# Isotope tracking of anthropogenic Cu and Zn in urbanized coastal environments: A review

Hyeryeong Jeong, Kongtae Ra, João Barreira, Daniel Ferreira Araujo

► To cite this version:

Hyeryeong Jeong, Kongtae Ra, João Barreira, Daniel Ferreira Araujo. Isotope tracking of anthropogenic Cu and Zn in urbanized coastal environments: A review. Marine Pollution Bulletin, 2025, 220, 118337 (20p.). 10.1016/j.marpolbul.2025.118337. hal-05206200

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# Isotope tracking of anthropogenic Cu and Zn in urbanized coastal environments: A review

Hyeryeong Jeong<sup>a, *</sup>, Kongtae Ra<sup>b,c</sup>, João Barreira<sup>d</sup>, Daniel F. Araújo<sup>a</sup>

## ARTICLE INFO

### Keywords:

- Metal stable isotopes

- Estuarine environment

- Metal pollution

- Tracing pollution sources

- Isotope tracers

## ABSTRACT

Copper (Cu) and zinc (Zn) are common trace metal contaminants in marine environments that, despite their importance for the health of marine organisms, can be toxic. Recently, the stable isotopes of these elements have emerged as powerful tracers for studying their cycles. Thus, this review aims to connect urban and marine interfaces under a "land-sea continuum" framework to understand the complex sources, pathways, and transformations of Cu and Zn in urbanized coastal environments, a perspective currently lacking in the literature. Here, we briefly establish the sampling and analytical aspects of isotope measurement of these elements in the natural matrices of marine realms, providing a recent compilation of reference materials for analytical control. The principles of isotope fractionation are introduced and contextualized within coastal ecosystems. We summarize the isotopic signatures of major anthropogenic sources—including road-deposited sediments, non-exhaust traffic-related emissions, industrial waste, and metallurgical byproducts—and highlight the challenges of distinguishing them when isotopic ranges overlap. In parallel, natural baselines such as ores, soils, suspended particulate matter (SPM), and riverine inputs are also reviewed to contextualize environmental variability. The review examines how source isotope signatures evolve with further isotope fractionation during estuarine transport and transfer processes in the water-sediment-biota interface. Finally, this review also identifies future research directions to trace the sources, pathways, and sinks of these contaminants along the land-sea continuum, as well as the legacy and ongoing impact of urban metal pollution at catchment-to-coastal scales.

## 1. Introduction

The unprecedented urbanization and economic development over the last century have increased human living standards, providing easier access to trade goods, public services, healthcare, and sanitation (Moore et al., 2003). However, the resulting urban densification of estuaries has exposed surrounding coastal ecosystems to chemical contaminants, including trace metals, as well as other stressors such as excessive sediment loads, nutrients, faecal microbiota, and stormwater (Han et al., 2024; Hu et al., 2024; Pereira et al., 2023).

Among trace metal contaminants, copper (Cu) and zinc (Zn) stand out as their anthropogenic fluxes are estimated to be almost equivalent to natural counterparts (Sen and Peucker-Ehrenbrink, 2012). Nevertheless, the escalating of their anthropogenic fluxes into marine environments should continue considering the growing global demands for

waste disposals, military and security uses, tourism, aquaculture, and natural resources (oil, gas, sand, minerals, plants, genes, etc.) (Araújo et al., 2019a; Guo et al., 2024; Packman et al., 2022; Tornero and Hanke, 2016). Both Cu and Zn have significant environmental relevance and are commonly found in high concentrations in urbanized coastal areas. They are essential elements that participate actively in many metabolic processes of marine organisms within an optimal concentration range. However, they can trigger toxic effects if bioaccumulated excessively (Crichton, 2016; Fu et al., 2016; Kaamoush et al., 2023). These metals are among the most frequently reported contaminants in marine sediments and biota, and they are monitored under national and international frameworks, as well as sediment quality guidelines worldwide. This includes countries like South Korea (MOF, 2013), the United States (USEPA, 1987, 1995, 1998), and the European Union (Crane, 2003).

Natural compartments (water, sediment, biota) of urbanized

<footnote><sup>a</sup> Ifremer, CCEM-Unité Contamination Chimique des Écosystèmes Marins (CCEM), F-44300 Nantes, France</footnote>

<footnote><sup>b</sup> Marine Environmental Research Center, Korea Institute of Ocean Science and Technology (KIOST), Busan 49111, Republic of Korea</footnote>

<footnote><sup>c</sup> Department of Ocean Science (Oceanography), KIOST School, University of Science and Technology (UST), Daejeon 34113, Republic of Korea</footnote>

<footnote><sup>d</sup> Univ Angers, Nantes Université, Le Mans Univ, CNRS, UMR 6112, Laboratoire de Planétologie et Géosciences, 49000 Angers, France</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: hrjeong617@gmail.com (H. Jeong).</footnote>
estuaries trap anthropogenic Cu and Zn transported via rivers, surface runoff, domestic sewage, industrial wastewater, and atmospheric deposition (Hartzell et al., 2017; Jeong et al., 2020d; Niu et al., 2021; Xu et al., 2016). Indeed, atmospheric urban emissions may transport anthropogenic metals beyond nericitic zones, affecting biogeochemical cycles and primary activities in oceans (Heimbürger et al., 2011; Von Glasow et al., 2013). Once they enter the coastal systems, Cu and Zn can undergo various processes that control their distribution in the sediment-water-biota interface (adsorption, complexation, precipitation, biological uptake, etc.). The numerous natural and anthropogenic sources, pathways, and biogeochemical processes complicate the assessment of anthropogenic Cu and Zn contamination, much like with other trace metals. Specifically, the source apportionment of emissions is not easily deconvolved from traditional elemental concentrations and requires new approaches to support environmental management strategies.

The precise isotope ratio analysis of Cu and Zn becomes a reality with the development of the multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) instruments and suitable sample preparation methods at the end of the 90s (Rosca et al., 2021; Yang et al., 2023, 2021; Zhai et al., 2023; Zhu et al., 2015). Thanks to the former analytical endeavours, pioneer studies soon demonstrated the distinction between signatures of Cu and Zn circulating in the “Anthroposphere” – part of the environment that is made or modified by humans – and those found in pristine environments. More active research in environmental applications using these isotope systems, compared to other trace metals (e.g., Ni, Cd, V), is driven by their relatively straightforward chemical separations, high concentrations in environmental media, simple instrumental settings, and a universal marine contamination history (Araújo et al., 2019b; Barreira et al., 2024; Briant et al., 2022; Jeong et al., 2023a). Cu and Zn isotopes become effective tools for source apportionment in urban environments (Chen et al., 2022; Souto-Oliveira et al., 2018, 2019). On the other hand, numerous studies have been dedicated to isotope tracking of anthropogenic Cu and Zn in aquatic marine pollution over the last decade (Araújo et al., 2017b; Jeong et al., 2023b; Shiel et al., 2013; Tonhá et al., 2020). However, these two fields of applications, “urban” and “marine”, have evolved almost independently, each one dealing with their own specificities. Given their widespread use in antifouling paints, brake pad materials, industrial discharges, and urban runoff, Cu and Zn serve as informative indicators of anthropogenic pressure along the land-sea interface. The integration of isotope data with elemental ratios (e.g., Cu/Sb, Zn/Cu) or complementary isotope systems (e.g., Pb, Sr) provides a more refined and multidimensional understanding of pollution sources in complex estuarine environments.

Thus, this review aims to connect urban and marine interfaces under a “land-sea continuum” framework to understand the complex sources, pathways, and transformations of Cu and Zn in urbanized coastal environments, a perspective that is currently missing in the literature. Taking this into account, this review aims to: (1) synthesize current knowledge on the isotopic signatures of natural and anthropogenic Cu and Zn in urban and industrial settings; and (2) examine their isotopic fractionation and behavior during transport along the fluvial-estuarine continuum and in post-depositional processes.

## 2. A primer about instrumental, nomenclature, and conventions

Isotopes are atoms with the same number of protons, but different numbers of neutrons. Therefore, they have different masses (Araújo et al., 2022; Wiederhold, 2015) and it influences the physicochemical properties of isotopes. Stable isotopes do not decay into different elements and stay stable status over time in contrast to radiogenic isotopes (Irrgeher and Prohaska, 2016; Jaouen and Pons, 2017). Isotopic variations of most metals, like Cu and Zn, are driven by mass-dependent fractionation (MDF) through various environmental processes such as oxidation, reduction, biological cycling, precipitation, adsorption,

diffusion, and evaporation (Wang et al., 2021a; Wiederhold, 2015). On the other hand, mass-independent fractionation (MIF) can occur in some light elements (e.g., oxygen and sulfur) (Wiederhold, 2015). For the heavy element, photochemical reactions, magnetic isotope effect, and nuclear volume effect can cause MIF of Hg isotopes (Zhang et al., 2020).

Traditional stable isotopes such as typically light elements (carbon; C, hydrogen; H, oxygen; O, nitrogen; N, and sulfur; S) were used for understanding ecological and biogeochemical processes over the past few decades using isotope ratio mass spectrometry (IRMS) (Harada et al., 2020; Lu et al., 2017). Thermal ionization mass spectrometry (TIMS) was established to measure of isotopic compositions with high precision and sensitivity (Di et al., 2021; Harvey and Baxter, 2009; Walczyk, 2004). TIMS application is developed in the field of geosciences, cosmochemical studies, and nuclear technologies (Abouchami et al., 2025; Aggarwal, 2016; Richter and Goldberg, 2003; Yang et al., 2024). However, TIMS has disadvantages of time-consuming, expensive operating cost, and limited sample capability (Li et al., 2012). MC-ICP-MS is widely used to new stable isotope systems so called “non-traditional” due to its with high ionization efficiency and rapid production of isotope data (Albarède and Beard, 2004; Balaram et al., 2022). It is equipped with Faraday cups and ion counters, and Faraday cup detectors with amplifiers in the instrument enable the precise and accurate isotopic measurements (Breton et al., 2015). Commonly called non-traditional stable isotopes, metal stable isotopes have been developed with improved analytical techniques using MC-ICP-MS (Li et al., 2019; Lu et al., 2017). Non-traditional stable isotopes can be applied to the environmental forensic field, ecological, biological, and geochemical sciences (Miller, 2013; Sullivan et al., 2022; Weiss et al., 2008; Yang et al., 2022). However, they still have limitations in methodologies that make it difficult to apply and expand the related research (Lu et al., 2017).

Differences of isotope ratio are very small in nature, therefore, delta (δ) notation is used for showing the variations efficiently (Brand et al., 2014; Brand and Coplen, 2012). Throughout this review, Cu and Zn stable isotopic compositions are expressed as a δ notation (‰) relative to standard reference material (ERM-AE647 for Cu and IRMM-3702 for Zn):

$$ \delta^{65}\text{Cu} = \left( \frac{\left( \frac{^{65}\text{Cu}}{^{63}\text{Cu}} \right)_{\text{sample}}}{\left( \frac{^{65}\text{Cu}}{^{63}\text{Cu}} \right)_{\text{ERM-AE647}}} - 1 \right) \times 1000 $$

$$ \delta^{66}\text{Zn} = \left( \frac{\left( \frac{^{66}\text{Zn}}{^{64}\text{Zn}} \right)_{\text{sample}}}{\left( \frac{^{66}\text{Zn}}{^{64}\text{Zn}} \right)_{\text{IRMM-3702}}} - 1 \right) \times 1000 $$

These δ-values can be converted to Cu and Zn isotope values based on now-exhausted standard reference materials (NIST 976 for Cu and JMC<sub>Lyon</sub> for Zn) using the following equation for comparison (Araújo et al., 2017a; Moeller et al., 2012).

$$ \delta^{65}\text{Cu}_{\text{ERM-AE647}} = \delta^{65}\text{Cu}_{\text{NIST976}} - 0.21\text{‰} $$

$$ \delta^{66}\text{Zn}_{\text{IRMM3702}} = \delta^{65}\text{Zn}_{\text{JMC-Lyon}} - 0.27\text{‰} $$

## 3. Copper and zinc isotope analysis

### 3.1. Sampling requirements for Cu and Zn isotope analyses in environmental samples

To ensure the quality and reproducibility of metal isotope data, all tools and containers in contact with samples should be acid-cleaned and handled under conditions that minimize contamination.

Precise and consistent measurements of metal stable isotopes in environmental research necessitate standardized and matrix-specific sampling and pre-treatment methodologies. In urban estuarine environments, sample classifications include suspended particulate matter (SPM), surface sediments, rainfall runoff, road-deposited sediments
(RDS), and non-exhaust emission (NEE) sources such as brake pads, tires, asphalt, road paint, and antifouling coatings.

Particulate materials, such as RDS and estuary sediments, are typically collected using sweeping instruments or grab samplers (Araújo et al., 2019b; Jeong et al., 2020; Logiewa et al., 2020; Niu et al., 2021; Zhao et al., 2016, 2010). The methodologies for desiccation and particle size segregation differ based on sample classification and research objectives. Estuarine sediments are often freeze-dried, whereas RDS and other urban particulate pollutants are often oven-dried at low temperatures (<60 °C). Research on size-dependent contamination patterns in RDS begins with an initial sieving process to remove coarse debris (>2 mm), followed by sieving into designated particle size categories (e.g., 500–1000 µm, 125–500 µm, 63–125 µm, and <63 µm) (Jeong et al., 2020; Jeong and Ra, 2021a; Owens et al., 2011; Zafra-Mejía et al., 2025). All fractions are preserved in acid-washed polypropylene containers to minimize contamination prior to analysis.

NEE sources comprise solid particulates originating from vehicle wear and infrastructure coatings. Brake pad and tire materials were acquired from commercially accessible goods produced in several nations. For paint-related materials, such as road paint and antifouling coatings, a thin layer of paint is placed to Teflon sheets and subsequently dried in an oven at 40–60 °C to eliminate solvents and moisture prior to homogenization. Subsequent to the drying step, paint residues are collected, cut into small pieces, and stored in acid-cleaned vials (Jeong et al., 2023b).

Typically, water samples are provided in pre-cleaned polyethylene containers. Niskin-X or the “PRISTINE” ultraclean CTD (UCC) sampler are employed to gather saltwater samples, which are further filtered via acid-cleaned capsule filters to isolate the dissolved phase (Kim et al., 2019; Nakaguchi et al., 2022; Rijkenberg et al., 2015; Takano et al., 2022). Filtered samples are acidified to a pH of <2 using ultrapure hydrochloric or nitric acid to inhibit metal precipitation and adsorption onto container walls before analysis (Bersuder et al., 2021; Choi et al., 2022; Nakaguchi et al., 2022; Seo et al., 2022; Takano et al., 2022). The concentration of dissolved metals can be determined using an automated pre-concentration system (seaFAST SP3; Elemental Scientific) with an inductively coupled plasma mass spectrometer (ICP-MS).

Diffusive gradient in thin films (DGT) passive samplers have been developed and applied for metal isotope monitoring in natural waters. DGT sampling enables the in situ pre-concentration of metals, thus removing the requirement for laborious chemical pre-treatment. This method incorporates isotopic variations over the deployment period and minimizes contamination risks during handling and storage (Desaulty et al., 2020, 2017).

During storm events, rainfall runoff samples and their corresponding total suspended solids (TSS) are collected using pre-cleaned containers. Following filtration, the solids are subjected to drying and processing in accordance with the established protocol for other particulate samples (Jeong et al., 2020; Jeong and Ra, 2021a).

## 3.2. Sample preparation, chromatographic purification and Cu and Zn isotope measurements

High-precision isotope analyses of metals in environmental samples using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) require careful sample purification of the analyte and optimized instrumental parameters. Seawater samples contain high contents of salts and evaporation is not feasible, requiring a pre-concentration step. For low concentration waters and seawater, NOBIAS Chelate-PA1 (Hitachi Hightech) or Chelex-100 (BioRad) resins are commonly used to collect trace metals by removing major matrix elements. After the pre-concentration of water samples or the total digestion of solid samples in high-purity mixed acids (e.g., HNO₃, HF, and HClO₄), Cu and Zn are separated through ion-exchange chromatography to remove matrix elements and isobaric interferences.

Copper and zinc are typically separated using an anion exchange

resin, like AG MP-1, under controlled acid molarity conditions. A two-step elution process is commonly employed for Cu to improve purity and remove interferences (Jeong et al., 2021a; Larner et al., 2011; Lauwens et al., 2017). Zn is typically eluted with dilute nitric acid (e.g., 0.5 N) or water (Borrok et al., 2007; Maréchal et al., 1999; Moeller et al., 2012).

The purified metal fractions are then dried and re-dissolved in 2–3 % HNO₃ prior to analysis. Measurements of isotope ratios are conducted using MC-ICP-MS. The instrumental mass bias is commonly corrected by the standard-sample bracketing (SSB), and can also combine with external normalization using a doping (Cu for Zn sample and Zn for Cu sample). The double-spike technique utilizing ⁶⁴Zn and ⁶⁷Zn can be employed to address mass bias in the chemical separation and isotopic measurement of Zn isotopes (Amet and Fitoussi, 2020; Bermin et al., 2006; Lemaitre et al., 2020; Moore et al., 2017).

Reference materials, including NIST976 or ERM-AE647 (Cu for Zn sample) and JMC<sub>Lyon</sub> or IRMM-3702 (Zn for Cu sample), are frequently utilized for the determination of express delta values (Jeong et al., 2021a; Maréchal et al., 1999; Moeller et al., 2012). Isotopic compositions are represented in delta (δ) notation, indicating per mil (‰) deviations from international reference materials. Sample preparation and isotopic analyses are conducted in clean laboratory environments to ensure analytical reproducibility and reduce contamination risks.

# 4. Mechanisms of isotope fractionation

## 4.1. Cu and Zn in coastal and estuarine processes

Coastal and estuarine zones are dynamic interfaces where land-driven inputs and marine processes intersect (Fig. 1). Trace metals, such as Cu and Zn, undergo complex transformations in these systems, influenced by both abiotic and biotic processes. These processes include adsorption-desorption interactions, redox transformations, complexation with organic and inorganic ligands, as well as biological processes (e.g., phytoplankton uptake, microbial assimilation, trophic transfer, and regeneration, Machado et al., 2016). These mechanisms affect both the mobility and bioavailability of metals, as well as their isotopic compositions (Junqueira et al., 2024; Komárek et al., 2022; Schilling et al., 2021).

In estuary salinity gradients, where riverine freshwater mix with seawater, the partitioning among dissolved, colloidal, and particulate phases is important in regulating metal speciation and transport (Abdou et al., 2022; Briant et al., 2021). Changes in pH and ionic strength associated with increasing salinity promote desorption of metals from particles through the formation of soluble chloride complexes and competition with ions in seawater (Behbahani et al., 2021; Liu et al., 2022). These geochemical shifts also enhance particle aggregation via flocculation and coagulation, thereby facilitating metal removal and deposition into sediments.

The region of optimal particle deposition and metal alteration generally occurs in the Maximum Turbidity Zone (MTZ), characterized by elevated suspended sediment concentrations resulting from hydrodynamic entrapment (Robert et al., 2004). Below this zone, other biogeochemical processes, including sediment diagenesis, redox-driven transformations, and bioturbation, might alter the fate and isotopic composition of trace metals. Thus, isotopic fractionation of Cu and Zn may occur due to various interconnected processes—adsorption, redox transformations, complexation, and biological uptake—along the freshwater-seawater mixing continuum (Desaulty and Petelet-Giraud, 2020; Junqueira et al., 2024; Komárek et al., 2022; Thapalia et al., 2010).

## 4.2. Isotope fractionation in the sediment-water-biota interface

Partitioning between dissolved and particulate phases in estuaries plays an important role in the behavior, fate, transport, and distribution
<figure><img src="image_3.png" /><figcaption>**Fig. 1.** The mechanisms of Cu and Zn stable isotope fractionation across an estuarine gradient, from freshwater to seawater. Anthropogenic and geogenic sources of Cu and Zn enter the estuarine system via urban runoff. During estuarine mixing, particulate-bound metals interact with mineral surfaces, inducing isotopic fractionation (e.g., preferential adsorption of lighter or heavier isotopes). In the maximum turbidity zone (MTZ), dynamic mixing and resuspension promote metal exchange between particulate and dissolved phases, contributing to isotope variations (Δ$^{65}$Cu and Δ$^{66}$Zn). Biogeochemical processes such as redox transformations and microbial assimilation further induce isotopic shifts. Sediment bioturbation, metal scavenging, and deposition also influence the fate and isotopic signatures of Cu and Zn.</figcaption></figure>

of trace metals, potentially accompanied by isotopic compositions of Cu and Zn during chemical and physical processes in aquatic environments (Petit et al., 2015, 2013) (Fig. 1). Abiotic processes such as adsorption to mineral surfaces can induce isotope fractionation: light Cu isotopes are preferentially adsorbed onto kaolinite and manganese oxides, whereas iron oxy(hydro)oxides tend to favor adsorption of heavier Cu (Balistrieri et al., 2008; Ijichi et al., 2018; Li et al., 2015; Wang et al., 2020). Redox processes also impact Cu isotope composition, as oxidized Cu$^{2+}$ species tend to be enriched in $^{65}$Cu, while reduced Cu$^{+}$ species are relatively light (Ehrlich et al., 2004; Fujii et al., 2014; Sherman, 2013; Wang et al., 2020).

Biotic processes also play an important role in shaping Cu isotopic signatures in estuarine environments through biological uptake by microorganisms. Laboratory experiments have shown that live bacterial cells preferentially assimilate the lighter Cu isotope across various conditions, resulting in an enrichment of $^{65}$Cu in the surrounding dissolved phase (Navarrete et al., 2011). In a French estuarine system (Garonne Estuary, France), $^{65}$Cu values of particulate matter are lighter in upstream regions with active phytoplankton, compared to heavier values in the turbidity maximum zone where phytoplankton is absent (Petit et al., 2013). Together, these observations indicate that microbial and phytoplankton uptake preferentially removes $^{63}$Cu, leading to isotopically lighter particulate matter and leaving the dissolved Cu pool relatively enriched in $^{65}$Cu (Table 1).

Zn isotope fractionation is basically governed by coordination chemistry, the interconversion between tetrahedral and octahedral complexes (Aucour et al., 2023; Gou et al., 2018) and can also occur through geochemical processes such as adsorption, precipitation, and evaporation (Tu et al., 2020). Fractionation magnitudes of Zn isotope (Δ$^{66}$Zn$_{solid-aq}$) ranged from -0.2 to over +1.0‰ depending on surface

type, pH, ionic strength, and surface coverage (Bryan et al., 2015; Komárek et al., 2022; Nelson et al., 2017; Pokrovsky et al., 2005). Stronger isotopic fractionation is associated with tetrahedral Zn surface complexes under high ionic strength and low surface loading, while octahedral coordination at high surface coverage yields smaller isotopic fractionation (Bryan et al., 2015; Komárek et al., 2022; Manceau et al., 2002). In estuarine environments, the dissolved Zn isotope composition tends to become heavier as the concentration of suspended particulate matter (SPM) increases. Zn isotopes in dissolved phase are heavier in the downstream of the estuary with high SPM concentration than in the upstream (Petit et al., 2015). During biological assimilation, cells preferentially incorporate the lighter isotope ($^{64}$Zn), resulting in the residual dissolved phase becoming relatively heavier (Conway and John, 2014; John and Conway, 2014). However, under conditions of intense particle-water interaction, such as in turbid estuaries with high suspended particulate matter (SPM), isotopically heavy Zn may be scavenged onto particles, leaving the dissolved pool is isotopically lighter (Conway and John, 2014; John and Conway, 2014).

### 4.3. *High temperature processes*

Zn isotopes undergo Rayleigh-type fractionation during smelting, with lighter isotopes ($^{64}$Zn) preferentially partitioning into gaseous emissions, and heavier isotopes ($^{66}$Zn) becoming enriched in solid residues such as slag ($^{66}$Zn up to +1.22 ‰) and effluents ($^{66}$Zn: 0.14–0.24 ‰). These patterns are consistent with kinetic and equilibrium isotope effects during volatilization and condensation. Electroplating steps may further modify isotopic signatures, although the extent of fractionation across individual metallurgical steps remains insufficiently constrained (Yin et al., 2016).
<caption>**Table 1**</caption>

Cu and Zn concentrations (mg/kg; dry weight) and isotopic compositions (‰) in various environmental samples and anthropogenic sources commonly found in urban areas. DM: dissolved matter; PM: particulate matter.

<table><thead><tr><th>Sample</th><th>Cu</th><th>Zn</th><th>δ<sup>65</sup>Cu<sub>AE647</sub></th><th>δ<sup>66</sup>Zn<sub>IRMM3702</sub></th><th>References</th></tr></thead><tbody><tr><td>Garonne river DM (France)</td><td>1.08<sup>a</sup><br>(0.82<sup>a</sup> to 1.32<sup>a</sup>)</td><td></td><td>-0.21<br>(-0.88 to 0.00)</td><td></td><td>Petit et al., 2013</td></tr><tr><td>Yangtze river DM (China)</td><td>2.15<sup>a</sup><br>(1.02<sup>a</sup> to 6.19<sup>a</sup>)</td><td></td><td>0.87<br>(0.27 to 1.44)</td><td></td><td>Wang et al., 2020</td></tr><tr><td>Itchen estuary DM (UK)</td><td>0.86<sup>b</sup><br>(0.59<sup>b</sup> to 1.10<sup>b</sup>)</td><td></td><td>0.44<br>(0.30 to 0.59)</td><td></td><td>Vance et al., 2008</td></tr><tr><td>Fluvial estuary DM (France)</td><td></td><td>1484<sup>a</sup><br>(850<sup>a</sup> to 4470<sup>a</sup>)</td><td></td><td>0.27<br>(-0.29 to 0.63)</td><td>Petit et al., 2015</td></tr><tr><td>River water DM (Germany)</td><td></td><td>111<br>(3 to 1680)</td><td></td><td>0.02<br>(-0.51 to 0.45)</td><td>Zimmermann et al., 2020</td></tr><tr><td>Runoff DM (Czech Republic)</td><td></td><td>32<sup>b</sup><br>(23<sup>b</sup> to 66<sup>b</sup>)</td><td></td><td>-0.16<br>(-0.32 to -0.04)</td><td>Andronikov et al., 2021</td></tr><tr><td>Garonne river PM (France)</td><td>58.38<br>(31.40 to 181.30)</td><td></td><td>-0.46<br>(-0.60 to -0.36)</td><td></td><td>Petit et al., 2013</td></tr><tr><td>Itchen estuary PM (UK)</td><td>0.83<sup>b</sup><br>(0.10<sup>b</sup> to 1.46<sup>b</sup>)</td><td></td><td>-0.68<br>(-1.23 to -0.45)</td><td></td><td>Vance et al., 2008</td></tr><tr><td>Runoff PM (Korea)</td><td>16,294<br>(1747 to 27,631)</td><td>9921<br>(3680 to 16,537)</td><td>0.01<br>(-0.11 to 0.15)</td><td>-0.11<br>(-0.21 to -0.02)</td><td>Jeong and Ra, 2021b</td></tr><tr><td>River PM (Brazil)</td><td>56<br>(35 to 97)</td><td>227<br>(193 to 280)</td><td>-0.20<br>(-0.26 to -0.09)</td><td>-0.21<br>(-0.36 to -0.12)</td><td>Guinoiseau et al., 2018</td></tr><tr><td>Fluvial estuary PM (France)</td><td></td><td>486<br>(199 to 2140)</td><td></td><td>0.12<br>(0.07 to 0.20)</td><td>Petit et al., 2015</td></tr><tr><td>Surface sed (France, Loire)</td><td>19.5<br>(6.2 to 36.0)</td><td>108<br>(32 to 179)</td><td>-0.30<br>(-0.45 to -0.13)</td><td>-0.04<br>(-0.14 to 0.06)</td><td>Araújo et al., 2019b</td></tr><tr><td>Surface sed (France, Toulon)</td><td>74<br>(4 to 305)</td><td>153<br>(19 to 695)</td><td>-0.27<br>(-1.00 to 0.13)</td><td>-0.21<br>(-0.54 to 0.01)</td><td>Araújo et al., 2019a</td></tr><tr><td>Road dust (UK)</td><td>188<br>(17 to 800)</td><td>288<br>(80 to 560)</td><td>-0.23<br>(-0.49 to 0.09)</td><td>-0.06<br>(-0.30 to 0.07)</td><td>Dong et al., 2017</td></tr><tr><td>Road dust (Brazil)</td><td>170<br>(74 to 294)</td><td>348<br>(236 to 532)</td><td>-0.07<br>(-0.13 to 0.04)</td><td>-0.15<br>(-0.19 to -0.13)</td><td>Souto-Oliveira et al., 2018</td></tr><tr><td>Road dust (Korea)</td><td>6060<br>(81 to 81,262)</td><td>1270<br>(119 to 3627)</td><td>-0.03<br>(-0.33 to 0.73)</td><td>-0.18<br>(-0.36 to 0.01)</td><td>Jeong and Ra, 2021b</td></tr><tr><td>Unpolluted soil (France)</td><td></td><td></td><td>-0.33<br>(-0.49 to -0.21)</td><td>-0.10<br>(-0.21 to -0.03)</td><td>Fekiacova et al., 2015</td></tr><tr><td>Polluted soil (France)</td><td></td><td></td><td>-0.17<br>(-0.27 to 0.03)</td><td>-0.35<br>(-0.62 to -0.13)</td><td>Fekiacova et al., 2015</td></tr><tr><td>Brake (UK)</td><td>12<br>(4 to 25)</td><td>28<br>(17 to 46)</td><td>0.30<br>(0.07 to 0.42)</td><td>-0.10<br>(-0.12 and -0.07)</td><td>Dong et al., 2017</td></tr><tr><td>Brake (Korea)</td><td>38,460<br>(54 to 120,254)</td><td>5791<br>(581 to 24,291)</td><td>0.15<br>(0.04 to 0.23)</td><td>-0.04<br>(-0.09 to 0.03)</td><td>Jeong et al., 2022</td></tr><tr><td>Tire (UK)</td><td>37<br>(26 to 43)</td><td>9500<br>(7400 to 13,000)</td><td>0.05<br>(-0.04 to 0.12)</td><td>-0.07<br>(-0.08 to -0.06)</td><td>Dong et al., 2017</td></tr><tr><td>Tire (Korea)</td><td>239<br>(11 to 914)</td><td>12,099<br>(9849 to 14,157)</td><td>-0.56<br>(-1.04 to -0.22)</td><td>-0.06<br>(-0.09 to -0.03)</td><td>Jeong, 2022</td></tr><tr><td>Road paint (UK)</td><td>2.9<br>(1.8 to 4.3)</td><td>19.2<br>(4.8 to 44.0)</td><td>0.03<br>(-0.39 to 0.35)</td><td>0.10<br>(-0.20 to 0.31)</td><td>Dong et al., 2017</td></tr><tr><td>Road paint (Korea)</td><td>153<br>(7 to 852)</td><td>42<br>(7 to 106)</td><td>0.13<br>(-0.05 to 0.44)</td><td>-0.24<br>(-0.66 to 0.11)</td><td>Jeong et al., 2022</td></tr><tr><td>Asphalt (Korea)</td><td>126<br>(118 to 129)</td><td>5440<br>(5237 to 5661)</td><td>0.01<br>(-0.02 to 0.04)</td><td>0.00<br>(-0.02 to 0.01)</td><td>Jeong et al., 2022</td></tr><tr><td>Antifouling paint (Korea)</td><td>35.5<sup>c</sup><br>(17.3<sup>c</sup> to 54.4<sup>c</sup>)</td><td>7.76<sup>c</sup><br>(0.01<sup>c</sup> to 25.46<sup>c</sup>)</td><td>0.22<br>(-0.16 to 0.36)</td><td>-0.10<br>(-0.34 to 0.03)</td><td>Jeong et al., 2023b</td></tr></tbody></table>

Recent experiments have shown that Zn isotopes can fractionate during equilibrium between silicate magmas and aqueous fluids (Guo et al., 2021). Zn isotopic composition of aqueous fluids is heavier than coexisting silicate magmas, with $\Delta^{66}\text{Zn}_{\text{fluid-magma}}$ from -0.22 ‰ to 0.97 ‰. This fractionation could be controlled by the Zn substitution mechanisms in the melt structure rather than by temperature or salinity (Guo et al., 2021).

High-temperature industrial operations such as ore smelting and coal combustion can induce Cu isotope fractionation. These processes typically follow Rayleigh-type fractionation, with lighter isotope ($^{63}\text{Cu}$) preferentially volatilized into gaseous emissions (e.g., fly ash), while the residual material becomes enriched in heavier isotopes ($^{65}\text{Cu}$). Smelting fly ash exhibited $\delta^{65}\text{Cu}$ values around -0.17 ‰, whereas coal and coal-burning fly ash showed distinctly heavier signatures, up to +2.23 ‰ and

+0.13 ‰, respectively (Xia et al., 2023).

High-temperature magmatic process can also induce isotope fractionation through redox-controlled crystallization and sulfide segregation (Sun et al., 2023). The $\delta^{65}\text{Cu}$ values ranged from -0.62 ‰ to -0.13 ‰ in Mid-ocean ridge basalt samples, associated with the crystallization of Fe-Ti oxides. Redox reactions during magma differentiation involving the shift between $\text{Cu}^+$ and $\text{Cu}^{2+}$ drive this isotope fractionation. Heavy Cu isotopes are preferentially incorporated into sulfide under oxidizing conditions, decreasing $\delta^{65}\text{Cu}$ values in the residual melt. Conversely, later reduction favor lighter Cu isotopes in sulfides, increasing $\delta^{65}\text{Cu}$ in the melt (Sun et al., 2023).

<footnote>a unit: µg/L.</footnote>

<footnote>b unit: µg/kg.</footnote>

<footnote>c unit: %.</footnote>
## 4.4. Electrolysis

### 4.4.1. Inquiring Zn isotope fractionation during the electrolysis step

Previous studies have reported δ<sup>66</sup>Zn<sub>IRMM3702</sub> values for electrochemically purified material (−0.05 ± 0.03; John et al., 2007; Shiel et al., 2010) as well as electroplated hardware (−0.63 ± 0.18 ‰; John et al., 2007). However, specific details regarding the production process of the electroplated hardware, which involved screws and chains from various stores, remain unclear (John et al., 2007). In contrast, the production of electrochemically purified Zn is better documented, particularly in the case of The Canadian Electrolytic Zinc Limited Refinery (CEZinc), whose industrial procedures have been described by the Canadian Ministry of the Environment (1996). The production processes at CEZinc include the sequence of “roasting of concentrated zinc ore; leaching, purification...; electrolysis (zinc recovery)” (Ministry of the Environment, 1996). The zinc isotope composition of electrochemically purified materials is very similar to that of natural zinc ores such as sphalerite (−0.16 ± 0.25 ‰; n = 108; Gagnevin et al., 2012; Kelley et al., 2009; Maréchal et al., 1999; Mondillo et al., 2018; Pašava et al., 2014; Sonke et al., 2008) and Braziliain willemite from the Vazante deposit (δ<sup>66</sup>Zn = −0.14 ± 0.09 ‰, n = 19; Araújo et al., 2017b; this study, see Supplementary Material). This last used in a Brazilian electroplating plant. This close match suggests that the industrial refining process introduces only minimal isotope fractionation, especially when metal recovery is high and roasting does not significantly alter the isotopic signature (Shiel et al., 2010).

### 4.4.2. Rayleigh Zn isotope fractionation model for the electroplating processes

Laboratory experiments on electrolysis have shown that the remaining solution becomes enriched in heavier isotopes compared to the electroplated material in cathodes (αsolution-electroplated >0) (Kavner et al., 2008). The extent of isotopic fractionation decreases linearly with increasing driving voltage, reaching a minimum value of αelectroplating = 1.0019 at the highest evaluated voltage of 800 mV (Kavner et al., 2008). Typical Zn electroplating operations in hydro-metallurgy commonly use voltages ranging from 3.2 to 3.9 V (Martins, 1976). Based on this information, we estimate a significantly lower magnitude of isotopic fractionation than α-electroplating = 1.0019 at 800 mV.

Studies directly investigating Zn isotope fractionation in full-scale electroplating plants are lacking. However, the effects of such processes can be inferred using field data obtained near a former electroplating facility (Industrial e Mercantil Ingá company) that operated in southeastern Brazil between the 1960s and 1990s. It is estimated that this plant achieved a Zn recovery efficiency during electrolysis of approximately 93.6 % using industrial-sized voltages exceeding 3.2 V (Fukubayashi, 1969).

According to the Rayleigh fractionation model, a homogeneous and stable isotope reservoir evolves over time as a phase is continuously removed from it. Considering a Rayleigh-type fractionation during electroplating, an initial δ<sup>66</sup>Zn in solution derived from Brazilian willemites, around −0.14 ‰ (n = 21), and an electroplating efficiency of 93.6 % (Fukubayashi, 1969), we observe that the attainment of a δ<sup>66</sup>Zn value of −0.05 ‰ for electrochemically purified Zn (John et al., 2007; Shiel et al., 2010) yield an electroplating isotope fractionation factor (αelectroplating) of approximately 1.00006 (Fig. 2). It is worth noting that this α value deviates from the linear relationship suggested by Kavner et al. (2008) between isotopic fractionation and voltage (Δ<sup>66</sup>Zn (‰) = −3.48(0.17) − 2.01(1.33) *V) observed at lower voltage levels. This deviation suggests that linearity may be compromised when scaling up to industrial voltages, highlighting the need for further exploration and understanding.

It is also worth noting that electroplating wastes analyzed from the same facility showed a slight enrichment in heavy Zn isotopes compared to the original ores (Δ<sup>66</sup>Zn waste-ore = 0.17 ‰, Tonhá et al., 2020). We

<figure><img src="image_4.png" /><figcaption>Fig. 2. Modeled Rayleigh isotopic fractionation of Zn during electrolysis, illustrating the progressive enrichment of δ<sup>66</sup>Zn in the residual solution as electroplating proceeds. The curves represent different α(solution-electroplated) values, with an estimated industrial electroplating efficiency of ~93.6 % (Fukubayashi, 1969). The δ<sup>66</sup>Zn values were from willemite ores (Araújo et al., 2017b; this study), and the resulting electroplated Zn is constrained by δ<sup>66</sup>Zn ≈ 0.49 ‰ (John et al., 2007; Shiel et al., 2010). The model also considers δ<sup>66</sup>Zn enrichment in recycled solutions during continuous circuit operation in hydrometallurgical plants.</figcaption></figure>

hypothesize that this shift results from the continuous recirculation of ore leachates within the electroplating circuit, progressively enriching the solution in the heavier isotope as lighter isotopes are preferentially deposited onto the cathode. While electroplating at high voltages typically induces only minor fractionation, this closed-loop recirculation can amplify isotopic shifts over time, especially when combined with variations in plating efficiency and ore composition.

## 5. Quantitative source apportionment using mixing models

Source apportionment of metal contaminants in complex urbanized estuarine systems has increasingly benefited from the application of mixing models that integrate stable isotope signatures with elemental concentration data. These models help quantify the relative contributions of multiple sources to environmental samples and have evolved from simple binary approaches to more sophisticated, probabilistic frameworks.

### 5.1. Mixing models

Binary mixing models represent a simple approach to isotope-based source apportionment, applicable when two distinct isotope end-members are assumed (Barreira et al., 2022; Bird et al., 2010; Huang et al., 2019; Wiederhold, 2015). The binary mixing model is one of the most widely used classical approaches, suitable when only two potential sources contribute to the mixture. Based on a mass balance, the isotope composition (δ<sub>mix</sub>) of a sample is modeled as a weighted average of two end-members (source A and B):

$$ \delta_{\text{mix}} = f_A \cdot \delta_A + f_B \cdot \delta_B $$

$$ f_A + f_B = 1 $$

Here, f<sub>A</sub> and f<sub>B</sub> are the fractional contributions from each source, and δ<sub>A</sub> and δ<sub>B</sub> are their respective isotopic compositions. Although simple, this approach is limited to scenarios with clearly distinguishable source signatures and assumes no isotopic alteration during transport or transformation.

The ternary mixing model extends this approach to three sources, requiring two independent isotopic tracers to solve the system. These
models have been applied to distinguish terrigenous, urban, and industrial contributions in estuarine sediments using combinations of Cu, Zn, and Pb isotopes.

## 5.2. IsoSource model

The IsoSource model, developed by the U.S. Environmental Protection Agency (EPA), is based on the binary and ternary mixing models. It applies the principle of mass conservation and uses an iterative calculation method to produce a combination of multiple source ratios. The number of possible source combinations is determined by the following equation (Phillips et al., 2005; Phillips and Gregg, 2003; Wang et al., 2021):

$$No.combinations = \frac{\left(\frac{100}{i}\right) + (s-1)}{s-1} = \frac{\left[\left(\frac{100}{i}\right) + (s-1)\right]!}{\left(\frac{100}{i}\right)!(s-1)!}$$

where i is increment percentage for each source and s is the number of sources.

## 5.3. MixSIAR model

The MixSIAR model in R software is a tool that utilizes Bayesian statistics based on the basic mass balance equations. It incorporates analytical uncertainty and source variability, estimating source contributions that sum to one. MixSIAR has been applied in ecological and environmental studies where multiple sources and isotopic systems are involved (Dai et al., 2023; Dietrich et al., 2021; Heikkinen et al., 2022; Hu et al., 2022; Longman et al., 2018; Tian et al., 2024; Wang et al., 2022a).

$$X_{ij} \sim N \left( \sum_{k} P_{k} (\mu_{jk} + \lambda_{jk}), \sum_{k} P_{k}^{2} (\omega_{jk}^{2} + \tau_{jk}^{2}) \right)$$

where $X_{ij}$ represents the tracer value of j of a mixture i, $P_k$ is the proportion of source k, $\mu_{ij}$ is the mean of source k for tracer j, $\lambda_{ij}$ is the mean trophic discrimination factor (TDF) for tracer j on source k, $\omega_{ij}^2$ is the TDF for source k variance for tracer j, and $\tau_{jk}^2$ is the discrimination factor variance for tracer j on source k.

## 5.4. Multivariate approaches

Positive Matrix Factorization (PMF) is a receptor model provided by U.S. EPA for calculate source apportionment in environmental pollution studies (Chen et al., 2022; Schleicher et al., 2023; Shao et al., 2024; Souto-Oliveira et al., 2021; Wang et al., 2022a). The main methods are expressed by following equations:

$$x_{ij} = \sum_{k=1}^{p} g_{ik} f_{kj} + e_{ij}$$

$$Q = \sum_{i=1}^{n} \sum_{j=1}^{m} \left[ \frac{x_{ij} - \sum_{k=1}^{p} g_{ik} f_{kj}}{u_{ij}} \right]^2$$

where $x_{ij}$ represents the metal content j in the sample i; $f_{kj}$ represents the metal content j in source k; $g_{ik}$ represents the contribution of source k to the sample i; $e_{ij}$ represents the residual matrix. The factor contributions and profiles are derived by the PMF model minimizing the objective function Q. This approach has recently been combined with multi-isotope fingerprinting (MIF) to improve source resolution in urban aerosol studies (Schleicher et al., 2023; Souto-Oliveira et al., 2021).

# 6. Cu and Zn isotope compositions in urbanized coastal environments

The following sections address to how Cu and Zn isotope characterization in urban particles occurring in aerosols and runoff waters allows tracking anthropogenic emissions in the estuarine pathway. We integrate industrial and mining-related data selectively and comparatively, using known isotope signatures of ores, intermediate products (e. g., slags, dusts, effluents), and end-of-pipe residues to supplement urban datasets. This strategy allows us to contextualize industrial signals without detracting from the primary focus on urban metal pathways. It also enhances source discrimination in estuarine environments where urban and industrial influences are co-located or temporally overlapping.

## 6.1. Natural sources

Zinc ores have been reported in previous studies (Table S1). The bulk silicate earth signature (BSE, $\delta^{66}$Zn = +0.01 ± 0.05 ‰ (2sd); Chen et al., 2013). Here we include new data from the willemites from Vazante Deposit (Brazil, Table S2). Zn ores like sphalerite, smithsonite, and willemite generally exhibit negative $\delta^{66}$Zn values, clustering between -0.69 ‰ and +0.16 ‰, although considerable variability is observed even within a single ore type (e.g., willemite: -0.69 ‰ to +1.12 ‰; this study; Araújo et al., 2017b; Mondillo et al., 2018).

The BSE is estimated to have an average $\delta^{65}$Cu of -0.15 ± 0.20 ‰ (2sd) (Liu et al., 2015). Cu ores exhibit wide range of $\delta^{65}$Cu values, reflecting hydrothermal evolution and alteration processes. Reported Cu isotope composition in pyrite the Iron Creek deposit ranged from -1.56 ‰ to -0.08 ‰ (Zaronikola et al., 2023), while chalcopyrite in the Dabu porphyry deposit shows an even broader range from -1.69 ‰ to 0.91 ‰ related to alteration assemblages and Rayleigh fractionation during fluid evolution (Wu et al., 2017).

## 6.2. Anthropogenic sources

### 6.2.1. Industrial sources

The isotopic compositions of Cu and Zn in anthropogenic sources largely reflect the original ore signatures, but are further fractionated during mining, metallurgical, and industrial processes. Fig. 3 compiles $\delta^{66}$Zn values for natural ores, industrial byproducts, and anthropogenic residues from mining and metallurgical activities. Processing effects, such as those introduced by roasting, electrolysis, and combustion, can alter isotopic signatures, generating a wide isotopic spread in downstream environmental matrices.

Isotope variability is evident in industrial byproducts, where even materials from the same industrial category can differ substantially in isotopic composition. For example, $\delta^{66}$Zn values in sludge samples from a single smelter varied by up to 0.86 ‰ (Bigalke et al., 2010), reflecting the influence of process-specific parameters, such as ore composition. This shows the need to expand isotope datasets across industrial sectors and to provide detailed source fingerprints—including process type and geographic origin—to improve source apportionment in estuaries impacted by mixed anthropogenic inputs.

Septeiba Bay (Brazil) serves as a clear example of how industrial sources can dominate local isotopic signatures in heavily urbanized estuarine systems. The local electroplating wastes produced from a Zn ore processing deposited in this region exhibits a $\delta^{66}$Zn value of 0.03 ‰, representing a small enrichment of +0.16 ‰ relative to the processed willemite ore, which has a $\delta^{66}$Zn value of -0.11 ± 0.13 ‰. Nevertheless, the mobile and bioavailable Zn from this industrial source obtained via acid-diluted leaching exhibits a distinct heavy isotopic signature ($\delta^{66}$Zn ≈ +0.58 ± 0.15 ‰; Tonhá et al., 2020), which is effectively transferred into surrounding sediments and can be used for source tracing and as an indicator of long-term anthropogenic legacy in estuarine archives. Thus, sediments located in the hot spot of the
<figure><img src="image_5.png" /><figcaption>**Fig. 3.** Zn isotope values in ores, products and wastes derived from anthropogenic processes. Source: Raw material - Chalcopyrite: Maréchal et al. (1999); Mason et al. (2005); Chalcopyrite + Pyrite: Mason et al. (2005); Chalcopyrite + Sphalerite: Maréchal et al. (1999); Chalcopyrite + Sphalerite + Galena: Mason et al. (2005); Covellite + Chalcopyrite + Pyrite + Silicate + Sphalerite: Mason et al. (2005); Galena: Mason et al. (2005); Mondillo et al. (2018); Galena + Quartz + Sphalerite: Mason et al. (2005); Hemimorphite: Mondillo et al. (2018); Pyrite + Chalcopyrite + Sphalerite: Mason et al. (2005); Pyrite + Chalcopyrite + Sphalerite + Silicate: Mason et al. (2005); Quartz + Chalcopyrite + Sphalerite: Mason et al. (2005); Silicate + Pyrite + Chalcopyrite + Sphalerite: Mason et al. (2005); Smithsonite: Albarède (2004); Mondillo et al. (2018); Wilkinson et al. (2005), Sphalerite: Gagnevin et al. (2012); Kelley et al. (2009); Maréchal et al. (1999); Mondillo et al. (2018); Pašava et al. (2014); Sonke et al. (2008); Sphalerite + Chalcopyrite + Galena: Mason et al. (2005); Sphalerite + Chalcopyrite + Pyrite: Mason et al. (2005); Sphalerite + Chalcopyrite: Mason et al. (2005); Sphalerite + Galena + Chalcopyrite + Pyrite: Mason et al. (2005); Sphalerite + Galena + Chalcopyrite: Mason et al. (2005); Zhou et al. (2014); Sphalerite + Pyrite + Dolomite: Zhou et al. (2014); Sphalerite + Pyrite + Galena + Chalcopyrite: Zhou et al. (2014); Willemite: Araújo et al. (2017b); Mondillo et al. (2018), this study; Coal: Wang et al. (2022b); Products - Refined Zn: John et al. (2007); Shiel et al. (2010); Electrolysis hardware: John et al. (2007); ZnO fume: Shiel et al. (2010); Galvanization hardware: John et al. (2007); Roasting ZnO: Shiel et al. (2010); Industrial raw material: John et al. (2007); Wastes - Blasting slag: Yin et al. (2018); Blasting dust: Yin et al. (2018); Coal ash: Sivry et al. (2008); Acid leaching + Electrolysis waste: Tonhá et al. (2020); Grilling dust: Mattielli et al. (2009); Melting slag: Bigalke et al. (2010); Yin et al. (2018); Smelter effluent/sludge: Bigalke et al. (2010); Shiel et al. (2010); Acid mine drainage (AMD): Liu et al. (2020); AMD precipitate: Liu et al. (2020); Mining ash: Wang et al. (2022b); Coal gangue: Wang et al. (2022b); Mining tailing: Sivry et al. (2008); Percolating water from mining tailing: Sivry et al. (2008). Std. dev. and statistical n under brackets derived from samples analyzed, not considering analytical replicates.</figcaption></figure>

contamination by the old wastes from the electroplating industry display $\delta^{66}\text{Zn}$ values around 0.5-1.0 ‰.

In addition to Zn, Cu isotope compositions also reflect metallurgical processing histories. Experimental studies on chalcopyrite (CuFeS₂) smelting have shown that $\delta^{65}\text{Cu}$ values vary by byproduct: slag tends to be isotopically heavier (up to +1.37 ‰), matte retains ore-like values (−0.28 ‰ to 0.53 ‰), and metallic Cu prills fall within intermediate ranges (Klein and Rose, 2020). Although high-temperature conditions typically limit fractionation, processes like oxidation and quenching can introduce significant shifts.

In estuarine environments, Cu isotope values in sediments and SPM are often more tightly clustered around slightly positive values compared to industrial/mining sources (Fig. S1). This may reflect a homogenization effect caused by low-temperature redox processes after deposition, which can overprint the original industrial signal (Asael et al., 2007; Bigalke et al., 2013; Wang et al., 2020). Thus, while industrial sources contribute unique and often traceable isotopic signatures, environmental processing can obscure their distinction from other urban sources, highlighting the importance of site-specific context and multi-proxy approaches.

Finally, in mining-impacted areas like the Iberian Pyrite Belt, sulfide ores show light $\delta^{66}\text{Zn}$ values (−0.28 ‰ to +0.02 ‰), whereas downstream dissolved Zn in rivers and estuaries exhibits more enriched signatures (up to +0.08 ‰), due in part to mixing with industrial discharges and acid mine drainage (Packman et al., 2023). This regional pattern reinforces the relevance of isotopes for identifying source mixing and transport, even in complex landscapes where urban, industrial, and mining legacies converge.

### 6.2.2. Traffic-related sources

Studies in estuarine and coastal environments have been conducted, focusing on containment derived from streams and rivers, marine activities in harbors, and outfalls at wastewater treatment plants (WWTPs) (Álvarez et al., 2002; Caeiro et al., 2005; Guan et al., 2018). The land basin is larger than the estuarine or coastal watershed. Most land basins are covered with impervious surfaces such as paved roads, parking lots, and buildings, on which a large amount of polluted RDS and topsoil has accumulated. RDS and surrounding soils are highly polluted with Zn, Cu, Cd and Pb due to traffic and industrial activities, and are hot spot for metal contamination in the terrestrial and estuarine environments
(Chang et al., 2022; Haynes et al., 2020; Lindfors et al., 2020). Although the effective management of non-point pollution sources is becoming important for the prevention and management of metal pollution worldwide, most of RDS is continuously discharged along with rainfall runoff into rivers, estuaries and coastal environments without any treatments (Järtskog et al., 2021; Jeong et al., 2020; Müller et al., 2020).

The isotopic signatures of Cu and Zn were used for tracing pollution sources of RDS in urban environments (Jeong and Ra, 2021b, 2021a), and previous studies characterized isotope signatures of NEE sources (Jeong, 2022; Jeong et al., 2022, 2023b). The fine RDS particles smaller than 63 µm were associated with the total suspended solids (TSS) in rainfall runoff (Fig. 4). These studies proposed that Cu contamination of RDS in intensive industrial area seems to be affected more by Cu-related industries than traffic activities. On the other hand, the major pollution sources of RDS, which causes metal pollution to the surrounding estuary and coast, derives from NEE sources associated traffic activities. Particles from brakes contain approximately 4 % Cu and demonstrate the highest Sb content (~0.8 %) among NEE sources (Fig. 5A; Jeong et al., 2022). In the manufacturing of brake pads, Sb compounds have been employed as lubricants (Dousova et al., 2020). The US National Toxicology Program (US-NTP) has classified Sb<sub>2</sub>O<sub>3</sub> as a human carcinogen based on carcinogenicity tests and mechanistic investigations (Bolan et al., 2022; NTP, 2018). Jeong et al. (2023b) has demonstrated significant enrichment of Sb in coastal sediments, suggesting that road dust from terrestrial regions impacts coastal areas via rainfall runoff. Hence, Sb warrants future attention for tracking coastal contamination and safeguarding public health in marine ecosystems, given its toxicity and carcinogenic potential in humans.

NEE sources are significantly enriched in toxic metals such as Cu, Zn, Sb, and Pb. Therefore, elemental ratios, Cu/Sb and Zn/Cu in RDS, serve as geochemical proxies for discriminating the relative contributions of traffic-related (vehicle) and non-traffic-related (non-vehicle) sources of metal contamination in urban environments (Amato et al., 2011; Bourotte et al., 2019; Hwang et al., 2016; Iijima et al., 2007; Jeong et al., 2020d). Recent studies have demonstrated that incorporating these elemental ratios with metal isotope signatures improves source identification and serve as a complementary tool in environmental forensic investigations (Jeong et al., 2022, 2023b, 2024) (Fig. 6). Characterization of Cu and Zn contamination sources in urbanized coastal environments using their isotopic signatures is shown in Fig. 5B. Data on Cu and Zn isotope in NEE sources such as brake pad, asphalt, road paint, curb, and tires produced by different manufactures and countries have been reported for the first time (Jeong, 2022; Jeong et al., 2022).

Cu isotopic compositions (δ<sup>65</sup>Cu) of NEE sources ranged from -1.04 ‰ to +0.44 ‰ (e.g., brake pad, tires, asphalt, road paint, and antifouling paint), whereas other environmental media (e.g., water, soils and

sediments) varied from -1.23 ‰ to +1.44 ‰ (Fig. 7). The δ<sup>65</sup>Cu values of NEE sources were comparable to those of TSS in rainfall runoff (-0.11 ‰ to +0.15 ‰), and fell within the range observed for road dust (-0.33 ‰ to +0.73 ‰) (Jeong and Ra, 2021a). Zn isotopic compositions of unpolluted soil tended to enrich heavier Zn isotopes compared to polluted soil (Fig. 6). Overall, NEE sources have relatively lighter Zn isotopic compositions than estuarine samples (dissolved and particulate phase of water column) (Petit et al., 2015).

### 6.2.3. Antifouling paints

Another important source of Cu contamination in estuarine and coastal environments is the use of antifouling paints (APs). Cu has been widely used as a biocide for APs because tributyltin (TBT) was banned due to its high toxicity (Almeida et al., 2007). A relatively high concentration of Cu has been shown in sediments near old shipyards (Choi et al., 2014; Jeong et al., 2020d). APs exhibit extremely high concentrations of Cu (~35 %) and Zn (~8 %) while tire samples contain approximately 1.2 % Zn. The Zn isotope values (δ<sup>66</sup>Zn) of APs ranged from -0.34 ‰ to +0.03 ‰, while the Cu isotope values (δ<sup>65</sup>Cu) varied from -0.16 ‰ to +0.36 ‰ (Jeong et al., 2023b).

In recent experimental data, δ<sup>65</sup>Cu and δ<sup>66</sup>Zn values in antifouling paints are fractionated during dissolution in seawater and subsequent adsorption onto marine sediments (Δ<sup>65</sup>Cu<sub>soln-solid</sub>: 0.91 ± 0.30 ‰ and Δ<sup>66</sup>Zn<sub>soln-solid</sub>: -0.14 ± 0.07 ‰; Jang et al., 2025). Zn isotope fractionation appears to be small and likely has a limited impact on source tracking of APs. In contrast, Cu isotopic signatures of these compounds tend to undergo more substantial fractionation, which complicates source attribution in real-world environments. These laboratory findings are consistent with previous studies showing that Cu isotope fingerprints of APs are not always directly preserved in sedimentary archives (Briant et al., 2022). This discrepancy suggests that multiple fractionation processes may affect Cu during its transport and transformation in aquatic systems. Especially, source identification in highly urbanized harbor areas posed challenges due to homogeneity of sediments in chemical compositions (concentrations and isotopic values) (Jeong et al., 2023b). Nevertheless, the elemental and isotopic characterization of NEE sources yielded distinct fingerprints, enabling their differentiation from APs. This characterization of NEE sources expands the isotope catalog of anthropogenic materials documented in the literature. The isotopic signatures of anthropogenic sources provide significant information for source identification and environmental forensics, enabling more accurate source tracking in urbanized estuaries with multiple pollution sources. Therefore, it is important to provide various isotopic signatures by country and manufacturer, but the lack of relevant data remains an obstacle to accurate interpretation of isotopic data in urbanized estuaries.

<figure><img src="image_6.png" /><figcaption>**Fig. 4.** Relationship between concentration and isotopic compositions of Cu and Zn in six different particle sizes in RDS and TSS in rainfall runoff (Jeong and Ra, 2021a).</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>**Fig. 5.** Metal concentrations (Cu, Zn, Pb, and Sb) (A) and relationship between Zn and Cu isotopic compositions (B) in brake pad, asphalt, curb, tire, and antifouling paint (¹Jeong et al., 2022, ²Jeong, 2022, ³Jeong et al., 2023b).</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>**Fig. 6.** Relationship between elemental ratios (Cu/Sb and Zn/Cu) and Cu isotopic compositions in anthropogenic sources and environmental samples (Jeong, 2022; Jeong et al., 2020c, 2022, 2023b, 2023e; Jeong and Ra, 2021a, 2021b).</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>**Fig. 7.** Cu (δ⁶⁵CuAE647) and Zn (δ⁶⁶ZnIRMM3702) isotopic composition in various environmental samples related to urbanized estuaries (¹Petit et al., 2013, ²Wang et al., 2020, ³Vance et al., 2008, ⁴Jeong and Ra, 2021a, ⁵Fekiacova et al., 2015, ⁶Araújo et al., 2019b, ⁷Araújo et al., 2019a, ⁸Araújo et al., 2021a, ⁹Dong et al., 2017, ¹⁰Souto-Oliveira et al., 2018, ¹¹Jeong et al., 2023b, ¹²Jeong et al., 2022, ¹³Jeong, 2022, ¹⁴Petit et al., 2015, ¹⁵Zimmermann et al., 2020, ¹⁶Andronikov et al., 2021, ¹⁷Guinoiseau et al., 2018, ¹⁸Jeong et al., 2021b, ¹⁹Araújo et al., 2017c, ²⁰Araújo et al., 2021b).</figcaption></figure>

<figure><img src="image_10.png" /></figure>

### 6.2.4. Atmospheric deposition

In urban environments, Cu and Zn occur mostly bound to dust and atmospheric particles (aerosols), these last ranging in size from below 1 µm up to at least 100 µm, which may be or become airborne, depending on their origin, physical characteristics, and ambient conditions (Kaonga et al., 2021). These urban solid particles can be natural (i.e., geogenic) or derived from anthropogenic sources, such as industries, thermal power stations, waste incinerators, exhaust and non-exhaust vehicular emissions, road dust, etc. (Ali et al., 2019; Manisalidis et al., 2020; Vlasov et al., 2021). Air currents transport smaller particles at long-range distances and may contaminate pristine remote areas, including the open ocean (Garnaud et al., 1999). Conversely, wet and dry local atmospheric fallout followed by urban runoff may transport trace metal contaminants from the atmosphere to watercourses downstream and ultimately to estuaries (Birch, 2024; Gunawardena et al., 2013; Sabin et al., 2005).

## 7. Cu and Zn isotope tracking in field studies

### 7.1. Urban and mining pollution

The tracking of pollution sources in estuarine environments should take account of potential isotopic fractionation during these biogeochemical processes. In the fluvial-estuarine geochemical pathways, urban particles reactivity, modulated by geochemical conditions (salinity, pH, organic ligands, redox process), control Cu and Zn exchanges in water column and their interactions with biotic interfaces. After deposition in bottom sediments, Cu and Zn can interchange with sediment and water phases during diagenesis.

It is well known that transition metals exist and bind in various forms such as free ions, hydroxide complexes, organic complexes and part of combined with mineral in the environment. The chemical forms of

existence for these metals determines mobility and bioavailability and give rise to isotopic fractionation, providing information about the relative abundance and alteration within the biogeochemical processes (Wiggenhauser et al., 2022). Especially, many transition metals form complexes with organic ligands. The dissolved phase of Cu binds very strongly to organic complexes, remaining very low concentrations of free Cu²⁺ in hydrosphere (e.g., rivers, estuaries, and oceans) (Blotevogel et al., 2022; Vance et al., 2008).

In addition to isotope fractionation of the dissolved and particulate phases in estuarine environments, suspended particulate matter (SPM) acts as a major carrier of terrestrial-derived metal contamination entering estuaries through rainfall runoff (Zeng and Han, 2020a). Most of the SPM originates on land and is transported through estuaries to coastal and open ocean regions. Araújo et al. (2019b) studied Cu and Zn stable isotopes in the Loire estuary sediments and concluded that Cu isotopic variations were primarily controlled by natural mineral sources, whereas Zn isotopic compositions reflected a mixture of terrigenous and urban inputs. Similarly, their research in a coastal bay with developed harbors (Araújo et al., 2019a) showed that while Cu isotopes allowed for the differentiation between natural and anthropogenic contamination, Zn isotopes were less effective in resolving mixed sources.

This limitation is largely attributed to the significant overlap in δ⁶⁶Zn values among various Zn sources, such as natural ores, smelter emissions, urban dust, and industrial residues. Moreover, intra-source isotopic variability arising from processes like high-temperature smelting and electrochemical treatments can produce a wide δ⁶⁶Zn range even within a single industrial site. As a result, Zn isotopic signatures from multiple sources often converge in the same range, making it difficult to disentangle their individual contributions. Therefore, Zn isotopes alone may not provide unambiguous source discrimination, and their application requires integration with other isotopic systems (e.g., Cu, Pb) or geochemical indicators (e.g., elemental ratios) to improve source
apportionment in complex estuarine environments. These studies show that Cu and Zn isotopes are affected not only by natural sources such as mineral composition but also by anthropogenic contaminants existing in the surrounding land basin, and regional difference may occur.

## 7.2. Estuarine mixing and anthropogenic influences

Recent field studies have enhanced the understanding of Cu and Zn isotope behavior in estuarine and coastal systems influenced by natural and anthropogenic influences. In the Peral River Estuary (PRE) of southeastern China, the Cu and Zn isotopes used to decipher source mixing and transport processes. The Zn isotope values ranged from -0.66 ‰ to +0.65 ‰ in water and from -1.45 ‰ to +0.63 ‰ in suspended particles, showing larger the δ⁶⁶Zn variations near industrial zones with heterogeneous source contributions (Ma et al., 2020). A significant correlation between Δ⁶⁶Znparticle-water and Zn concentrations in fine particles (0.8–10 µm) suggested that Zn partitioning governs isotopic differences. A strong correlation between predicted and observed δ⁶⁶Zn values based on salinity variations suggests that Zn isotope compositions can reliably trace estuarine mixing processes in the PRE. Another study in PRE, Zn isotope variations followed a Rayleigh fractionation pattern at low salinities, while Cu isotope compositions reflected a three-endmember mixing process involving riverine input, seawater, and external anthropogenic sources such as benthic fluxes and wastewater discharges (Ruan et al., 2024).

In the Scheldt Estuary, isotope fractionation of sediments and SPM revealed substantial for Zn (δ⁶⁶Zn = 0.21 ‰ to 1.13 ‰) and Cu (δ⁶⁵Cu = -0.38 ‰ to 0.23 ‰). These isotopic variations in Cu and Zn across salinity and metal concentrations indicate mixing between terrestrial and marine influences (Petit et al., 2008).

In the Ria of Huelva estuary (southern Spain), Zn exhibited non-conservative behavior during estuarine mixing, with up to 97 % of dissolved Zn removed to particulates and accompanied by a small isotopic shift toward lighter δ⁶⁶Zn values (Packman et al., 2023). Despite this attenuation, Cd and Zn isotope signatures largely reflected regionally averaged inputs from acid mine drainage (AMD), highlighting their potential use as tracers for anthropogenic contamination even under complex estuarine conditions.

## 7.3. Post-depositional transformation and legacy pollution

Industrial and mining activities often introduce Cu and Zn with distinct isotopic signatures that reflect ore mineralogy and processing intensity. However, post-depositional processes such as leaching, re-adsorption, and redox cycling can also significantly alter these signatures, complicating the isotopic fingerprint in sediments.

Sepetiba Bay offers a well-studied case where industrial Zn inputs from electroplating wastes exhibit a heavy isotopic signal (δ⁶⁶Zn = +0.58 ± 0.15 ‰), particularly in the labile fraction of electroplating residues (Tонhá et al., 2020). Sequential extraction showed that this signal is preserved in exchangeable and acetic-acid-soluble fractions, indicating that post-depositional redistribution does not fully obscure the original isotopic imprint. Similarly, in the Ria of Huelva, AMD-derived Zn persists in the dissolved phase even after partial removal onto particles, retaining an isotopically heavy signature traceable across the estuarine gradient (Packman et al., 2023). This highlights the resilience of industrial Zn signals, particularly in systems where continuous or legacy contamination dominates. While bulk sediment isotope values may become homogenized over time, specific geochemical fractions (acid-soluble or oxidizable phases) retain distinct industrial fingerprints (Nitzsche et al., 2024). Therefore, targeted extractions coupled with isotope analyses can help to improve resolution in tracing industrial inputs.

Experimental and field studies have shown that weathering of industrial residues can produce extreme isotopic shifts. For instance, leaching of Zn-bearing slags can yield Δ⁶⁶Znslag-leachate values up to 2.37

‰ (Yin et al., 2018). These fractionations are driven by pH-dependent solubility, redox transitions, and secondary mineral formation—factors particularly relevant in estuarine sediments with fluctuating oxygenation.

## 8. Multi-isotope approach for Cu and Zn in environmental study

Fig. 8 presents the concentration and isotopic composition of Cu for various environmental samples related to the estuarine environment. The concentrations and isotope compositions of Cu exhibited large variations depending on the sample type (Δ⁶⁵Cu<sub>max-min</sub>: ~2.67 ‰). The Cu concentration in dissolved phase of estuarine water was lower than that in other environmental samples, but the variation of δ⁶⁵Cu value (~2.32 ‰) was considerable (Petit et al., 2013; Vance et al., 2008; Wang et al., 2020). Other environmental samples except for mussel showed relatively small isotopic differences compared to the dissolved phase of estuarine water.

The δ⁶⁶Zn values ranged from -0.66 ‰ to +1.16 ‰ in various environmental samples (Fig. 9). The isotopic difference was approximately -1.82 ‰, which was smaller than the ~2.67 ‰ for the δ⁶⁵Cu value. There was a small difference in the concentration of Zn in dissolved phase of estuarine water (Petit et al., 2015; Zimmermann et al., 2020). However, the difference in δ⁶⁶Zn values was large, similar to that of Cu. δ⁶⁶Zn values in bivalve mollusks such as oysters and mussels showed positive values (Araújo et al., 2021b, 2017c; Jeong et al., 2021b), but other environmental samples (e.g., surface sediments, river sediments, road dust and NEE sources) showed a predominantly negative value.

Fig. 10A exhibits the relationship between Cu and Zn concentrations in various environmental samples related to the estuaries. Except for the NEE sources, all environmental samples showed a good correlation among them. Generally, the transition metals in environmental samples are highly related to particle sizes of sediments and organic matters. Finer particle sizes and higher organic content tend to increase the concentration of these metals. Particles from tires and brake pads had extremely high concentrations of Zn and Cu, respectively. In the case of Cu and Zn, it appears to be possible to distinguish specific pollution sources of these metals that are highly associated with their contamination. Most environmental samples such as soil, sediment, and road dust reflect the results of various contamination sources. The correlation of elemental concentrations can make it difficult to clearly explain contamination pathways or to identify the exact origins of metal contamination.

Fig. 10B shows the bi-plot of between δ⁶⁵Cu and δ⁶⁶Zn values of this study. As shown in Fig. 10A, road dust has relatively high concentration of Cu and Zn compared to the surface sediments. There is no significant difference between δ⁶⁶Zn values in surface sediments and road dust. The δ⁶⁵Cu values are negative in surface sediments and positive in road dust. However, the Cu-Zn dual isotope system does not always provide a straightforward distinction of anthropogenic sources due to the overlapping isotopic ranges of multiple urban and environmental materials. Therefore, as previously discussed, the integration of additional elemental proxies—such as Cu/Sb and Zn/Cu ratios— with multi-isotope data can enhance source discrimination and improve the resolution of anthropogenic input tracking in complex coastal systems.

Environmental samples are also contaminated with Cu and Zn as well as other transition metals (Heidari et al., 2021; Huang et al., 2022). However, there are still few isotope studies where transition elements have been studied together (Dietrich et al., 2021; Xie et al., 2019; Yang et al., 2020). In case of industrial area of Korea, the combination of isotopic signature for between Pb and either Cu or Zn suggested to be more useful tool for differentiating contamination sources than Cu and Zn isotopes (Jeong and Ra, 2021a).

RDS samples have a high Sb concentration due to brake pads (Jeong et al., 2020d; Jeong and Ra, 2021b). Developing a methodology for Sb isotopes and applying this isotope together with Cu and Zn can be
<figure><img src="image_11.png" /></figure>

**Fig. 8.** Bi-plot between concentrations and isotopic composition for Cu in various environmental samples. DM and PM refer to dissolved matter and particulate matter, respectively. The red rectangle indicates the range of concentrations and δ⁶⁵Cu values of non-exhaust emission sources from UK, Brazil and South Korea (Dong et al., 2017; Jeong et al., 2022; Souto-Oliveira et al., 2018) (¹Vance et al., 2008, ²Petit et al., 2013, ³Wang et al., 2020, ⁴Jeong and Ra, 2021a, ⁵Araújo et al., 2019b, ⁶Araújo et al., 2019a, ⁷Jeong et al., 2020c, ⁸Araújo et al., 2021a, ⁹Dong et al., 2017, ¹⁰Souto-Oliveira et al., 2018). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

<figure><img src="image_12.png" /></figure>

**Fig. 9.** Bi-plot between concentrations and isotopic composition for Zn in various environmental samples. DM and PM refer to dissolved matter and particulate matter, respectively. The red rectangle indicates the range of concentrations and δ⁶⁵Zn values of non-exhaust emission sources from UK, Brazil and South Korea (Dong et al., 2017; Jeong et al., 2022; Souto-Oliveira et al., 2018) (¹Petit et al., 2015, ²Zimmermann et al., 2020, ³Andronikov et al., 2021, ⁴Jeong and Ra, 2021a, ⁵Araújo et al., 2019b, ⁶Araújo et al., 2019a, ⁷Jeong et al., 2021b, ⁸Araújo et al., 2017c, ⁹Araújo et al., 2021b, ¹⁰Dong et al., 2017, ¹¹Souto-Oliveira et al., 2018). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

powerful for tracking traffic activities, especially the wear of brake pads, in urban environments. Furthermore, it would be interesting topics to combine geological tracers such as Sr, Nd, and Li isotopes with contamination-related metal isotopes (e.g., Cu, Zn, Pb, Ni, Cd, Cr, and Hg) as well. Therefore, approaches using multiple metal isotopes can exert synergistic effects through explaining both environmental pollution and geological processes.

Stable isotope data of transition metals on not only potential sources

but also many types of environmental samples are still scarce. In order to understand the biogeochemical process and to trace anthropogenic sources of transition metals in the estuarine environments, it will be important to establish and isotopic database for as many transition metals and potential contamination source as possible.
<figure><img src="image_13.png" /><figcaption>Fig. 10. Bi-plots of concentration and isotopic composition for between Cu and Zn in various environmental samples (¹Araújo et al., 2019b; ²Araújo et al., 2019a, ³Dong et al., 2017, ⁴Souto-Oliveira et al., 2018, ⁵Jeong and Ra, 2021a, ⁶Jeong et al., 2022, ⁷Jeong, 2022, ⁸Fekiacova et al., 2015).</figcaption></figure>

## 9. Summary and future perspectives

This review shows the utility of Cu and Zn stable isotopes as useful tracers to identify anthropogenic metal sources and elucidate their

biogeochemical processes along the land-sea continuum. Isotopic signatures of Cu and Zn have been applied to identify urban pollution sources from traffic-related non-exhaust emissions (NEE), industrial residues, antifouling paints, and atmospheric deposition. High
temperature industrial operations—such as smelting, electrolysis, and combustion—indicate distinct isotope compositions from the natural baseline of pristine sediments, water, and biota. In some cases, however, isotope values of industrial residues overlap with natural materials, reinforcing the importance of combining with additional isotope systems or approaches. Moreover, post-depositional processes, such as adsorption, redox cycling, and biological uptake can further fractionate isotopic compositions, potentially obscuring or modifying original source signals. Hence, a comprehensive interpretation of isotope data needs to consider the biogeochemical transformation to avoid misattribution and improve environmental diagnostics. To advance the application of Cu and Zn isotopes in environmental studies, we propose the following research directions:

* Expand paired isotope analyses of dissolved and particulate phases across salinity gradients in estuarine–coastal systems.

* Improve understanding isotope fractionation during metal sorption in seawater (under high ionic strength conditions) and in the presence of organic ligands or resuspension events.

* Expand isotope datasets in porewater to enhance understanding of fractionation dynamics at the sediment–water interface.

* Conduct experimental and modelling studies to better constrain isotope fractionation during electroplating and to develop predictive models for estimating the isotopic signals of industrial byproducts.

* Although biological materials were not the focus of this review, future studies would benefit from utilizing marine organisms as bioindicators to trace metal bioaccumulation, trophic transfer, and potential risks to ecosystems and human health.

* Integrate metal speciation with isotope approaches to refine understanding of metal bioavailability and uptake mechanisms.

Given the transboundary nature of metal pollution, driven by global trade in raw materials and manufactured commodities, environmental contamination by metals can no longer be considered a local concern. International collaboration is therefore important to harmonize analytical approaches, expand global isotope databases, and enhance our collective ability to trace, manage, and mitigate anthropogenic metal pollution in estuarine and coastal settings.

## CRediT authorship contribution statement

**Hyeryeong Jeong:** Writing – review & editing, Writing – original draft, Visualization, Validation, Methodology, Conceptualization.
**Kongtae Ra:** Writing – review & editing, Writing – original draft, Visualization, Funding acquisition.
**João Barreira:** Writing – review & editing, Visualization, Data curation.
**Daniel F. Araújo:** Writing – review & editing, Writing – original draft, Validation, Conceptualization.

## Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Acknowledgements

This research was supported by project from Korea Institute of Ocean Science and Technology (PEA0201).

## Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.marpolbul.2025.118337.

## Data availability

Data will be made available on request.

## References

Abdou, M., Tercier-Waeber, M.-L., Dutruch, L., Bossy, C., Pougnet, F., Coynel, A., Bakker, E., Blanc, G., Schäfer, J., 2022. Estuarine dissolved speciation and partitioning of trace metals: a novel approach to study biogeochemical processes. Environ. Res. 208, 112596. https://doi.org/10.1016/j.envres.2021.112596.

Abochami, W., Wombacher, F., Galer, S.J.G., 2025. Cadmium isotope fractionation and neutron capture effects in lunar samples. Geochem. Cosmochim. Acta 389, 43–58. https://doi.org/10.1016/j.gca.2024.12.001.

Aggarwal, S.K., 2016. Thermal ionisation mass spectrometry (TIMS) in nuclear science and technology – a review. Anal. Methods 8, 942–957. https://doi.org/10.1039/C5AY02816G.

Albarède, F., 2004. The stable isotope geochemistry of copper and zinc. Rev. Mineral. Geochem. 55, 409–427. https://doi.org/10.2138/gsrmg.55.1.409.

Albarède, F., Beard, B., 2004. Analytical methods for non-traditional isotopes. Rev. Mineral. Geochem. 55, 113–152. https://doi.org/10.2138/gsrmg.55.1.113.

Ali, M.U., Liu, G., Yousaf, B., Ullah, H., Abbas, Q., Munir, M.A.M., 2019. A systematic review on global pollution status of particulate matter-associated potential toxic elements and health perspectives in urban environment. Environ. Geochem. Health 41, 1131–1162. https://doi.org/10.1007/s10653-018-0203-z.

Almeida, E., Diamantino, T.C., de Sousa, O., 2007. Marine paints: the particular case of antifouling paints. Prog. Org. Coat. 59, 2–20. https://doi.org/10.1016/j.porgcoat.2007.01.017.

Álvarez, E.A., Mochón, M.C., Sánchez, J.C.J., Rodríguez, M.T., 2002. Heavy metal extractable forms in sludge from wastewater treatment plants. Chemosphere 47, 765–775. https://doi.org/10.1016/S0045-6535(02)00021-8.

Amato, F., Viana, M., Richard, A., Furger, M., Prévôt, A.S.H., Nava, S., Lucarelli, F., Bukowiecki, N., Alastuey, A., Reche, C., Moreno, T., Pandolfi, M., Pey, J., Querol, X., 2011. Size and time-resolved roadside enrichment of atmospheric particulate pollutants. Atmos. Chem. Phys. 11, 2917–2931. https://doi.org/10.5194/acp-11-2917-2011.

Amet, Q., Fitoussi, C., 2020. Chemical procedure for Zn purification and double spike method for high precision measurement of Zn isotopes by MC-ICPMS. Int. J. Mass Spectrom. 457, 116413. https://doi.org/10.1016/j.ijms.2020.116413.

Andronikov, A.V., Novak, M., Olehle, F., Christny, V., Sebek, O., Andronikova, I.E., Stepanova, M., Sipkova, A., Hruska, J., Myska, O., Chuman, T., Veselovsky, F., Curik, J., Prechova, E., Komarek, A., 2021. Catchment runoff in industrial areas exports legacy pollutant zinc from the topsoil rather than geogenic Zn. Environ. Sci. Technol. 55, 8035–8044. https://doi.org/10.1021/acs.est.1c01167.

Araújo, D., Machado, W., Weiss, D., Mulholland, D.S., Boaventura, G.R., Viers, J., Garnier, J., Dantas, E.L., Babinski, M., 2017c. A critical examination of the possible application of zinc stable isotope ratios in bivalve mollusks and suspended particulate matter to trace zinc pollution in a tropical estuary. Environ. Pollut. 226, 41–47. https://doi.org/10.1016/j.envpol.2017.04.011.

Araújo, D.F., Boaventura, G.R., Viers, J., Mulholland, D.S., Weiss, D., Araújo, D., Lima, B., Ruiz, I., Machado, W., Babinski, M., Dantas, E., 2017a. Ion exchange chromatography and mass Bias correction for accurate and precise Zn isotope ratio measurements in environmental reference materials by MC-ICP-MS. J. Braz. Chem. Soc. 28 (2), 225–235. https://doi.org/10.5935/0103-5053.20160167.

Araújo, D.F., Boaventura, G.R., Machado, W., Viers, J., Weiss, D., Patchineelam, S.R., Ruiz, I., Rodrigues, A.P.C., Babinski, M., Dantas, E., 2017b. Tracing of anthropogenic zinc sources in coastal environments using stable isotope composition. Chem. Geol. 449, 226–235. https://doi.org/10.1016/j.chemgeo.2016.12.004.

Araújo, D.F., Ponzevera, E., Briant, N., Knoery, J., Bruzac, S., Sireau, T., Brach-Papa, C., 2019a. Copper, zinc and lead isotope signatures of sediments from a mediterranean coastal bay impacted by naval activities and urban sources. Appl. Geochem. 111, 104440. https://doi.org/10.1016/j.apgeochem.2019.104440.

Araújo, D.F., Ponzevera, E., Briant, N., Knoery, J., Sireau, T., Mojtahid, M., Metzger, E., Brach-Papa, C., 2019b. Assessment of the metal contamination evolution in the Loire estuary using Cu and Zn stable isotopes and geochemical data in sediments. Mar. Pollut. Bull. 143, 12–23. https://doi.org/10.1016/j.marpolbul.2019.04.034.

Araújo, D.F., Ponzevera, E., Briant, N., Knoery, J., Bruzac, S., Sireau, T., Pellouin-Grouhel, A., Brach-Papa, C., 2021a. Differences in copper isotope fractionation between mussels (regulators) and oysters (hyperaccumulators): insights from a ten-year biomonitoring study. Environ. Sci. Technol. 55, 324–330. https://doi.org/10.1021/acs.est.0c04691.

Araújo, D.F., Ponzevera, E., Weiss, D.J., Knoery, J., Briant, N., Yepez, S., Bruzac, S., Sireau, T., Brach-Papa, C., 2021b. Application of Zn isotope compositions in oysters to monitor and quantify anthropogenic Zn bioaccumulation in marine environments over four decades: a “mussel watch program” upgrade. ACS EST Water 1, 1035–1046. https://doi.org/10.1021/acsestwater.1c00010.

Araújo, D.F., Knoery, J., Briant, N., Vigier, N., Ponzevera, E., 2022. “Non-traditional” stable isotopes applied to the study of trace metal contaminants in anthropized marine environments. Mar. Pollut. Bull. 175, 113398. https://doi.org/10.1016/j.marpolbul.2022.113398.

Asael, D., Matthews, A., Bar-Matthews, M., Halicz, L., 2007. Copper isotope fractionation in sedimentary copper mineralization (Timna Valley, Israel). Chem. Geol. 243, 238–254. https://doi.org/10.1016/j.chemgeo.2007.06.007.

Aucour, A.M., Sarret, G., Blommaert, H., Wiggenhauser, M., 2023. Coupling metal stable isotope compositions and X-ray absorption spectroscopy to study metal pathways in
soil-plant systems: a mini review. Metalomics 15, mfad016. https://doi.org/
10.1093/mtomcs/mfad016.

Balaram, V., Rahaman, W., Roy, P., 2022. Recent advances in MC-ICP-MS applications in earth and environmental sciences: challenges and solutions. Geosyst. Geoenviron. 1, 100019. https://doi.org/10.1016/j.geogoeco.2021.100019.

Balistrieri, L.S., Borrok, D.M., Wanty, R.B., Ridley, W.I., 2008. Fractionation of Cu and Zn isotopes during adsorption onto amorphous Fe(III) oxyhydroxide: experimental mixing of acid rock drainage and ambient river water. Geochim. Cosmochim. Acta 72, 311–328. https://doi.org/10.1016/j.gca.2007.11.013.

Barreira, J., Araújo, D.F., Soares, R., Sanders, C.J., Weiss, D.J., Machado, W., 2022. Didactic strategy for the teaching of isotope mixing models for stable isotopes relevant to biogeochemistry based on the analogy with color composition. J. Chem. Educ. 99, 2610–2619. https://doi.org/10.1021/acs.ajchemed.2c00253.

Barreira, J., Araújo, D.F., Rodrigues, B.Q.A., Tonhá, M.S., Mendes, R.D.A., Souto-Oliveira, C.E., Babinski, M., Knoery, J., Sanders, C.J., Garnier, J., Machado, W., 2024. Copper isotopes as a tool to trace contamination in mangroves from an urbanized watershed. Environ. Pollut. 340, 122785. https://doi.org/10.1016/j.
envolp.2023.122785.

Behbahani, A., Ryan, R.J., McKenzie, E.R., 2021. Impacts of salinity on the dynamics of fine particles and their associated metals during stormwater management. Sci. Total Environ. 777, 146135. https://doi.org/10.1016/j.scitotenv.2021.146135.

Bermin, J., Vance, D., Archer, C., Statham, P.J., 2006. The determination of the isotopic composition of Cu and Zn in seawater. Chem. Geol. 226, 280–297. https://doi.org/
10.1016/j.chemgeo.2005.09.025.

Bersuder, P., Amouroux, I., Belzunce-Segarra, M.J., Bolam, T., Caetano, M., Carvalho, I., Correia Dos Santos, M., Fones, G.R., Gonzalez, J.-L., Guesdon, S., Larreta, J., Marras, B., McHugh, B., Menet-Nédélec, F., Menchaca, I., Gabet, V.M., Montero, N., Nolan, M., Regan, F., Robinson, C.D., Rosa, N., Sanz, M.R., Rodríguez, J.G., Schintu, M., White, B., Zhang, H., 2021. Concurrent sampling of transitional and coastal waters by diffusive gradient in thin-films (DGT) and spot sampling for trace metals analysis. MethodsX 8, 101462. https://doi.org/10.1016/j.mex.2021.101462.

Bigalke, M., Weyer, S., Koza, J., Wilcke, W., 2010. Stable Cu and Zn isotope ratios as tracers of sources and transport of Cu and Zn in contaminated soil. Geochim. Cosmochim. Acta 74, 6801–6813. https://doi.org/10.1016/j.gca.2010.08.044.

Bigalke, M., Kersten, M., Weyer, S., Wilcke, W., 2013. Isotopes trace biogeochemistry and sources of Cu and Zn in an intertidal soil. Soil Sci. Soc. Am. J. 77, 680–691. https://doi.org/10.2136/sssjaa2012.0225.

Birch, G., 2024. Review and assessment of road-derived metals as a major contributor of metallic contaminants to urban stormwater and the estuarine environment (Sydney estuary, Australia). J. Hazard. Mater. 465, 133096. https://doi.org/10.1016/j.
jhazmat.2023.133096.

Bird, G., Brewer, P.A., Macklin, M.G., Nikolova, M., Kotsev, T., Mollov, M., Swain, C., 2010. Quantifying sediment-associated metal dispersal using Pb isotopes: application of binary and multivariate mixing models at the catchment-scale. Environ. Pollut. 158, 2158–2169. https://doi.org/10.1016/j.envpol.2010.02.020.

Blotevogel, S., Oliva, P., Denaix, L., Audry, S., Viers, J., Schreck, E., 2022. Stable Cu isotope ratios show changes in Cu uptake and transport mechanisms in *Vitis vinifera* due to high Cu exposure. Front. Plant Sci. 12.

Bolan, N., Kumar, M., Singh, E., Kumar, A., Singh, L., Kumar, S., Keerthanan, S., Hoang, S.A., El-Naggar, A., Vithanage, M., Sarkar, B., Wijesekara, H., Diyabanage, S., Sooriyakumar, P., Vinu, A., Wang, H., Kirkham, M.B., Shaheen, S. M., Rinklebe, J., Siddique, K.H.M., 2022. Antimony contamination and its risk management in complex environmental settings: a review. Environ. Int. 158, 106908. https://doi.org/10.1016/j.envint.2021.106908.

Borrok, D.M., Wanty, R.B., Ridley, W.I., Wolf, R., Lamothe, P.J., Adams, M., 2007. Separation of copper, iron, and zinc from complex aqueous solutions for isotopic measurement. Chem. Geol. 242, 400–414. https://doi.org/10.1016/j.
chemgeo.2007.04.004.

Bourrotte, C.L.M., Sugauara, L.E., Marchi, M.R.R.D., Souto-Oliveira, C.E., 2019. Trace metals and PAHs in topsoils of the university campus in the megacity of São Paulo, Brazil. An. Acad. Bras. Ciênc. 91, e20180334. https://doi.org/10.1590/0001-
3765201920180334.

Brand, W.A., Coplen, T.B., 2012. Stable isotope deltas: tiny, yet robust signatures in nature. Isotopes Environ. Health Stud. 48, 393–409. https://doi.org/10.1080/
10256016.2012.666977.

Brand, W.A., Coplen, T.B., Vogl, J., Rosner, M., Prohaska, T., 2014. Assessment of international reference materials for isotope-ratio analysis (IUPAC technical report). Pure Appl. Chem. 86, 425–467. https://doi.org/10.1515/pac-2013-1023.

Breton, T., Lloyd, N.S., Trinquier, A., Bouman, C., Schwieters, J.B., 2015. Improving precision and signal/noise ratios for MC-ICP-MS. Procedia Earth Planet. Sci. 13, 240–243. https://doi.org/10.1016/j.proeps.2015.07.056, 11th Applied Isotope Geochemistry Conference AIG-11.

Briant, N., Chiffoleau, J.-F., Knoery, J., Araújo, D.F., Ponzevera, E., Crochet, S., Thomas, B., Brach-Papa, C., 2021. Seasonal trace metal distribution, partition and fluxes in the temperate macrotidal Loire Estuary (France). Estuar. Coast. Shelf Sci. 262, 107616. https://doi.org/10.1016/j.ecss.2021.107616.

Briant, N., Freydier, R., Araújo, D.F., Delpoux, S., Elbaz-Poulichet, F., 2022. Cu isotope records of Cu-based antifouling paints in sediment core profiles from the largest European Marina, The Port Camargue. Sci. Total Environ. 849, 157885. https://doi.
org/10.1016/j.scitotenv.2022.157885.

Bryan, A.L., Dong, S., Wilkes, E.B., Wasylenki, L.E., 2015. Zinc isotope fractionation during adsorption onto Mn oxyhydroxide at low and high ionic strength. Geochim. Cosmochim. Acta 157, 182–197. https://doi.org/10.1016/j.gca.2015.01.026.

Caeiro, S., Costa, M.H., Ramos, T.B., Fernandes, F., Silveira, N., Coimbra, A., Medeiros, G., Painho, M., 2005. Assessing heavy metal contamination in Sado

estuary sediment: an index analysis approach. Ecol. Indic. 5, 151–169. https://doi.
org/10.1016/j.ecolind.2005.02.001.

Chang, X., Jia, Z., Feng, J., Duan, T., Li, Y.-X., 2022. Refining the diagnostics of non-point source metals pollution to urban lakes based on interaction normalized PMF coupled with Bayesian network. Environ. Pollut. 304, 119149. https://doi.org/10.1016/j.
envolp.2022.119149.

Chen, H., Savage, P.S., Teng, F.-Z., Helz, R.T., Moynier, F., 2013. Zinc isotope fractionation during magmatic differentiation and the isotopic composition of the bulk earth. Earth Planet. Sci. Lett. 369–370, 34–42. https://doi.org/10.1016/j.
espl.2013.02.037.

Chen, Z., Ding, Y., Jiang, X., Duan, H., Ruan, X., Li, Z., Li, Y., 2022. Combination of UNMIX, PMF model and Pb-Zn-Cu isotopic compositions for quantitative source apportionment of heavy metals in suburban agricultural soils. Ecotoxicol. Environ. Saf. 234, 113369. https://doi.org/10.1016/j.ecoenv.2022.113369.

Choi, J.Y., Hong, G.H., Ra, K., Kim, K.-T., Kim, K., 2014. Magnetic characteristics of sediment grains concurrently contaminated with TBT and metals near a shipyard in Busan, Korea. Mar. Pollut. Bull. 85, 679–685. https://doi.org/10.1016/j.
marpolbul.2014.03.029, 7th International Conference on Marine Pollution and Ecotoxicology.

Choi, S., Choi, M.-S., Joe, D., Park, S., Kim, J., Ra, K., Kim, I., Kim, K.-T., Lee, K.-S., Lim, J.-S., 2022. Dissolved Pb concentrations and stable Pb isotope ratios in the Ulleung Basin, East/Asia Japan. Ocean Sci. J. 57, 436–450. https://doi.org/10.1007/
s12601-022-00072-0.

Conway, T.M., John, S.G., 2014. The biogeochemical cycling of zinc and zinc isotopes in the North Atlantic Ocean. Global Biogeochem. Cycles 28, 1111–1128. https://doi.
org/10.1002/2014GB004862.

Crane, M., 2003. Proposed development of sediment quality guidelines under the European water framework directive: a critique. Toxicol. Lett. 142, 195–206. https://doi.org/10.1016/S0378-4274(03)00069-9. Hot Spot Pollutants: Pharmaceuticals in the Environment.

Crichton, R.R., 2016. Metal toxicity - An introduction. In: Crichton, R.R., Ward, R.J., Hider, R.C. (Eds.), Metal Chelation in Medicine. The Royal Society of Chemistry, pp. 1–23. https://doi.org/10.1039/9781782623892-00001.

Dai, W.-J., Li, X.-D., Fu, Y.-C., Ding, S.-Y., Li, Q.-K., Zhao, Z.-Q., 2023. Identification and contribution of potential sources to atmospheric lead pollution in a typical megacity: insights from isotope analysis and the Bayesian mixing model. Sci. Total Environ. 892, 164567. https://doi.org/10.1016/j.scitotenv.2023.164567.

Desaulty, A.-M., Petelet-Giraud, E., 2020. Zinc isotope composition as a tool for tracing sources and fate of metal contaminants in rivers. Sci. Total Environ. 728, 138599. https://doi.org/10.1016/j.scitotenv.2020.138599.

Desaulty, A.-M., Méheut, M., Guerrot, C., Berho, C., Millot, R., 2017. Coupling DGT passive samplers and multi-collector ICP-MS: a new tool to measure Pb and Zn isotopes composition in dilute aqueous solutions. Chem. Geol. 450, 122–134. https://doi.org/10.1016/j.chemgeo.2016.12.023.

Desaulty, A.-M., Perret, S., Maubec, N., Négrel, P., 2020. Tracking anthropogenic sources in a small catchment using Zn-isotope signatures. Appl. Geochim. 123, 104788. https://doi.org/10.1016/j.apgegeochem.2020.104788.

Di, Y., Krestianinov, E., Zink, S., Amelin, Y., 2021. High-precision multidynamic Sr isotope analysis using thermal ionization mass spectrometer (TIMS) with correction of fractionation drift. Chem. Geol. 582, 120411. https://doi.org/10.1016/j.
chemgeo.2021.120411.

Dietrich, M., Krekeler, M.P.S., Househlar, M., Widom, E., 2021. Quantification of Pb pollution sources in complex urban environments through a multi-source isotope mixing model based on Pb isotopes in lichens and road sediment. Environ. Pollut. 288, 117815. https://doi.org/10.1016/j.envpol.2021.117815.

Dong, S., Ochoa Gonzalez, R., Harrison, R.M., Green, D., North, R., Fowler, G., Weiss, D., 2017. Isotopic signatures suggest important contributions from recycled gasoline, road dust and non-exhaust traffic sources for copper, zinc and lead in PM10 in London, United Kingdom. Atmos. Environ. 165, 88–98. https://doi.org/10.1016/j.
amtosenv.2017.06.020.

Dousova, B., Lhotka, M., Buzek, F., Cejkova, B., Jackova, I., Bednar, V., Hajek, P., 2020. Environmental interaction of antimony and arsenic near busy traffic nodes. Sci. Total Environ. 702, 134642. https://doi.org/10.1016/j.scitotenv.2019.134642.

Ehrlich, S., Butler, I., Halicz, L., Rickard, D., Oldroyd, A., Matthews, A., 2004. Experimental study of the copper isotope fractionation between aqueous Cu(II) and covellite. CuS. Chem. Geol. 209, 259–269. https://doi.org/10.1016/j.
chemgeo.2004.06.010.

Fekiacova, Z., Cornu, S., Pichat, S., 2015. Tracing contamination sources in soils with Cu and Zn isotopic ratios. Sci. Total Environ. 517, 96–105. https://doi.org/10.1016/j.
scitotenv.2015.02.046.

Fu, Z., Wu, F., Chen, L., Xu, B., Feng, C., Bai, Y., Liao, H., Sun, S., Giesy, J.P., Guo, W., 2016. Copper and zinc, but not other priority toxic metals, pose risks to native aquatic species in a large urban lake in Eastern China. Environ. Pollut. 219, 1069–1076. https://doi.org/10.1016/j.envpol.2016.09.007.

Fujii, T., Moynier, F., Blichter-Toft, J., Albarède, F., 2014. Density functional theory estimation of isotope fractionation of Fe, Ni, Cu, and Zn among species relevant to geochemical and biological environments. Geochim. Cosmochim. Acta 140, 553–576. https://doi.org/10.1016/j.gca.2014.05.051.

Fukubayashi, H., 1969. The electrodeposition of zinc; changes in current efficiency and surface structure resulting from various addition agents. In: Master Thesis in
Mineralurgical Engineering. Missouri University of Science and Technology.

Gagnevin, D., Boyce, A.J., Barrie, C.D., Menuge, J.F., Blakeman, R.J., 2012. Zn, Fe and S isotope fractionation in a large hydrothermal system. Geochim. Cosmochim. Acta 88, 183–198. https://doi.org/10.1016/j.gca.2012.04.031.

Garnaud, S., Mouchel, J.-M., Chebbo, G., Thévenot, D.R., 1999. Heavy metal concentrations in dry and wet atmospheric deposits in Paris district: comparison
with urban runoff. Sci. Total Environ. 235, 235-245. https://doi.org/10.1016/S0048-9697(99)00199-0.

Gou, W., Li, Wei, Ji, J., Li, Weiqiang, 2018. Zinc isotope fractionation during sorption onto Al oxides: atomic level understanding from EXAFS. Environ. Sci. Technol. 52, 9087-9096. https://doi.org/10.1021/acs.esst.8b01414.

Guan, J., Wang, J., Pan, H., Yang, C., Qu, J., Lu, N., Yuan, X., 2018. Heavy metals in Yinma River sediment in a major Phaeozems zone, Northeast China: distribution, chemical fraction, contamination assessment and source apportionment. Sci. Rep. 8, 12231. https://doi.org/10.1038/s41598-018-30197-z.

Guinoiseau, D., Bouchez, J., Gélabet, A., Louvat, P., Moreira-Turcq, P., Filizola, N., Benedetti, M.F., 2018. Fate of particulate copper and zinc isotopes at the Solimões- Negro river confluence, Amazon Basin, Brazil. Chem. Geol. 489, 1-15. https://doi. org/10.1016/j.chemgeo.2018.05.004.

Gunawardena, J., Egodawatta, P., Ayoko, G.A., Goonetilleke, A., 2013. Atmospheric deposition as a source of heavy metals in urban stormwater. Atmos. Environ. 68, 235-242. https://doi.org/10.1016/j.atmosenv.2012.11.062.

Guo, D., Wang, Y., Zhang, Y., Duan, J., Guan, F., Hou, B., 2024. Effects of marine eutrophication environment on microbial corrosion: a review. Mar. Pollut. Bull. 205, 116637. https://doi.org/10.1016/j.marpolbul.2024.116637.

Guo, H., Xia, Y., Wu, F., Huang, F., 2021. Zinc isotopic fractionation between aqueous fluids and silicate magmas: an experimental study. Geochim. Cosmochim. Acta 311, 226-237. https://doi.org/10.1016/j.gca.2021.06.028.

Han, X., Wu, H., Li, Q., Cai, W., Hu, S., 2024. Assessment of heavy metal accumulation and potential risks in surface sediment of estuary area: a case study of Dagu river. Mar. Environ. Res. 196, 106416. https://doi.org/10.1016/j. marenvres.2024.106416.

Harada, Y., Connolly, R.M., Fry, B., Maher, D.T., Sippo, J.Z., Jeffrey, L.C., Bourke, A.J., Lee, S.Y., 2020. Stable isotopes track the ecological and biogeochemical legacy of mass mangrove forest dieback in the Gulf of Carpentaria, Australia. Biogeosciences 17, 5599-5613. https://doi.org/10.5194/bg-17-5599-2020.

Hartzell, S.E., Unger, M.A., McGee, B.L., Yonkos, L.T., 2017. Effects-based spatial assessment of contaminated estuarine sediments from Bear Creek, Baltimore Harbor, MD, USA. Environ. Sci. Pollut. Res. 24, 22158-22172. https://doi.org/10.1007/ s11356-017-9667-0.

Harvey, J., Baxter, E.F., 2009. An improved method for TIMS high precision neodymium isotope analysis of very small aliquots (1-10 ng). Chem. Geol. 258, 251-257. https://doi.org/10.1016/j.chemgeo.2008.10.024.

Haynes, H.M., Taylor, K.G., Rothwell, J., Byrne, P., 2020. Characterisation of road-dust sediment in urban systems: a review of a global challenge. J. Soil. Sediment. 20, 4194-4217. https://doi.org/10.1007/s11368-020-02804-y.

Heidari, M., Darijani, T., Alipour, V., 2021. Heavy metal pollution of road dust in a city and its highly polluted suburb: quantitative source apportionment and source- specific ecological and health risk assessment. Chemosphere 273, 129656. https:// doi.org/10.1016/j.chemosphere.2021.129656.

Heikkinen, R., Hämäläinen, H., Kiljunen, M., Kärkkäinen, S., Schilder, J., Jones, R.I., 2022. A Bayesian stable isotope mixing model for coping with multiple isotopes, multi-isotopic stable and small sample sizes. Methods Ecol. Evol. 13, 2586-2602. https://doi.org/10.1111/2041-210X.13989.

Heimbürger, L.-E., Migon, C., Cossa, D., 2011. Impact of atmospheric deposition of anthropogenic and natural trace metals on Northwestern Mediterranean surface waters: a box model assessment. Environ. Pollut. 159, 1629-1634. https://doi.org/ 10.1016/j.envpol.2011.02.046.

Hu, J., Chen, W., Zhao, Z.-Q., Lu, R., Cui, M., Dai, W., Ma, W., Feng, X., Wan, X., Wang, N., 2022. Source tracing of potentially toxic elements in soils around a typical coking plant in an industrial area in northern China. Sci. Total Environ. 807, 151091. https://doi.org/10.1016/j.scitotenv.2021.151091.

Hu, X., Zhai, X., Jin, Y., Wade, T.L., Zhou, X., Zhuang, T., Ning, J., Song, X., Cai, W., Chen, Z., Li, X., 2024. Ecological risk assessment of dissolved heavy metals in the Yangtze River Estuary and Zhejiang coastal waters, China. Mar. Pollut. Bull. 205, 116570. https://doi.org/10.1016/j.marpolbul.2024.116570.

Huang, C., Zhang, L., Meng, J., Yu, Y., Qi, J., Shen, P., Li, X., Ding, P., Chen, M., Hu, G., 2022. Characteristics, source apportionment and health risk assessment of heavy metals in urban road dust of the Pearl River Delta, South China. Ecotoxicol. Environ. Saf. 236, 113490. https://doi.org/10.1016/j.eeoenv.2022.113490.

Huang, S., Song, Q., Zhang, Y., Yuan, D., Sun, L., Chen, Y., Jiang, R., Lin, H., 2019. Application of an isotope binary mixing model for determination of precise mercury isotopic composition in samples with low mercury concentration. Anal. Chem. 91, 7063-7069. https://doi.org/10.1021/acs.analchem.8b05940.

Hwang, H.-M., Fiala, M.J., Park, D., Wade, T.L., 2016. Review of pollutants in urban road dust and stormwater runoff: part 1. Heavy metals released from vehicles. Int. J. Urban Sci. 20, 334-360. https://doi.org/10.1080/12265934.2016.1193041.

Iijima, A., Sato, K., Yano, K., Tago, H., Kato, M., Kimura, H., Furuta, N., 2007. Particle size and composition distribution analysis of automotive brake abrasion dusts for the evaluation of antimony sources of airborne particulate matter. Atmos. Environ. 41, 4908-4919. https://doi.org/10.1016/j.atmosenv.2007.02.005.

Ijichi, Y., Ohno, T., Sakata, S., 2018. Copper isotopic fractionation during adsorption on manganese oxide: effects of pH and desorption. Geochem. J. 52, e1-e6. https://doi. org/10.2343/geochemj.2.0516.

Irgeher, J., Prohaska, T., 2016. Application of non-traditional stable isotopes in analytical ecogeochemistry assessed by MC ICP-MS - a critical review. Anal. Bioanal. Chem. 408, 369-385. https://doi.org/10.1007/s00216-015-9025-3.

Jang, S., Choi, M., Jeong, Y.J., Joe, D., Yang, D., Lee, M., Kim, J., 2025. Isotopic characteristics of antifouling paints and fractionation of Cu and Zn isotopes during dissolution by seawater and their adsorption to marine sediments. Mar. Pollut. Bull. 211, 117423. https://doi.org/10.1016/j.marpolbul.2024.117423.

Jaouen, K., Pons, M.-L., 2017. Potential of non-traditional isotope studies for bioarchaeology. Archaeol. Anthropol. Sci. 9, 1389-1404. https://doi.org/10.1007/ s12520-016-0426-9.

Järlskog, I., Strömvall, A.-M., Magnusson, K., Galfi, H., Björklund, K., Polukarova, M., Garção, R., Markiewicz, A., Aronsson, M., Gustafsson, M., Norin, M., Blom, L., Andersson-Sköld, Y., 2021. Traffic-related microplastic particles, metals, and organic pollutants in an urban area under reconstruction. Sci. Total Environ. 774, 145503. https://doi.org/10.1016/j.scitotenv.2021.145503.

Jeong, H., 2022. Toxic metal concentrations and Cu-Zn-Pb isotopic compositions in tires. J. Anal. Sci. Technol. 13, 2. https://doi.org/10.1186/s40543-021-00312-3.

Jeong, H., Ra, K., 2021a. Multi-isotope signatures (Cu, Zn, Pb) of different particle sizes in road-deposited sediments: a case study from industrial area. J. Anal. Sci. Technol. 12, 39. https://doi.org/10.1186/s40543-021-00292-4.

Jeong, H., Ra, K., 2021b. Characteristics of potentially toxic elements, risk assessments, and isotopic compositions (Cu-Zn-Pb) in the PM10 fraction of road dust in Busan, South Korea. Atmosphere 12, 1229. https://doi.org/10.3390/atmos12091229.

Jeong, H., Choi, J.Y., Lee, J., Lim, J., Ra, K., 2020. Heavy metal pollution by road- deposited sediments and its contribution to total suspended solids in rainfall runoff from intensive industrial areas. Environ. Pollut. 265, 115028. https://doi.org/ 10.1016/j.envpol.2020.115028.

Jeong, H., Choi, J.Y., Lee, J., Ra, K., 2020c. Investigations of Pb and Cu isotopes to trace contamination sources from the artificial Shihwa Lake in Korea. J. Coast. Res. 95, 1122-1127. https://doi.org/10.2112/SI95-218.1.

Jeong, H., Choi, J.Y., Lim, J., Shim, W.J., Kim, Y.O., Ra, K., 2020d. Characterization of the contribution of road deposited sediments to the contamination of the close marine environment with trace metals: case of the port city of Busan (South Korea). Mar. Pollut. Bull. 161, 111717. https://doi.org/10.1016/j.marpolbul.2020.111717.

Jeong, H., Ra, K., Choi, J.Y., 2021a. Copper, zinc and lead isotopic delta values and isotope ratios of various geological and biological reference materials. Geostand. Geoanal. Res. 45, 551-563. https://doi.org/10.1111/ggr.12379.

Jeong, H., Ra, K., Won, J.-H., 2021b. A nationwide survey of trace metals and Zn isotopic signatures in mussels (Mytilus edulis) and oysters (Crassostrea gigas) from the coast of South Korea. Mar. Pollut. Bull. 173, 113061. https://doi.org/10.1016/j. marpolbul.2021.113061.

Jeong, H., Ryu, J.-S., Ra, K., 2022. Characteristics of potentially toxic elements and multi-isotope signatures (Cu, Zn, Pb) in non-exhaust traffic emission sources. Environ. Pollut. 292, 118339. https://doi.org/10.1016/j.envpol.2021.118339.

Jeong, H., Araújo, D.F., Garnier, J., Mulholland, D., Machado, W., Cunha, B., Ponzevera, E., 2023a. Copper and lead isotope records from an electroplating activity in sediments and biota from Septepita Bay (southeastern Brazil). Mar. Pollut. Bull. 190, 114848. https://doi.org/10.1016/j.marpolbul.2023.114848.

Jeong, H., Araújo, D.F., Knöry, J., Briant, N., Ra, K., 2023b. Isotopic (Cu, Zn, and Pb) and elemental fingerprints of antifouling paints and their potential use for environmental forensic investigations. Environ. Pollut. 322, 121176. https://doi.org/10.1016/j. envpol.2023.121176.

Jeong, H., Lee, Y., Moon, H.-B., Ra, K., 2023e. Characteristics of metal pollution and multi-isotopic signatures for C, Cu, Zn, and Pb in coastal sediments from special management areas in Korea. Mar. Pollut. Bull. 188, 114642. https://doi.org/ 10.1016/j.marpolbul.2023.114642.

Jeong, H., Araújo, D.F., Ra, K., 2024. Combined copper isotope and elemental signatures in bivalves and sediments from the Korean coast: applicability for monitoring anthropogenic contamination. Mar. Pollut. Bull. 208, 116930. https://doi.org/ 10.1016/j.marpolbul.2024.116930.

John, S.G., Conway, T.M., 2014. A role for scavenging in the marine biogeochemistry cycling of zinc and zinc isotopes. Earth Planet. Sci. Lett. 394, 159-167. https://doi. org/10.1016/j.epsl.2014.02.053.

John, S.G., Geis, R.W., Saito, M.A., Boyle, E.A., 2007. Zinc isotope fractionation during high-affinity and low-affinity zinc transport by the marine diatom *Thalassiosira oceanica*. Limnol. Environ. 52, 2710-2714. https://doi.org/10.4319/ lo.2007.52.6.2710.

Junqueira, T.P., Vriens, B., Leybourne, M.I., Harrison, A.L., Sullivan, K.V., Jeong, H., Araújo, D.F., 2024. Applications of zinc stable isotope analysis in environmental and biological systems: a review. Geochem. Explor. Environ. Anal. 24, geochem2024- 003. https://doi.org/10.1144/geochem2024-003.

Kaamoush, M., El-Agawany, N., Omar, M.Y., 2023. Environmental toxicological evaluation (in vitro) of copper, zinc and cybutryne on the growth and amino acids content of the marine alga *Dunaliella salina*. Egypt. J. Aquat. Res. 49, 23-32. https:// doi.org/10.1016/j.ejar.2022.07.004.

Kaonga, C.C., Kosamu, I.B.M., Utembe, W.R., 2021. A review of metal levels in urban dust, their methods of determination, and risk assessment. Atmosphere 12, 891. https://doi.org/10.3390/atmos12070891.

Knaver, A., John, S.G., Sass, S., Boyle, E.A., 2008. Redox-driven stable isotope fractionation in transition metals: application to Zn electroplating. Geochim. Cosmochim. Acta 72, 1731-1741. https://doi.org/10.1016/j.gca.2008.01.023.

Kelley, K.D., Wilkinson, J.J., Chapman, J.B., Crowther, H.L., Weiss, D.J., 2009. Zinc isotopes in sphalerite from base metal deposits in the red dog district, Northern Alaska. Econ. Geol. 104, 767-773. https://doi.org/10.2113/gsecongeo.104.6.767.

Kim, S.H., Ra, K., Kim, K.-T., Jeong, H., Lee, J., Kang, D.-J., Rho, T., Kim, I., 2019. R/V Isabu-based first ultraclean seawater sampling for ocean trace elements in Korea. Ocean Sci. J. 54, 673-684. https://doi.org/10.1007/s12601-019-0030-x.

Klein, S., Rose, T., 2020. Evaluating copper isotope fractionation in the metallurgical operational chain: an experimental approach. Archaeometry 62, 134-155. https:// doi.org/10.1111/arcm.12564.

Komárek, M., Ratié, Gildas, Vaňková, Zuzana, Šípková, Adéla, Chrastný, V., 2022. Metal isotope complexation with environmentally relevant surfaces: opening the isotope
fractionation black box. Crit. Rev. Environ. Sci. Technol. 52, 3573-3603. https://doi.org/10.1080/10643389.2021.1955601.

Larner, F., Rehkämper, M., Coles, B.J., Kreissig, K., Weiss, D.J., Sampson, B., Unsworth, C., Strekopytov, S., 2011. A new separation procedure for Cu prior to stable isotope analysis by MC-ICP-MS. J. Anal. At. Spectrom 26, 1627. https://doi.org/10.1039/c1ja10067.

Lauwens, S., Costas-Rodríguez, M., Van Vlierberghe, H., Vanhaecke, F., 2017. High-precision isotopic analysis of Cu in blood serum via multi-collector ICP-mass spectrometry for clinical investigation: steps towards improved robustness and higher sample throughput. J. Anal. At. Spectrom 32, 597-608. https://doi.org/10.1039/C6JA00433D.

Lemaitre, N., De Souza, G.F., Archer, C., Wang, R.-M., Planquette, H., Sarthou, G., Vance, D., 2020. Pervasive sources of isotopically light zinc in the North Atlantic Ocean. Earth Planet. Sci. Lett. 539, 116216. https://doi.org/10.1016/j.epsl.2020.116216.

Li, C.-F., Li, Xian-Hua, Li, Q.-L., Guo, J.-H., Li, Xiang-Hui, Yang, Y.-H., 2012. Rapid and precise determination of Sr and Nd isotopic ratios in geological samples from the same filament loading by thermal ionization mass spectrometry employing a single-step separation scheme. Anal. Chim. Acta 727, 54-60. https://doi.org/10.1016/j.aca.2012.03.040.

Li, D., Liu, S.-A., Li, S., 2015. Copper isotope fractionation during adsorption onto kaolinite: experimental approach and applications. Chem. Geol. 396, 74-82. https://doi.org/10.1016/j.chemgeo.2014.12.020.

Li, Wei, Gou, W., Li, Weiqiang, Zhang, T., Yu, B., Liu, Q., Shi, J., 2019. Environmental applications of metal stable isotopes: silver, mercury and zinc. Environ. Pollut. 252, 1344-1356. https://doi.org/10.1016/j.envpol.2019.06.037.

Lindfors, S., Österlund, H., Lundy, L., Viklander, M., 2020. Metal size distribution in rainfall and snowmelt-induced runoff from three urban catchments. Sci. Total Environ. 743, 140813. https://doi.org/10.1016/j.scitotenv.2020.140813.

Liu, C., Wang, R., Gao, H., Wu, X., Yin, D., 2022. Transport of trace metals and their bioaccumulation in zooplankton from Changjiang (Yangtze River) to the East China Sea. Sci. Total Environ. 851, 158156. https://doi.org/10.1016/j.scitotenv.2022.158156.

Liu, S.-A., Huang, J., Liu, J., Wörner, G., Yang, W., Tang, Y.-J., Chen, Y., Tang, L., Zheng, J., Li, S., 2015. Copper isotopic composition of the silicate earth. Earth Planet. Sci. Lett. 427, 95-103. https://doi.org/10.1016/j.epsl.2015.06.061.

Liu, Y., Gao, T., Xia, Y., Wang, Z., Liu, C., Li, S., Wu, Q., Qi, M., Lv, Y., 2020. Using Zn isotopes to trace Zn sources and migration pathways in paddy soils around mining area. Environ. Pollut. 267, 115616. https://doi.org/10.1016/j.envpol.2020.115616.

Logiewa, A., Miazgowicz, A., Krennhuber, K., Lanzerstorfer, C., 2020. Variation in the concentration of metals in road dust size fractions between 2 µm and 2 mm: results from three metallurgical centres in Poland. Arch. Environ. Contam. Toxicol. 78, 46-59. https://doi.org/10.1007/s00244-019-00686-x.

Longman, J., Veres, D., Ersek, V., Phillips, D.L., Chauvel, C., Tamas, C.G., 2018. Quantitative assessment of Pb sources in isotopic mixtures using a Bayesian mixing model. Sci. Rep. 8, 6154. https://doi.org/10.1038/s41598-018-24474-0.

Lu, D., Zhang, T., Yang, X., Su, P., Liu, Q., Jiang, J., 2017. Recent advances in the analysis of non-traditional stable isotopes by multi-collector inductively coupled plasma mass spectrometry. J. Anal. At. Spectrom 32, 1848-1861. https://doi.org/10.1039/C7JA00260B.

Ma, L., Wang, W., Xie, M.-W., Wang, W.-X., Evans, R.D., 2020. Using Zn isotopic signatures for source identification in a contaminated estuary of Southern China. Environ. Sci. Technol. 54, 5140-5149. https://doi.org/10.1021/acs.est.9b05955.

Machado, Anderson Abel de Souza, Kate Spencer, Werner Kloas, Marco Toffolon, Christiane, Zarfl., 2016. Metal Fate and Effects in Estuaries: A Review and Conceptual Model for Better Understanding of Toxicity. Sci. Total Environ. 541, 268-281. https://doi.org/10.1016/j.scitotenv.2015.09.045.

Manceau, A., Lanson, B., Drits, V.A., 2002. Structure of heavy metal sorbed birnnesite. Part III: Results from powder and polarized extended X-ray absorption fine structure spectroscopy. Geochim. Cosmochim. Acta 66 (15), 2639-2663. https://doi.org/10.1016/S0016-7037(02)00869-4.

Manisalidis, I., Stavropoulou, E., Stavropoulos, A., Bezirtzoglou, E., 2020. Environmental and health impacts of air pollution: a review. Front. Public Health 8. https://doi.org/10.3389/fpubh.2020.00014.

Maréchal, C.N., Télouk, P., Albarède, F., 1999. Precise analysis of copper and zinc isotopic compositions by plasma-source mass spectrometry. Chem. Geol. 156, 251-273. https://doi.org/10.1016/S0009-2541(98)00191-0.

Martins, 1976. Panorama do Zinco no Brasil. Ministério da Fazenda. Geologia e Metalurgia. III Simposio de Mineracao. Available at.

Mason, T.F.D., Weiss, D.J., Chapman, J.B., Wilkinson, J.J., Tessalina, S.G., Spiro, B., Horstwood, M.S.A., Spratt, J., Coles, B.J., 2005. Zn and Cu isotopic variability in the Alexandrinka volcanic-hosted massive sulphide (VHMS) ore deposit, Urals, Russia. Chem. Geol. 221, 170-187. https://doi.org/10.1016/j.chemgeo.2005.04.011.

Mattielli, N., Petit, J.C.J., Deboudt, K., Flament, P., Perdrix, E., Taillez, A., Rimetz-Planchon, J., Weis, D., 2009. Zn isotope study of atmospheric emissions and dry depositions within a 5 km radius of a Pb-Zn refinery. Atmos. Environ. 43, 1265-1272. https://doi.org/10.1016/j.atmosenv.2008.11.030.

Miller, J.R., 2013. Forensic assessment of metal contaminated rivers in the 21st century using geochemical and isotopic tracers. Minerals 3, 192-246. https://doi.org/10.3390/min3020192.

Ministry of the Environment, 1996. FACT SHEET No. 8. Canadian Electrolytic Zinc Limited. In: Minister of Supply and Services Canada 1996 Catalogue No. En 153-6/8-1996F, ISBN 0-662-23358-1. Available at https://publications.gc.ca/collections/collection_2016/eccc/En153-6-8-1996-eng.pdf. Accessed in May 16.

Moeller, K., Schoenberg, R., Pedersen, R.-B., Weiss, D., Dong, S., 2012. Calibration of the new certified reference materials ERM-AE633 and ERM-AE647 for copper and

IRMM-3702 for zinc isotope amount ratio determinations. Geostand. Geoanal. Res. 36, 177-199. https://doi.org/10.1111/j.1751-908X.2011.00153.x.

MOF (Ministry of Ocean and Fisheries), 2013. Marine Water and Sediment Quality Standard in Korea.

Mondillo, N., Wilkinson, J.J., Boni, M., Weiss, D.J., Mathur, R., 2018. A global assessment of Zn isotope fractionation in secondary Zn minerals from sulfide and non-sulfide ore deposits and model for fractionation control. Chem. Geol. 500, 182-193. https://doi.org/10.1016/j.chemgeo.2018.09.033.

Moore, M., Gould, P., Keary, B.S., 2003. Global urbanization and impact on health. Int. J. Hyg. Environ. Health 206, 269-278. https://doi.org/10.1078/1438-4639-00223.

Moore, R.E.T., Larner, F., Coles, B.J., Rehkämper, M., 2017. High precision zinc stable isotope measurement of certified biological reference materials using the double spike technique and multiple collector-ICP-MS. Anal. Bioanal. Chem. 409, 2941-2950. https://doi.org/10.1007/s00216-017-0240-y.

Müller, A., Österlund, H., Marsalek, J., Viklander, M., 2020. The pollution conveyed by urban runoff: a review of sources. Sci. Total Environ. 709, 136125. https://doi.org/10.1016/j.scitotenv.2019.136125.

Nakaguchi, Y., Sakamoto, A., Asatani, T., Minami, T., Shitashima, K., Zheng, L., Sohrin, Y., 2022. Distribution and stoichiometry of Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in the Seas of Japan and Okhotsk. Mar. Chem. 241, 104108. https://doi.org/10.1016/j.marchem.2022.104108.

Navarrete, J.U., Borrok, D.M., Viveros, M., Ellzey, J.T., 2011. Copper isotope fractionation during surface adsorption and intracellular incorporation by bacteria. Geochim. Cosmochim. Acta 75, 784-799. https://doi.org/10.1016/j.gca.2010.11.011.

Nelson, J., Wasylenki, L., Bargar, J.R., Brown Jr., G.E., Maher, K., 2017. Effects of surface structural disorder and surface coverage on isotopic fractionation during Zn(II) adsorption onto quartz and amorphous silica surfaces. Geochim. Cosmochim. Acta 215, 354-376. https://doi.org/10.1016/j.gca.2017.08.003.

Nitzsche, K.N., Yoshimura, T., Ishikawa, N.F., Kawahata, H., Ogawa, N.O., Suzuki, K., Araoka, D., Ohkouchi, N., 2024. Zinc isotope fractionation during the sorption of Zn to minerals and organic matter in sediment cores affected by anthropogenic pollution. Appl. Geochem. 169, 106047. https://doi.org/10.1016/j.apgechem.2024.106047.

Niu, L., Li, J., Luo, X., Fu, T., Chen, O., Yang, Q., 2021. Identification of heavy metal pollution in estuarine sediments under long-term reclamation: ecological toxicity, sources and implications for estuary management. Environ. Pollut. 290, 118126. https://doi.org/10.1016/j.envpol.2021.118126.

NTP, 2018. Report on Carcinogens Monograph on Antimony Trioxide October, Office of the Report on Carcinogens, National Toxicology Program, National Institute of Environmental Health Sciences. National Institutes of Health, Research Triangle Park, US.

Owens, P.N., Caley, K.A., Campbell, S., Koiter, A.J., Droppo, I.G., Taylor, K.G., 2011. Total and size-fractionated mass of road-deposited sediment in the city of Prince George, British Columbia, Canada: implications for air and water quality in an urban environment. J. Soils Sediment. 11, 1040-1051. https://doi.org/10.1007/s11368-011-0383-y.

Packman, H., Little, S.H., Baker, A.R., Bridgestock, L., Chance, R.J., Coles, B.J., Kreissig, K., Rehkämper, M., van de Flierdt, T., 2022. Tracing natural and anthropogenic sources of aerosols to the Atlantic Ocean using Zn and Cu isotopes. Chem. Geol. 610, 121091. https://doi.org/10.1016/j.chemgeo.2022.121091.

Packman, H., Little, S.H., Nieto, J.M., Basallote, M.D., Pérez-López, R., Coles, B., Kreissig, K., Van De Flierdt, T., Rehkämper, M., 2023. Tracing acid mine drainage and estuarine Zn attenuation using cd and Zn isotopes. Geochim. Cosmochim. Acta 360, 36-56. https://doi.org/10.1016/j.gca.2023.09.001.

Pašava, J., Tornos, F., Chrastný, V., 2014. Zinc and sulfur isotope variation in sphalerite from carbonate-hosted zinc deposits, Cantabria, Spain. Miner. Depos. 49, 797-807. https://doi.org/10.1007/s00126-014-0535-2.

Pereira, J.G., Raikar, S.S., Bhatti, A.G., Fatarpekar, P.G., Nasnodkar, M.R., 2023. Metal bioavailability, bioaccumulation, and toxicity assessment through sediment and edible biota from intertidal regions of the Aghanashini Estuary, India. Mar. Environ. Res. 191, 106172. https://doi.org/10.1016/j.marenvres.2023.106172.

Petit, J.C.J., De Jong, J., Chou, L., Mattielli, N., 2008. Development of Cu and Zn isotope MC-ICP-MS measurements: application to suspended particulate matter and sediments from the Scheldt Estuary. Geostand. Geoanal. Res. 32, 149-166. https://doi.org/10.1111/j.1751-908X.2008.00867.x.

Petit, J.C.J., Schäfer, J., Coynel, A., Blanc, G., Deycard, V.N., Derriennic, H., Lancelleur, L., Dutruch, L., Bossy, C., Mattielli, N., 2013. Anthropogenic sources and biogeochemical reactivity of particulate and dissolved Cu isotopes in the turbidity gradient of the Garonne River (France). Chem. Geol. 359, 125-135. https://doi.org/10.1016/j.chemgeo.2013.09.019.

Petit, J.C.J., Schäfer, J., Coynel, A., Blanc, G., Chiffoleau, J.-F., Auger, D., Bossy, C., Derriennic, H., Mikolaczyk, M., Dutruch, L., Mattielli, N., 2015. The estuarine geochemical reactivity of Zn isotopes and its relevance for the biomonitoring of anthropogenic Zn and Cd contaminations from metallurgical activities: example of the Gironde fluvial-estuarine system, France. Geochim. Cosmochim. Acta 170, 108-125. https://doi.org/10.1016/j.gca.2015.08.004.

Phillips, D.L., Gregg, J.W., 2003. Source partitioning using stable isotopes: coping with too many sources. Oecologia 136, 261-269. https://doi.org/10.1007/s00442-003-1218-3.

Phillips, D.L., Newsome, S.D., Gregg, J.W., 2005. Combining sources in stable isotope mixing models: alternative methods. Oecologia 144, 520-527. https://doi.org/10.1007/s00442-004-1816-8.

Pokrovsky, O.S., Viers, J., Freydier, R., 2005. Zinc stable isotope fractionation during its adsorption on oxides and hydroxides. J. Colloid and Interface Sci. 291 (1), 192-200. https://doi.org/10.1016/j.jcis.2005.04.079.
Richter, S., Goldberg, S.A., 2003. Improved techniques for high accuracy isotope ratio measurements of nuclear materials using thermal ionization mass spectrometry. Int. J. Mass Spectrom. 229, 181–197. https://doi.org/10.1016/S1387-3806(03)00338-5.

Rijkenberg, M.J.A., De Baar, H.J.W., Bakker, K., Gerringa, L.J.A., Keijzer, E., Laan, M., Laan, P., Middag, R., Ober, S., Van Ooijen, J., Ossebaar, S., Van Weerlee, E.M., Smit, M.G., 2015. "PRISTINE", a new high volume sampler for ultraclean sampling of trace metals and isotopes. Mar. Chem. 177, 501–509. https://doi.org/10.1016/j.marchem.2015.07.001.

Robert, S., Blanc, G., Schäfer, J., Lavaux, G., Abril, G., 2004. Metal mobilization in the Gironde estuary (France): the role of the soft mud layer in the maximum turbidity zone. Mar. Chem. 87, 1–13. https://doi.org/10.1016/S0304-4203(03)00088-4.

Rosca, C., König, S., Pons, M.-L., Schoenberg, R., 2021. Improved protocols for Zn purification and MC-ICP-MS analyses enable determination of small-scale Zn isotope variations. Chem. Geol. 586, 120440. https://doi.org/10.1016/j.chemgeo.2021.120440.

Ruan, Y., Zhang, R., Yang, S.-C., Jiang, Z., Chen, S., Conway, T.M., Huang, K.-F., Boyle, E. A., Zhou, M., John, S.G., 2024. Iron, nickel, copper, zinc, and their stable isotopes along a salinity gradient in the Pearl River Estuary, southeastern China. Chem. Geol. 645, 121893. https://doi.org/10.1016/j.chemgeo.2023.121893.

Sabin, L.D., Lim, J.H., Stolzenbach, K.D., Schiff, K.C., 2005. Contribution of trace metals from atmospheric deposition to stormwater runoff in a small impervious urban catchment. Water Res. 39, 3929–3937. https://doi.org/10.1016/j.watres.2005.07.003.

Schilling, K., Basu, A., Kaplan, A., Perkins, W.T., 2021. Metal distribution, bioavailability and isotope variations in polluted soils from Lower Swansea Valley, UK. Environ. Geochem. Health 43, 2899–2912. https://doi.org/10.1007/s10653-020-00794-x.

Schleicher, N.J., Ram, K., Norra, S., Schrader, S., 2023. Editorial: fine particulate matter pathways—monitoring and modelling. Front. Environ. Sci. 11, 1187784. https://doi.org/10.3389/fenvs.2023.1187784.

Sen, I.S., Peucker-Ehrenbrink, B., 2012. Anthropogenic disturbance of element cycles at the earth's surface. Environ. Sci. Technol. 46, 8601–8609. https://doi.org/10.1021/es0310261.

Seo, H., Kim, G., Kim, T., Kim, I., Ra, K., Jeong, H., 2022. Trace elements (Fe, Mn, Co, Cu, Cd, and Ni) in the East Sea (Japan Sea): distributions, boundary inputs, and scavenging processes. Mar. Chem. 239, 104070. https://doi.org/10.1016/j.marchem.2021.104070.

Shao, F., Li, K., Ouyang, D., Zhou, J., Luo, Y., Zhang, H., 2024. Sources apportionments of heavy metal(loid)s in the farmland soils close to industrial parks: integrated application of positive matrix factorization (PMF) and cadmium isotopic fractionation. Sci. Total Environ. 924, 171598. https://doi.org/10.1016/j.scitotenv.2024.171598.

Sherman, D.M., 2013. Equilibrium isotopic fractionation of copper during oxidation/reduction, aqueous complexation and ore-forming processes: predictions from hybrid density functional theory. Geochim. Cosmochim. Acta 118, 85–97. https://doi.org/10.1016/j.gca.2013.04.030.

Shiel, A.E., Weis, D., Orians, K.J., 2010. Evaluation of zinc, cadmium and lead isotope fractionation during smelting and refining. Sci. Total Environ. 408, 2357–2368. https://doi.org/10.1016/j.scitotenv.2010.02.016.

Shiel, A.E., Weis, D., Cossa, D., Orians, K.J., 2013. Determining provenance of marine metal pollution in French bivalves using Cd, Zn and Pb isotopes. Geochim. Cosmochim. Acta 121, 155–167. https://doi.org/10.1016/j.gca.2013.07.005.

Sivry, Y., Riotte, J., Sonke, J.E., Audry, S., Schäfer, J., Viers, J., Blanc, G., Freydier, R., Dupré, B., 2008. Zn isotopes as tracers of anthropogenic pollution from Zn-ore smelters The Riou Mort-Lot River system. Chem. Geol. 255, 295–304. https://doi.org/10.1016/j.chemgeo.2008.06.038.

Sonke, J., Sivry, Y., Viers, J., Freydier, R., Dejonghe, L., Andre, L., Aggarwal, J., Fontan, F., Dupre, B., 2008. Historical variations in the isotopic composition of atmospheric zinc deposition from a zinc smelter. Chem. Geol. 252, 145–157. https://doi.org/10.1016/j.chemgeo.2008.02.006.

Souto-Oliveira, C.E., Babinski, M., Araújo, D.F., Andrade, M.F., 2018. Multi-isotopic fingerprints (Pb, Zn, Cu) applied for urban aerosol source apportionment and discrimination. Sci. Total Environ. 626, 1350–1366. https://doi.org/10.1016/j.scitotenv.2018.01.192.

Souto-Oliveira, C.E., Babinski, M., Araújo, D.F., Weiss, D.J., Ruiz, I.R., 2019. Multi-isotope approach of Pb, Cu and Zn in urban aerosols and anthropogenic sources improves tracing of the atmospheric pollutant sources in megacities. Atmos. Environ. 198, 427–437. https://doi.org/10.1016/j.atmosenv.2018.11.007.

Souto-Oliveira, C.E., Kamigauti, L.Y., Andrade, M. de F., Babinski, M., 2021. Improving source apportionment of urban aerosol using multi-isotopic fingerprints (MIF) and positive matrix factorization (PMF): cross-validation and new insights. Front. Environ. Sci. 9. https://doi.org/10.3389/fenvs.2021.623915.

Sullivan, K.V., Kidder, J.A., Junqueira, T.P., Vanhaecke, F., Leybourne, M.I., 2022. Emerging applications of high-precision Cu isotopic analysis by MC-ICP-MS. Sci. Total Environ. 838, 156084. https://doi.org/10.1016/j.scitotenv.2022.156084.

Sun, P., Niu, Y., Chen, S., Guo, P., Duan, M., Chen, Y., Gong, H., Xiao, Y., Wang, X., 2023. Copper isotope fractionation during magma differentiation: evidence from lavas on the East Pacific Rise at 10°30' N. Geochim. Cosmochim. Acta 356, 93–104. https://doi.org/10.1016/j.gca.2023.07.016.

Takano, S., Liao, W.-H., Ho, T.-Y., Sohrin, Y., 2022. Isotopic evolution of dissolved Ni, Cu, and Zn along the Kuroshio through the East China Sea. Mar. Chem. 243, 104135. https://doi.org/10.1016/j.marchem.2022.104135.

Thapalia, A., Borrok, D.M., Van Metre, P.C., Musgrove, M., Landa, E.R., 2010. Zn and Cu isotopes as tracers of anthropogenic contamination in a sediment core from an urban lake. Environ. Sci. Technol. 44, 1544–1550. https://doi.org/10.1021/es902933y.

Tian, K., Liang, Q., He, Y., Ma, J., Zhao, T., Wu, Q., Hu, W., Huang, B., Khan, K.S., Teng, Y., 2024. Quantitative assessment of Cd sources in rice grains through Cd

isotopes and MixSIAR model in a typical e-waste dismantling area of Southeast China. Sci. Total Environ. 954, 176217. https://doi.org/10.1016/j.scitotenv.2024.176217.

Tonná, M.S., Garnier, J., Araújo, D.F., Cunha, B.C.A., Machado, W., Dantas, E., Araújo, R., Kutter, V.T., Bonnet, M.-P., Seyler, P., 2020. Behavior of metallurgical zinc contamination in coastal environments: a survey of Zn from electroplating wastes and partitioning in sediments. Sci. Total Environ. 743, 140610. https://doi.org/10.1016/j.scitotenv.2020.140610.

Tornero, V., Hanke, G., 2016. Chemical contaminants entering the marine environment from sea-based sources: a review with a focus on European seas. Mar. Pollut. Bull. 112, 17–38. https://doi.org/10.1016/j.marpolbul.2016.06.091.

Tu, Y.-J., You, C.-F., Kuo, T.-Y., 2020. Source identification of Zn in Erren River, Taiwan: an application of Zn isotopes. Chemosphere 248, 126044. https://doi.org/10.1016/j.chemosphere.2020.126044.

USEPA, 1987. An overview of sediment quality in the United States. In: EPA 905/9-88-002. Office of Water Regulations and Standards, Washington, DC, and EPA Region 5, Chicago.

USEPA, 1995. An SAB Report: Review of the Agency's Approach for Developing Sediment Criteria for Five Metals. EPA-SAB-EPEC-95-020, Washington DC, USA.

USEPA, 1998. EPA'S Contaminated Sediment Management Strategy. EPA-823-R-98-001, Washington, DC.

Vance, D., Archer, C., Bermin, J., Perkins, J., Statham, P.J., Lohan, M.C., Ellwood, M.J., Mills, R.A., 2008. The copper isotope geochemistry of rivers and the oceans. Earth Planet. Sci. Lett. 274, 204–213. https://doi.org/10.1016/j.epsl.2008.07.026.

Vlasov, D., Kosheleva, N., Kasimov, N., 2021. Spatial distribution and sources of potentially toxic elements in road dust and its PM10 fraction of Moscow megacity. Sci. Total Environ. 761, 143267. https://doi.org/10.1016/j.scitotenv.2020.143267.

Von Glasow, R., Jickells, T.D., Baklanov, A., Carmichael, G.R., Church, T.M., Gallardo, L., Hughes, C., Kanakidou, M., Liss, P.S., Mee, L., Raine, R., Ramachandran, P., Ramesh, R., Sundseth, K., Tsunogai, U., Uematsu, M., Zhu, T., 2013. Megacities and large urban agglomerations in the coastal zone: interactions between atmosphere, land, and marine ecosystems. Ambio 42, 13–28. https://doi.org/10.1007/s13280-012-0343-9.

Walczky, T., 2004. TIMS versus multicollector-ICP-MS: coexistence or struggle for survival? Anal. Bioanal. Chem. 378, 229–231. https://doi.org/10.1007/s00216-003-2053-4.

Wang, D., Zheng, L., Ren, M., Li, C., Dong, X., Wei, X., Zhou, W., Cui, J., 2022b. Zinc in soil reflecting the intensive coal mining activities: evidence from stable zinc isotopes analysis. Ecotoxicol. Environ. Saf. 239, 113669. https://doi.org/10.1016/j.ecoenv.2022.113669.

Wang, J., Yu, D., Wang, Y., Du, X., Li, G., Li, B., Zhao, Y., Wei, Y., Xu, S., 2021. Source analysis of heavy metal pollution in agricultural soil irrigated with sewage in Wuqing, Tianjin. Sci. Rep. 11, 17816. https://doi.org/10.1038/s41598-021-96367-8.

Wang, L., Jin, Y., Weiss, D.J., Schleicher, N.J., Wilcke, W., Wu, L., Guo, Q., Chen, J., O'Connor, D., Hou, D., 2021a. Possible application of stable isotope compositions for the identification of metal sources in soil. J. Hazard. Mater. 407, 124812. https://doi.org/10.1016/j.jhazmat.2020.124812.

Wang, Q., Zhou, L., Little, S.H., Liu, J., Feng, L., Tong, S., 2020. The geochemical behavior of Cu and its isotopes in the Yangtze River. Sci. Total Environ. 728, 138428. https://doi.org/10.1016/j.scitotenv.2020.138428.

Wang, Y., Li, Y., Yang, S., Liu, J., Zheng, W., Xu, J., Cai, H., Liu, X., 202a. Source apportionment of soil heavy metals: a new quantitative framework coupling receptor model and stable isotopic ratios. Environ. Pollut. 314, 120291. https://doi.org/10.1016/j.envpol.2022.120291.

Weiss, D.J., Rehkdmper, M., Schoenberg, R., McLaughlin, M., Kirby, J., Campbell, P.G.C., Arnold, T., Chapman, T., Peel, K., Gioia, A.S., 2008. Application of nontraditional stable-isotope systems to the study of sources and fate of metals in the environment. Environ. Sci. Technol. 42, 655–664. https://doi.org/10.1021/es0780785.

Wiederhold, J.G., 2015. Metal stable isotope signatures as tracers in environmental geochemistry. Environ. Sci. Technol. 49, 2606–2624. https://doi.org/10.1021/es046836e.

Wiggenhauser, M., Moore, R.E.T., Wang, P., Bienert, G.P., Laursen, K.H., Blotevogel, S., 2022. Stable isotope fractionation of metals and metalloids in plants: a review. Front. Plant Sci. 13. https://doi.org/10.3389/fpls.2022.840941.

Wilkinson, J.J., Weiss, D.J., Mason, T.F.D., Coles, B.J., 2005. Zinc isotope variation in hydrothermal systems: preliminary evidence from the Irish midlands ore field. Econ. Geol. 100, 583–590. https://doi.org/10.2113/gsecongeo.100.3.583.

Wu, S., Zheng, Y., Wang, D., Chang, H., Tan, M., 2017. Variation of copper isotopes in chalcopyrite from Dabu porphyry Cu-Mo deposit in Tibet and implications for mineral exploration. Ore Geol. Rev. 90, 14–24. https://doi.org/10.1016/j.oreorev.2017.10.001.

Xia, B., Huang, Y., Pei, X., Liu, C., 2023. Application of Cu isotopes to identify Cu sources in soils impacted by multiple anthropogenic activities. Sci. Total Environ. 905, 167114. https://doi.org/10.1016/j.scitotenv.2023.167114.

Xie, R.C., Rehkämper, M., Grasse, P., van de Flierdt, T., Frank, M., Xue, Z., 2019. Isotopic evidence for complex biogeochemical cycling of cd in the eastern tropical South Pacific. Earth Planet. Sci. Lett. 512, 134–146. https://doi.org/10.1016/j.epsl.2019.02.001.

Xu, F., Qiu, L., Cao, Y., Huang, J., Liu, Z., Tian, X., Li, A., Yin, X., 2016. Trace metals in the surface sediments of the intertidal Jiaozhou Bay, China: sources and contamination assessment. Mar. Pollut. Bull. 104, 371–378. https://doi.org/10.1016/j.marpolbul.2016.01.019.

Yang, L., Methven, B., Mester, Z., Meija, J., 2023. Determination of the isotopic composition of copper in a certified reference material HICU-1 by MC-ICP-MS using
gravimetric isotope mixture calibration. J. Anal. At. Spectrom 38, 2080-2086.
https://doi.org/10.1039/D3JA00212H.

Yang, S.-C., Hawco, N.J., Pinedo-González, P., Bian, X., Huang, K.-F., Zhang, R., John, S. G., 2020. A new purification method for Ni and Cu stable isotopes in seawater provides evidence for widespread Ni isotope fractionation by phytoplankton in the North Pacific. Chem. Geol. 547, 119662. https://doi.org/10.1016/j.chemgeo.2020.119662.

Yang, Y.-H., Tang, S.-H., Liu, W.-G., Yan, Y., Xie, L.-W., Huang, C., Wu, S.-T., Wang, H., Yang, J.-H., Wu, F.-Y., 2024. Rb, Sr, Sm and Nd elemental concentrations and Sr and Nd isotopic ratios of 13 Chinese rock reference materials using isotope dilution TIMS and MC-ICP-MS. Int. J. Mass Spectrom. 500, 117234. https://doi.org/10.1016/j.ijms.2024.117234.

Yang, Z., Jackson, S.E., Skulski, T., 2021. Characterization of four copper materials for application as reference materials for high precision copper isotope analysis by laser ablation inductively coupled plasma multi-collector mass spectrometry. Front. Chem. 9, 617205. https://doi.org/10.3389/fchem.2021.617205.

Yang, Z., Song, W., Wen, H., Zhang, Y., Fan, H., Wang, F., Li, Q., Yang, T., Zhou, Z., Liao, S., Zhu, C., 2022. Zinc, cadmium and sulphur isotopic compositions reveal biological activity during formation of a volcanic-hosted massive sulphide deposit. Gondw. Res. 101, 103-113. https://doi.org/10.1016/j.gr.2021.07.024.

Yin, N.-H., Sivry, Y., Benedetti, M.F., Lens, P.N.L., Van Hullebusch, E.D., 2016. Application of Zn isotopes in environmental impact assessment of Zn-Pb metallurgical industries: a mini review. Appl. Geochem. 64, 128-135. https://doi.org/10.1016/j.apgeochem.2015.09.016.

Yin, N.-H., Van Hullebusch, E.D., Benedetti, M., Lens, P.N.L., Sivry, Y., 2018. Zn isotopes fractionation during slags' weathering: one source of contamination, multiple isotopic signatures. Chemosphere 195, 483-490. https://doi.org/10.1016/j.chemosphere.2017.11.184.

Zafra-Mejía, C.A., Hernández-Medina, D., Suárez, J., Naves, J., Anta, J., 2025. Understanding sediment wash-off in road drainage systems under intense rainfall and high sediment masses: insights from a large-scale modeling facility. Sci. Total Environ. 959, 178195. https://doi.org/10.1016/j.scitotenv.2024.178195.

Zaronikola, N., Holley, E.A., Mathur, R., Pace, D., 2023. Copper isotopes and constraints on the ore genesis process of Cu-Co ore deposits at the Idaho Cobalt Belt, USA. Minerals 13, 1355. https://doi.org/10.3390/min13111355.

Zeng, J., Han, G., 2020a. Tracing zinc sources with Zn isotope of fluvial suspended particulate matter in Zhujiang River, Southwest China. Ecol. Indic. 118, 106723. https://doi.org/10.1016/j.ecolind.2020.106723.

Zhai, H.-Y., Wang, X.-C., Li, C.-F., Wilde, S.A., Li, X.-Z., Xu, B., Zhang, X.-L., Zhang, P., 2023. High-precision zinc isotopic characterization of twenty soil reference materials from China determined by MC-ICP-MS. RSC Adv. 13, 19030-19038. https://doi.org/10.1039/D3RA00603D.

Zhang, H., Tan, Q., Zhang, L., Fu, X., Feng, X., 2020. A laboratory study on the isotopic composition of Hg(0) emitted from Hg-enriched soils in Wanshan Hg mining area. J. Geophys. Res.: Atmos. 125, e2020JD032572. https://doi.org/10.1029/2020JD032572.

Zhao, H., Li, X., Wang, X., Tian, D., 2010. Grain size distribution of road-deposited sediment and its contribution to heavy metal pollution in urban runoff in Beijing, China. J. Hazard. Mater. 183, 203-210. https://doi.org/10.1016/j.jhazmat.2010.07.012.

Zhao, H., Chen, X., Hao, S., Jiang, Y., Zhao, J., Zou, C., Xie, W., 2016. Is the wash-off process of road-deposited sediment source limited or transport limited? Sci. Total Environ. 563-564, 62-70. https://doi.org/10.1016/j.scitotenv.2016.04.123.

Zhou, J.-X., Huang, Z.-L., Zhou, M.-F., Zhu, X.-K., Muchez, P., 2014. Zinc, sulfur and lead isotopic variations in carbonate-hosted Pb-Zn sulfide deposits, Southwest China. Ore Geol. Rev. 58, 41-54. https://doi.org/10.1016/j.oregeorev.2013.10.009.

Zhu, Z.-Y., Jiang, S.-Y., Yang, T., Wei, H.-Z., 2015. Improvements in cu-Zn isotope analysis with MC-ICP-MS: a revisit of chemical purification, mass spectrometry measurement and mechanism of Cu/Zn mass bias decoupling effect. Int. J. Mass Spectrom. 393, 34-40. https://doi.org/10.1016/j.ijms.2015.10.009.

Zimmermann, T., Mohamed, A.F., Reese, A., Wieser, M.E., Kleeberg, U., Prófrock, D., Irgeher, J., 2020. Zinc isotopic variation of water and surface sediments from the German Elbe River. Sci. Total Environ. 707, 135219. https://doi.org/10.1016/j.scitotenv.2019.135219.