were 3482 (1689-61228), 2642 (1109-4849), and 840 (478-1273), respectively. The spatial variability was similar among these PAH groups, with the highest levels occurring in Nayband National Marine Park (NNMP). Physicochemical environmental factors, such as sediment grain size, and total organic carbon (TOC) contents, are significant factors of PAH distribution. These findings suggest that PAH pollution level is moderate-to-high, supporting the current view that mangrove ecosystems are under intensive anthropogenic impacts, such as petrochemical, oil and gas loads, port activities, and urbanization. Non-parametric multidimensional scaling (NPMDS) ordination demonstrated that NNMP mangrove is the critical site exhibiting high loading of PAH pollutants. Here, for the first time in this region, Soil quality guidelines (SQGs), Toxic equivalency quotient (TEQ), Mutagenic equivalency quotient (MEQ), and composition indices comprising Mean maximum permissible concentration quotient (m-MPC-Q), and Mean effect range median quotient (m-ERM-Q) methods were used to have a comprehensive risk assessment for PAH compounds and confirmed medium-to-high ecological risks of PAHs in the study area, particularly in the western part of the Gulf, highlighting the industrial impacts on the environment.

Using unsupervised machine learning models to drive groundwater chemistry and associated health risks in Indo-Bangla Sundarban region

Groundwater is an essential resource in the Sundarban regions of India and Bangladesh, but its quality is deteriorating due to anthropogenic impacts. However, the integrated factors affecting groundwater chemistry, source distribution, and health risk are poorly understood along the Indo-Bangla coastal border. The goal of this study is to assess groundwater chemistry, associated driving factors, source contributions, and potential non-carcinogenic health risks (PN-CHR) using unsupervised machine learning models such as a self-organizing map (SOM), positive matrix factorization (PMF), ion ratios, and Monte Carlo simulation. For the Sundarban part of Bangladesh, the SOM clustering approach yielded six clusters, while it yielded five for the Indian Sundarbans. The SOM results showed high correlations among Ca2+, Mg2+, and K+, indicating a common origin. In the Bangladesh Sundarbans, mixed water predominated in all clusters except for cluster 3, whereas in the Indian Sundarbans, Cl--Na+ and mixed water dominated in clusters 1 and 2, and both water types dominated the remaining clusters. Coupling of SOM, PMF, and ionic ratios identified rock weathering as a driving factor for groundwater chemistry. Clusters 1 and 3 were found to be influenced by mineral dissolution and geogenic inputs (overall contribution of 47.7%), while agricultural and industrial effluents dominated clusters 4 and 5 (contribution of 52.7%) in the Bangladesh Sundarbans. Industrial effluents and agricultural activities were associated with clusters 3, 4, and 5 (contributions of 29.5% and 25.4%, respectively) and geogenic sources (contributions of 23 and 22.1% in clusters 1 and 2) in Indian Sundarbans. The probabilistic health risk assessment showed that NO3- poses a higher PN-CHR risk to human health than F- and As, and that potential risk to children is more evident in the Bangladesh Sundarban area than in the Indian Sundarbans. Local authorities must take urgent action to control NO3- emissions in the Indo-Bangla Sundarbans region.

Brownfield-related studies in the context of climate change: A comprehensive review and future prospects

The global climate change events are expected to augment the vulnerability of persistent organic pollutants within the global brownfield areas to a certain extent, consequently heightening the risk crises faced by these brownfields amidst the backdrop of global environmental changes. However, studies addressing brownfield risks from the perspective of climate change have received limited attention. Nonetheless, the detrimental consequences of brownfield risks are intrinsically linked to strategies for mitigating and adapting to sustainable urban development, emphasizing the critical importance of their far-reaching implications. This relevance extends to concerns about environmental quality, safety, health risks, and the efficacy of chosen regeneration strategies, including potential secondary pollution risks. This comprehensive review systematically surveys pertinent articles published between 1998 and 2023. A selective analysis was conducted on 133 articles chosen for their thematic relevance. The findings reveal that: (1) Under the backdrop of the climate change process, brownfield restoration is necessitated to provide scientific and precise guidance. The integration of brownfield considerations with the dynamics of climate change has progressively evolved into a unified framework, gradually shaping a research paradigm characterized by "comprehensive + multi-scale + quantitative" methodologies; (2) Research themes coalesce into five prominent clusters: "Aggregation of Brownfield Problem Analysis", "Precision Enhancement of Brownfield Identification through Information Technology", "Diversification of Brownfield Reutilization Assessment", "Process-Oriented Approaches to Brownfield Restoration Strategies", and "Expansion of Ecological Service Functions in Brownfield Contexts"; (3) Application methodologies encompass five key facets: "Temporal and Spatial Distribution Patterns of Pollutants", "Mechanisms and Correlations of Pollution Effects", "Evaluation of Pollution Risks", "Assessment of Brownfield Restoration Strategies", and "Integration of Brownfield Regeneration with Spatial Planning". Future brownfield research from the climate change perspective is poised to reflect characteristics such as "High-Precision Prediction, Comprehensive Dimensionality, Full-Cycle Evaluation, Low-Risk Exposure, and Commitment to Sustainable Development".

PAH levels in sediments from a coastal area heavily subjected to anthropogenic pressure (Asturias, north of Spain)

Ninety-two sediment samples collected along the Asturias coastline (north of Spain), were studied based on their concentrations of 16PAHs. Concentrations of Σ16PAH showed an average of 12.650 mg kg-1 d.w., which is higher than most other studies conducted around the world. The origins of PAHs present in the sediments are mainly from fuel combustion in industrial processes. The main source of PAH to the coastal system seems to be the Nalón River, which played a significant past role related to different industrial activities, highlighting thermal power stations located in the basin. On the other hand, the Avilés Estuary, hotspot of the regional heavy metallurgical industry was the area with the highest concentrations of Σ16PAH, with an average of 5 to 6 times higher than the rest studied. The risk assessment of Σ16PAH concentrations in the study area showed a high potential risk of contamination transfer to other environmental compartments.

Environmental bioavailability of arsenic, nickel and chromium in soils impacted by high geogenic and anthropogenic background contents

High arsenic, chromium and nickel in soils can pose a hazard to the ecosystem and/or human health. Large areas can be affected by elevated potentially toxic elements (PTE) background contents, entailing a significant effort for managing the potential risk. Assessing the environmental hazard associated to PTE-contaminated soils requires the determination of soil PTE environmental bioavailability, which reflects the capacity of these elements to be transferred to living organisms. Here we assess the environmental bioavailability of As, Cr and Ni in topsoils from the Liège basin and Belgian Lorraine, two areas in Wallonia, Belgium, affected by elevated As, Cr and Ni background contents. The source of soil As, Cr and Ni differs in Liège and Lorraine: anthropogenic in the former location and geogenic in the latter. The environmental bioavailability of PTE was determined using two complementary approaches: (1) by chemical fractionation with the Community Bureau of Reference (BCR) three-step sequential extraction protocol and (2) by estimating the phytoavailability using a plant-based biotest (Lolium multiflorum as plant model). The results show that total As (6-130 mg·kg-1), Cr (15-268 mg·kg-1), and Ni (8-140 mg·kg-1) contents in the Liège and Lorraine soils frequently exceed the soil clean-up standards. However, no positive correlation was found between the total contents and BCR extraction results or rye-grass contents, except for As in Liège soils. Total As, Cr or Ni contents surpassing soil standards do not necessarily result in elevated mobile, potentially mobilizable and phytoavailable contents. In general, environmental bioavailability of As, Cr and Ni is higher in soils from Liège basin compared to those sampled in Belgian Lorraine. The mobile and potentially mobilizable fractions of As, Cr and Ni account for <30 % of their total contents following the BCR extractions. Our study provides valuable information for sustainable management at the regional scale of soils containing high PTE contents.

Industrial impact on sustainable dairy farms: Essential elements, hazardous metals and polycyclic aromatic hydrocarbons in forage and cow's milk

Sustainable dairy farms are characterised by the self-production of forage for animal feed. These farms are sometimes located near industrial areas, entailing a risk of food chain contamination with hazardous metals and polycyclic aromatic hydrocarbons (PAHs). Accordingly, evaluating the impact of pollution on forage and milk is of great interest. In this study, the effects of industrial factors on sustainable forage from 43 dairy farms and possible correlations between inorganic elements and PAHs were studied. Spearman's correlation and principal component analysis (PCA) were performed for the forage and milk. Most of the inorganic elements in the forage were below the maximum residual limits for cadmium (Cd) and lead (Pb), established in EU 2013/1275 and EU 2019/1869, respectively. However, arsenic (As) and mercury (Hg) levels were above their respective limits in the forage (EU 2019/1869). No milk samples exceeded the maximum residual limits for Pb (EU 488/2014) or Cd (EU 1881/2006) in dairy products. Heavy-weight PAHs (HW-PAHs, four or more aromatic rings) were detected in forage but not in milk. In the forage samples, HW-PAHs were positively correlated with Zn and Cd. In addition, some hazardous metals (chromium (Cr), iron (Fe), As, Hg, and Pb) also were positively correlated with Zn and Cd. Interestingly, no correlations were found between forage pollutants and milk, suggesting that these pollutants have a low transfer rate to milk. The PCA results highlighted the predominant contribution of PAHs to the global variance in forage samples collected at different distances from industrial areas. In milk, the contributions of hazardous metals and PAHs were more balanced than in forages. Finally, when distances to potential pollution sources were included in the PCA of forage samples, a negative correlation was observed between the former and the concentrations of HW-PAHs, Cd, and Zn, suggesting that thermal power plants and steel factory emissions were the main sources of polluting forage in this area.

Trace metals from different anthropic sources on the mid-west coast of Asturias: Concentrations, dispersion and environmental considerations

The central coast of Asturias (Spain), which has suffered significant anthropogenic impacts during the last 150 years, has been studied using 71 sediment samples to establish a preliminary scenario of the geochemical and environmental state of sediments, relating them to their potential sources. In general, As (max 28.5 μg g-1), Cd (max 1.1 μg g-1), Pb (max 123.5 μg g-1) and Zn (max 572 μg g-1) were the elements that presented the greatest concern due to 97.2 % of the sediment samples presented Cd concentrations higher than the regional baseline, 91.5 % of the samples for Zn, 90.1 % for Pb and 78.9 % for As. Additionally, Hg presents a particular case due to the existence of a natural geological anomaly which favours the presence of high concentrations. Nevertheless, anthropic activity contributes with a significant effect on the concentration of this element in the coastal environment.

Magnetic separation for arsenic and metal recovery from polluted sediments within a circular economy

Several metals and metalloids (e.g., As, Cd, Cu, Pb, Zn) are toxic at low concentrations, thus their presence in sediments can raise environmental concern. However, these elements can be of economic interest, and several techniques have been used for their recovery and some of them have been widely applied to mining or to industrial soils, but not to sediments. In this work, wet high-intensity magnetic separation (WHIMS) was applied for As, Cd, Cu, Pb and Zn recovery from polluted sediments. A composite sample of 50 kg was taken in the Avilés estuary (Asturias, North Spain) with element concentrations above the legislation limits. Element distribution was assessed using wet-sieving and ICP-MS analysis, revealing that the 125-500 μm grain-size fraction accounts for the 62 w% of the material and that element concentration in this fraction is lower than in the other grain size fractions. Subsequently, WHIMS was applied at three different voltage intensities for the 125-500 μm and <125 μm fractions, revealing excellent recovery ratios, especially for the coarser material. Furthermore, magnetic property measurements coupled to microscopy analysis revealed that the success of the technique derives from concentrating metal-enriched iron oxides particles (ferro- and para-magnetic material) in a mixture of quartz and other minerals (diamagnetic particles). These results indicate the feasibility of the magnetic separation for metal and metalloid recovery from polluted sediments, and thus offer a double benefit of coastal area restoration and valuable material recovery in the context of a circular economy.

Source apportionment and quantitative risk assessment of heavy metals at an abandoned zinc smelting site based on GIS and PMF models

The abandoned smelters have caused serious hazards to the surrounding environment and residents. Taking an abandoned zinc smelter in southern China as an example, a total of 245 soil samples were collected to study spatial heterogeneity, source apportionment, and source-derived risk assessment of heavy metal(loid)s (HMs) in the region. The results showed that the mean values of all HMs concentrations were higher than the local background values, with Zn, Cd, Pb, and As contamination being the most serious and their plume penetrating to the bottom layer. Four sources were identified by principal component analysis and positive matrix factorization, with their contributions to the HMs contents ranked as: surface runoff (F2, 63.2%) > surface solid waste (F1, 22.2%) > atmospheric deposition (F3, 8.5%) > parent material (F4, 6.1%). Among these, F1 was a determinant source of human health risk with a contribution rate of 60%. Therefore, F1 was considered to be the priority control factor, but it only accounted for 22.2% of HMs contents contribution. Hg dominated the ecological risk with a contribution of 91.1%. Pb (25.7%) and As (32.9%) accounted for the non-carcinogenic risk, while As (95%) dominated the carcinogenic effect. The spatial characteristics of human health risk values derived from F1 indicated that high-risk areas were mainly distributed in the casting finished products area, electrolysis area, leaching-concentration area, and fluidization roasting area. The findings highlight the significance of priority control factors (including HMs, pollution sources and functional areas) for consideration in the integrated management of this region, thus saving costs for effective soil remediation.

Impact of Potentially Toxic Compounds in Cow Milk: How Industrial Activities Affect Animal Primary Productions

Potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) frequently coexist in soils near industrial areas and sometimes in environmental compartments directly linked to feed (forage) and food (milk) production. However, the distribution of these pollutants along the dairy farm production chain is unclear. Here, we analyzed soil, forage, and milk samples from 16 livestock farms in Spain: several PTEs and PAHs were quantified. Farms were compared in terms of whether they were close to (<5 km) or far away from (>5 km) industrial areas. The results showed that PTEs and PAHs were enriched in the soils and forages from farms close to industrial areas, but not in the milk. In the soil, the maximum concentrations of PTEs reached 141, 46.1, 3.67, 6.11, and 138 mg kg^-1 for chromium, arsenic, cadmium, mercury, and lead, respectively, while fluoranthene (172.8 µg kg^-1) and benzo(b)fluoranthene (177.4 µg kg^-1) were the most abundant PAHs. Principal component analysis of the soil PTEs suggested common pollution sources for iron, arsenic, and lead. In the forage, the maximum contents of chromium, arsenic, cadmium, mercury, and lead were 32.8, 7.87, 1.31, 0.47, and 7.85 mg kg^-1, respectively. The PAH found in the highest concentration in the feed forage was pyrene (120 µg kg^-1). In the milk, the maximum PTE levels were much lower than in the soil or the feed forages: 74.1, 16.1, 0.12, 0.28, and 2.7 µg kg^-1 for chromium, arsenic, cadmium, mercury, and lead, respectively. Neither of the two milk samples exceeded the 20 µg kg^-1 limit for lead set in EU 1881/2006. Pyrene was the most abundant PAH found in the milk (39.4 µg kg^-1), while high molecular weight PAHs were not detected. For PTEs, the results showed that soil-forage transfer factors were higher than forage-milk ratios. Our results suggest that soils and forages around farms near industries, as well as the milk produced from those farms, have generally low levels of PTE and PAH contaminants.

Determination of contamination sources and geochemical behaviors of metals in soil of a mine area using Cu, Pb, Zn, and S isotopes and positive matrix factorization

The use of multiple isotopic ratios and statistical methods can substantially increase the reliability and precision of determining contamination sources and pathways. In this study, contamination sources were differentiated in three subareas in one mine area and geochemical processes were investigated using Cu, Pb, Zn, and S isotopes and positive matrix factorization (PMF). Soil samples downstream of the adit seepages exhibited distinctly higher δ⁶⁵Cu values than those from other areas. δ⁶⁵Cu in adit seepages increased substantially from ore sulfides owing to large isotopic fractionation during oxidative dissolution. Although δ⁶⁵Cu decreased during sulfide precipitation in seepage-contaminated soil, the discrimination of δ⁶⁵Cu was still valid. Therefore, δ⁶⁵Cu is particularly useful for differentiating between contamination by sulfides (tailings) and water (adit seepages). Moreover, sulfide precipitation following sulfate reduction was verified by the decreased δ⁶⁶Zn and δ³⁴S in the soil. In addition, the plot of ²⁰⁸Pb/²⁰⁶Pb versus Pb^-1 distinguished contamination sources. Furthermore, PMF analysis confirmed the determination of sources and differentiated between contamination by As- and Cu-enriched tailings. The effect of Cu-enriched tailings further downstream suggested that the lower specific gravity of chalcopyrite compared to that of arsenopyrite affected the distribution of soil contamination.

Occurrence and spatiotemporal distribution of PAHs and OPAHs in urban agricultural soils from Guangzhou City, China

The occurrence of polycyclic aromatic hydrocarbon (PAH) derivatives in the environment is of growing concern because they exhibit higher toxicity than their parent PAHs. This study evaluated the large-scale occurrence and spatiotemporal distribution of 16 PAHs and 14 oxygenated PAHs (OPAHs) in urban agricultural soils from seven districts of Guangzhou City, China. Linear correlation analysis was conducted to explore the relationship between PAH and OPAH occurrence and a series of parameters. The compositional analysis, principal component analysis, diagnostic ratios, and principal component analysis coupled with a multiple linear regression model were used to identify the sources of PAHs and OPAHs in the soils. The average concentrations of ΣPAHs and ΣOPAHs (59.6 ± 31.1-213 ± 115.5 μg/kg) during the flood season were significantly higher than those during the dry season (42.1 ± 13.3-157.2 ± 98.2 μg/kg), which were due to relatively strong wet deposition during the flood season and weak secondary reactions during the dry season. Linear correlation analysis showed that soil properties, industrial activities, and agricultural activities (r = 0.27-0.96, p < 0.05) were responsible for the spatial distribution of PAHs during the dry season. The PAH distribution was mainly affected by precipitation during the flood season. The concentrations of ΣOPAHs were only related to the soil properties during the dry season because their occurrence was sensitive to secondary reactions, climate and meteorological conditions, and their water solubility. Our results further showed that coal combustion and traffic emissions were the dominant origins of PAHs and OPAHs during both the seasons. Wet deposition and runoff-induced transport also contributed to PAH and OPAH occurrence during the flood season. The results of this study can improve our understanding of the environmental risks posed by PAHs and OPAHs.

Analysis of driving factors of spatial distribution of heavy metals in soil of non-ferrous metal smelting sites: Screening the geodetector calculation results combined with correlation analysis

Heavy metals (HMs) discharged from smelting production may pose a major threat to human health and soil ecosystems. In this study, the spatial distribution characteristics of HMs in the soil of a non-ferrous metal smelting site were assessed. This study employed the geodetector (GD) by optimizing the classification condition and supplementing the correlation analysis (CA). The contribution of driving factors, such as production workshop distributions, hydrogeological conditions, and soil physicochemical properties, to the distribution of HMs in soil in the horizontal and vertical dimensions was assessed. The results showed that the main factors underlying the spatial distribution of As, Cd, Hg, Pb, Sb, and Zn in the horizontal direction were the distance from the sintering workshop (the maximum q value of that factor, q=0.28), raw material yard (q=0.14), and electrolyzer (q=0.29), while those in the vertical direction were the soil moisture content (q=0.17), formation lithology (q=0.12), and soil pH (q=0.06). The findings revealed that the CA is a simple and effective method to supplement the GD analysis underlying the spatial distribution characteristics of HMs at site scale. This study provides useful suggestions for environmental management to prevent HMs pollution and control HMs in the soil of non-ferrous metal smelting sites.

Antagonistic Cd and Zn isotope behavior in the extracted soil fractions from industrial areas

The remobilization of metals accumulated in contaminated soils poses a threat to humans and ecosystems in general. Tracing metal fractionation provides valuable information for understanding the remobilization processes in smelting areas. Based on the difference between the isotopic system of Cd and Zn, this work aimed to couple isotope data and their leachability to identify possible remobilization processes in several soil types and land uses. For soil samples, the δ^66/64Zn values ranged from 0.12 ± 0.05‰ to 0.28 ± 0.05‰ in Avilés (Spain) and from - 0.09 ± 0.05‰ to - 0.21 ± 0.05‰ in Příbram (Czech Republic), and the δ^114/110Cd ranged from - 0.13 ± 0.05‰ to 0.01 ± 0.04‰ in Avilés and from - 0.86 ± 0.27‰ to - 0.24 ± 0.05‰ in Příbram. The metal fractions extracted using chemical extractions were always enriched in heavier Cd isotopes whilst Zn isotope systematics exhibited light or heavy enrichment according to the soil type and land uses. Coupling Zn and Cd systematics provided a tool for deciphering the mechanisms behind the remobilization processes: leaching of the anthropogenic materials and/or metal redistribution within the soil components prior to remobilization.

Metal(loid) concentrations, bioaccessibility and stable lead isotopes in soils and vegetables from urban community gardens

Community gardens are "green oases" of recent cities with many benefits for human society. From a human health perspective, these benefits can be damaged by chemical contamination of soil and cultivated vegetables. Using geochemical approaches, this study characterised (i) total metal(loid) concentrations in soils and two commonly grown vegetables in urban community gardens (Bratislava, Slovakia), (ii) gastrointestinal bioaccessibility using a modified physiologically based extraction test (PBET), and (iii) stable lead (Pb) isotopes in order to identify sources of metal(loid)s, solubilisation in the human body and migration of Pb from soil to vegetables. While some soils could be considered contaminated when compared to the Slovak legislation for agricultural soil, the bioaccessibility of metal(loid)s did not exceed 20% in the intestinal phase, with the exception of cadmium (Cd). Tomatoes and lettuce contained low total and bioaccessible concentrations of metal(loid)s, being safe for people who consume their own grown vegetables. There were differences in Pb isotope composition among bulk soils, vegetables and bioaccessible Pb, with less radiogenic Pb being preferentially mobilised. Statistical methods considering the compositional nature of the geochemical data and the enrichment factor (EF) distinguished well metal(loid)s of natural origin (As, Co, Cr, Fe, Mn, Ni, V) from those with anthropogenic contributions. This research has shown the usefulness of integrating different methodologies to better understand the geochemistry of metal(loid)s in urban soils with their highly diversified sources.

Goethite-based carbon foam nanocomposites for concurrently immobilizing arsenic and metals in polluted soils

Although different amendments have been used for the immobilization of metals and metalloids in contaminated soils, in most of them there are still important challenges that need to be faced in order to achieve an optimal result. In this work, a new material based on a carbon foam impregnated with goethite nanoneedles has been developed with the aim of evaluating its effect on the mobility and availability of As, Cd, Cu, Pb and Zn in an industrial soil. For this purpose, leaching, sequential extraction and phytotoxicity studies have been carried out. The results were compared with the same carbon foam without goethite impregnation. When the soil was treated with goethite-based carbon foam nanocomposite, the mobility of metal(loid)s was markedly reduced, with the exception of Zn, which showed moderate immobilization. The presence of acid groups on the surface of the carbon foam, together with a high surface area, led to a strong immobilization of pollutants. Moreover, the modification of the foams using goethite nanoneedles, imply that the novel nanocomposite obtained is effective to remediate simultaneously metal and metalloid-polluted soils, without any relevant effect on soil toxicity.