# Widespread occurrence of amphibole minerals in Paris urban dust samples: a mineralogical tracer of urban wear?

Pierre Le Pape, Guillaume Morin, Benoît Baptiste, Thierry Allard, Etienne Balan, Ludovic Delbes, Claire Carvallo, Clara Vaccaro, Maëva Philippe, Sophie Ayrault, et al.

► To cite this version:

Pierre Le Pape, Guillaume Morin, Benoît Baptiste, Thierry Allard, Etienne Balan, et al. Widespread occurrence of amphibole minerals in Paris urban dust samples: a mineralogical tracer of urban wear?. Applied Geochemistry, 2025, 190, pp.106497. 10.1016/j.apgeochem.2025.106497. hal-05231908

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Submitted on 1 Sep 2025

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# 1. Introduction

In urban environments, standing as highly anthropized areas (Norra, 2009), the functioning of eco- and hydro-systems is influenced, among other processes, by soil artificialization. As urbanized areas have an increasing footprint, and are expected to further develop in the future (UN World urbanization prospects, 2019), it is of major importance to understand how these artificialization processes gradually modify the structure of continental matter fluxes, i.e. the nature and transfer modes of solid particles. Since transportation of matter through the particulate form strongly contributes to the biogeochemical cycling of both essential nutrients and contaminants from the local to the regional scale (Le Pape et al., 2012; Gaillardet et al., 1999; Meybeck and Ragu, 1997; Viers et al., 2009), it is of particular interest to study and quantify the nature and amount of mineral particles emitted by urban areas. In addition, it is of major importance to estimate the chemical reactivity of anthropogenic mineral particles (e.g. Sivry et al., 2014), and to document how those emitted from urban anthropogenic activities would be eventually prone to modifying the balance of continental hydro- and eco-systems (e. g. Puisney-Dakhli et al., 2023).

In urban environments, particles are generated by geogenic wearing processes such as weathering and erosion, which locally affect artificialized techno- and/or embanked-soils. They are also emitted by additional anthropogenic sources such as exhaust and non-exhaust traffic emissions (Almeida et al., 2006; Amato et al., 2009; Bressi et al., 2014; Pierson and Brachaczek, 1982; Thorpe and Harrison, 2008), waste incinerators (Bressi et al., 2014; Douglas et al., 2017), and/or wear/erosion of waterproofed manufactured materials such as building or road surfaces (Amato et al., 2011; Wang et al., 2022; Paltinean et al., 2016). Such particles of diverse origins mix to form composite urban dusts that are either transported by air or water runoff on impermeable surfaces depending on their nature, size, or emission pathways. Ultimately, urban dust particles that are transported along continental pathways via river waters settle in continental sedimentary reservoirs in which they harbor a particular chemical reactivity at their interface with solution, possibly exerting driving forces on local biogeochemical reactions (e.g. Philippe et al., 2023). Sediment reservoirs downstream urban areas include bottom sediments, locally-accumulating particles depending on the nature and level of river artificialization, and sediments of floodplains or estuaries, in which the gradual influx of urban-sourced particles will accumulate in the form of sedimentary archives. Such archives can then record the intensity of urban wear and its potential for modifying quantitatively the balance of continental biogeochemical cycles.

Urban influence is currently mostly measured through the prism of contamination, for instance by monitoring chemical indicators such as trace elements in waters and sediments (e.g. Priadi et al., 2011a; Le Pape et al., 2012), size measurements of particulate matter (PM) aerosols (Karagulian et al., 2015) or road dust particles (Gunawardana et al., 2014) and chemistry of road sediment deposits (Varrica et al., 2003; Gunawardana et al., 2012; Haynes et al., 2020). Other recent research works target contaminants in specific bio-indicators such as lichens, tree barks, biofilms, or other living organisms (Parzych et al., 2016; Catinon et al., 2009 Ancion et al., 2010; Bourgeault et al., 2010). However, only few approaches based on the study of mineralogical and crystal-chemical characteristics of selected groups of particles are used to monitor urban wear, partly due to the difficulty to isolate anthropogenic-from geogenic-sourced components. Thus, studies focused on the detailed analysis of mineralogical composition of urban dust materials to detect mineral particles emitted from specific man-made manufactured materials on the basis of their mineralogical signature are lacking. In the current context of expansion of artificialized urban areas, the possibility of detecting specific mineralogical components in mineral fluxes should be expected. Indeed, the signature of minerals exclusively used in specific types of activities such as concrete, building or road materials, or specific alloy metallic particles should

become more and more visible in the pool of particle emitted to the environment.

The mineralogy of environmental particles, including those present in urban areas, can primarily be studied by means of powder X-Ray Diffraction (XRD), which indicates the main major mineralogical phases present in a sample (Brindley and Brown, 1980; Moore and Reynolds, 1989), with a detection limit of approx. 1 wt%, depending on the crystallinity of the considered phases. XRD investigations can be followed by electron microscopy analyses, to highlight the presence of additional minor nanocrystalline or amorphous phases non visible by XRD whose crystal-chemical composition and morphological characteristics can provide information on particle chemical reactivity or pathways in urban environments (Lu et al., 2008; Paltinean et al., 2016; Yang et al., 2016). Thus, mineralogy criteria advantageously complete the classically performed measurements of particle size and bulk chemistry, since the mineralogical nature of particles is a crucial property defining its solubility and physico-chemical reactivity at the interface with organic matter, contaminants, and/or biological interfaces (Brown and Calas, 2011).

In this study, we have gathered samples of different nature, including road deposited sediments, suspended particulate matter, and urban dusts sampled in the Paris region (France) within the last decade. We detect in most samples a mineralogical component belonging to the amphibole group (Hawthorne et al., 2012) whose origin cannot be sourced in local geology in such a sedimentary context. We then perform a range of mineralogical analyses to understand both the nature of the amphibole detected and its possible sources and pathways in urban media. Finally, we discuss the environmental implications of this finding.

# 2. Material and methods

## 2.1. Sampling

Samples analyzed in this study include urban dusts, stormwater highway pond samples, road aggregates, and river suspended particulate matter (Table 1). Most of them were collected in the Paris city at strongly artificialized locations made of concrete, cement and other road or building construction materials. Geogenic materials could also be provided by embanked soil material whose origin cannot be formally sourced. The Paris basin in the sampling area is mainly constituted of Tertiary deposits (Brunet and Le Pichon, 1982), in particular Eocene and Oligocene formations (Diffe, 1980). Both series generally consists in an alternation of sand, clay, limestone and marl beds. Resulting mineralogy thus includes a large diversity of clay minerals, quartz, calcite, dolomite, feldspars, iron oxides and pyrite as trace minerals and gypsum.

Details about a part of the samples listed in Table 1 can be found in former studies. For stormwater basin samples, sampling was performed with the approval of stormwater basin managers, and details on sampling procedure can be found in Philippe et al. (2023). Samples of road material (bitumen, road aggregates) were collected on the road or on the road gutter while already detached or almost detached from the road tread. Sampling details for chosen samples of suspended particulate matter (SPM) can be found in Le Pape et al. (2012) for the Orge River and Priadi et al. (2011b) for the Seine River. Urban dust samples were generally sampled using a clean brush and/or plastic spatula. Samples for which the dust was encrusted were scratched on the surface using a plastic spatula (e.g. bike wheel). One of the samples of urban dust (RDS-V3, road sediment recover in a gutter) was sampled a decade ago for another study and stored dry at room temperature (Le Pape et al., 2012).

One punctual sampling of suspended particulate matter (SPM) was performed in the Seine River in March 2022 for this study, consisting of approximately 20 L of Seine water at the "Quai St Bernard" site. Then the water was filtered on 0.22 µm filters, which were scratched once dried using a plastic spatula to collect approximately 20 mg of particles.
## 2.2. XRD analyses

Powder X-ray diffraction (XRD) analysis was performed on a Panalytical™ Xpert-pro diffractometer in the Bragg-Brentano geometry using Co Kα radiation. For analysis, samples were crushed in an agate mortar and measured with a 0.016° step in 2θ, counting for a total time between 6 and 12 h on a 2–100° 2θ interval, depending on samples. When the sample quantity was low, deposits were performed on low-background Si holders.

Multiphase Rietveld analysis of selected XRD patterns was performed for selected samples using the nd1.3 code (Berar and Baldinozzi, 1998). The starting crystallographic parameters were taken from the crystal structure data reported by Evans and Yang (1998), Antao et al. (2008), Markgraf and Reeder (1985), Althoff (1977), Harlow and Brown (1980), Wenk and Nakajima (1980), Colville and Ribbe (1968), Bailey (1969), Rothbauer (1971), Brigatti and Davoli (1990), Zanazzi et al. (2007), Bish and Post (1989), for ferro-actinolite, quartz, calcite, dolomite, albite, plagioclase, orthose, microcline, muscovite, biotite, chlorite and kaolinite, respectively. Appropriate mineral phases were included in the refinement for each analyzed sample and scale factors were refined for all included phases. An overall zero-point shift parameter was refined as well as the unit-cell parameters for major phases, except for naturally occurring quartz that served as peak position calibrant. Line-shape parameters were refined for major phases and fixed to

appropriate values for minor phases. Site occupancy parameters were refined for FeMg-actinolite in the road aggregate sample only (see Table 2 for details) and were fixed to these refined values for the other samples. Site occupancy factors were fixed to literature values for all other phases. Atomic positions and Debye-Waller parameters were fixed to literature values for all phases. Quantitative mineralogical analysis was derived from Rietveld-refined scale factors, using the classical approach without internal standard (Snyder and Bish, 1989)

For suspended particulate matter (SPM) samples, obtaining a better signal to noise ratio required the analysis using synchrotron radiation, which was performed on the CRISTAL beamline of the SOLEIL synchrotron. For this measurement, samples were crushed in an agate mortar, inserted in borosilicate capillaries, and measured at 24 keV in Debye-Scherrer geometry on a 2-circle diffractometer equipped with a MYTHEN2 X9K detector. Data was collected for 1 h using a 2θ step of 0.004° and the background of the capillary was subtracted prior to data analysis. For comparison with the dataset obtained at the laboratory, synchrotron powder XRD data recorded at 24 keV were recalculated with the Co Kα radiation.

For the "Orsay_Gdust" sample (Table 1) containing amphibole, a single crystal XRD analysis was performed on a selected amphibole grain using a 4-circles Xcalibur S diffractometer at the X-ray platform of IMPMC. The crystal was mounted on a kapton loop (Mitegen®) using vacuum grease. The experiment was then carried out at 293K using Mo

<caption>**Table 1**</caption>

List of samples used in this study with details on sampling site, sampling date, sample type and, when relevant, the studies in which more details on the samples can be found.

<table><thead><tr><th>Sample label</th><th>Sampling site</th><th>Sampling date</th><th>sample type</th><th>bibliographic reference</th></tr></thead><tbody><tr><td>Marcoussis_CDCA</td><td>Stormwater basin Marcoussis A N104</td><td>01/28/20</td><td>sediment/crust</td><td>Philippe et al. (2023)</td></tr><tr><td>Marcoussis_RDSA</td><td>Stormwater basin Marcoussis A N104</td><td>01/28/20</td><td>road dust</td><td>Philippe et al. (2023)</td></tr><tr><td>Marcoussis_RDSB</td><td>Stormwater basin Marcoussis B N104</td><td>02/13/20</td><td>road dust</td><td>Philippe et al. (2023)</td></tr><tr><td>Marcoussis_CDA</td><td>Stormwater basin Marcoussis A N104</td><td>01/28/20</td><td>sediment</td><td>Philippe et al. (2023)</td></tr><tr><td>Orsay_Gdust</td><td>Stormwater basin Orsay N118</td><td>01/23/20</td><td>road dust</td><td>Philippe et al. (2023)</td></tr><tr><td>Orsay_Drain1_2</td><td>Stormwater basin Orsay N118</td><td>01/23/20</td><td>sediment</td><td>Philippe et al. (2023)</td></tr><tr><td>Orsay_Drain2_3</td><td>Stormwater basin Orsay N118</td><td>01/23/20</td><td>sediment</td><td>Philippe et al. (2023)</td></tr><tr><td>Car wing</td><td>A car riding essentially in the Ile de France region</td><td>April 2021</td><td>dust</td><td>This study</td></tr><tr><td>Bike wing</td><td>A bike riding in Paris and close suburbs</td><td>09/14/23</td><td>dust</td><td>This study</td></tr><tr><td>Bike brake</td><td>Brake of the wheel where dust was sampled</td><td>09/14/23</td><td>dust</td><td>This study</td></tr><tr><td>RS_AUS</td><td>Austerlitz bridge sidewalk left shore</td><td>03/09/22</td><td>dust/sediment</td><td>This study</td></tr><tr><td>RS_PAN</td><td>Sidewalk border to street Place du Pantheon</td><td>03/09/22</td><td>road dust</td><td>This study</td></tr><tr><td>RS_POL</td><td>Poliveau street between pavements sidewalk/street</td><td>03/09/22</td><td>road/sidewalk sediment</td><td>This study</td></tr><tr><td>BS_LAR</td><td>Larrey street in a wall interstice</td><td>03/09/22</td><td>building wall sediment</td><td>This study</td></tr><tr><td>RS_JUS</td><td>Fossés St Bernard street in between pavements</td><td>03/09/22</td><td>road/sidewalk sediment</td><td>This study</td></tr><tr><td>S_JUS2</td><td>Dust on the border of the Jussieu university level</td><td>03/09/22</td><td>sediment</td><td>This study</td></tr><tr><td>S_PAR</td><td>Sediment incrusted on an metallic surface St Germain boulevard</td><td>03/09/22</td><td>sediment</td><td>This study</td></tr><tr><td>RS_AUSN</td><td>Austerlitz bridge sidewalk middle</td><td>03/09/22</td><td>road/sidewalk sediment</td><td>This study</td></tr><tr><td>Roof_Jus</td><td>Encrusted dusts on ventilation structures</td><td>09/08/22</td><td>encrusted dust</td><td>This study</td></tr><tr><td>RW_W_FSM</td><td>St Martin Boulevard</td><td>09/15/22</td><td>dust on a store wall</td><td>This study</td></tr><tr><td>RDS_V3</td><td>Pond Godeau street in Viry-Chatillon</td><td>01/31/11</td><td>Road dust sediment</td><td>PhD thesis Le Pape et al., 2012</td></tr><tr><td>Road_Agg_Jussieu_street</td><td>Jussieu street</td><td>05/09/22</td><td>road aggregate</td><td>This study</td></tr><tr><td>Road_Agg_inner_Jussieu</td><td>Street in Jussieu side St Bernard street</td><td>May 2022</td><td>road aggregate</td><td>This study</td></tr><tr><td>Road_Agg_Fbg_St_Martin</td><td>St Martin Boulevard</td><td>09/15/22</td><td>Road aggregates plus dust</td><td>This study</td></tr><tr><td>Road_Bit_Fbg_St_Martin_new</td><td>St Martin Boulevard</td><td>09/22/22</td><td>Bitumen</td><td>This study</td></tr><tr><td>Road_Agg_Fbg_St_martin_new</td><td>St Martin Boulevard</td><td>09/22/22</td><td>road aggregate</td><td>This study</td></tr><tr><td>Road_Agg_Gare_de_lyon_new</td><td>Diderot Boulevard</td><td>05/24/22</td><td>road aggregate</td><td>This study</td></tr><tr><td>SPM_Seine_Paris</td><td>Quais St Bernard</td><td>March 2022</td><td>filtered SPM</td><td>This study</td></tr><tr><td>SPM_Orge_V1</td><td>Orge River - Pond Godeau street in Viry-Chatillon - concrete channel</td><td>06/03/10</td><td>filtered SPM</td><td>Le Pape et al. (2012) - supp. info</td></tr><tr><td>SPM_Orge_V2</td><td>Orge River - Pond Godeau street in Viry-Chatillon - concrete channel</td><td>09/27/10</td><td>filtered SPM</td><td>Le Pape et al. (2012) - supp. info</td></tr><tr><td>Sediment_Trap_Seine_Triel</td><td>Trap accumulating SPM In Triel/Seine</td><td>06/01/09</td><td>filtered SPM</td><td>Priadi et al. (2011b)</td></tr></tbody></table>
<caption>**Table 2**</caption>

Rietveld refinement parameters for actinolite in the road aggregate sample (R. Agg. Jussieu street), road pond sediment (Marcoussis CDCA, Marcoussis RDSA) and urban dust samples (RS_AUS). Corresponding plots are reported in Figs. 4 and 5.

<table><thead><tr><th>Sample</th><th>a</th><th>b</th><th>c</th><th>β</th><th><i>M</i><sup>1</sup><i>Fe</i><sub>occ</sub></th><th><i>M</i><sup>2</sup><i>Fe</i><sub>occ</sub></th><th><i>M</i><sup>3</sup><i>Fe</i><sub>occ</sub></th><th>wt%</th></tr></thead><tbody><tr><td>R. Agg. Jussieu street</td><td>9.874(10)</td><td>18.141(20)</td><td>5.301(7)</td><td>104.75(8)</td><td>1.00*</td><td>0.54(2)</td><td>0.46(2)</td><td>17(1)</td></tr><tr><td>Marcoussis CDCA</td><td>9.87(3)</td><td>18.15(6)</td><td>5.3011*</td><td>104.8(4)</td><td>1.00*</td><td>0.54*</td><td>0.46*</td><td>8(2)</td></tr><tr><td>Marcoussis RDSA</td><td>9.86(44)</td><td>18.11(10)</td><td>5.3011*</td><td>104.7(7)</td><td>1.00*</td><td>0.54*</td><td>0.46*</td><td>3(1)</td></tr><tr><td>RS_AUS</td><td>9.85(7)</td><td>18.14(14)</td><td>5.30(3)</td><td>104.6(8)</td><td>1.00*</td><td>0.54*</td><td>0.46*</td><td>1(1)</td></tr></tbody></table>

Note: $x'_{Fe}$ was refined assuming Fe only in the octahedral sites and converted to $x_{Fe}$ assuming $x_{Mg} = 1-x_{Fe}$ and by approximating the ratio between diffusion factors of Mg and Fe by their Z number ratio, i.e. $12(1-x_{Fe}) + 26(x_{Fe}) = 26 x'_{Fe}$, which yields $x_{Fe} = (26 x'_{Fe} - 12)/14$.

Kα radiation (sealed X-ray tube) and the diffracted intensities were collected using a Sapphire CCD detector. 11420 reflections were measured up to 2θ = 61° and indexed with the monoclinic cell a = 9.8891(3) Å, b = 18.1633(4) Å, c = 5.3171(2) Å, β = 104.852(3)°, which was consistent with the known structure of actinolite (Evans and Yang, 1998). The crystal structure was then solved in the monoclinic, space group C2/m with the Olex2 suite (Dolomanov et al., 2009), and with the olex2. solve (Bourhis et al., 2015) structure solution program using charge flipping method. The model was then refined with the SHELXL (Sheldrick, 2015) refinement package using a least squares minimisation procedure. The H position was located in the Fourier difference map. The Fe and Mg occupations were refined on the M1, M2 and M3 sites, considering a total occupancy of 100 % and only these 2 elements on each site. The final stoichiometry indicated the amphibole grain initially selected with the binocular magnifier has a FeMg-actinolite composition (Hawthorne et al., 2012).

## 2.3. SEM & TEM analysis

Scanning electron microscopy (SEM) analysis associated with Energy dispersive X-ray microanalysis (EDXS) were performed on crushed and non-crushed samples deposited on carbon film supported copper grids using a specific sample holder on a GEMINI ZEISS Ultra55 Field emission Gun Scanning electron microscope equipped with a Bruker Si-drift detector for EDXS acquisition.

After being located on the TEM grids using SEM, selected particles of amphibole minerals were observed by Transmission electron microscopy (TEM) and scanning transmission electron microscopy coupled to EDXS (STEM-EDXS), using a JEOL 2100F equipped with a field emission gun microscope and operating at 200 kV. Qualitative chemical mapping and local elemental composition were obtained by EDXS using a JEOL Si-drift detector. Selected area diffraction patterns (SAED) proving that particles belong to the amphibole group were measured on the selected particles presented in the article.

## 2.4. Other analysis

The sample of road aggregate labeled "Road_Agg_Jussieu_Street" containing 17 wt% amphibole as determined by Rietveld analysis was analyzed in diffuse reflectance spectroscopy. The diffuse reflectance spectra were recorded in the 2800–10000 cm⁻¹ range with a 4 cm⁻¹ resolution on pure powder samples using a Nicolet 6700 FTIR spectrometer equipped with a white-light source, quartz beamsplitter, nitrogen-cooled MCT (mercury cadmium telluride) detector, reference aluminum mirror and Collector II diffuse reflectance accessory. The single-beam signals were obtained as co-addition of 400 scans, and the spectra are reported as remission functions f(R) obtained using the Kubelka-Munk transformation of the reflectance spectra (Fig. SI-1).

For this same sample, a magnetization curve was measured with a Vibrating Sample Magnetometer from Princeton Measurements Corporation at the IPGP-IMPMC Mineral Magnetism Analytical Facility, in a maximum field of 1 T (Fig. SI-2).

## 3. Results

All samples considered in this study, listed in Table 1, were analyzed by powder X-ray diffraction to determine the major mineral phases constituting the samples. Most of them, containing in particular quartz, calcite, dolomite, feldspars as well as phyllosilicates (usual XRD (001) reflections at 14 Å, 10 Å and 7 Å), reflect the mineralogy of the Paris sedimentary basin, with main contributors being the surface soils and sediments of the Seine watershed. Additionally, some of these same minerals such as quartz, feldspars and chlorites are also employed in construction materials (concrete, embankment) that are well represented in the Paris urban area, for instance in buildings and roads. Thus, wear of such urban materials also contribute to these mineral components. Fig. 1 provides the X-Ray powder diffraction patterns for samples collected in stormwater basins receiving road runoff waters along two heavily trafficked motorways (around 50 000 vehicles per day, Philippe et al., 2023) of the Ile de France region (N118, N104). Samples from these basins show the main mineralogical signature of the previously cited surface minerals with an additional peak at low angle (8.4 Å), positioned at classical distances of minerals of the amphibole group. Fig. 2 shows X-Ray powder diffraction patterns obtained for samples of urban dust sampled in the city of Paris or in its close suburbs, including samples collected on car and bike wheels, corresponding to dust accumulated over the course of their everyday ride. Again, for these samples, a barely visible to clearly observable peak is detected at 8.4 Å, attributed to minerals of the amphibole group. Note that only one Bragg reflection in a powder XRD pattern is generally not enough to formally identify a mineral. However, no other mineral than amphibole would fit in such different samples and contexts. As this 8.4 Å Bragg reflection was essentially detected near roads (Figs. 1 and 2), we pursued the investigation by sampling some road materials, including road aggregates, i.e. pellets initially embedded in road tread (Fig. SI-3) and associated bitumen matrix to search for amphiboles.

X-Ray powder diffraction patterns for those road aggregates/pellets samples constituting road treads are presented in Fig. 3. In some of them, and in particular in the "Road_Agg_Jussieu_Street" sample, a mineral of the amphibole group detected at 8.4 Å stands as a major mineralogical component (Fig. 4). Further Rietveld analysis of the X-Ray diffractogram for this amphibole-rich sample shows that this mineral contributes to 17 (1) wt% of the road aggregate, and harbors crystallographic parameters that fit well with those of an iron-rich amphibole of FeMg-actinolite composition (Table 2). This road aggregate is additionally composed of chlorite, quartz, calcite, feldspars and phyllosilicates. The analysis of this sample by IR spectroscopy in the near-infrared range confirmed that the observed overtones are consistent with a FeMg-actinolite mineral (Fig. SI-1). Additional analysis of a magnetization curve of this "Road Agg. Jussieu street" sample presented in Fig. SI-2 shows an important paramagnetic contribution that cannot fully be attributed to the amphibole at this stage, since a Fe-containing chlorite is also present in the investigated road aggregate. Interestingly, the ferromagnetic contribution presents a "wasp-waisted" shape characteristic of the mixture of two magnetic populations with very different coercivities (Roberts et al., 1995). A low-coercivity component is often observed in urban dust (e.g., Letaïef et al., 2024), and can be considered as the
<figure><img src="image_2.png" /><figcaption>Fig. 1. Full powder XRD patterns of highway stormwater retention ponds sediments sampled in the Ile-de-France region near Paris (see Table 1 for full details on the samples) and zoom on the low angle region. The red frames indicate the characteristic region at low angle where are found Bragg reflections corresponding to amphibole minerals. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)</figcaption></figure>

<figure><img src="image_3.png" /><figcaption>Fig. 2. Full XRD powder patterns of urban dust samples collected on pavement, car wheel, bike wheel, window edge and building roof in downtown Paris and near the Orge river (see Table 1 for full details on the samples) and zoom on the low angle region. The red frames indicate the characteristic region at low angle where are found Bragg reflection corresponding to amphibole minerals. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)</figcaption></figure>

signature of anthropogenic, mostly vehicle-related metallic particulate matter, caused by exhaust and abrasion processes (e.g., Hofman et al., 2017; Tribaudino et al., 2022). However, the high-coercivity component is more unusual and could be attributed to elongated magnetic inclusions that are often observed in silicates (Feinberg et al., 2005)

(Fig. SI-2). Additionally, an amphibole grain was extracted from the mineral powder of the sample “Orsay_Gdust” (Table 1, Fig. 1) and was analyzed by single crystal X-ray diffraction (Table 3, Tables SI-1-6). This analysis, allowing a crystal structure refinement, also converged towards a FeMg-actinolite of “Ca₂.₁₅Fe₂.₅₆Mg₂.₄₄Si₈O₂₂(OH)₂” formula
<figure><img src="image_4.png" /><figcaption>**Fig. 3.** Full powder XRD patterns of detrital road aggregates and bitumen pieces samples from downtown Paris streets (see Table 1 for full details on the samples) and zoom on the low angle region. The red frames indicates the characteristic region at low angle where are found Bragg reflections corresponding to amphibole minerals. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>**Fig. 4.** Rietveld refinement of the XRD powder pattern of the crushed road aggregate sample from Jussieu street (« Road_Agg_Jussieu_Street ») allowing the quantification of all the mineral components in the sample. Refinement parameters for FeMg-actinolite are reported in the associated Table 2.</figcaption></figure>

(Table 3). From a formal point of view, such an amphibole type should be designed as a "ferro-magnesio-actinolite" according to the nomenclature proposed by Hawthorne et al. (2012). Rietveld analysis was further performed on other selected samples representative of urban road environments in which the amphibole mineralogical species was present in sufficient amount (Fig. 5). The associated crystallographic parameters determined (Table 2) also show a good agreement with the FeMg-actinolite previously observed, thus strengthening the fact that this peculiar mineral could be the one present in our broad set of samples.

To formally identify the mineral at the scale of the particles, we followed the investigation by using electron microscopies. SEM

associated to EDXS microanalysis was used to analyze the amphibole particles in selected samples (Fig. 6). Examples are presented in Fig. 6 for two samples of road dusts, one sample of stormwater pond sediment, and the crushed road aggregate "Road_Agg_Jussieu_Street" containing FeMg-actinolite as a major mineralogical component. Additional images are presented in supplement information including for other samples (Fig. SI-4). The particles present different sizes and morphology, from massive amphibole of more than 100 µm to micrometric elongated bunch of particles, observed in particular in the crushed "Road_Agg_Jussieu_Street" sample. At the crystal-chemical level, EDXS micro-analysis indicated that the chemical compositions are qualitatively close for all the amphiboles probed in the different samples, with the detected
<caption>**Table 3**</caption>

Crystal data and structure refinement for FeMg-actinolite from X-ray diffraction of a 180x70x45 µm³ single crystal selected in the Orsay_Gdust sample (Table 1). Other additional refined parameters (distances, angles, etc.) are available in tables listed in supporting information (Tables SI-1-6).

<table><thead><tr><th>Identification code</th><th>Actinolite</th></tr></thead><tbody><tr><td>Empirical formula (Fe/Mg ratio refined)</td><td>Ca<sub>2.15</sub>Fe<sub>2.56</sub>H<sub>2</sub>Mg<sub>2.44</sub>O<sub>24</sub>Si<sub>8</sub></td></tr><tr><td>Formula weight</td><td>899.56</td></tr><tr><td>Temperature/K</td><td>293.00</td></tr><tr><td>Crystal system</td><td>monoclinic</td></tr><tr><td>Space group</td><td>C2/m</td></tr><tr><td>a/Å</td><td>9.8891(3)</td></tr><tr><td>b/Å</td><td>18.1633(4)</td></tr><tr><td>c/Å</td><td>5.3171(2)</td></tr><tr><td>α/°</td><td>90</td></tr><tr><td>β/°</td><td>104.852(3)</td></tr><tr><td>γ/°</td><td>90</td></tr><tr><td>Volume/Å<sup>3</sup></td><td>923.14(5)</td></tr><tr><td>Z</td><td>2</td></tr><tr><td>ρ<sub>calc</sub>/cm<sup>3</sup></td><td>3.236</td></tr><tr><td>μ/mm<sup>-1</sup></td><td>3.335</td></tr><tr><td>F(000)</td><td>890.0</td></tr><tr><td>Crystal size/mm<sup>3</sup></td><td>0.179 × 0.068 × 0.044</td></tr><tr><td>Radiation</td><td>Mo Kα (λ = 0.71073)</td></tr><tr><td>2θ range for data collection/°</td><td>7.93 to 61</td></tr><tr><td>Index ranges</td><td>-14 ≤ h ≤ 14, -25 ≤ k ≤ 25, -7 ≤ l ≤ 7</td></tr><tr><td>Reflections collected</td><td>11420</td></tr><tr><td>Independent reflections</td><td>1452 [R<sub>Int</sub> = 0.0334, R<sub>sigma</sub> = 0.0172]</td></tr><tr><td>Data/restraints/parameters</td><td>1452/0/107</td></tr><tr><td>Goodness-of-fit on F<sup>2</sup></td><td>1.318</td></tr><tr><td>Final R indexes [I ≥ 2σ(I)]</td><td>R<sub>1</sub> = 0.0338, wR<sub>2</sub> = 0.0635</td></tr><tr><td>Final R indexes [all data]</td><td>R<sub>1</sub> = 0.0364, wR<sub>2</sub> = 0.0643</td></tr><tr><td>Largest diff. peak/hole/e Å<sup>-3</sup></td><td>0.51/-0.48</td></tr></tbody></table>

presence of major constitutive elements as Mg, Si, Ca and Fe. Observations of the crushed “Road_Agg_Jussieuzesl” sample show in particular the existence of preferential cleavage orientations for the massive particles, which allow them to subdivide into elongated particles of inferior sizes. The investigation was pursued by TEM observations on the amphibole particles identified by SEM for the samples RS_AUS and BS_LAR and on another particle of the “Road_Agg_Jussieu_Street” sample, presented respectively in Figs. 7–9. In Fig. 7, the chemical composition for the particle of sample RS_AUS is confirmed by EDXS analysis

with Mg, Si, Ca and Fe as major elements, and the measured SAED pattern obtained is fully consistent with inter-reticular distances of a FeMg-actinolite mineral and angle (98°) measured between the (002) and (-1-12) reticular planes. In Fig. 8, chemical mapping of a more massive particle shows again a characteristic composition of Mg, Si, Ca and Fe as major elements. The chemical composition is confirmed for the FeMg-actinolite (Fig. 9) and the detailed examination of particle morphology shows the existence of cleavage planes as observed by SEM for a more massive particle, forming at this scale some nanometric and elongated fibers. Additional investigations on the same particles at high resolution (HRTEM) reveal that the edges of particles are often amorphized (e.g. Fig. 7), which could for instance result from local dissolution processes during transport.

The widespread observations of these amphibole minerals in samples of the Paris region in the vicinity of roads in our broad set of samples raise questions about their possible contribution to sedimentary fluxes. To further evaluate this point, we performed X-Ray diffraction analyses on samples of suspended particulate matter (SPM), some of them collected more than a decade ago at high population density area of the Orge River (V1, V2, Le Pape et al., 2012) or in the Seine River downstream the city of Paris (sediment trap at Triel, Priadi et al., 2011). In Fig. 10, powder XRD patterns are presented for the cited samples plus for a single sample punctually collected in the Seine River in 2022. For each sample, the main reflection peak of the amphibole mineral detected at 8.4 Å is visible but barely emerged from background, which does not ensure its presence. To overcome this and lower the signal to noise ratio, we analyzed those samples by X-Ray diffraction using synchrotron light, which allowed the clear detection of the 8.4 Å distance peak, characteristic of minerals of the amphibole group in the SPM samples (Fig. 11). It means that those minerals are visible by XRD in sediment fluxes transported by the river between sedimentary reservoirs, including in a punctual sample of 20L of water sampled in the Seine River in Paris (“SPM Seine_Paris”, Fig. 11).

## 4. Discussion

### 4.1. Sources of amphibole minerals in urban media

The widespread observation of minerals of the amphibole group in

<figure><img src="image_6.png" /><figcaption>**Fig. 5.** Rietveld refinement of the XRD powder pattern of selected road pond sediments and urban dust samples allowing the quantification of all the mineral components in the sample. Refinement parameters for FeMg-actinolite are reported in Table 2.</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>**Fig. 6.** SEM-EDX analysis of amphibole particles in samples of urban dusts (RS_AUS, BS_LAR), stormwater road basin (Marcoussis_RDSA) and crushed road aggregate (Road_Agg_Jussieu_street). All particles identified as amphiboles present a close chemical composition, including Mg, Al, Si, Ca and Fe. Additional SEM observations of amphibole particles in the same samples as well as for others investigated are shown in Fig. SI-4. SEM observations show that amphibole particles harbor various sizes, can be massive or present as bunches of elongated fibers. Observations also show that the bigger particles present characteristic cleavage planes likely producing particles of smaller sizes.</figcaption></figure>

urban dust samples in the vicinity of road traffic areas questions their
source in such urban media. Our investigation shows that some road
aggregates, embedded in bitumen of road tread are enriched with those
minerals, in particular with a FeMg-actinolite type amphibole. Indeed,
an important part of particles emitted from road traffic are found to
derive directly from road wear (Pierson and Brachaczek, 1982; Wang
et al., 2022; Kupiainen et al., 2016; Amato et al., 2011). This finding
suggests that the wearing processes of aggregates contained in some
road treads, likely due to grain frictions under the influence of vehicle
traffic (Brattli, 1994), could be a source of dust emission that bears
amphibole particles. Indeed, this has already been observed in Northern
European countries (Anastasio and Hoff, 2013), particularly where road
wear is intense due to the use of studded tyres on road submitted to ice
and snow (Räisänen et al., 2005). Moreover, the occurrence of
actinolite-type amphibole minerals has already been reported (Léocat,
2020) in the context of roadwork. This occurrence has even been

monitored, for instance in the field of construction works where the
workers are particularly exposed to amphibole dust, as reported in
non-academic documents produced by French roadwork companies. For
instance, a close type of actinolitic amphibole was previously detected
by SEM-EDXS on leaves of *Parietaria officinalis* (Tribaudino et al., 2022),
surrounding a high traffic road in Torino city (Italia). The occurrence of
these amphiboles was there attributed to the close outcrops made of
ophiolite in western alps and/or to the use of these minerals in orna-
mental stones, railway ballast and road asphalt. Additionally, an
investigation recently led by the ANSES agency in France (report
ANSES, 2015) also indicates that commonly used urban materials such
as concrete, and other construction materials in general, could also
contain such actinolite-type minerals. This is attributed to the fact that
amphibole could be found in some quarries used for road material
supply, for instance in quartz veins of dolerite rocks (Lahondère et al.,
2018). In the Paris Ile-de-France area, whose basement is a sedimentary
<figure><img src="image_8.png" /><figcaption>**Fig. 7.** Transmission electron microscopy analysis of a FeMg-actinolite type amphibole particle in the Road sediment RS_AUS sample. Selected area diffraction pattern (SAED) obtained on the particle exhibits cristallographical parameters characteristic of a FeMg-actinolite amphibole as described by XRD Rietveld in samples of this study. EDX spectrum also show a chemical composition that is overall in agreement with the one observed in other samples using TEM- and SEM-EDX.</figcaption></figure>

basin, amphibole does not belong to the local geology. This means that amphibole minerals, in particular fine particles, could originate from igneous regions by air transport over important distances. Another possible source could be the residual signature of brake pads of vehicles, in which amphibole asbestos was used in the past, in minor amount compared to chrysotile, and before asbestos ban (Raghunathan et al., 2024). Although the contribution of different potential sources is not yet estimated, our results point to the wear and emission of pieces of materials used in road pavements such as road aggregates which could have been conveyed from regions including igneous rocks, the closer of which are the Armorican range, Central range or the Alps (Aertgeerts et al., 2020; Cagnard and Lahondère, 2020).

The fact that this mineralogical signature of amphibole is pervasive and can be found almost everywhere in our urban samples, including as trace in samples representative of matter fluxes between sedimentary reservoirs such as river suspended matter material (SPM), means that an important quantity of these minerals is currently present in roads and possibly other construction materials of the Parisian region, and/or as residual dust in the streets. For instance, in some road treads recently replaced (« Road Agg_Fbg_St_Martin_new », « Road Agg_Gare_de_Lyon_new », Fig. 3), the XRD signature of amphibole is no longer detectable, whereas the minerals could still be measured in local dust particles accumulated on building walls, probably resulting from powder produced by old pavement wear (« RW_W FSM », Fig. 2). Since road tread and underlying embankment sediments are documented to be often constituted of other construction recycled materials, including from the road itself, the persisting signature of amphibole minerals,

possibly far from the initial aggregate sources zones, could be explained by such subcycling processes. Indeed, re-use and recycling of old or used construction materials has long been performed in the field of construction work to avoid both expensive waste production and transport of new material onsite. The terms of this practice is regulated by the law and remain a matter of research (e.g. Adomako, 2023).

## 4.2. Modes of amphibole transport

Our investigation suggests that road materials are sources of amphibole minerals in urban media since the more enriched samples observed in this study are road aggregates found in road pavement. This is further corroborated by the fact that samples of stormwater basins, directly dedicated to receiving runoff waters from roads and associated dust particles, are also particularly enriched in amphibole, including in peri-urban areas. This suggests that runoff water is an important vector of transportation for the amphibole-containing dusts deposited and/or produced by road materials. This is in agreement with the observation of detectable amphibole XRD signal in both the urban Orge and Seine Rivers suspended particulate matter. Indeed, the amphibole minerals measured in SPM probably come from (1) meteoritic water runoff on road and urban surfaces and further transfer to the river after rain events and (2) remobilization of the stock already present in bottom river sediments as a function of river hydrodynamics. Otherwise, all types of vehicles circulating in urban spaces are also obviously vectors of transport of amphibole containing dust particles, thus standing as urban archives continuously collecting mineralogical signals. For instance,
<figure><img src="image_9.png" /><figcaption>**Fig. 8.** Transmission electron microscopy analysis of a FeMg-actinolite type amphibole particle in the building sediment BS_LAR sample. Chemical maps derived from EDX measurements as well as provided EDX spectrum show a chemical composition that is overall in agreement with the one observed in other samples using TEM- and SEM-EDX.</figcaption></figure>

amphibole minerals were detected both on bike and car wheels riding essentially in Paris and the Ile-de-France region (Fig. 2). This implies that vehicles can accumulate road/urban dust at amphibole-rich locations and can potentially re-emit the particles somewhere else, for instance due to leaching by meteoritic waters during a rain event, which would also contribute to disseminate at a larger scale this specific mineralogical signature. However, further studies are needed to elucidate the spatio-temporal dynamics of urban dust accumulation and emission from vehicles, as well as to estimate the importance of such transport pathway in the global scheme. Additionally, in one sample, we detected traces of amphibole even though the sampling spot is not directly exposed to transport *via* water runoff. This former sample, called « Roof_Jus » was sampled as a dry crust on an aluminum pipe on the roof of a 30 m building. This indicates that other pathways of transport of amphibole particles are possible, and that the possibility of air transport should be further considered (Paltinean et al., 2016). Thus, we conclude that the global scheme of distribution modes and transport of amphibole particles in urban media, including road runoff, vehicles, and air transport, is strongly unconstrained and thus deserves to be refined.

### 4.3. Environmental implications: fluxes and public exposition

The widespread occurrence of amphibole particles in urban dust samples of this study carried out in the Paris region, with no geological local source identified, raises a question about the current stock of these

minerals available in the Paris urban media, considering both amphibole containing road treads and other construction materials, plus the sum of already accumulated amphibole-containing dust and bottom river sediments. Indeed, urban surfaces are submitted to wear through weathering and erosion. In particular, as roads are intensely used in big cities, important wear is observed leading to frequent repair and replacement works. Such wearing processes are logically amplified in the current context of increasing extreme climatic events such as alternate drought periods and intense storms, these latter contributing to urban floods. The fact that the presence of amphibole minerals could be measured in a punctual sampling of SPM in only 20L of water in the Seine River gives an idea of the important fluxes of these minerals that could be produced by urban wear and further exported downstream. If we consider a conservative and probably underestimated value of 0.1 wt% of SPM constituted of amphibole minerals together with a low export scenario materialized by low waterflow conditions on a hydrological year, this would lead to a 25 t emission of these minerals by the Seine River downstream Paris per year (considering 70 t of SPM exported per day, Tessier, 2003). Then considering the reverse overestimated scenario materialized by high waterflow conditions (considering 50 000 t of SPM exported per day, Tessier, 2003), this would allow to estimate a total mass of amphibole export of 18 000 t per year downstream the Paris megacity. Of course, such simple low and high export estimations could be strongly refined, in particular by measuring more precisely the variations in mass of amphibole in SPM depending on the hydrological conditions and by properly considering fluctuations between low water
<figure><img src="image_10.png" /><figcaption>**Fig. 9.** Transmission electron microscopy analysis of a FeMg-actinolite type amphibole particle in the crushed Road_Aggregate_Jus sample. A STEM-HAADF image is provided as well as chemical maps derived from EDX measurements. Presented spectrum shows the typical chemical composition of the amphibole observed in the samples (Figure SEM-EDX). TEM image shows that the particle termination harbors elongated subparticles.</figcaption></figure>

conditions during drought events and high water following rain events. Hence, we posit that given such estimated fluxes, this mineralogical marker could probably be used to measure the intensity of urban wear and urbanization influence on continental matter fluxes, and that amphibole could constitute a non-negligible and measurable amount of minerals in deposited sedimentary archives downstream the megacity of Paris. Further investigations are thus needed to conclude if this mineralogical signature can be a marker of urban spreading in the Paris region since gradual increase of urbanized surfaces has been identified as characteristic of the Anthropocene period.

From a sanitary perspective, and considering the current issue of air pollution by aerosols in urban megacities (e.g. Molina, 2021), the presence of such amphibole minerals, of multiple sizes and morphologies, casts a doubt on the effects of human exposition to urban dusts (Wylie and Korchevskiy, 2023). Only fibrous actinolite-type amphiboles belong to the minerals that are officially listed as asbestos, but there is an ongoing debate in the literature about whether or not micrometric cleavage fragments of massive amphiboles in the asbestos size range should be considered as potentially harmful particles (ANSES reports, e. g. Gualtieri, 2020). Here, we show that the massive FeMg-actinolite amphibole grains observed can cleave along the (001) and (110)

planes, thus producing particles of smaller size, as documented in Figs. 6–9. The micrometric particles produced could be accounted for « elongated mineral particles », as described in the literature (Gunter, 2018). Additionally, the presence of structural Fe in the fine FeMg-actinolite particles implies that the risk of generation of highly reactive radical species cannot be excluded (O'Day et al., 2022; Andreozzi et al., 2017; Pollastri et al., 2015). In France, the risk of producing potentially harmful fine actinolite particles by cleavage of more massive particles has been evoked in particular in the field of roadwork, which has led to dedicated inquiries of the ANSES agency, responsible for ruling on French sanitary issues (ANSES reports 2015, 2017, 2022). The ANSES agency concludes that a potential harmful effect of such type of fine particle cannot be excluded. Besides, to date and to our knowledge, no risk has been considered for public exposition to such particles by public authorities since the situations taken into account were limited to roadwork areas, where drilling and crushing activities imply a severe risk of emission. The fact that amphibole is pervasively detected in samples of urban dust, in particular in the vicinity of roads, suggests that common people could be exposed to such particles, including to the micrometric cleavage pieces evoked by construction work companies. For instance, the fact that amphibole
<figure><img src="image_11.png" /><figcaption>**Fig. 10.** Full powder XRD patterns of suspended particulate matter samples collected in the Orge and Seine Rivers (see Table 1 for full details on the samples) and zoom on the low angle region. The red frames indicate the characteristic region at low angle where are found Bragg reflection corresponding to amphibole minerals. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)</figcaption></figure>

<figure><img src="image_12.png" /><figcaption>**Fig. 11.** Synchrotron powder XRD patterns of suspended particulate matter samples collected in the Orge (Le Pape et al., 2012) and Seine Rivers (this study) and zoom on the low angle region. The red frames indicate the characteristic region at low angle where are found Bragg reflection corresponding to amphibole minerals. High signal to noise ratio obtained using Synchrotron radiation allow a better detection of the crystalline amphibole component in the mineral mix compared to lab-experiment (Fig. 10). Note that the diffractograms were initially recorded at 24 keV and were recalculated at the Co Ka for comparison with the lab. dataset presented Figs. 1–5. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)</figcaption></figure>

particles could be detected on building walls along roads suggest that dust could travel by air, at least at the street level, as shown in previous studies for PM₁₀ (Kupiainen et al., 2016). Additionally, one of our measurements also shows that the mineralogical signal of amphibole is detected on a crust deposited on metallic surface of a building roof, which would suggest air travelling and deposition on larger scales. This would be consistent with the fact that 14 % of PM₂.₅ were estimated to originate from road traffic in Paris (Bressi et al., 2014). Further research would be necessary to evaluate the exact pathways of such amphibole particles in urban environments, as well as to quantitatively estimate their statistical sizes and morphologies. Additionally, searching for such non-asbestiform but micrometric amphibole particles in aerosols would

be of interest to document possible air fluxes.

## 5. Conclusion

This study documents the fact that amphibole minerals are pervasively found in samples of dust and sediments in general in the vicinity of roads in the Paris area, in the absence of local geological source identified. Even if other sources than construction materials cannot be excluded in urban environments, our investigations point to road aggregates constituting road treads as an important source for such minerals. Indeed, amphibole minerals were also detected in road stormwater ponds sediments not in direct contact with other urban infrastructures
except roads. Amphibole minerals, here determined to be mainly ferro-
magnesio-actinolite in the samples studied in detail, are suspected to be
transported by runoff waters on street surfaces towards aquatic envi-
ronments since these minerals are detected in river suspended matter. As
the amphibole mineralogical signature has also been detected by XRD in
samples not connected to road runoff, such as building walls and one
sample of building roof, the possibility of air transport has to be
considered for describing amphibole cycling in urban environments.
Since the amphibole mineralogical signature can be detected in punctual
sampling of river suspended particulate matter for more than 10 years,
we expect that important fluxes are produced as a result of global
wearing processes of the Paris megacity. Investigation at the scale of
particles using electron microscopies indicates that the amphiboles in
our samples are predominantly massive particles, which can easily
cleave, for instance as a result of crushing and or friction processes, into
micrometric elongated particles whose related health issues are
currently under debate and would probably deserve further research.

CRediT authorship contribution statement

Pierre Le Pape: Writing – review & editing, Writing – original draft, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. **Guillaume Morin:** Writing – review & editing, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. **Benoît Baptiste:** Writing – review & editing, Methodology, Investigation, Formal analysis, Data curation. **Thierry Allard:** Writing – review & editing. **Etienne Balan:** Writing – review & editing, Methodology, Investigation, Formal analysis. **Ludovic Delbes:** Investigation. **Claire Carvallo:** Writing – review & editing, Methodology, Investigation, Formal analysis, Data curation. **Clara Vaccaro:** Writing – review & editing, Methodology, Investigation. **Maëva Philippe:** Writing – review & editing, Investigation. **Sophie Ayrault:** Writing – review & editing, Investigation. **Cécile Quantin:** Writing – review & editing, Investigation. **Gaël Monvoisin:** Investigation. **François Guyot:** Writing – review & editing, Methodology, Investigation, Formal analysis, Data curation.

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

Nicolas Pons, Romain Lafon, and Diogo Barreiros Scatamburlo, stu-
dents of the SPRINT Licence at Sorbonne University (Paris, France) are
acknowledged for their participation in sampling campaigns for some
samples in 2022, as well as for their help in sample preparation for XRD
analysis during their L2 internship at IMPMC. Erik Elkaim is acknowl-
edged for his technical support at the CRISTAL beamline of the SOLEIL
synchrotron. Our colleague Julie Aufort of the IMPMC environmental
mineralogy group is acknowledged for her critical proofreading of the
manuscript. This project benefited from discussions with colleagues of
the PIREN-Seine, program in the framework of which some of the
samples studied here were collected. The DIRIF service is acknowledged
for providing us access to the stormwater basins and for sharing infor-
mation about their management.

**Appendix A. Supplementary data**

Supplementary data to this article can be found online at https://doi.
org/10.1016/j.apgeochem.2025.106497.

Data availability

Data will be made available on request.

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