Lead isotopes in environmental sciences: a review

Do efflorescent salts from worn lead-acid automotive batteries represent potential non-exhaust emissions to urban pollution? A Pb isotope perspective

Automotive lead-acid batteries have been used for decades, and despite the development of alternative battery technologies, they are still widely used around the world, especially in developing countries. Several studies on the production, recycling, and environmental impact of the lead-acid battery industry have been carried out; however, the contribution of batteries used in operating vehicles to urban pollution (i.e., non-exhaust emission) remains unexplored. Worn lead-acid batteries trigger the formation of efflorescent salts containing potentially toxic elements that precipitate on battery terminals, which could be dispersed during vehicle transport. This research focused on determining the nature of Pb associated with this type of efflorescent salts to identify the sources that influence Pb in the urban dust of Hermosillo city, northwestern Mexico. Pb isotope systematics was used to determine the anthropogenic end-member contributing to the composition of urban dust. Pb isotope data of efflorescent salts revealed less-radiogenic compositions. The findings of this research highlight that efflorescent salts related to acid-lead batteries may represent an anthropogenic source of contaminants associated with non-exhaust emissions. The contribution of efflorescent salts potentially influences the Pb isotope compositions of urban dust and may help to understand Pb inputs from non-exhaust emissions to urban dust.

Coupling metal concentrations and drift simulations for tracing emissions from offshore wind farms

During the last decade offshore wind energy production has become an important source of renewable energy. To ensure safe operation during the lifetime of an offshore wind turbine, the steel structures need to be protected against corrosion. This work evaluates potential metal emissions and environmental impacts from galvanic anodes used for corrosion protection of offshore wind farms (OWFs) by applying a novel multi-tracer approach. A total of 235 surface water samples from different German North Sea OWFs were taken between 2016 and 2022 and analyzed for their concentration of 32 metals via online preconcentration/matrix removal ICP-MS/MS. The concentrations were assessed for temporal and spatial trends with an emphasis on the previously proposed OWF tracers Al, Cd, Pb, Zn, Ga and In. By comparing patterns of In concentrations and Gd anomalies together with modelled drift trajectories of water masses, a differentiation of riverine and OWF-induced metal load was achieved. Results suggest that elevated In concentrations may be linked to OWF corrosion protection systems. Other metal concentrations remained within natural variability. This study demonstrates that the applied tracer approach is effective in identifying OWF-induced metal emissions. Furthermore, it highlights the necessity for long-term monitoring of these tracers to further investigate this emerging source of contamination.

Local honey reflects environmental changes in metal concentrations and lead isotope ratios during COVID-19 restrictions in Brussels, Belgium, and Vancouver, Canada

Effective methods for measuring sudden environmental changes are crucial for understanding how cities respond to shifts in human activity. This study examines atmospheric metal outputs during the COVID-19 restrictions using honey samples collected from three land use types in Brussels Capital Region (BCR), Belgium, and Metro Vancouver Regional District (MVRD), Canada to study changes as the result of restrictions. By comparing these cities with distinct sizes, ages, and structures, we assess how urban environments responded to pandemic-induced restrictions. We present honey samples, analyzed for metal concentration and Pb isotope ratios, to provide insights into the impacts of reduced human activity in different land use types. In BCR, significant increases of Al, Cd, Cr, Cu, Fe, Ni, Pb, Ti, and V were observed in suburban sites, while in MVRD, significant decreases of Cr, Pb, Sb, Ti, and V were observed in suburban sites. The increase in metal concentrations in BCR suburban sites indicates a shift in metal emission patterns due to changes in human activity during the restrictions. Conversely, the decrease in metal concentrations in MVRD suburban areas aligns with expectations of reduced pollution during restrictions. Pb isotope ratios of BCR vary more widely and do not show any spatial trends by land use, suggesting that Pb concentrations in BCR may be more homogenized. In MVRD, significant differences in 208Pb/206Pb were observed during the restrictions, wherein honey sampled from rural sites had more radiogenic (lower 208Pb/206Pb) Pb isotope ratios. This difference suggests that honey may be more sensitive to Pb isotope ratio changes in environments with a less extensive history of metal use, such as rural British Columbia. This research demonstrates the potential of honey as a biomonitor for sudden environmental shifts. This study contributes to a global geochemical honey database, enabling tracking of environmental trends across diverse urban settings worldwide.

Accessing the Past: A Sediment Core Revealing Anthropogenic Impacts of Technology-Critical Elements on the Marine Environment

One group of elements attracting more and more attention are so-called technology-critical elements (TCEs). In comparison with legacy pollutants, the anthropogenic impact of TCEs on the environment might still be minor, but various applications introduce them to the most remote places in the world including the marine environment. One area prone to pollution is the Baltic Sea, partly due to the lack of water exchange with the North Sea. In this study, a sediment core from the German Baltic Sea was used to analyze a total of 42 elemental mass fractions. Based on radiometric dating of 210Pb and 137Cs, results were classified in a recent (2020-2000) and a past period (< 1920), calculating background concentrations based on the Median + 2 Median Absolute Deviation (M2MAD) and the Tukey Inner Fence (TIF). Six legacy pollutants (Ni, Cu, Zn, As, Cd, Pb) and six TCEs (Ga, Ge, Nb, La, Gd, Ta) are discussed in detail. Anthropogenic impacts of both groups were assessed, and local enrichment factors were calculated showing an increase for the legacy pollutants (past period (≤ 0.8); recent period (≥ 1.2)), but also a minor increase for Ga, Ge and Nb (past period (0.9); recent period (1.1)). Values ≥ 1.5, indicating anthropogenic impact, were found for Cu, Zn, Cd and Pb, but also for Ge. Proposed background values may be considered as baseline for future studies.

Wildlife trade investigations benefit from multivariate stable isotope analyses

The investigation of wildlife trade and crime has benefitted from advances in technology and scientific development in a variety of fields. Stable isotope analysis (SIA) represents one rapidly developing approach that has considerable potential to contribute to wildlife trade investigation, especially in complementing other methods including morphological, genetic, and elemental approaches. Here, we review recent progress in the application of SIA in wildlife trade research to highlight strengths, shortcomings, and areas for development in the future. SIA has shown success in species identification, determination of geographic provenance, and differentiating between captive-bred and wild individuals. There are also emerging applications of SIA in wildlife trade research including the use of labelling for traceability, more in-depth analyses such as compound specific isotope analysis (CSIA), the use of trace metal isotopes, and monitoring the health of individuals (e.g. dietary history and nutritional status). While these applications have shown the utility of SIA in wildlife trade investigations, there are a number of limitations and issues where standardisation of analytical procedures would improve the comparability and interpretation of results. First, there is high variation within many stable isotopes geographically and within tissues - this variation presents opportunities for tracking and monitoring but can also challenge detection of patterns when variation is high. Second, the choice of isotopes and tissues within an organism (and ideally, multiple isotopes and tissues) should be considered carefully as different isotopes and tissue types have variable strengths and weaknesses depending on the research question. Third, validation of SIA methods remains underutilised in the field but is critical for applying SIA broadly to wildlife trade investigations and, particularly, for applications in forensics and in court. Fourth, standards are essential for comparisons across studies. Fifth, while some reference databases exist for the use of SIA in wildlife trade research (e.g. ivory), there are still few comprehensive reference databases available. Development of robust reference databases should be a priority for advancing the use of SIA in wildlife trade research, and ecological study more broadly. Ultimately, further recognition of these primary challenges (and development of solutions) within wildlife SIA research will improve the potential for this technique in tackling the threat of overexploitation to global biodiversity - particularly in concert with the application of other investigative techniques such as genetics and elemental analysis.

Anthropogenic Lead (Pb) deposition history of the western Indian Ocean from coral-based Pb/Ca ratio and Pb isotope records

Despite the rapid industrial growth and urban expansion along the coastline of the Western Indian Ocean, knowledge of both historical and current levels of anthropogenic lead (Pb) contamination, as well as its impact on the biosphere, remains limited compared to other industrialized regions. We present a twenty-four year long coralline record (1989-2013) of Pb/Ca ratio and Pb isotopes from the Lakshadweep coral reef in the Western Indian Ocean. This new record provides critical insight into source(s), possible transport pathways, and temporal trends in Pb deposition during the studied interval. The long-term trend in the surface seawater Pb concentration ([Pb]SW), reconstructed from the coralline Pb/Ca record, reveals almost doubling in [Pb]SW from ~50 pmol/kg in the year 1990 to ~107 pmol/kg in the year 2013. Bayesian mixing model calculations reveal that among the potential Pb polluting sources to this region, anthropogenic aerosol from the hinterland of the continents was the dominant contributor of Pb (23-89 %). A compilation of available Pb records from the Indian Ocean reveals that Pb isotope distribution patterns in the western and central equatorial Indian Oceans are distinctly different from those observed in the eastern Indian Ocean. The western Indian Ocean records exhibit lower Pb isotope ratios (206Pb/207Pb and 208Pb/207Pb) compared to the East Indian Ocean, suggesting a greater influence of anthropogenic Pb on seawater concentration. These findings highlight the spatio-temporally spread of anthropogenic Pb pollution and its potential impact on the biosphere in the Indian Ocean and therefore emphasize the urgent need for region-specific environmental management strategies. PLAIN LANGUAGE SUMMARY: This study reconstructs the history of lead (Pb) pollution in the Western Indian Ocean. We analyzed a specimen of coral, collected from Lakshadweep, to create a 24-year-long (years 1989 to 2013) for Pb concentration and isotopic composition of seawater in the Western Indian Ocean. Using the coralline Pb/Ca ratio and Pb isotope data, we have reconstructed surface ocean Pb concentration ([PbSW]) and isotopic composition to understand the sources, transport pathways, and temporal depositional trends over the western Indian Ocean during the past two decades. This reconstruction of [PbSW] reveals a doubling from ~50 pmol/kg in the year 1990 to ~107 pmol/kg in the year 2013. Our investigations to fingerprint the Pb source(s) to our study area reveal that majority of the anthropogenic Pb has been contributed by aerosol deposition sourced from the hinterland of the surrounding continents. Our investigation also revealed that the western Indian Ocean is more contaminated by anthropogenic Pb compared to the eastern Indian Ocean. These findings highlight the need for region-specific monitoring efforts in the Indian Ocean as well as the formulation of environmental strategies to mitigate the impact of Pb pollution.

Source apportionment and emission projections of heavy metals from traffic sources in India: Insights from elemental and Pb isotopic compositions

The study investigates the sources of metals in urban road dusts using elemental concentration and Pb isotopic ratios. The elemental concentrations are also utilized to determine the present heavy metal emissions as well as projected emissions till 2045. Bayesian mixing model for source apportionment highlights the significant contributions of both exhaust and non-exhaust sources to the metal-enriched urban road dusts, with each contributing approximately 40 %. Emission analysis reveals that India's projected electric vehicle (EV) penetration may not be sufficient to suppress the metal emissions from vehicular exhausts. Further challenge is posed by high metal concentrations in the non-exhaust sources, that dominates the emission of some metals compared to exhaust sources. If the metal concentrations remain unchanged, the emission analysis predicts alarming increases in total emissions from all the exhaust and non-exhaust sources by 174 %, 176 %, 163 % and 184 % for Ni, Cu, Zn and Pb, respectively, from 2022 to 2045. Thus, it is crucial to reduce the metal concentrations in traffic emission sources and also impose better regulatory measures to improve the urban metal pollution scenario.

Tracing the impact of former uranium mine sites using stable Pb isotopes: A review

Tracing pollution originating from uranium (U) mining activities is a key challenge due to the diversity of U sources (geochemical background versus U-ore) and its daughter radionuclides. Among the available tracers that can be used to highlight the impact of these activities on the environment, the application of Pb stable isotopes is relevant. This paper is an overview of the use of Pb isotopes for tracing U-mining impacts due to mining and milling activities. For this purpose, this work outlines the different Pb isotope sources in the environment with a focus on the primary U-rich ores until the mineralized area. This information is an important prerequisite for the understanding of Pb fate during the physical and chemical processing of U-ores. Moreover, an important review regarding the Pb isotope composition of the different types of U mining waste is carried out. Finally, an additional part of analytical procedures including sample preparation and Pb isotopic analysis are also be presented.

A crustal Pb isotope map of southeastern Australia

Lead isotopes are a powerful geochemical tracer and a popular tool applied across a broad range of scientific fields, e.g., earth sciences, archaeology, and forensic sciences. Here we present a Pb isotope dataset collected from 232 igneous samples, spanning a ca. 2.3 million km2 area in southeastern Australia, and over 3 billion years of Earth history. This contribution provides a range of isotopic maps showing the spatial variability of Pb isotopes (206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb), magma source U/Pb and Th/U, and model ages. The samples selected for this study encompass U- and Th-poor media (i.e., K-feldspar), and U- and Th-bearing sampling media (i.e., whole-rock), providing a temporally and spatially resolved image of U and Th distribution in the crust, and their influence on crustal Pb through radiogenic ingrowth. This dataset has the potential to benefit a wide variety of different disciplines and is an important resource for addressing earth science questions ranging from unravelling crustal differentiation and architecture, through tracing magma source U- and Th-enrichment, to mineral deposit genesis.

High precision blood lead radiogenic isotope signatures in a community exposed to Pb contaminated soils and implications for the current Pb exposure of the European population

Our study provides the most comprehensive dataset for high-precision radiogenic isotopes of lead (Pb) in blood for the western European population. It investigates their potential for elucidating the contribution of soil Pb to blood Pb using a human biomonitoring survey involving 81 adults and 4 children living in the urban area of Liège (Belgium). Soils in the area show moderate (median of 360 mg/kg) to high (95th percentile of 1000 mg/kg) Pb concentrations, due to former metal processing activities. Blood lead levels (BLL) measured in the study population are, on average, quantitatively consistent with a ∼ 20 % increase due to the exposure to Pb from soils, as estimated by a single-compartment biokinetic model. Consistently, its isotopic composition does not represent an endmember that fully accounts for the variability of Blood lead isotope (BLI) compositions measured in the study population. While some individuals show more thorogenic BLI ratios (relatively more enriched in 208Pb), which could be consistent with a greater exposure to local soils and/or by their country of birth, the BLI data mostly follow a trend roughly parallel to the European Standard Lead Pollution (ESLP) line, within the European leaded gasoline field, even two decades after the withdrawal of this source. Differences in BLI are probably associated with factors related to the presence of Pb in dwellings (pipes, paint) and drinking water distribution system, suggesting that the anthropogenic Pb in use, relevant to human exposure, may contain ore components of different origins, including the Australian Pb ore signature.

Cadmium contamination in sediments from a mangrove wetland: Insights from lead isotopes

Cadmium (Cd) pollution has gained significant attention in mangrove sediments due to its high toxicity and mobility. However, the sources of Cd and the factors influencing its accumulation in these sediments have remained elusive. In this study, we utilized lead (Pb) isotopic signatures for the first time to assess Cd contamination in mangrove sediments from the northern region of the Beibu Gulf. A strong correlation was observed between Cd and Pb concentrations in the mangrove sediments, suggesting a shared source that can be estimated using Pb isotopic signatures. By employing a Bayesian mixing model, we determined that 70.1 ± 8.2 % of Cd originated from natural sources, while 12.9 ± 4.9 %, 9.8 ± 3.7 %, and 7.1 ± 3.4 % were attributed to agricultural activities, non-ferrous metal smelting, and coal combustion, respectively. Our study clearly suggests that natural Cd could also dominate the high Cd content. Agricultural activities were the most important anthropogenic Cd sources, and the increased anthropogenic Cd accumulation in mangrove sediment was related to organic matter. This study introduces a novel approach for assessing Cd contamination in mangrove sediment, providing useful insights into Cd pollution in coastal wetlands.

An electrochemiluminescence device for visualized detection of lead in practical samples

Lead (Pb2+) pollution poses a significant threat to human health due to its potential accumulation through the food chain. In response to this challenge, an array of electrochemiluminescence (ECL) devices has been developed for the accurate and visualized detection of trace Pb2+, achieving an ultra-low limit of detection (LOD) of 9.8 pg L-1. The device utilizes a Pb2+-specific aptamer DNA chain, modified on gold nanoparticles (AuNPs), to create an efficient ECL probe. The integration of this ECL probe into an indium tin oxide (ITO) substrate results in a Pb2+ specific array device. With the assistance of an up-response ECL imaging system, this setup enables the accurate and visualized determination of trace Pb2+, not only in standard solution containing interference ions, but also in practical samples of Lycium ruthenicum Murr., Glycyrrhiza uralensis and lake water. This work advances the visual detection of Pb2+ using ECL-based technology, demonstrating significant potential for enhancing food safety.

Traceability and dispersion of highly toxic soluble phases from historical mine tailings: insights from Pb isotope systematics

Dispersion of potentially toxic elements associated with efflorescent crusts and mine tailings materials from historical mine sites threaten the environment and human health. Limited research has been done on traceability from historical mining sites in arid and semi-arid regions. Pb isotope systematics was applied to decipher the importance of identifying the mixing of lead sources involved in forming efflorescent salts and the repercussions on traceability. This research assessed mine waste (sulfide-rich and oxide-rich tailings material and efflorescent salts) and street dust from surrounding settlements at a historical mining site in northwestern Mexico, focusing on Pb isotope composition. The isotope data of tailings materials defined a trending line (R2 = 0.9); the sulfide-rich tailings materials and respective efflorescent salts yielded less radiogenic Pb composition, whereas the oxide-rich tailings and respective efflorescent salts yielded relatively more radiogenic compositions, similar to the geogenic component. The isotope composition of street dust suggests the dispersion of tailings materials into the surroundings. This investigation found that the variability of Pb isotope composition in tailings materials because of the geochemical heterogeneity, ranging from less radiogenic to more radiogenic, can add complexity during environmental assessments because the composition of oxidized materials and efflorescent salts can mask the geogenic component, potentially underestimating the influence on the environmental media.

Sphagnum moss and peat comparative study: Metal release, binding properties and antioxidant activity

Peat is the main constituent of cultivation substrates and a precious non-renewable fossil material. Peatlands provide important ecosystem services and allow the absorption and storage of carbon. Protecting peatlands helps tackle climate change and contributes to biodiversity conservation. Due to its importance, it is necessary to implement strategies to reduce the use of peat, such as replacing it with biomass-based alternative growing media constituents, such as Sphagnum moss. In this study, we compared the metal release and binding properties at two different pH, antioxidant activity, and total phenolic content of peat and Sphagnum moss from the Tierra del Fuego (TdF) region of southern Patagonia. Levels of the elements were determined by inductively coupled plasma mass spectrometry (ICP-MS), while the types and amounts of functional groups were characterized and compared using Fourier transform infrared (FTIR) spectroscopy. The total phenol level and antioxidant capacity were assessed using the Folin-Ciocalteu method and 2,2-diphenyl-1-picrylhydrazyl test. There are generally higher concentrations of leachable elements in peat than in Sphagnum moss at pH = 2, except Cs, Rb, Ti, and Zr. In contrast, at pH = 5, levels of all leached elements are highest in Sphagnum moss. Sphagnum moss shows a higher metal adsorption capacity than peat, except for Be, Mn, Tl, and Zn. Finally, the results showed that both matrices contained similar total phenolic contents: 0.018 ± 0.011 mg gallic acid equivalent (GAE) per gram dry sample for peat and 0.020 ± 0.007 mg GAE g-1 for Sphagnum moss. Instead, Sphagnum moss extracts showed a significantly higher antioxidant activity [0.026 ± 0.028 mmol Trolox equivalents (TE) g-1] than that estimated in peat (0.009 ± 0.005 mmol TE g-1). Humic acids, carboxylic acids, and phenolic and lignin groups were identified as the functional groups that mainly determined the antioxidant activity of the Sphagnum moss compared to peat. The present study resulted in an advancement of knowledge of these materials for more thoughtful future use and possible replacements.

Elevated lead mobility in sediments of a eutrophic drinking water reservoir during spring and summer seasons: Insights from isotopic signatures

Lead (Pb) pollution in sediments remains a major concern for ecosystem quality due to the robust interaction at the sediment/water interface, particularly in shallow lakes. However, understanding the mechanism behind seasonal fluctuations in Pb mobility in these sediments is lacking. Here, the seasonal variability of Pb concentration and isotopic ratio were investigated in the uppermost sediments of a shallow eutrophic drinking lake located in southeast China. Results reveal a sharp increase in labile Pb concentration during autumn-winter period, reaching ∼ 3-fold higher levels than during the spring-summer seasons. Despite these fluctuations, there was a notable overlap in the Pb isotopic signatures within the labile fraction across four seasons, suggesting that anthropogenic sources are not responsible for the elevated labile Pb concentration in autumn-winter seasons. Instead, the abnormally elevated labile Pb concentration during autumn-winter was probably related to reduction dissolution of Fe/Mn oxides, while declined labile Pb concentration during spring-summer may be attributed to adsorption/precipitation of Fe/Mn oxides. These large seasonal changes imply the importance of considering seasonal effects when conducting sediment sampling. We further propose a solution that using Pb isotopic signatures within the labile fraction instead of the bulk sediment can better reflect the information of anthropogenic Pb sources.

Spatiotemporal and multi-isotope assessment of metal sedimentation in the Great Lakes

This study investigates spatiotemporal dynamics in metal sedimentation in the North American Great Lakes and their underlying biogeochemical controls. Bulk geochemical and isotope analyses of n = 72 surface and core sediment samples show that metal (Cu, Zn, Pb) concentrations and their isotopic compositions vary spatially across oligotrophic to mesotrophic settings, with intra-lake heterogeneity being similar or higher than inter-lake (basin-scale) variability. Concentrations of Cu, Zn, and Pb in sediments from Lake Huron and Lake Erie vary from 5 to 73 mg/kg, 18-580 mg/kg, and 5-168 mg/kg, respectively, but metal enrichment factors were small (<2) across the surface- and core sediments. The isotopic signatures of surface sediment Cu (δ65Cu between -1.19‰ and +0.96‰), Zn (δ66Zn between -0.09‰ and +0.41‰) and Pb (206/207Pb from 1.200 to 1.263) indicate predominantly lithogenic metal sourcing. In addition, temporal trends in sediment cores from Lake Huron and Lake Erie show uniform metal concentrations, minor enrichment, and Zn and Pb isotopic signatures suggestive of negligible in-lake biogeochemical fractionation. In contrast, Cu isotopic signatures and correlation to chlorophyll and macronutrient levels suggest more differentiation from source variability and/or redox-dependent fractionation, likely related to biological scavenging. Our results are used to derive baseline metal sedimentation fluxes and will help optimize water quality management and strategies for reducing metal loads and enrichment in the Great Lakes and beyond.

Pb isotopic fingerprinting of uranium pollution: New insight on uranium transport in stream-river sediments

Uranium mill tailings (UMT) present a significant environmental concern due to high levels of radioactive and toxic elements, including uranium (U), thorium (Th), and lead (Pb), which can pose serious health risks to aquatic ecosystems. While Pb isotopic tracers have been widely utilized in environmental studies to identify elemental sources and geological processes, their application in U geochemistry remains relatively limited. In this study, we investigate the distribution and migration of U in stream-river sediments surrounding a decommissioned U hydrometallurgical area, employing Pb isotopes as tracers. Our findings reveal significant enrichment and ecological risk of U, Pb, and Th in the sediments. Uranium predominantly associates with quartz and silicate minerals, and its dispersion process is influenced by continuous leaching and precipitation cycles of typical U-bearing minerals. Furthermore, we establish a compelling positive relationship (r2 = 0.97) between 208Pb/207Pb and 206Pb/207Pb in the stream-river sediments and sediment derived from UMT. Application of a binary Pb mixing model indicates that anthropogenic hydrometallurgical activities contribute to 2.5-62.7% of the stream-river sediments. Notably, these values are lower than the 6.6-89.6% recorded about 10 years ago, prior to the decommissioning of the U hydrometallurgical activity. Our results underscore the continued risk of U pollution dispersion even after decommission, highlighting the long-term environmental impact of UMT.

Characterization of the inhalable fraction (< 10 μm) of soil from highly urbanized and industrial environments: magnetic measurements, bioaccessibility, Pb isotopes and health risk assessment

Soil in urban and industrial areas is one of the main sinks of pollutants. It is well known that there is a strong link between metal(loid)s bioaccessibility by inhalation pathway and human health. The critical size fraction is < 10 μm (inhalable fraction) since these particles can approach to the tracheobronchial region. Here, soil samples (< 10 μm) from a highly urbanized area and an industrialized city were characterized by combining magnetic measurements, bioaccessibility of metal(loids) and Pb isotope analyses. Thermomagnetic analysis indicated that the main magnetic mineral is impure magnetite. In vitro inhalation analysis showed that Cd, Mn, Pb and Zn were the elements with the highest bioaccessibility rates (%) for both settings. Anthropogenic sources that are responsible for Pb accumulation in < 10 μm fraction are traffic emissions for the highly urbanized environment, and Pb related to steel emissions and coal combustion in cement plant for the industrial setting. We did not establish differences in the Pb isotope composition between pseudo-total and bioaccessible Pb. The health risk assessment via the inhalation pathway showed limited non-carcinogenic risks for adults and children. The calculated risks based on pseudo-total and lung bioaccessible concentrations were identical for the two areas of contrasting anthropogenic pressures. Carcinogenic risks were under the threshold levels (CR < 10-4), with Ni being the dominant contributor to risk. This research contributes valuable insights into the lung bioaccessibility of metal(loids) in urban and industrial soils, incorporating advanced analytical techniques and health risk assessments for a comprehensive understanding.

Entrapment of atmospheric particle bound heavy metals by ferns as evidenced by lead (Pb) isotope and MixSIAR: Implications for improving air quality

Plant metal uptake can occur through both soil-root and atmospheric transfer from leaves. The latter holds potential implications for development of biofiltration systems. To explore this potential, it is crucial to understand entrapment capacity and metal sources within plants. As ferns absorb materials from atmosphere, this study focuses on two abundant fern species growing in densely populated and highly polluted regions of Eastern India. Gravimetric quantification, elemental concentration and Pb isotopic analyses were performed by segregating the ferns into distinct components: foliage dusts (loose dust (LD) and wax-bound dust (WD)) and plant tissue (leaves and roots). To understand metal sources, the study analyzes soil, and atmospheric particulates (PM10 and dust fall (DF)). Results indicate that, while LDs have soil dust influence, wax entraps atmospheric particulates and translocates them inside the leaves. Furthermore, roots demonstrate dissimilar isotopic ratios from soil, while displaying close association with atmospheric particulates. Isotopic composition and subsequent mixing model reveal dominant contribution from DF in leaves (53-73%) and roots (33-86%). Apart from DF, leaf Pb is sourced from PM10 (21-38%) with minimal contribution from soil (6-10%). Conversely, in addition to dominance from DF, roots source Pb primarily from soil (12-62%) with a meagre 2-8% contribution from PM10.

Assessment of particulate Zn and Pb sources in the Orne watershed (Northeast France) using geochemical tools

The Orne River, a tributary of the Moselle River, was highly impacted by industrial activities for more than one century. Land use along the Orne River is highly contrasted, with local specificity from its source to its junction with the Moselle River. The intense industrial activity left behind tons of steelmaking wastes (SMW) on the land surface and within the Orne riverbed. To assess the sources of particulate Zn and Pb transported as suspended sediment in the Orne River, different sets of samples from likely Zn- and Pb-bearing particle sources within the Orne watershed were collected. Three sets of samples were taken from potential sources representing detrital, urban, and inherited industrial particles. Mineralogy, element contents, and Zn and Pb isotope compositions were obtained to characterize and reveal the fingerprint of each set of samples. Soil samples were collected on distinct geomorphological areas characterized by different soil types and land uses. They all display detrital minerals assigned to the geological background. Urban dusts and steelmaking residues display specific mineral phases (sulfates and iron oxides, respectively). Element compositions present strong discrepancies between the distinct sets of samples. SMWs are particularly enriched in Fe, Zn, and Pb. Concerning isotopic composition, SMWs exhibit δ66Zn values ranging from - 0.67 to 1.66‰. Urban samples display δ66Zn values between - 0.11 and 0.13‰, and soils present δ66Zn values between - 0.24 and 0.47‰. The 206Pb/204Pb ratio was estimated to range from 17.550 to 18.807 for soils, from 17.973 to 18.219 for urban samples, and from 18.313 to 18.826 for SMWs. For each of the three sets of samples (soils, urban, industrial), variations of geochemical fingerprint were observed. For soils, the relatively large variations of Zn and Pb isotopic compositions were attributed to distinct land use and the contribution of atmospheric deposition. For industrial samples, the variations were more intense and may be attributed either to distinct industrial processes in the production of pig iron or to distinct furnace-flume treatment modes. The three sets of samples (urban, industrial, and detrital) could be distinguished based on Zn and Pb contents and isotopes. Finally, this study not only highlighted the sources that released particulate Zn and Pb into the Orne River system, it also demonstrated that urban particles are well defined in terms of Zn and Pb isotopic signatures, and those isotopic signatures could be extrapolated to other case studies.

Differentiating anthropogenic effects from natural metal(loid) levels in residential soil near a zinc smelter in South Korea

Metal(loid)s pose a significant hazard due to inherent toxicity. Individuals are particularly exposed to metal(loid)s in soil through direct or indirect contact. Identifying metal(loid) sources in soil is required for exposure mitigation to anthropogenic metal(loid)s, while metal(loid)s are natural constitutes of soil. Metal(loid) concentrations and Pb isotopes were determined in residential soil profiles impacted by a Zn smelter to distinguish the anthropogenic effect from natural levels. One hundred sixty-nine core soil samples were collected from depths down to 5.5 m below ground level at 19 sites and were divided into Zn-Cd-As- and As-contaminated groups based on the worrisome level (WL) of soil contamination. The Zn-Cd-As-contaminated group (n = 62) was observed at depths < 1 m, showed high Zn levels (mean of 1168 mg/kg) and Cd and As frequently exceeding WLs, and had low 206Pb/207Pb ratios close to the Zn smelter. In contrast, the As-contaminated group (n = 96) was observed at depths > 1 m, did not have other metals exceeding WLs, and showed a wide range of 206Pb/207Pb ratios far away from the Zn smelter. The results indicated that the pollution sources of Zn-Cd-As- and As-contaminated soils were fugitive dust emissions from smelter stacks and geology, respectively. The metal(loid)s in host rock set geochemical baselines in soil profiles, while smelting activities affected the upper layers over 50 years. This study demonstrated the effectiveness of utilizing the vertical distribution of metal(loid) concentrations and Pb isotopes in soil profiles for distinguishing between anthropogenic and geogenic origins, in combination with baseline assessment.

Measuring Pb isotope ratios in fresh snow filtrate refines the apportioning of contaminant sources in the Arctic

The remoteness and low population in the Arctic allow us to study global environmental processes, where the analysis of indicators can provide useful information about local and distant pollution sources. Fresh snow represents a convenient indicator of regional and transboundary atmospheric contamination sources, entrapping aerosols, and particulates like a natural autosampler of the environment. Lead stable isotopes are widely used to trace and monitor local and distant pollution sources. However, the behavior of Pb within different snow components is still not thoroughly studied, and its significance could be underestimated if only larger particulates are accounted for. We collected snow and samples from potential sources (fuel, rocks, coal) in three Arctic localities: Nuuk (Greenland), Reykjavik (Iceland), and Longyearbyen (Svalbard). We separated the filtrate from the filter residue through 0.45 μm nitrocellulose membranes to isolate the low-diameter particles associated with long-range transport from larger particles of mostly local natural origin. Filtrates yielded higher EFs (enrichment factor as the Pb/Al ratio relative to the upper crust) than filtration residues (80 ± 104 and 2.1 ± 1.1, respectively), and Pb isotope signals similar to fuel and coal (206Pb/207Pb are 1.199 ± 0.028 in coal, 1.168 ± 0.029 in filtrates, 1.163 ± 0.013 in fuel, 1.137 ± 0.045 in residues, and 0.985 ± 0.020 in rocks). In contrast to filtrates, the filter residues present wider ranges of Pb isotope compositions and crustal contributions and lower EFs, so we suggest that filtrate contains Pb from fuel combustion more selectively, while the residue carries a more considerable contribution of local mineral dust that can mask the contribution of other anthropogenic or distant natural sources. These findings add weight to the notion that filtrates are a more selective measure of metal deposition from long-range anthropogenic emissions compared to analyzing bulk melted snow or only filter residues.

Atmospheric pollution by potentially toxic elements: measurement and risk assessment using lichen transplants

The lichen Usnea articulata collected from an unpolluted area was exposed for 6 months at 26 sites for the sample chosenusing a stratified random design, and the content of potentially toxic elements (PTEs) including As, Cd, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sn, V, and Zn, was assessed using ICP-MS. The health risk for both adults and children was then calculated using the PTEs concentrations. The results showed that despite the hostile urban conditions, transplanted lichens depicted clear deposition patterns of airborne PTEs, mostly associated with industrial sites, where As and other elements showed remarkably high values. The cumulative hazard index was below the risk threshold, both for adults and children. For the entire population (particularly children) residing in areas surrounding industrial sites, As and Cr appeared to be potentially carcinogenic elements.

The migration and transformation mechanism of vanadium in a soil-pore water-maize system

The migration mechanism of vanadium (V) in the soil-pore water-maize system has not been revealed. This study conducted pot experiments under artificial control conditions to reveal V's distribution and transport mechanism under different growth stages and V content gradient stress. The V content in the soil pore water gradually increased by an order of magnitude. The V content of pore water in the no-plant group was higher than that in the plant group, indicating that the maize roots absorbed V. The V exists in the form of pentavalent oxygen anions, in which H2VO4- occupies the most significant proportion. With increasing V content, the root area, root number, root length, and tip number decreased significantly. The malondialdehyde content in maize leaves showed an increasing trend, indicating the degree of lipid peroxidation was gradually enhanced. The V content was in the order of root > leaf > stem > fruit and maturity stage > flowering stage > jointing stage, respectively. The transfer coefficient reached a maximum under natural conditions, and increased gradually with the growth. The results of synchrotron radiation X-ray absorption near edge structure (XANES) analysis showed that Fe in maize roots mainly comprised of Fe2O3 and Fe3O4. The Fe in the soil is primarily existed in lepidocrocite and Fe2O3. The μ-XRF analysis showed that V and Fe enriched in the roots with a positive relationship, indicating the synergistic absorption of V and Fe by roots. Part of the Fe2+ reduced V5+ to V4+ or V3+ in the forms of VO2+, V(OH)2+, or V(OH)3 (s), and fixed V at the root. Soil weak acid-soluble fraction V and soil total V were vital factors to maize extraction. This study provides new insights into V biogeochemical behavior and a scientific basis for correctly evaluating its ecological and human health risks.

Spatial-temporal variation, source apportionment and risk assessment of lead in surface river sediments over ∼20 years of rapid industrialisation in the Pearl River Basin, China

Lead (Pb) is a highly toxic element and is not essential to the human body. Lead pollution caused by human activities and a high geological background is considered a global environmental issue. According to the China Geochemical Baseline (CGB) project, the Pearl River Basin had the highest Pb content in alluvial sediments of 30 first-level basins in China. For this reason, it is of great significance to determine the temporal and spatial variations in Pb and their influencing factors in the Pearl River Basin. In this study, 956 stream sediment samples collected in the 1980 s (early stage) and 129 river sediment samples collected from 2008 to 2010 (late stage) were used to study the background value and spatial-temporal variation characteristics of Pb in river sediments in the Pearl River Basin. The Pb source apportionment and an ecological risk assessment were also carried out. The background value of Pb (36.2 mg·kg-1) in the river sediments of the Pearl River Basin was significantly higher than that in China (22.1 mg·kg-1). The parent rocks determine the Pb background in sediments and the high Pb background areas mainly comprised carbonate rocks and acid volcanic rocks. Over 20 years of rapid industrialisation, the average Pb increased from 43.3 to 68.3 mg·kg-1 in the Pearl River Basin. The BCR analysis revealed that Pb mainly existed in the reducible phase (48 % on average) and residue phase (42 % on average). The enrichment factor and geo-accumulation index indicated that the late-stage sediments experienced more Pb pollution than the early-stage sediments. However, the risk assessment code (RAC) showed that there was a low ecological risk of Pb in the late-stage sediments. The factor analysis results for the two rounds of data were significantly different. The Pb content in early-stage sediments was closely related to Al2O3 and Zr, while Pb in the late-stage sediments was mainly related to Zn, As, Sb, Au and Hg, indicating that the increase in Pb in the later samples was mainly influenced by human activities. The Pb isotope composition of the late-stage sediments confirmed that low Pb content was mainly controlled by natural sources, while high Pb content was significantly affected by anthropogenic sources. Combining the results of spatial-temporal variation, chemical speciation and source apportionment indicated that the rapid rise of Pb in late-stage sediments in certain areas could be attributed to mining and smelting activities during the process of industrialisation over 20 years. The anthropogenic exogenous Pb could be immobilised by Fe-Mn (hydro)oxides when it entered the soil, so although there was a high background the ecological risk of Pb in river sediments was low. In the future, Pb pollution control and remediation needs to be strengthened in the Pearl River Basin to avoid the outbreak of potential ecological risks linked to Pb.

Control priority based on source-specific DALYs of PM2.5-bound heavy metals by PMF-PSCF-IsoSource model in urban and suburban Beijing

To determine the priority control sources, an approach was proposed to evaluate the source-specific contribution to health risks from inhaling PM2.5-bound heavy metals (PBHMs). A total of 482 daily PM2.5 samples were collected from urban and suburban areas of Beijing, China, between 2018 and 2019. In addition to the PMF-PSCF model, a Pb isotopic IsoSource model was built for more reliable source apportionment. By using the comprehensive indicator of disability-adjusted life years (DALYs), carcinogenic and noncarcinogenic health risks could be compared on a unified scale. The study found that the annual average concentrations of the total PBHMs were significantly higher in suburban areas than in urban areas, with significantly higher concentrations during the heating season than during the nonheating season. Comprehensive dust accounted for the largest contribution to the concentration of PBHMs, while coal combustion contributed the most to the DALYs associated with PBHMs. These results suggest that prioritizing the control of coal combustion could effectively reduce the disease burden associated with PBHMs, leading to notable public health benefits.

The French Mussel Watch Program reveals the attenuation of coastal lead contamination over four decades

The mid-20th century industrial peak caused severe global lead (Pb) marine contamination. Although Europe initiated Pb emission reduction regulations in the 1980s, the short- and long-term impacts remain unclear. This study investigates the evolution of Pb contamination on the French coast through elemental and isotope analysis in oysters and mussels from the French "Mussel Watch" Program. Observations at 114 monitoring stations over four decades have shown decreasing Pb levels in these bivalve mollusks. In 1988, 95 % exceeded the background reference values; this level had dropped to 39 % by 2021. The Pb isotope ratios in bivalves from eight target sites revealed a reduction in bioaccumulated anthropogenic Pb, albeit without complete elimination. The long residence time of legacy Pb combined with inputs from diffuse urban sources likely explains the persistent presence of anthropogenic Pb on the French coast. This study endorses the importance of continuous biomonitoring to evaluate environmental regulations and policies.

Historic distribution of Polycyclic Aromatic Compounds (PAC) in a Skagerrak fjord, Swedish west coast as reflected in a high-resolution sediment record and compared to the Environmental Quality Standards (EQS)

We present the historic distribution of Polycyclic Aromatic Compounds (PAC) in a Skagerrak fjord, a relatively unexploited area, on the Swedish west coast. PACs encompass various compounds, including PAHs, alkyl-PAHs, nitro-PAHs, and oxy-PAHs. These compounds, have environmental implications due to their harmful properties. Using a high-resolution sediment record, PAC variations including standard PAHs, nitro-PAHs and oxy-PAHs were investigated over the last approximately 170 years, comparing them with other European records. The sediment record reveals a significant increase in PAC levels during the 1940s-1950s, followed by peaks in the 1960s and 1970s, and a subsequent decrease in the 1980s. These trends align with industrial growth and evolving stronger environmental regulations in the region. The highest recorded concentration of PACs (1950-1970) reached levels comparable to present-day polluted urban environments. The study also compared PAH levels with EQS values. Results indicated that PAH levels exceeded EQS standards, potentially posing risks to sediment-dwelling organisms.

Combining Cd and Pb isotope analyses for heavy metal source apportionment in facility agricultural soils around typical urban and industrial areas

Facility agriculture enhances food production capabilities. However, concerns persist regarding heavy metal accumulation resulting from extensive operation of this type of farming. This study integrated the total content, five fractions, and isotope composition of Cd and Pb in intensively farmed soils in regions characterized by industrialization (Shaoguan, SG) and urbanization (Guangzhou, GZ), to assess the sources and mechanisms causing metals accumulation. We found significantly more severe Cd/Pb accumulation and potential mobility in SG than GZ. Cd displayed higher accumulation levels and potential mobility than Pb. The distinct isotopic signals in SG (-0.54 to 0.47‰ for δ114/110Cd and 1.1755 to 1.1867 for 206Pb/207Pb) and GZ (-0.86 to 0.12‰ for δ114/110Cd and 1.1914 to 1.2012 for 206Pb/207Pb) indicated significant differences in Cd/Pb sources. The Bayesian model revealed that industrial activities and related transportation accounted for over 40% and approximately 30%, respectively, of the average contributions of Cd/Pb in SG. While urban-related (26.6%) and agricultural-related (26.3%) activities primarily contributed to Cd in GZ. The integration of δ114/110Cd and 208Pb/206Pb has further enhanced the regional contrast in sources. The present study established a comprehensive tracing system for Cd-Pb, providing crucial insights into the accumulation and distribution of these metals in facility agricultural soils.

Vanishing lead in the Loire River estuary: An example of successful environmental regulation

The behavior, and history of lead (Pb) contamination in the ecosystem of the Loire estuary was examined using elemental concentrations and Pb isotope data in water, sediment, bivalves, shrimps, and fish. In the estuary and in the surrounding coastal area, Pb concentrations in water and sediment decreased compared to concentrations determined in the 1980s, with concentrations ranging from 15.8 to 65.7 mg kg-1 in the surface sediment, 0.04-0.26 nM in the water column, and 48.0-77.9 mg kg-1 in suspended particles. Pb biomonitoring using blue mussels collected by the French Mussel Watch Program over the last 40 years showed a concentration decrease from 3.8 to 0.8 mg kg-1. A similar trend is observed in an estuarine sediment core. Changes in accompanying Pb isotope compositions strongly suggest a binary mixing process between Pb derived from terrigenous material and anthropogenic sources. Thus, environmental regulations restricting the release of lead into the environment contribute to a decrease in estuarine levels of this pollutant, which occurs on a decadal time scale.

Copper isotopes as a tool to trace contamination in mangroves from an urbanized watershed

This study investigates the chronology of copper (Cu) contamination and its stable isotopes within an emblematic Brazilian mangrove impacted by multiple urban and industrial Cu sources, deforestation, and eutrophication. In particular, it tests Cu isotopes as tracers of anthropogenic inputs into an anthropized watershed impacted by multiple sources. To do so, we used multi-isotopic approaches (δ65Cu, δ13C, and δ15N), elemental analyses (Al, Ca, Fe, P, Cu, C, and N), and selective and sequential extractions in a210Pb-dated sediment core. This geochemical "toolbox" allowed identifying two main stages of Cu evolution in the sediment core. In the first stage, before 1965, Cu isotope fingerprints responded to landscape changes, indicating a shift from marine to geogenic dominance due to the remobilization and erosion of terrestrial materials. In the second stage, after 1965, the sediment geochemical profile showed increased Cu total concentrations with a higher bioavailability (as reflected by sequential extraction data) accompanying changes in Cu isotope signatures towards anthropogenic values. The findings evidence that local industrial sources, possibly combined with diffuse urban sources, export Cu into downstream mangroves with a distinguishable isotope signature compared to natural values. This study demonstrates the applicability of Cu isotopes as new environmental forensic tools to trace anthropogenic sources in mangrove sediments. Incorporated into a robust geochemical toolbox that combines inorganic and organic proxies for sedimentary materials, this new tool provides a comprehensive understanding of Cu dynamics in mangrove ecosystems, shedding light on the historical and current sources of Cu.

Coupling isotopic signatures and partial extraction method to examine lead pollution in mangrove sediments

Elevated lead (Pb) has been widely observed in mangrove sediments due to human activities, yet understanding the sources of Pb in these sediments and the factors influencing Pb accumulation is challenging. Here, we combined Pb isotopes with partial extraction methods to study Pb contamination levels in mangrove sediments from the eastern and western parts of the Maowei Sea, China. Our results showed that the Pb in the leachate and residual fraction was mainly from anthropogenic and natural sources, respectively. The use of 204Pb isotope analysis can reveal some overlooked differences between anthropogenic and natural sources. Calculation by Bayesian mixing model showed no significant difference in the total anthropogenic contribution between the two sites, but the relative contribution of each end member differed. The contribution of Pb/Zn ores was much higher in the eastern sites (30.9 ± 5.1%) than in the west (18.4 ± 5.5%), while that of agricultural activities was much lower in the east (5.2 ± 3.1%) than in the west (13.5 ± 4.6%). The elevated anthropogenic Pb accumulation in mangrove sediments was ascribed to organic matter. This study provides more data on Pb isotopic composition and new insights into Pb biogeochemistry in the mangrove environment.

Pollution revealed by stable lead isotopes in recent snow from the northern and central Tibetan Plateau

Lead (Pb) isotopes are less fractionated than those from different sources, and thus were used to trace the sources of Pb in the environment. To investigate the sources of Pb in the atmosphere of the Tibetan Plateau, stable Pb isotopes (206Pb, 207Pb and 208Pb) in acidified snow pit samples collected from five glaciers (i.e., Qiyi-QY, Meikuang-MK, Yuzhufeng-YZF, Hariqin-HRQ and Xiaodongkemadi-XDKMD) in May 2016 of the northern and central Tibetan Plateau were measured. The results showed narrow ranges of 1.158-1.187 for 206Pb/207Pb and 2.450-2.489 for 208Pb/207Pb respectively. The 206Pb/207Pb ratios in all samples were obviously lower than the environmental background value of 1.196, indicating the primary contributions of anthropogenic sources. At least 60% of Pb was contributed by various human activities, which was supported by the Pb isotopes in the snow pit samples from the QY, MK, YZF, HRQ and XDKMD glaciers. By comparing Pb isotope data, we found that the primary anthropogenic sources are coal combustion, mining and smelting activities in northwestern China and mixed emissions from cities located in western China and close to the glaciers. These sources contributed to the Pb in the northern glaciers (QY and MK) in particular. Coal combustion in India probably contributes to the central glaciers (HRQ and XDKMD). Another potential source could be parts of central Asia (e.g., Kyrgyzstan and Uzbekistan) through long range transport. The above potential source areas of contaminants were traced further by the air mass back-trajectory tracing method.

Investigation of potential metal emissions from galvanic anodes in offshore wind farms into North Sea sediments

To evaluate potential metal emissions from offshore wind farms (OWFs), 215 surface sediment samples from different German North Sea OWFs taken between 2016 and 2022 were analyzed for their mass fractions of metals and their isotopic composition of Sr. For the first time, this study provides large-scale elemental data from OWFs of the previously proposed galvanic anode tracers Cd, Pb, Zn, Ga and In. Results show that mass fractions of the legacy pollutants Cd, Pb and Zn were mostly within the known variability of North Sea sediments. At the current stage the analyzed Ga and In mass fractions as well as Ga/In ratios do not point towards an accumulation in sediments caused by galvanic anodes used in OWFs. However, further investigations are advisable to evaluate long-term effects over the expected lifetime of OWFs, especially with regard to the current intensification of offshore wind energy development.

Isotopic Signatures and Outputs of Lead from Coal Fly Ash Disposal in China, India, and the United States

Despite extensive research and technology to reduce the atmospheric emission of Pb from burning coal for power generation, minimal attention has been paid to Pb associated with coal ash disposal in the environment. This study investigates the isotopic signatures and output rates of Pb in fly ash disposal in China, India, and the United States. Pairwise comparison between feed coal and fly ash samples collected from coal-fired power plants from each country shows that the Pb isotope composition of fly ash largely resembles that of feed coal, and its isotopic distinction allows for tracing the release of Pb from coal fly ash into the environment. Between 2000 and 2020, approx. 236, 56, and 46 Gg Pb from fly ash have been disposed in China, India, and the U.S., respectively, posing a significant environmental burden. A Bayesian Pb isotope mixing model shows that during the past 40 to 70 years, coal fly ash has contributed significantly higher Pb (∼26%) than leaded gasoline (∼7%) to Pb accumulation in the sediments of five freshwater lakes in North Carolina, U.S.A. This implies that the release of disposed coal fly ash Pb at local and regional scales can outweigh that of other anthropogenic Pb sources.

The Historic Built Environment As a Long-Term Geochemical Archive: Telling the Time on the Urban "Pollution Clock"

This study introduces a novel methodology for utilizing historic built environments as reliable long-term geochemical archives, addressing a gap in the reconstruction of past anthropogenic pollution levels in urban settings. For the first time, we employ high-resolution laser ablation mass spectrometry for lead isotope (206Pb/207Pb and 208Pb/206Pb) analysis on 350-year-old black crust stratigraphies found on historic built structures, providing insights into past air pollution signatures. Our findings reveal a gradual shift in the crust stratigraphy toward lower 206Pb/207Pb and higher 208Pb/206Pb isotope ratios from the older to the younger layers, indicating changes in lead sources over time. Mass balance analysis of the isotope data shows black crust layers formed since 1669 primarily contain over 90% Pb from coal burning, while other lead sources from a set of modern pollution including but not limited to leaded gasoline (introduced after 1920) become dominant (up to 60%) from 1875 onward. In contrast to global archives such as ice cores that provide integrated signals of long-distance pollution, our study contributes to a deeper understanding of localized pollution levels, specifically in urban settings. Our approach complements multiple sources of evidence, enhancing our understanding of air pollution dynamics and trends, and the impact of human activities on urban environments.

A Self-Assembled G-Quadruplex/Hemin DNAzyme-Driven DNA Walker Strategy for Sensitive and Rapid Detection of Lead Ions Based on Rolling Circle Amplification

Herein, a sensitive biosensor is constructed based on a novel rolling circle amplification (RCA) for colorimetric quantification of lead ion (Pb2+). At the detection system, GR5 DNAzymes are modified on the surface of an immunomagnetic bead, and Pb2+ is captured by the aptamer, inducing the disintegration of the GR5 DNAzyme and the release of the DNA walker. After the introduction of the template DNA, T4 DNA ligase, and phi29 DNA polymerase, an RCA is initiated for the sensitivity improvement of this method. Moreover, a G4-hemin DNAzyme is formed as a colorimetric signal, owing to its peroxide-like activity to catalyze the TMB-H2O2 substrate. Under the optimized conditions, the limit of detection (LOD) of this fabricated biosensor could reach 3.3 pM for Pb2+ with a concentration in the range of 0.01-1000 nM. Furthermore, the results of real samples analysis demonstrate its satisfactory accuracy, implying its great potential in the rapid detection of heavy metals in the environment.

Yellow-legged gull populations (Larus michahellis) link the history of landfills to soil eutrophication and time-related vegetation changes on small Mediterranean islands

Seabird colonies have a strong influence on both the physical and chemical soil parameters and plant communities of the islands where they settle to nest. Scientists have studied the effects of the demographic explosion of seabird populations, but few have explored the long-term effects when the colonies were in decline. The aim of this study was to investigate diachronic changes over a 24 year period of soil parameters, floristic composition and plant functionnal types (Raunkiaer growth forms and Grime life strategies) up to the decrease of the number of nesting yellow-legged gulls (Larus michahellis Naumann, 1840) on Mediterranean islands. We used 78 permanent plots to survey the vegetation and the soil parameters on 9 islands and one mainland area within the Calanques National Park (south east of France), for three periods (i.e., 1997, 2008, 2021). Since 1997, the increase of nesting gulls has caused a nitrogen and pH increase and organic carbon and C/N ratio decrease, although the values were still higher than mainland plots without nesting gulls. This has led to changes in plant species composition e.g., higher values of N favouring the development of ruderal plant species, still present in high frequency in 2021. Furthermore, plant species highly tolerant to disturbances (i.e., R Grime strategy) in harsh environments were still favoured even after the decline of gull abundance. However, both the frequency of the chamaephytes and the vegetation cover has increased with the decline of gull colony. In 2021, measures of trace elements' concentrations and calculation of pollution load index (Cu, Pb and Zn) reveals relatively low multi-contamination levels on the mainland and the archipelagos. On naturally oligotrophic and semi-arid Mediterranean islands, gull colonies induce a persistent alteration in soil characteristics that still influences plant communities (composition and functional types), 11 years after the decline in bird abundance.

Lead exposure in brown bears is linked to environmental levels and the distribution of moose kills

Lead (Pb) is heterogeneously distributed in the environment and multiple sources like Pb ammunition and fossil fuel combustion can increase the risk of exposure in wildlife. Brown bears (Ursus arctos) in Sweden have higher blood Pb levels compared to bears from other populations, but the sources and routes of exposure are unknown. The objective of this study was to quantify the contribution of two potential sources of Pb exposure in female brown bears (n = 34 individuals; n = 61 samples). We used multiple linear regressions to determine the contribution of both environmental Pb levels estimated from plant roots and moose (Alces alces) kills to blood Pb concentrations in female brown bears. We found positive relationships between blood Pb concentrations in bears and both the distribution of moose kills by hunters and environmental Pb levels around capture locations. Our results suggest that the consumption of slaughter remains discarded by moose hunters is a likely significant pathway of Pb exposure and this exposure is additive to environmental Pb exposure in female brown bears in Sweden. We suggest that spatially explicit models, incorporating habitat selection analyses of harvest data, may prove useful in predicting Pb exposure in scavengers.

Unraveling the source(s) and fate of Pb in urban soils and sediments of Ibadan metropolis using lead isotopes

In this study an attempt was made to determine the source(s) and nature of Pb in environmental media of Ibadan, one of the largest cities in west Nigeria. Seventy-three samples comprising forty stream sediments, twenty-five soils and eight rocks samples were used for the study. Mineralogical compositions of the samples were determined by X-ray diffraction. The elemental constituents were determined using ICP-MS; while the Pb isotopes were determined using Sector-field ICP-MS. Sequential analysis of selected samples was carried out using a modified Tessier's five-step method. The dominant minerals identified were quartz, kaolinite, k-feldspar, and plagioclase. The concentrations (mg/kg) of Pb in soils, sediments, and rocks ranged from 13.00-470.00; 89.00-3288.00 and 2.90-20.30, respectively. The ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, ²⁰⁸Pb ranged from 1.72-47.41; 30.69-779.68; 27.00-664.46 and 65.67-1642.27 in the soils and sediments, respectively, while they ranged from 0.02-0.07; 0.56-2.33; 0.38-1.56 and 1.19-4.13 in the rocks. Further evaluation of Pb concentration in the soils and sediments revealed high to extreme Pb pollution status, while the calculated Pb isotopic ratios (IRs) in the soil and sediments varied from that of the underlying bedrocks. The IRS in soils and sediments were characterized by low (1.161-1.172 and 1.127-1.200, and 2.281-2.444 and 2.276-2.474) ^206/207 Pb and ^208/207 Pb, while those of the rocks were high (1.456-1.753 and 2.647-3.149), indicating additional anthropogenic sourcing of Pb in the soils and sediments. The analyzed Pb revealed fractions more partitioned in the reactive geochemical phases with the Pb partitioned in the exchangeable (0.11-0.23%), carbonate (9.00-43.58%), reducible (8.32-13.53%) and organic/sulfides (42.78-82.45%) phases. This implies that there may be enhanced mobility of Pb in the environmental samples and ultimately bio-adsorption into living tissues in the environment.

Copper and lead isotope records from an electroplating activity in sediments and biota from Sepetiba Bay (southeastern Brazil)

An old electroplating plant in Sepetiba Bay discharged metal-enriched wastes into the surrounding mangroves for 30 years (from the 1960s to 1990s), resulting in a hotspot zone of legacy sediments highly concentrated in toxic trace metals. This study applies Cu and Pb isotope systems to investigate the contributions of past punctual sources relative to emerging modern diffuse sources. The electroplating activity imprinted particular isotopic signatures (average δ⁶⁵Cu_SRM-976: 0.4 ‰ and ²⁰⁶Pb/²⁰⁷Pb: 1.14) distinct from the natural baseline and urban fluvial sediments. The isotopic compositions of tidal flat sediments show intermediate isotope compositions reflecting the mixing of Cu and Pb from the hotspot zone and terrigenous materials carried by rivers. Oyster isotope fingerprints match legacy sediments, attesting that anthropogenic Cu and Pb are bioavailable to the biota. These findings confirm the interest in combining two or more metal isotope systems to discriminate between modern and past metal source emissions in coastal environments.

Complexities in attributing lead contamination to specific sources in an industrial area of Philadelphia, PA

Globally, lead (Pb) contamination is one of the top ten chemical exposure issues affecting public health. The identification of specific Pb sources provides valuable information to determine assignment of liability for site cleanup, improve sampling plans and develop remedial strategies. This paper examines Pb concentrations and Pb isotopic data from samples collected at and near the site of a Pb paint production facility with a long operating history. Although high soil Pb concentrations were found at the site, Pb concentrations in surrounding neighborhoods did not simply decline with distance from the site. We evaluated soil concentrations and isotopic mixing lines to explore potential sources of Pb pollution. Three-isotope plots showed overlap of site samples and the surrounding neighborhood, consistent with pollution from the facility affecting offsite soils. A major challenge in separation of potential sources, however, is that the isotopic signatures of other potential Pb sources fall within the range of the soil data. The long operational site history, soil disturbances, the presence of nearby smelters, and other local and remote sources affect identification of lead sources. This analysis demonstrates that source attribution can be confounded by incomplete site and material sourcing information. An integrated approach that includes in-depth site characterization and an evaluation of historical activities (e.g., Pb ores used over time, amounts of Pb emitted by all area smelters, land use changes, and soil disturbances) is important for determining source attribution. This analysis provides insight into future site investigations where soil lead contamination has resulted from a long industrial history in an urban setting.

Risk Evaluation of Pollutants Emission from Coal and Coal Waste Combustion Plants and Environmental Impact of Fly Ash Landfilling

Emission factors (EFs) of gaseous pollutants, particulate matter, certain harmful trace elements, and polycyclic aromatic hydrocarbons (PAHs) from three thermal power plants (TPPs) and semi-industrial fluidized bed boiler (FBB) were compared. EFs of particulate matter, trace elements (except Cd and Pb), benzo[a]pyrene, and benzo[b]fluoranthene exceed the upper limits specified in the EMEP inventory guidebook for all combustion facilities. The comparison of trace elements and PAHs content in fly ashes (FAs) from lignite and coal waste combustion in TPPs and FBB, respectively, as well as the potential environmental impact of FAs disposal, was performed by employing a set of ecological indicators such as crustal enrichment factor, risk assessment code, risk indices for trace elements, and benzo[a]pyrene equivalent concentration for PAHs. Sequential analysis shows that the trace elements portion is the lowest for water-soluble and exchangeable fractions. The highest enrichment levels in FAs are noticed for As and Hg. Based on toxic trace elements content, FAs from TPPs represent a very high ecological risk, whereas fly ash from FBB poses a moderate ecological risk but has the highest benzo[a]pyrene equivalent concentration, indicating its increased carcinogenic potential. Lead isotope ratios for Serbian coals and FAs can contribute to a lead pollution global database.

Identification of atmospheric particulate matter derived from coal and biomass burning and from non-exhaust traffic emissions using zinc isotope signatures

Improving urban air quality is a global challenge. To implement successful abatement measures that reduce atmospheric particulate matter (APM) and associated metal concentrations, precise source apportionment is needed. For this, apportioning contributions from coal and biomass burning and differentiating these from non-exhaust traffic emissions in urban APM is critical. Recent studies characterising the metal isotope composition of urban APM, and potential source materials suggested that non-traditional isotope systems could prove unique fingerprinting tools. Zinc isotopes should be able to separate APM derived from uncontrolled combustion (fly ash, isotopically heavy) from non-exhaust traffic sources (tyre and brake wear, intermediate) and from controlled industrial emissions (flue gas, light). To test this hypothesis, we determined zinc isotope ratios of APM (TSP, PM_2.5, PM₁) in Beijing (coal combustion for residential heating) and Varanasi (biomass burning in pre-monsoon periods). In Beijing, δ⁶⁶Zn_Lyon values of PM_2.5 ranged from -0.41 to +1.01‰ in 2015 (avg = +0.25 ± 0.50‰, n = 19). Aerosols (including TSP, PM_2.5 and PM₁ samples) from the heating period were significantly (t-test, p < 0.001) heavier (avg = +0.90 ± 0.12‰, n = 7) than those from the non-heating period (avg = +0.14 ± 0.36‰, n = 23). Average δ⁶⁶Zn_Lyon values of PM_2.5 in Varanasi in spring 2015 were +0.82 ± 0.11‰ (n = 4). Extent and direction of isotope fractionation is in line with that expected from theoretical models and the isotope signatures observed agree with previously determined ratios of source materials. Our study links for the first time comprehensively the heavy zinc isotope compositions in APM to coal and biomass burning and shows that zinc isotope compositions of aerosols can discriminate between non-exhaust traffic and combustion sources.

Slight transition in Chinese atmospheric Pb isotopic fingerprinting due to increasing foreign Pb

Atmospheric lead (Pb) pollution negatively affects human health and ecosystem, and extensive research is required to identify its sources and develop robust mitigation methods. In this study, the concentration and isotopic composition of Pb in fine particulate matter (PM_2.5) at five sites in the China's Beijing-Tianjin-Hebei (BTH) region were analyzed. The results showed that the Pb concentration in the BTH region declined along the northwest direction in winter owing to the East Asian monsoon. Pb isotopic signatures confirmed that anthropogenic activities significantly contributed to Pb pollution, compared with natural sources. With the increasing import of foreign Pb (with a relatively lower ²⁰⁸Pb/²⁰⁶Pb ratio) to China, we hypothesized that the unique isotopic signature of Pb in Chinese aerosols may decline over time. Therefore, the application of the isotopic approach for quantifying Pb transported from China should be carefully appraised in future research to provide a realistic estimate of the contribution of local sources and the transboundary effect consistent with air mass trajectories analysis. This study provides a theoretical reference for supporting the utilization of Δ²⁰⁸Pb values for better clarify the transboundary impact of Pb pollution and to reduce international disputes.

Spatial and temporal trends in δ66Zn and 206Pb/207Pb isotope ratios along a rural transect downwind from the Upper Silesian industrial area: Role of legacy vs. present-day pollution

Transect sampling is an under-exploited tool in isotope studies of atmospheric pollution. Few studies have combined Zn and Pb isotope ratios to investigate whether atmospheric pollution at a receptor site is dominated by a different anthropogenic source of each of these toxic elements. It has been also unclear whether pollution abatement strategies in Central Europe have already resulted in regionally well-mixed background isotope signature of atmospheric Zn and Pb. Zinc and lead isotope ratios were determined in snow collected along a rural transect downwind from the Upper Silesian industrial area (southern Poland). Spatial and temporal gradients in δ⁶⁶Zn and ²⁰⁶Pb/²⁰⁷Pb ratios at four sites were compared with those of ore and coal collected in eight Czech and Polish mining districts situated at distances of up to 500 km. Snow pollution was extremely high 8 km from Olkusz in 2011 (1670 μg Zn L^-1; 240 μg Pb L^-1), sharply decreased between 2011 and 2018, and remained low in 2019-2021. Snow pollution was lower at sites situated 28-68 km from Olkusz. Across study sites, mean δ⁶⁶Zn and ²⁰⁶Pb/²⁰⁷Pb ratios of snow were -0.13‰ and 1.155, respectively. With an increasing distance from Olkusz, the δ⁶⁶Zn values first increased and then decreased, while the ²⁰⁶Pb/²⁰⁷Pb ratios first decreased and then increased. The δ⁶⁶Zn values in snow plotted closer to those of Upper Silesian ores (-0.20‰) than to the δ⁶⁶Zn values of Upper Silesian stone coal (0.52‰), showing predominance of smelter-derived over power-plant derived Zn pollution. The ²⁰⁶Pb/²⁰⁷Pb ratios of Upper Silesian coal (1.171) and Upper Silesian ores (1.180) were higher compared to those of snow. A²⁰⁶Pb/²⁰⁷Pb vs.²⁰⁸Pb/²⁰⁷Pb plot identified legacy pollution from leaded gasoline as the low-radiogenic mixing end-member. Across the transect sites, only the last sampling campaign exhibited a high degree of isotope homogenization for both Zn and Pb.

Isotopic (Cu, Zn, and Pb) and elemental fingerprints of antifouling paints and their potential use for environmental forensic investigations

Antifouling paints (APs) are one of the important sources of Cu and Zn contamination in coastal environments. This study applied for the first-time a multi-isotope (Cu, Zn, and Pb) and multi-elemental characterization of different AP brands to improve their tracking in marine environments. The Cu and Zn contents of APs were shown to be remarkably high ∼35% and ∼8%, respectively. The δ⁶⁵Cu_AE647, δ⁶⁶Zn_IRMM3702, and ²⁰⁶Pb/²⁰⁷Pb of the APs differed depending on the manufacturers and color (-0.16 to +0.36‰, -0.34 to +0.03‰, and 1.1158 to 1.2140, respectively). A PCA analysis indicates that APs, tires, and brake pads have also distinct elemental fingerprints. Combining isotopic and elemental ratios (e.g., Zn/Cu) allows to distinguish the environmental samples. Nevertheless, a first attempt to apply this approach in highly urbanized harbor areas demonstrates difficulties in source apportionments, because the sediment was chemically and isotopically homogeneous. The similarity of isotope ranges between the harbor and non-exhaust traffic emission sources suggests that most metals are highly affected by urban runoff, and that APs are not the main contributors of these metals. It is suspected that AP-borne contamination should be punctual rather than dispersed, because of APs low solubility properties. Nevertheless, this study shows that the common coastal anthropogenic sources display different elemental and isotopic fingerprints, hence the potential for isotope source tracking applications in marine environments. Further study cases, combined with laboratory experiments to investigate isotope fractionation during releasing the metal sources are necessary to improve non-traditional isotope applications in environmental forensics.

Decline of anthropogenic lead in South Atlantic Ocean surface waters from 1990 to 2011: New constraints from concentration and isotope data

Anthropogenic emissions have severely perturbed the marine biogeochemical cycle of lead (Pb). Here, we present new Pb concentration and isotope data for surface seawater from GEOTRACES section GA02, sampled in the western South Atlantic in 2011. The South Atlantic is divided into three hydrographic zones: equatorial (0-20°S), subtropical (20-40°S), and subantarctic (40-60°S). The equatorial zone is dominated by previously deposited Pb transported by surface currents. The subtropical zone largely reflects anthropogenic Pb emissions from South America, whilst the subantarctic zone presents a mixture of South American anthropogenic Pb and natural Pb from Patagonian dust. The mean Pb concentration of 16.7 ± 3.8 pmol/kg is 34 % lower than in the 1990s, mostly driven by changes in the subtropical zone, with the fraction of natural Pb increasing from 24 % to 36 % between 1996 and 2011. Although anthropogenic Pb remains predominant, these findings demonstrate the effectiveness of policies that banned leaded gasoline.

A lifelong journey of lead in soil profiles at an abandoned e-waste recycling site: Past, present, and future

Heavy metal pollutants resulting from human activities consistently move from the topsoil to the subsoil profiles under the influence of rainfall leaching. This study intends to predict the long-term transport of heavy metals at an abandoned e-waste recycling site with respect to historical pollution activities, land use, and metal pollutant dynamics. Our results showed that the site was seriously contaminated with heavy metals (Cd, Cu, Pb, and Zn) in the soil profiles. More specifically, Cu and Zn accumulated primarily in the upper layers of the soil profile owing to their weak mobility, while significant migration of Cd and Pb was observed in the deeper soil layers. Furthermore, to clarify the fate of Pb in soil profiles, Pb isotopes and the Hydrus model were used to trace the sources of Pb contamination and predict its long-term distribution. The Pb isotope results suggest that past e-waste recycling activities significantly contributed to the heavy metal concentration in the soil profiles; however, other anthropogenic sources such as vehicle exhaust had smaller impacts. Moreover, our model findings predicted that within the next 30 years, 60% of Pb contaminants will be concentrated in the surface soil. Together these results provide a theoretical foundation and scientific basis for evaluating, controlling, and remediating abandoned e-waste recycling sites.