Environmental and Earth Sciences

Abstract: Little is known about the vertical distribution of microplastics (MPs) in deep stratified lakes. This study investigates the MPs in the large and deep Lake Trichonis during the thermal stratification period, using two nets of different porosity (50 μm and 200 μm) in three depth strata. Fibers dominated upon fragments having an average abundance of 10.63 ± 1.00 items/m³ and 3.10 ± 0.52 items/m³ respectively in the samples of the 50 μm net in the entire water column, while the respective values for the 200 μm net were 1.4 and 7.4 times greater. Fibers had highest abundance within the thermocline, and most of them were blue having length 12 mm. There were only abundance differences between the two nets and no qualitative disparities concerning color, size, shape and polymer types. There was strong positive correlation between the abundance of fibers and the adults of the dominant copepod Eudiaptomus drieschi, which accumulated also within the thermocline. Considering that the adults of E. drieschi are among the preferred prey of Atherina boyeri, the most important commercial fish, certain issues arise concerning possible fibers’ bioaccumulation on the food web. The study highlights the importance of investigating MPs in connection with biotic elements.

Abstract: Tropospheric ozone (O³) is a phytotoxic air pollutant that can impair visible foliar injury (O³ VFI) and reduces photosynthesis in sensitive forest species. Viburnum lantana L. has been widely used as an in situ bioindicator of O³ pollution in mountainous areas of Europe; however, field-observed O³-induced VFI as well as critical levels (CLs) established to protect forests, have not been validated. This study validated field-observed O³ effects in V. lantana through experiments carried out in a Free-air O³ eXposure infrastructure (FO₃X) and determined which O³ metric (exposure-based—AOT40 or flux-based—POD₁) best explains O³ effect on leaf physiology and VFI. V. lantana saplings were subjected to ambient air (AA) conditions and elevated O³ levels at 1.5× and 2.0× AA. Throughout the experimental period (T1: 2-month and T2: 3.5-month O³ exposure) measurements were taken for the Plant Injury Index (PII), light-saturated net photosynthetic rate (A_sat), stomatal conductance (g_s), leaf color index (SPAD), and the maximum photochemical efficiency of photosystem II (Fv/Fm). O³ VFI was first observed in 2.0× after 16 days. As a result, O³ treatment influenced PII, which was significantly higher in the 2.0× (9.06 ± 3.24) than in the 1.5× and AA treatments (1.31 ± 0.62 and 1.29 ± 0.71) at T2. The A_sat, SPAD, and Fv/Fm were significantly affected by O³ treatments; no significant difference in g_s was found. POD1 better explained variability in O³ VFI and physiological parameters, with CLs proposed for V. lantana of 1.61 mmol m^–2 and 1.22 mmol m^–2 for a 4% reduction of A^sat and g_s, and a CL of 7.82 mmol m^–2 for the onset of O³ VFI.

Abstract: Particle pollution has been recognized as a major part of environmental pollution. More specifically, the inhalation of very small (ultrafine) airborne particulate matter (PM) that is emitted from the burning of fossil fuels poses the most serious threat to human health. High-efficiency retention of these particles is one of the most challenging environmental problems, since conventional techniques like electrostatic precipitators, bag filters or cyclones have low collection efficiency in the respirable range (0.1 μm–1.0 μm). Acoustically induced agglomeration of ultrafine particles is a promising technique to increase the size of small particles before they enter a conventional filter. During this process, high-intensity acoustic fields are applied to the flue gas stream, inducing interaction effects among suspended particles that give rise to collisions and agglomeration. The preconditioned aerosol can then be filtered within conventional filters with higher collection efficiency. The present work reports the results of a numerical investigation of the effect of ultrasound preconditioning on the particle size distribution as a function of parameters related to the ultrasound system design, such as the acoustic frequency and intensity, and the initial mass loading. Particle agglomeration is modeled via the solution of the population balance equation (PBE) with the Multi-Monte Carlo (MMC) method. Results show that acoustic agglomeration can shift particle size distribution towards larger values of diameters and reduce the total number concentration of particles, thus leading to increased capture efficiency of conventional filters.

Abstract: The accelerating accumulation of atmospheric carbon dioxide (CO₂) from fossil fuel combustion represents one of the foremost environmental challenges of the twenty-first century. This paper presents the design, theoretical basis, and experimental framework of a novel artificial photosynthesis system capable of capturing CO₂ from combustion flue gases and converting it into oxygen (O₂) and energy-rich compounds, directly mimicking the biochemical process performed by trees. The proposed system integrates a sodium carbonate (Na₂CO₃) absorption tower for CO₂ capture, a thermal desorption unit for solvent regeneration, and a cobalt oxide-catalyzed photosynthetic reactor for CO₂-to-O₂ conversion. System performance is quantified using non-dispersive infrared (NDIR) sensors for CO₂ measurement and electrochemical oxygen sensors for O₂ detection. Stoichiometric analysis indicates that 1 kg of captured CO₂ yields approximately 0.73 kg of O₂, and national-scale deployment projections suggest energy savings of approximately $200 billion per year by 2030 alongside a potential reduction of 302,600 million metric tons of CO₂ emissions. Comparative analysis with existing decarbonization approaches—including carbon capture and storage (CCS), hydrogen production, and enhanced oil recovery (EOR)—demonstrates that artificial photosynthesis offers a fundamentally superior outcome by permanently transforming CO₂ into life-sustaining O₂ rather than merely sequestering or displacing it. This work establishes a laboratory-scale proof of concept and a systematic experimental roadmap for scaling the technology to industrial application.

Abstract: The increasing presence of microplastics (MPs) in freshwater ecosystems poses significant threats to aquatic biota; yet, species-level information on the presence of MPs in Indian riverine ecosystems is scarce. This study assessed 220 fish samples from twelve species and various trophic levels for MP ingestion, organ-level accumulation, polymer type, and ecological risk at four locations along the River Yamuna in India. MPs were detected in all the studied species and organs, indicating their widespread distribution across various ecological habitats and trophic levels. A total of 1,678 MPs were quantified, which were significantly higher in fish from urban Delhi compared to upstream regions. The gastrointestinal tract had the highest MP concentrations (751), followed by gills (605) and muscle tissues (322), thus confirming ingestion as the primary route of MP uptake and their subsequent translocation into internal organs. Fibers dominated the MP community (>78%), with transparent (44%) and blue (19.5%) particles being the most abundant. ATR-FTIR analysis revealed the presence of ten different polymers, with polyethylene (≈24%) and polypropylene (≈21%) contributing to approximately 45% of MPs. Significant organ-level correlations (r/ρ = 0.635-0.958) and spatial variability (Kruskal-Wallis, H = 11.03, p = 0.011) indicated coordinated MP accumulation influenced by urban pollution. The Polymer Hazard Index analysis revealed a high PHI value (Category IV), mainly contributed by the widespread distribution of highly toxic polymers such as polycarbonate and polyimide.

Abstract: A three-year (January 2020–December 2022) daily dataset of 16 polycyclic aromatic hydrocarbons (PAHs) co-sampled with PM2.5 and a suite of meteorological variables at a Mediterranean coastal urban site in southern Italy (Pomigliano d’Arco, Campania) is presented and analysed. Raw PAH time series were decomposed into a long-term trend component (LT), a seasonal component (ST), and a residual component (RT) using an iterative missing-value-robust Kolmogorov–Zurbenko (KZ) moving-average filter. Spearman rank correlations between PAH concentrations and four meteorological predictors (mean temperature, relative humidity, mean wind speed, and maximum wind speed) were computed for each congener. Diagnostic molecular ratios — Fluoranthene/(Fluoranthene+Pyrene), BaP/BghiP, Indeno[1,2,3-cd]pyrene/(IcdP+BghiP), and Benz[a]anthracene/(BaA+Chrysene) — were evaluated seasonally and subjected to an information-theoretic Bayesian mixture modelling procedure (SNOB/MML) to estimate the number and nature of prevailing emission source classes. Total PAH concentrations (sum of 16 congeners) ranged from <1 ng m−3 in summer to 46 ng m−3 during winter high-pollution episodes, with BaP peaking at ≈6.7 ng m−3. Pronounced seasonal variability was driven primarily by residential heating emissions, and the incremental lifetime cancer risk (ILCR) for inhalation exposure reached 1.03×10−4 (95% CI: 0.88−1.20×10−4) during the heating season, exceeding standard regulatory thresholds. An anomalous near-background PAH signal during spring 2020 is attributed to the COVID-19 national lockdown, which reduced total PAH concentrations by approximately 85% relative to the seasonal component predicted by the iterative moving-average filter for the same calendar window. Source apportionment via diagnostic ratios identifies residential/biomass combustion as the dominant cold-season source and vehicular emissions as the prevailing warm-season source. These results provide a novel characterisation of PAH pollution dynamics in the undersampled southern Mediterranean and offer insights for targeted abatement policies.

Abstract: Urban noise pollution disproportionately affects Latin American cities, where rapid urbanization, weak governance and limited monitoring networks coexist with diverse economic activities. This study compares the spatial and temporal dynamics of environmental noise between two Colombian municipalities with contrasting urban typologies: Soledad (Atlántico), a metropolitan city dominated by traffic and aircraft noise, and Montelíbano (Córdoba, ~86,647 inhabitants), a mid-sized municipality whose acoustic environment is conditioned by ferronickel mining (Cerro Matoso), heavy-duty transport and small-scale aviation. A two-tier methodology was applied: (i) field monitoring under Colombian Resolution 627 of 2006 (LAeq) at 80 points in Soledad and 30 points in Montelíbano, covering daytime and night-time periods including replicates; and (ii) noise dispersion modelling in SoundPLAN Essential v5.1/6.0 using the ISO 9613-2 propagation method, calibrated with field measurements through an iterative residual-minimization process. Results show that Soledad exhibits a strong day–night gradient (mean LAeq diurnal = 67.7 dB(A); nocturnal = 61.7 dB(A); 96.2% non-compliance at night) with linear-corridor acoustic patterns driven by arterial roads and the Ernesto Cortissoz airport, while Montelíbano displays a near-flat day–night profile (diurnal = 67.1 dB(A); nocturnal = 67.0 dB(A)) consistent with continuous mining-industrial operations. The modelled maps reproduce the measured patterns with mean residuals of −2.72 dB(A) (day) and −2.92 dB(A) (night) in Montelíbano (75% within ±5 dB(A), consistent with international SoundPLAN benchmarks), and mean residuals of +5.78 dB(A) (day) and +1.43 dB(A) (night) in Soledad, the latter reflecting the greater acoustic heterogeneity of a larger urban environment. These findings demonstrate that urban typology shapes acoustic patterns in fundamentally different ways, with implications for sustainable land-use planning, public health and the design of differentiated noise-mitigation policies.

Abstract: Sandy beaches in the Central Region of Veracruz (RCV) face constant anthropogenic pressure from port and urban activities. This study aimed to evaluate total hydrocar-bon (TH) concentrations in the intertidal interstitial water of five beaches in the RCV, analyzing their variability by depth (15 and 30 cm) and seasonality (northerly winds, dry, and rainy seasons). TH determination was performed using gas chromatography (GC-FID), following the NMX-AA-117-SCFI-2001 and NOM-138-SEMARNAT/SSA1-2012 standards. Results showed concentrations ranging from 0.86 to 6.53 µg L⁻¹. Significant spatial differences were identified (p < 0.05); An-tepuerto beach presented the highest levels due to its proximity to the port, while Far-allón showed the lowest concentrations, confirming its role as a reference site. No sig-nificant variations were detected by depth or season (p > 0.05), indicating temporal stability associated with continuous anthropogenic inputs. Although levels comply with Mexican regulations, the continuous presence of TH represents a potential risk to benthic biota and the integrity of the Veracruz Reef System (SAV). This study pro-vides a critical baseline for strengthening coastal ecosystem management strategies in the Gulf of Mexico.

Abstract: Microplastic contamination in coral reef environments is increasingly recognized as a global concern; however, the extent to which polymer composition can resolve contamination sources and transport processes remains poorly understood. In this study, we assessed the abundance, composition, and diversity of microplastics (< 300 µm) across multiple reef systems in the Cuban archipelago using high-resolution spectroscopic analysis. Microplastic abundance varied substantially among sites, with a median concentration of 66 particles L⁻¹ (IQR: 45–115 particles L⁻¹), ranging from 8 to 218 particles L⁻¹. A total of 11 polymer types were identified, with polyethylene (PE), polypropylene (PP), and polyamide (PA) dominating the assemblages and accounting for approximately 77% of detected particles. While these polymers were consistently observed across all sites, indicating a pervasive regional background signal, highly impacted reefs exhibited more complex polymer profiles, including the enrichment of polyurethane (PU), polytetrafluoroethylene (PTFE), and polyvinyl chloride (PVC), reflecting localized anthropogenic inputs. Multivariate analysis revealed distinct compositional groupings associated with different contamination regimes. Notably, some sites exhibited elevated microplastic abundances while remaining dominated by common polymers, indicating a decoupling between contamination levels and source-specific signatures. This pattern suggests that regional transport and mixing processes, including circulation through the Caribbean basin and the Yucatán Channel, play a major role in shaping microplastic distributions in reef environments. These findings demonstrate that polymer composition provides critical information beyond abundance alone, enabling the differentiation between source-driven contamination and transport-driven accumulation. The integration of polymer-specific analysis with abundance and diversity metrics offers a robust framework for improving source apportionment and informing monitoring and management strategies in coral reef systems.

Abstract: Microplastics are particles derived from polymer degradation, and their occurrence and abundance have been assessed across various environments and compartments. The method commonly used for their evaluation and quantification in sediments involves a marine salt solution for decantation. However, due to the high incidence of plastics in marine environments, this salt may already contain a considerable concentration of microplastics and must be carefully filtered to minimize interference during laboratory processing. To assess the importance of this procedure, sediment samples from an estuarine environment, in which the salt used for laboratory sorting was not filtered, were compared with samples from semiarid reservoirs, in which the salt underwent filtration before decantation. All other procedures were identical, performed by the same team under controlled airborne contamination conditions. The Mann–Whitney test applied to samples with and without NaCl filtration revealed a significantly lower incidence of microplastics in samples whose salt had been filtered. Based on these findings, a filtration protocol for NaCl used in sediment decantation was developed, emphasizing an accessible, low-cost product widely applied in natural environmental quality assessments. Only through the standardization of methodologies and sampling units will it be possible to compare environments in terms of actual anthropogenic impact, generating outcomes that provide scientific support for conservation actions and impact mitigation.

Abstract: In this study we develop a Land-Use Random Forest (LURF) model for the Campania Region (southern Italy) that combines 2022 daily PM10 observations from 13 quality-controlled ARPA Campania stations with a rich set of spatial predictors to produce daily concentration maps at 1000 m × 1000 m resolution, from which annual statistics (mean, percentiles, and exceedances) are derived through temporal aggregation. The predictor space includes resident population, land-cover and imperviousness indicators, road-network metrics derived from OpenStreetMap, meteorological fields from the ERA5 reanalysis, satellite aerosol optical depth (AOD) from MODIS Terra and Aqua—scaled by ERA5 boundary-layer height (AOD/pbl)—daily mean PM10 from a nested CHIMERE simulation, and a binary categorical predictor (IdDust) flagging days affected by Saharan dust transport events. The hyperparameters for the LURF model are selected via a nested inner grid search; generalisation performance is assessed through a spatially aware leave-location-out cross-validation (LLO-CV) scheme, which prevents optimistic bias arising from spatial autocorrelation among neighbouring stations. Under LLO-CV, the LURF achieves R2=0.54, RMSE =11.1 μg m−3, and MAE =8.0 μg m−3, against R2=−1.11, RMSE =23.6 μg m−3, and MAE =19.1 μg m−3 for the raw CHIMERE output evaluated on the same observations. The inclusion of IdDust as a categorical covariate allows the Random Forest to partition the training distribution between dusty and non-dusty regimes, improving the representation of episodic high-PM10 events and reducing systematic underestimation at the upper tail of the concentration distribution. CTM-derived PM10 and ERA5 boundary-layer and pressure fields emerge as the dominant predictors, collectively accounting for the majority of explained variability, while IdDust ranks among the physically interpretable secondary predictors. The 1000 m maps highlight marked urban–rural contrasts, resolving hotspots in the Naples metropolitan area and along major motorway corridors that remain unresolved at typical CTM grid spacings. By embedding physically based CTM output, satellite aerosol diagnostics, and dust-event classification within a flexible machine-learning framework, the proposed approach offers a low-cost, operationally tractable tool for high-resolution PM10 exposure assessment in regions characterised by complex terrain and heterogeneous emission sources.

Abstract: Recent offshore hydrocarbon discoveries along the Senegalese–Mauritanian margin increase the need to quantify oil-spill risk under the highly dynamic circulation of the southern Canary Current upwelling system. We investigate seasonal pollutant dispersion along the Senegalese Grande Côte using Lagrangian particle-tracking experiments forced by CROCO ocean model outputs. The analysis focuses on the role of wind-driven circulation, Ekman transport, and upwelling variability in controlling cross-shore and alongshore transport pathways. Results show a strong seasonal contrast. During the cold season (January–May), intensified northerly winds drive coastal upwelling and offshore Ekman transport, enhancing surface divergence and promoting the export of particles away from the coast. This regime limits nearshore accumulation but favors broader offshore dispersion over the continental shelf. In contrast, during the warm season (June–September), weakened upwelling-favorable winds and the establishment of anticyclonic circulation north of the Cape induce onshore transport and coastal retention. Particle-release experiments reveal enhanced trapping and accumulation along the Grande Côte during this period. The Kayar region and the Cape Verde Peninsula exhibit relatively higher exposure during the cold season, whereas the inner shelf along the Grande Côte becomes particularly vulnerable during the warm season. These findings demonstrate that seasonal wind forcing and associated Ekman dynamics exert first-order control on oil-spill pathways. Incorporating this variability into contingency planning is essential, as the inner continental shelf of the Senegalese Grande Côte is a dynamically sensitive, high-risk zone under the warm-season circulation regime.

Abstract: Reliable and timely estimation of air pollution exposure at high spatial and temporal resolution remains challenging in complex urban environments, where pollutant concentrations vary due to traffic emissions, urban morphology, and meteorological conditions. This study presents a physics-informed machine learning framework for near–real-time estimation of NO₂ concentrations at fine spatial scales. The approach combines a limited set of steady-state Computational Fluid Dynamics (CFD) simulations with operational meteorological and air-quality data. CFD simulations under specific wind directions are first used to characterize site-specific dispersion patterns. These outputs are then scaled using hourly meteorological observations to generate physics-based concentration descriptors. A machine learning predictor, implemented using Random Forest and Extreme Gradient Boosting, is trained to refine these estimates by incorporating additional environmental and observational features. The method is applied to a 1 km × 1 km urban district in Antwerp, Belgium, within the FAIRMODE intercomparison framework. Validation against measurements from 105 passive samplers collected over one month shows substantial improvement compared to standalone dispersion modeling, with coefficients of determination up to R² = 0.965 and reduced bias across locations. These findings demonstrate that integrating physical modeling with machine learning enables accurate and computationally efficient high-resolution exposure assessment in urban settings.

Abstract: Nanoplastics are produced abiotically and biotically from larger pieces of plastic. Although nanoplastic toxicity has received more attention recently, its biological effects have not been adequately investigated. In this study, the toxicity of nanoplastics (NPs) with an average size of <80 nm was carried out in the larvae of Artemia nauplii, an indicator organism of the aquatic environment, according to the OECD guideline 202 protocol. As a result, depending on exposure durations (24-96 h) and concentrations (50-300 μg/mL), the survival rate of nano-HDPE treated larvae was significantly reduced (p < 0.05). The larvae took up and internalized nano-HDPE at a concentration of 99.74 µg/mL, which is the calculated LC50 value. There was also a significant increase in biochemical markers in larvae at LC50 (p < 0.05). However, it was observed that this caused oxidative stress, cell membrane damage, limb loss and malformation in larvae treated with nano-HDPE.

Abstract: Chromium is one of the most prevalent toxic heavy metals in the environment and is known to cause cancer, and cellular damage. Various treatments can effectively remove Chromium ion from wastewater. However, majority of those methods are not environmentally friendly. Here, we investigated the efficacy of stem cactus activated carbon (SCAC) and commercial activated carbons (CAC) to remove hexavalent chromium from synthetic and real wastewater. In this study, the stem cactus adsorbent was thoroughly characterized. The effect of initial concentration of Cr (VI), contact time, adsorbent dose, shaking speed, and pH on the adsorption process were examined using Micro Plasma Atomic Emission Spectroscopy and UV-Vis Spectroscopy. The data were analyzed using R-software (version 4.4.3 (2025-02-28)) and Origin (2022). The trends in removal efficiency were examined descriptively using line graph. The adsorption equilibrium isotherms and kinetics models were fitted to the data to evaluate the biosorption mechanisms and compare the sorption capabilities of the two biosorbents (SAC and CAC). Under optimal conditions (0.15g SCAC, pH 2, contact time 60 min, shaking speed 200rpm, and an initial Cr (VI) concentration of 6mg/L), Cr (VI) removal efficiencies reached 98.4% and 99.2% from real and synthetic wastewaters, respectively. The adsorption data fitted both the Langmuir and Freundlich isotherm models, suggesting mixed homogenous and heterogenous surface characteristics on the adsorbent. The adsorption process is an endothermic process and respects the pseudo second order kinetics model. The present study suggests that plant-based adsorbents represent an effective alternative for Cr (VI) ion removal.

Abstract: Communities in Mississippi located near petrochemical refining facilities face ongoing risks from heavy metal contamination in soils, threatening environmental quality, food safety, and public health. This pilot study evaluated the phytoremediation potential of Nerium oleander and cabbage (Brassica oleracea) in a residential fence-line community within the Cherokee Forest subdivision of East Pascagoula, Mississippi, impacted by long- term petrochemical and shipyard activities. Plants were grown directly in contaminated garden soils under natural field conditions. Soil and plant tissue concentrations of lead (Pb), cadmium (Cd), zinc (Zn), and nickel (Ni) were measured using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Phytoremediation effectiveness was assessed through removal efficiency, translocation factor, and bioaccumulation factor. Re- sults showed significant reductions (p < 0.01) in all soil metals, with cadmium removal exceeding 97%. Nerium oleander exhibited substantially higher metal uptake and trans- location capacity than cabbage, achieving a maximum cadmium translocation factor of 9.99 and bioaccumulation factors up to 5.67. In contrast, cabbage showed lower transloca- tion efficiency, indicating limited remediation potential but suitability as a food crop after soil treatment. These findings highlight Nerium oleander as an effective, sustainable, and community-acceptable phytoremediation solution.

Abstract:

Using native tree species, the phytostabilisation of heavy metal contaminants at former mining and industrial sites can provide ways to prevent metal spread and leaching into the environment and bring the sites back into the economic circuit. In this study, mixed afforestations with young trees from seven Central European species showing contrasted autecology (Picea abies, Fagus sylvatica, Acer pseudoplatanus, Alnus incana, Populus tremula, Salix viminalis and Betula pendula) were exposed during five years to mixed soil contamination (Zn/Cu/Pb/Cd = 1349/317/70/8 mg kg⁻¹). The metal uptake, their allocation belowground in root tissues and aboveground, the functional traits and the nutrient responses were compared. Despite high metal availability, all tree species showed low metal uptake and similar metal concentrations in their roots. The mobile metals (Zn, Cd) accumulated in the shoot and foliage of early successional species with acquisitive ecological strategy only, whereas the late-successional species blocked the transfer of all heavy metals from the roots to the aboveground organs. All species showed good tolerance to metal contamination, with large interspecific differences regarding the biomass production and some nutrient concentrations, in apparent relation to the varying species’ ecological strategies and independent of the metal treatment. Zn allocation within fine root tissues could enhance transient spatial and temporal metal immobilisation, especially when associated to protective or defence structures, which also contributed to metal detoxification. Higher transfer of mobile metals to aboveground organs in pioneer tree species was clearly related to their acquisitive ecological strategies, in the context of higher nutrient demand in foliage and lesser defence and protection of vegetative organs. The implications of findings for phytostabilisation applications are discussed.

Abstract: This study presents a monitoring system designed as an integrated surveillance and decision support tool for the terrestrial and the ocean environments. The developed system integrates in situ ocean sensor for monitoring purposes as well as a real-time communication tool for data transfer combined with a power generating module to sustain power for all modules. The system is applied for a period of around six months in different seasons to detect, identify gradients of radioactivity in the atmosphere. The gross gamma-ray intensity as detected by the system was interpreted in qualitative manner according to the rainfall events. The background gamma-ray spectra during dry periods for different seasons are also discussed in terms of seasonality. The results of the analysis offer actionable insights through existing mechanisms to support authorities in rapid response and policy planning related to marine radioactivity issues.

Abstract: Abandoned mine sites pose environmental and public health hazards due to the presence of metals in them. We extend our study beyond merely assessing total elemental contents to evaluate the contamination and potential spread of metals from contaminated mining sites into adjacent and surrounding ecosystems. Rather, we employ geo-chemical fractionation methods to measure the elemental fractions and binding forms of Pb, Cd, Mn, Cu, and Zn. We go on to estimate the mobility of these metals in soils collected from abandoned mine sites. The soil pH of the sites ranges from acidic to slightly acidic (4.88–6.48), exhibits moderate electrical conductivity and has varying cation exchangeable capacities (16.97–29.57 meq/100g). The overall concentrations of Pb, Cd, Mn, Cu, and Zn surpass FAO/WHO standards, suggesting a notable human impact stemming from past mining activities. The geochemical fractionation analyses indicate a higher proportion of Pb (88%) and Cd (75%) are present in the residual fraction, suggesting low mobility and indicating a possible source to be associated with geogenic or the parent material or geological sources. The dominance of Mn (83%), Cu (73%), and Zn (66%), on the other hand, in mobile fractions and non-residual forms, suggests that pollution is possibly traced to anthropogenic activities at the mining sites. The mobility and by extension the ecotoxicology of Pb, Cd, Zn, and Cu, may be tied to changes in pH, salinity (EC), as well as bulk density and porosity of the mining sites.

Abstract: Microplastics (MPs) adsorb hazardous substances and are ingested by a wide range of organisms; therefore, indicators for managing their environmental concentrations are needed. Ideally, threshold values should be based on health impacts. However, the diversity of MPs and the complexity of their environmental behavior make it difficult to establish unified environmental concentration standards. In this study, we propose a threshold for the presence of MPs on sandy beaches based on “visual cleanliness,” derived from the amount of MPs that people find psychologically unacceptable. Three types of MPs were used: white polypropylene (PP), blue PP, and white polystyrene (PS; expanded polystyrene). For defining a narrow-range cleanliness threshold, volume concentration was more appropriate than mass concentration. White particles were expected to be less noticeable because they tended to blend with white shell fragments, which are ubiquitous on beaches. In contrast, blue particles were expected to be less acceptable owing to their rarity. However, we found no difference in unacceptability between white PP and blue PP. The threshold, defined as the volume concentration at which half of the respondents find MPs psychologically unacceptable, ranged from 1 to 2 cm3-MPs/m2-sand. Gender, age, travel time to the beach, and frequency of beach visits did not influence unacceptability. Strong concern about marine plastic pollution and experience in cleaning public spaces were associated with a tendency toward low tolerance for MP contamination on beaches.