Ocean acidification impairs seagrass performance under thermal stress in shallow and deep water.

Despite the effects of ocean acidification (OA) on seagrasses have been widely investigated, predictions of seagrass performance under future climates need to consider multiple environmental factors. Here, we performed a mesocosm study to assess the effects of OA on shallow and deep Posidonia oceanica plants. The experiment was run in 2021 and repeated in 2022, a year characterized by a prolonged warm water event, to test how the effects of OA on plants are modulated by thermal stress. The response of P. oceanica to experimental conditions was investigated at different levels of biological organization. Under average seawater temperature, there were no effects of OA in both shallow and deep plants, indicating that P. oceanica is not limited by current inorganic carbon concentration, regardless of light availability. In contrast, under thermal stress, exposure of plants to OA increased lipid peroxidation and decreased photosynthetic performance, with deep plants displaying higher levels of heat stress, as indicated by the over-expression of stress-related genes and the activation of antioxidant systems. In addition, warming reduced plant growth, regardless of seawater CO2 and light levels, suggesting that thermal stress may play a fundamental role in the future development of seagrass meadows. Our results suggest that OA may exacerbate the negative effects of future warming on seagrasses.

Enzymatic Synthesis and Structural Modeling of Bio-Based Oligoesters as an Approach for the Fast Screening of Marine Biodegradation and Ecotoxicity.

Given the widespread use of esters and polyesters in products like cosmetics, fishing nets, lubricants and adhesives, whose specific application(s) may cause their dispersion in open environments, there is a critical need for stringent eco-design criteria based on biodegradability and ecotoxicity evidence. Our approach integrates experimental and computational methods based on short oligomers, offering a screening tool for the rapid identification of sustainable monomers and oligomers, with a special focus on bio-based alternates. We provide insights into the relationships between the chemical structure and properties of bio-based oligomers in terms of biodegradability in marine environments and toxicity in benchmark organisms. The experimental results reveal that the considered aromatic monomers (terephthalic acid and 2,5-furandicarboxylic acid) accumulate under the tested conditions (OECD 306), although some slight biodegradation is observable when the inoculum derives from sites affected by industrial and urban pollution, which suggests that ecosystems adapt to non-natural chemical pollutants. While clean seas are more susceptible to toxic chemical buildup, biotic catalytic activities offer promise for plastic pollution mitigation. Without prejudice to the fact that biodegradability inherently signifies a desirable trait in plastic products, nor that it automatically grants them a sustainable "license", this study is intended to facilitate the rational design of new polymers and materials on the basis of specific uses and applications.

Interdisciplinary approach to solve unusual mortalities in the European common frog (Rana temporaria) in two high-mountain ponds affected by climate change.

The global decline in amphibian populations is a major environmental issue. Chytridiomycosis, Ranaviruses and the red-leg syndrome have been identified in unusual mortality events. However, these infections do not account for all causes of declining amphibian populations. Moreover, several cases of amphibian mortality are difficult to solve without resorting to an interdisciplinary approach. Two cases of unusual mortality in Rana temporaria occurred at two high-mountain ponds (northwest Italy) in April and May 2021. Water and frog samples were analysed to understand the possible causes responsible for the unusual mortalities. Results of the main physicochemical (pH, conductivity, dissolved oxygen, chemical and biochemical oxygen demand) and nutrient (ammonia/ammonium, nitrite, nitrate, total phosphorus) parameters revealed a good condition of the water quality, with the absence of the main cyanotoxins (microcystins/nodularins). However, unseasonably high spring water temperatures were recorded in both ponds (12.73 °C and 14.21 °C for Frog Pond and Selleries Pond, respectively). Frogs (n = 50; snout-vent length: 7.0-9.8 cm; body mass: 85-123 g) collected from Frog Pond mainly presented bumps on the ventral cavity and dermal ulceration associated with the isolation of Carnobacterium maltaromaticum. On the other hand, frogs (n = 5; snout-vent length: 8.0-9.1 cm; body mass: 87-92 g) from Selleries Pond presented petechiae and dermal ulcerations on the rear limbs associated with the isolation of Aeromonas salmonicida and A. sobria. In both mortality events, the interdisciplinary approach revealed an association between frog mortalities and the isolation of bacteria. Isolated bacteria are considered opportunistic pathogens, and the high values of the water temperature has certainly led a stress on the frogs, favouring the spread of bacteria and the death of the frogs. Further studies are needed to assess the pathophysiological effects of the opportunistic bacteria here isolated, clarifying the interactions between emerging pathogens and climate change.

Ecotoxicity of marine sediments: Sampling and laboratory artifacts and their impacts on risk classification.

Assessing the ecotoxicological risk of marine sediments is now a critical factor in deciding how to treat dredged material in harbor and coastal areas. Although ecotoxicological analyses are routinely required by some regulatory agencies in Europe, laboratory skills necessary to perform them are often underestimated. According to the Italian Ministerial decree No. 173/2016, ecotoxicological tests are performed on the solid phase and elutriates, and the classification of sediment quality is defined using the "Weight of Evidence" (WOE) approach. However, the decree does not provide adequate information regarding the preparation techniques and laboratory skills. As result, a wide variability among laboratories occurs. An error in the classification of ecotoxicological risk has a negative impact on the whole environmental quality and/or the economy and management of the interested area. Thus, the main aim of this study was to determine if such variability can affect the ecotoxicological outcomes of tested species and WOE associated classification, producing different options for the management of dredged sediments. Four different sediment types were selected to assess the ecotoxicological responses and their changes as a function of variability of the following factors: a) the storage time laps (STL) for both the solid phase and the elutriates; b) the methods used to prepare the elutriates (centrifugation vs. filtration), and the conservation method used for the elutriates (freshly prepared vs. freezing). Results suggest a wide variability of ecotoxicological responses among the four sediment samples here considered, differentiated according to chemical pollution, grain-size texture, and macronutrient contents. The storage time laps significantly affect the physicochemical parameters and the ecotoxicity of both the solid phase test and elutriates. For the elutriates preparation, centrifugation is preferred to filtration to preserve a better representation of sediment heterogeneity. Freezing of elutriates does not seem to show any significant effects on the toxicity. Findings allow to define a weighted schedule of the storage time of sediments and elutriates useful for laboratories to scale analytical priority and strategies related to different sediment types.

Polyethylene microplastics reduce filtration and respiration rates in the Mediterranean sponge Petrosia ficiformis.

Microplastic (MP) pollution represents a distinctive mark of the Anthropocene. Despite the increasing efforts to determine the ecological impacts of MP on marine biodiversity, our understanding of their toxicological effects on invertebrate species is still limited. Despite their key functional roles, sponges (Phylum Porifera) are particularly understudied in MP research. These filter-feeders extract and retain particles from the water column, across a broad size range. In this study, we carried out a laboratory experiment to assess the uptake of MPs (polyethylene, PE) by the Mediterranean sponge Petrosia ficiformis, how MPs influence key biological process after different times of exposure (24h and 72h) and whether they can be subsequently eliminated. MP uptake increased with time of exposure, with 30.6% of the inoculated MP particles found in sponge samples after 72h. MPs impaired filtration and respiration rates and these effects were still evident 72h after sponges had been transferred in uncontaminated water. Our study shows that time of exposure represents a key factor in determining MP toxicity in sponges. In addition, our results suggest that sponges are able to incorporate foreign particles and may thus be a potential bioindicator for MP pollutants.

Short-term physiological and biometrical responses of Lepidium sativum seedlings exposed to PET-made microplastics and acid rain.

Plastics enter in terrestrial natural system primarily by agricultural purposes, while acid rain is the result of anthropogenic activities. The synergistic effects of microplastics and acid rain on plant growth are not known. In this study, different sizes of polyethylene terephthalate (PET) and acid rain are tested on Lepidium sativum, in two separate experimental sets. In the first one we treated plants only with PET, in the second one we used PET and acid rain together. In both experimentations we analyzed: i) plant biometrical parameters (shoot height, leaf number, percentage inhibition of seed germination, fresh biomass), and ii) oxidative stress responses (hydrogen peroxide; ascorbic acid and glutathione). Results carried out from our experiments highlighted that different sizes of polyethylene terephthalate are able to affect plant growth and physiological responses, with or without acid rain supplied during acute toxicity (6 days). SHORT DESCRIPTION: This study showed that different sizes of PET microplastics affect physiological and biometrical responses of Lepidum sativum seedlings, with or without acid rain; roots and leaves responded differently.

Ecotoxicity of nano-metal oxides: A case study on daphnia magna.

In Europe REACH framework directive imposes data acquisition concerning toxicity on acquatic species before the commercialization of chemicals to assess environmental risks. According to official methods, exposure tests are performed under in vitro and standardized conditions: OECD's guideline rules external variables such as water type, feeding conditions, and exposure time. As consequence, such obtained results could be different from effects observed in natural environments. This study collects effects within 24-96 h of exposure to nano metal-oxides (ZnO, TiO2) on D. magna obtained by the exposure under standard OECD conditions comparing them with results obtained by the exposure under more similar conditions to natural environment (i.e. mixture, feeding). High doses exposure determines gas-bubble disease. Animals exposed to LC10 actively ingest nanoparticles under both fasting and feeding conditions. Furthermore, body burial by a coat of nanoparticles thicker in mixtures than in single dispersions was recorded. Furthermore, results show that: (i) effects increase over time; (ii) n-ZnO results less effective than n-TiO2 in both single dispersion, and mixture; (iii) the presence of surfactant increases toxicity of nanoparticles; (iv) immobilization is a more sensitive endpoint than mortality; (v) feeding increases test sensitiveness improving differences among treated and controls till 96 h and allowing longer exposure times than standard OECD test. As general remark, this study provides evidence that in vitro ecotoxicological results obtained under standardized OECD conditions could be significant different to animals' responses under natural (feeding and mixtures) exposure conditions.

Effects of Different Microplastic Types and Surfactant-Microplastic Mixtures Under Fasting and Feeding Conditions: A Case Study on Daphnia magna.

This study evaluates the mortality and immobilization on Daphnia magna after 24-96 h of exposure to microplastic dispersions (PP, PE, PVC, PVC/PE), and to microplastic + surfactant solutions both under fasting and feeding conditions. The tested microplastics were analysed with µFT-IR to determine their chemical composition, purity, and dimensions. The results show that: (i) exposure under fasting conditions produces acceptable results on negative controls no later than 24 h; (ii) the dispersion of microplastics forms homo-agglomerates that are able to affect animals' motility and cause mortality and immobilization; (iii) different types of tested microplastic produce different effects on endpoints (the most toxic is PVC + surfactant); (iv) in all cases, the effects were reduced under feeding conditions (i.e. 4 times reduction of PE toxicity); (v) effects of surfactant on observed toxicity are microplastic-type dependent; (vi) the age of the animal affected the mortality and immobilization responses after exposure under both fasting and feeding conditions.

Seasonal Fluctuations of Trace Elements from Different Habitats of Orbetello Lagoon (Thyrrenian Sea, Italy).

This study evaluated seasonal fluctuations of trace elements of major ecotoxicological concern in sediments and their uptakes by the aquatic vegetation indifferent undisturbed habitats from the Orbetello lagoon, correlating measured levels to abiotic and biotic drivers to scale the significant of their effect on observed seasonal variability of trace elements. Results show that under natural undisturbed conditions, observed seasonal fluctuations in different habitats are statistically correlated to temperature, salinity, and turbidity of water and total nutrients in sediments. These variables and the habitat type dominated by macroalgae (C. linum) play a significant role as drivers of variability for measured trace elements in sediments. This study represents a reference undisturbed condition of natural seasonal trends of trace elements in different habitat types before the occurrence of numerous impacting activities on sediments and could represent a useful baseline for further management evaluations after the occurrence of sediment disturbance actions planned for the near future.

Biomonitoring of chemicals in biota of two wetland protected areas exposed to different levels of environmental impact: results of the "PREVIENI" project.

The PREVIENI project (funded by the Ministry of Environment) investigated the exposure to endocrine disrupters in samples of human population and environmental biota in Italy. The environmental biomonitoring considered two Italian WWF Oasis, with the aim to compare the presence and effects of endocrine disruptors in organisms from two protected natural areas, respectively, upstream and downstream a chemical emission site. Chemical analysis of pollutants' tissue levels was made on tissues from earthworm, barbell, trout, and coot, selected as bioindicator organisms. The contaminants considered were as follows: the perfluorinated compounds perfuoroctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), polychlorinated biphenyls (PCBs 58 congeners), polybrominated diphenyl ethers (PBDEs, 13 congeners), polycyclic aromatic hydrocarbons (PAHs, 16 compounds), toxic trace elements, the phthalate di-2-ethylexyl phthalate (DEHP) and its primary metabolite, bisphenol A, synthetic musk compounds (musk xylene, musk ketone, tonalide, and galaxolide), and p-nonylphenol. The analyses showed low concentrations of most pollutants in all species from both areas, compared to available literature; noticeable exceptions were the increases of DEHP's primary metabolite, PBDE, PAHs, Hg, and Pb in barbells, and of PCB and Cd in earthworms from the downstream area. The results showed the presence of endocrine disruptors, including those considered as "non-persistent," in bioindicators from protected areas, albeit at low levels. The results provide a contribution to the evaluation of reference values in biota from Mediterranean Europe and support the relevance of monitoring exposure to pollutants, in particular for freshwater environment, also in protected areas.

Phthalates and perfluorinated alkylated substances in Atlantic bluefin tuna (Thunnus thynnus) specimens from Mediterranean Sea (Sardinia, Italy): Levels and risks for human consumption.

Atlantic blue fin tuna (Thunnus thynnus) is a species of great importance for Mediterranean Sea area, from both ecological and commercial points of view. The scientific literature reports few data on the contamination of this fish by emerging organic compounds such as perfluorinated alkylated substances(PFASs) and phthalates, being the latter never been studied in tuna. This study therefore investigated the presence of the PFASs perfluorooctane sulphonate (PFOS) and perfluoroctanoic acid (PFOA) and the phthalate di-2-ethylhexyl phthalate (DEHP), also monitored by its metabolite mono-2-ethylhexyl phthalate(MEHP), to assess both the state of contamination of Atlantic bluefin tuna specimen and the risk due to the toxicity of these compounds for human consumption. While PFOA was never found, detectable levels of PFOS (0.4-1.88 ng/g), DEHP (9-14.62 ng/g) and MEHP (1.5-6.30 ng/g) were found. The results were elaborated relating the accumulation to the size and age of the individuals and showed a correlation between the levels of different pollutants investigated.

Environmental quality assessment of Grand Harbour (Valletta, Maltese Islands): a case study of a busy harbour in the Central Mediterranean Sea.

Contamination levels by plastic debris, trace elements and persistent organic pollutants were assessed and related to macrobenthic diversity within soft bottoms of Grand Harbour (Malta, Central Mediterranean). Sediment toxicity was evaluated by ecotoxicological method, deploying Bacteria (Vibrio fischeri), Echinodermata (Paracentrotus lividus) and Crustacea (Corophium orientale). Univariate analysis (Pearson's test) was used to test relationships between biodiversity indices, pollutants and grain size. A multivariate approach (PERMANOVA) was applied to investigate for any significant differences among sampling stations concerning plastic abundances and to test the relationship between infaunal abundances and pollutant concentrations (the BIOENV test). Significant differences in the plastic abundances were found between sampling stations. The lowest value for Shannon-Wiener biodiversity index was associated to the highest sediment pollution level. Multivariate analyses suggest that MBT and TBT were factors that most influenced macrozoobenthic abundance and biodiversity. The bivalve Corbula gibba and the introduced polychaete Monticellina dorsobranchialis were the most abundant found species.

Early warning tools for ecotoxicity assessment based on Phaeodactylum tricornutum.

Phaeodactylum tricornutum was exposed to various toxic substances (zinc, copper or dodecylbenzenesulfonic acid sodium salt) in accordance with the AlgalToxkit(®) protocol based on the UNI EN ISO 10253 method in order to quantitatively compare the responses obtained by traditional growth-rate inhibition tests with morphological (biovolume) and physiological (chlorophyll-a, phaeophytin ratio) endpoints. A novel approach is proposed for detecting early and sub-lethal effects based on biovolume quantification using confocal microscopy coupled with an image analysis system. The results showed that effects on both biovolume and the photosynthetic complex are sensitive and powerful early warning tools for evaluating sub-lethal effects of exposure. Specifically, biovolume showed significant sensitive and early responses for the tested surfactant. Qualitatively, we also observed structural anomalies and effects on natural auto-fluorescence in exposed cells that also represent potentially useful tools for ecotoxicological studies.

Assessing combined effects of long-term exposure to copper and marine heatwaves on the reef-forming serpulid Ficopomatus enigmaticus through a biomarker approach.

Sessile benthic organisms can be affected by global changes and local pressures, such as metal pollution, that can lead to damages at different levels of biological organization. Effects of exposure to marine heatwaves (MHWs) alone and in combination with environmentally relevant concentration of copper (Cu) were evaluated in the reef-forming tubeworm Ficopomatus enigmaticus using a multi-biomarker approach. Biomarkers of cell membrane damage, enzymatic antioxidant defences, metabolic activity, neurotoxicity, and DNA integrity were analyzed. The exposure to Cu alone did not produce any significant effect. Exposure to MHWs alone produced effects only on metabolic activity (increase of glutathione S-transferase) and energy reserves (decrease in protein content). MHWs in combination with copper was the condition that most influenced the status of cell homeostasis of exposed F. enigmaticus. The combination of MHWs plus Cu exposure induced increase of protein carbonylation and glutathione S-transferase activity, decrease in protein/carbohydrate content and carboxylesterase activity. This study on a reef-forming organism highlighted the additive effect of a climate change-related stressor to metals pollution of marine and brackish waters.

Navigating a Microplastic Sea: How the Pacific Cupped Oyster (Magallana gigas) Respond to Microplastic Pollution in Lagoons.

Microplastic pollution poses an escalating concern, particularly in coastal lagoons rich in biodiversity. This study delved into the occurrence of microplastics (MPs) in Magallana gigas (formerly Crassostrea gigas) from the Orbetello and Varano coastal lagoons (Italy), also investigating the response of these filter-feeding organisms to various colors (P = pink; B = blue; W = white) of high-density polyethylene (HDPE) MP fragments. Oysters were exposed for 7 days under controlled conditions. Subsequently, the oysters underwent analysis for both MP presence and biochemical markers of oxidative stress. Diverse ingestion rates of HDPE were noted among oysters from the two lagoons, eliciting antioxidant responses and modifying baseline activity. The two-way ANOVA revealed the significant effects of treatment (control; HDPE_B; HDPE_P; HDPE_W), site, and the interaction between treatment and site on all biomarkers. Non-metric multidimensional scaling showed a divergent effect of HDPE color on biomarkers. Further investigation is warranted to elucidate the mechanisms underlying the influence of MP color, dose-dependent effects, and the long-term impacts of exposure. Comprehending these intricacies is imperative for devising effective strategies to mitigate plastic pollution and safeguard marine health.

Impact of global change on environmental hazards of different clays: A case study on Aliivibrio fischeri.

The effects of global change in marine ecosystems are expected to lower pH from the current 8.1-7.5-7.0, which will have significant impacts on marine species. The purpose of this study is to investigate whether the ecotoxicity of ten different natural clays change significantly in response to the acidification process and what factors are associated with the observed changes. In this study, the ecotoxicological response of a bacterium (Aliivibrio fischeri) was tested under current (pH= 8.1) and acidified (pH 7.5 and 7.0) conditions. The ecotoxicity detected in the solid phase test (SPT protocol) and in the contact water was affected by the pH, which increased the ecotoxicity from 2/10 clays (pH 8.10) to 7/10 clays (pH 7.00), also shifting the detected effects from low to high toxicity values. The analyses performed on the natural clays studied show that pH can affect the release of metals, metalloids and rare earths from the clays into the contact water phase, affecting the toxicity observed. This phenomenon depends on the type of clay and is closely related to its mineralogical composition. As consequence, in a globally changing scenario, ecotoxicity, even of natural materials such as clay, cannot be considered stable, but must be accurately revaluated depending on the mineralogical and chemical composition of the clay. Moreover, the mineralogical composition of clays showed different efficiency in absorbing bacteria on the surface of clay particles. It was found that live bacterial cells were absorbed on the clay surface in numbers that were dependent on both clay types and pH levels.

Chemical pollution and ecotoxicological effects of high-density polyethylene microplastics in Mytilus galloprovincialis from two Italian lagoon ecosystems.

Transitional water ecosystems have low water exchanges and can trap chemicals and microplastics (MPs). In this study, MPs, trace elements, polycyclic aromatic hydrocarbon-PHAs levels and the oxidative stress response were assessed in Mytilus galloprovincialis from two Italian lagoon ecosystems (Orbetello and Varano). In addition, the ecotoxicological effects induced by the exposure of M. galloprovincialis to high-density polyethylene-HDPE MPs were also determined. Levels of trace elements were almost always comparable among the sites, whereas MPs were found only in mussels from Orbetello. PAHs were always under the limit of quantification. Glutathione peroxidase and malondialdehyde levels were significantly higher in mussels from Varano. As regard the exposure test, it was found a significant effect of treatment, site and their interaction on mortality and biochemical biomarkers in both fed and unfed mussels. However, principal component analysis suggests similar effects of both color and nourishment condition on biochemical biomarkers. These findings warrant further investigation.

Multiple approach for assessing lagoon environmental status based on water bodies quality indices and microplastics accumulation.

Lagoon environments, like all the marine-coastal areas, offer a wide variety of ecosystem services, but at the same time are affected by pressing human activities that lead to deterioration of the environmental quality, loss of biodiversity, habitat destruction and pollution. Since the well-being of population and local economy depend on the environmental status of these ecosystems, it is essential to adopt long-term management tools to achieve the Good Environmental Status sensu European Marine Strategy Framework Directive and Water Framework Directive. A Nature 2000 site (Lesina lagoon, south Italy) was assessed within a project aimed at protecting and restoring biodiversity and lagoon habitat through integrated monitoring, suitable management, and good practices. Here we provide an assessment of the lagoon integrity based on a multi-metrics approach, highlighting match/mismatch among environmental quality indicators and microplastics (MP) pollution. Some environmental quality indices based on ecosystem components as vegetation, macroinvertebrates and water trophic variables were applied together with an accurate evaluation of MPs abundance, distribution, and composition to assess the ecological status of Lesina lagoon before and after cleaning actions with litter removal. Overall, all the ecological descriptors outlined a clear lagoon spatial gradient, with a western saltier and organic-enriched area characterized by the absence of vegetation, macrozoobenthos with lower diversity and richness and high MPs occurrence. The focus on macrozoobenthos, considered as a key component of the lagoon ecosystem, identified much more sites in "poor" status than the other indicators here considered. Moreover, it was found a negative relationship between the Multivariate Marine Biotic Index and MPs items in sediment, suggesting that MP pollution has a negative impact on macrobenthic fauna, concurring to the deterioration of the benthic ecological status.

Understanding Marine Biodegradation of Bio-Based Oligoesters and Plasticizers.

The study reports the enzymatic synthesis of bio-based oligoesters and chemo-enzymatic processes for obtaining epoxidized bioplasticizers and biolubricants starting from cardoon seed oil. All of the molecules had MW below 1000 g mol-1 and were analyzed in terms of marine biodegradation. The data shed light on the effects of the chemical structure, chemical bond lability, thermal behavior, and water solubility on biodegradation. Moreover, the analysis of the biodegradation of the building blocks that constituted the different bio-based products allowed us to distinguish between different chemical and physicochemical factors. These hints are of major importance for the rational eco-design of new benign bio-based products. Overall, the high lability of ester bonds was confirmed, along with the negligible effect of the presence of epoxy rings on triglyceride structures. The biodegradation data clearly indicated that the monomers/building blocks undergo a much slower process of abiotic or biotic transformations, potentially leading to accumulation. Therefore, the simple analysis of the erosion, hydrolysis, or visual/chemical disappearance of the chemical products or plastic is not sufficient, but ecotoxicity studies on the effects of such small molecules are of major importance. The use of natural feedstocks, such as vegetable seed oils and their derivatives, allows the minimization of these risks, because microorganisms have evolved enzymes and metabolic pathways for processing such natural molecules.

Robinia pseudoacacia L. (Black Locust) Leaflets as Biomonitors of Airborne Microplastics.

Here we investigate the suitability of Robinia pseudoacacia L. (black locust) leaflets as a novel biomonitor of airborne microplastics (MPs) including tyre wear particles (TWPs). Leaflets were collected from rural roadside locations (ROs, n = 5) and urban parks (UPs, n = 5) in Siena, Italy. MPs were removed by washing, identified by stereomicroscope, and analysed for polymer type by Fourier transform infrared spectroscopy. Daily MP deposition was estimated from leaf area. The mass magnetic susceptibility and the bioaccumulation of traffic-related potentially toxic elements (PTEs) were also analysed. The total number of MPs at ROs was significantly higher at 2962, dominated by TWPs, compared with 193 in UPs, where TWPs were not found. In contrast, total microfibres were significantly higher in UPs compared with ROs (185 vs. 86). Daily MP deposition was estimated to range from 4.2 to 5.1 MPs/m2/d across UPs and 29.9-457.6 MPs/m2/d across ROs. The polymer types at ROs were dominated by rubber (80%) from TWPs, followed by 15% polyamide (PA) and 5% polysulfone (PES), while in UPs the proportion of PES (44%) was higher than PA (22%) and polyacrylonitrile (11%). The mean mass magnetic susceptibility, a proxy of the bioaccumulation of traffic-related metallic particles, was higher at ROs (0.62 ± 0.01 10-8 m3/kg) than at UPs (-0.50 ± 0.03 10-8 m3/kg). The content of PTEs was similar across sites, except for significantly higher concentrations of Sb, a tracer of vehicle brake wear, at ROs (0.308 ± 0.008 µg/g) compared with UPs (0.054 ± 0.006 µg/g). Our results suggest that the waxy leaflets and easy determination of surface area make Robinia an effective biomonitor for airborne MPs including TWPs.