Christos Panagiotopoulos

Recently, a new type of domestic drinking water purification system, based on advanced oxidation processes, has been launched on the market. The absence of control and regulation on the by-products generated in such systems could induce a degradation of water quality and risks for the consumer. In this context, the by-products formation and tap water toxicity evolution were investigated with a newly commercialized off-line system (LED UV-A/chlorine) in severe conditions. The transformation products of 6 emerging organic contaminants (atrazine, carbamazepine, clofibric acid, N,N-Diethyl-meta-toluamide, ibuprofen and metolachlor) were identified by LC/TOF. Degradation pathways were proposed based on MS data and transient radical species characterization. Acute toxicity assessments were conducted on Caco-2 cells, Daphnia magna and Aliivibrio fisheri (Microtox®). The transformation products resulted from reactions with hydroxyl and chlorine radicals through hydroxylation, ketonization, chlorination and scissions of the aliphatic chain on ether or amine functions. No cytotoxicity was noticed and different behaviours were observed for the ecotoxicity (decrease, rise before decreasing, no change) depending on the compounds and the organism tested. This work provides new insights into the benefits and potential risks associated with the use of such technologies and underlines the necessity of a legal framework.

Microplastics (MPs) are now widespread in marine environments, yet knowledge is still lacking regarding the contribution of common single-use items to marine MP contamination. Among these items, cigarette butts (CBs) and disposable face masks (DFMs) are globally pervasive plastic wastes, yet their microplastic release under environmentally relevant marine conditions remains poorly quantified. In this study, CBs and DFMs were incubated in natural seawater under laboratory-controlled conditions for 67 days. MP release was monitored under both biotic and abiotic conditions to assess microbial influence on fragmentation dynamics. MP generation showed contrasting responses to microbial activity depending on polymer type. CBs released more MPs under abiotic conditions (15 227 ± 7 190 MPs CB-1), whereas DFMs exhibited greater release under biotic conditions (40 767 ± 7 197 MPs DFM-1), indicating that microbial activity reduced MP accumulation from cellulose acetate-based materials while enhancing fragmentation of polypropylene-based materials. The MPs emitted consisted predominantly of fibers (~85%) and fragments (~15%), with modified cellulose acetate (95%) dominating CB-derived particles and polypropylene (89%) dominating DFM-derived particles. Our global-scale estimates indicate that degradation of CBs (10 quadrillion MPs y-1; 62 000 tons of cellulose acetate MPs y-1) and DFMs (15.9 trillion MPs y-1; 3 800 tons of polypropylene MPs y-1) could release substantial quantities of MPs annually into coastal marine environments, posing significant ecological risks with potential implications for marine ecosystem integrity and human exposure.

Atmospheric biological particles, including pollen and other plant-derived materials, constitute a substantial fraction of coarse particulate matter, particularly during flowering seasons. Olive trees represent one of the most widespread crops in southern Europe, and olive oil is a major economic resource for the region. Approximately 95% of global olive cultivation is concentrated in the Mediterranean basin (Sofiev et al., 2017). Pollen production from an area with complete olive coverage can reach up to 10¹⁰ pollen grains m⁻² season⁻¹, with an average grain diameter of 20.1 ± 4.0 μm. Olive pollen is considered among the most allergenic tree pollens in Europe, inducing respiratory symptoms such as rhinitis and asthma in humans (Liccardi et al., 1996), while also acting as a significant atmospheric source of organic matter and nutrients to terrestrial and aquatic ecosystems (Rösel et al., 2012; Violaki et al., 2021).In this study, a series of chamber experiments was conducted to investigate the response of olive pollen to atmospheric stressors, with a particular focus on NOx pollution. Olive pollen (Olea europaea L.) was collected between 5 and 7 May 2024 from Puglia, southern Italy (https://www.bonapol.com/). Prior to chamber exposure, comprehensive lipidomic, biological, and chemical characterizations were performed, including analyses of metals, major ions, and carbon content.A robust analytical workflow for pollen lipidomics was developed and applied before and after chamber aging. Using LC-Q-TOF/MS with ESI in both positive and negative ionization modes, approximately 480 lipid species spanning 41 lipid classes were identified. Phosphatidylcholines (PC) were the dominant class (66%), followed by diacylglyceryl carboxyhydroxymethylcholine (DGCC, 19%), and ether monogalactosyldiacylglycerols (MGDG, 8%). A significant decrease in major membrane lipids (PC, PG, SM, DGDG, and MGDG) was observed after aging, indicating lipid degradation processes. In contrast, oxidized lipid species, including oxidized triacylglycerols (OxTG), oxidized phosphatidylcholines (OxPC), and ether-linked lipids, showed a pronounced increase, highlighting oxidative transformations induced by atmospheric aging. Overall, these results highlight the sensitivity of lipids in pollen grains to atmospheric aging and emphasize the importance of considering oxidative processing when assessing the chemical evolution of primary biological aerosol particles. ReferencesLiccardi et al., Int Arch Allergy Immunol. Nov;111(3):210-7, 1996.Rösel, et al., Aquatic Sciences, 74, 87–99, 2012.Sofiev, et al., Atmos. Chem. Phys., 17, 12341–12360, 2017.Violaki, et al., npj Clim Atmos Sci 4, 63, 2021.

Health effects associated with particulate matter (PM) exposure are closely linked to the ability of particles to induce the formation of reactive oxygen species (ROS) and trigger oxidative stress. Accordingly, the oxidative potential (OP) of PM is considered a more health-relevant toxicity metric than mass concentration alone. However, in densely populated and ecologically sensitive areas in the northwestern Mediterranean, the main sources contributing to OP remain poorly constrained, particularly regarding differences between urban and rural environments.This sutdy systematically evaluated the OP of total suspended particulate matter (TSP) at an urban coastal site (Endoume) and a rural coastal site (Banyuls) in the region. OP was quantified using the dithiothreitol (DTT) assay and evaluated the contributions of primary emission sources and secondary formation to OP. Chemical tracers, dual carbon isotopes (¹³C & ¹⁴C), and positive matrix factorization (PMF) were used to apportion the main local sources.The results reveal pronounced differences in both magnitude and source contribution to OP between urban and rural coastal aerosols. The annual mean organic-carbon-normalized DTT activity (DTTm) at Endoume was 20.0 ± 9.1 pmol min⁻¹ μg⁻¹ and 17.0 ± 5.3 pmol min⁻¹ μg⁻¹ at Banyuls (Mann–Whitney U test, p = 0.06). The annual mean volume-normalized OP (DTTv) was comparable at both sites (≈ 0.04 ± 0.02 pmol min⁻¹ m⁻³, Mann–Whitney U test, p 0.75); in summer, ship emission emerged as the dominant driver (V–DTTv: ρ > 0.9, p < 0.01); while in autumn and winter, the contribution from biomass burning (BB) increased substantially (DTTv–nssK⁺: ρ = 0.74, p < 0.01). In contrast, the OP at Banyuls was dominated by traffic emission in spring (Zn–DTTv: ρ > 0.7, p < 0.01), whereas BB and ship emission jointly influenced OP in summer (V–Ni: ρ ≈ 0.7, p < 0.01). Additionally, dust and sea salt contributed significantly to OP at both sites, with a more pronounced influence at Banyuls (nss-Ca²⁺–DTTv: ρ ≈ 0.85, p < 0.01). Carbon isotope analysis showed that autumn samples at both sites exhibited lower OCNF and DTTv values, indicating that the influence of FF on OP may be more pronounced.PMF results further show that at Banyuls, traffic emission and BB together accounted for approximately 25% of OPv, with natural dust contributing about 14%, whereas at Endoume, industrial emissions (25%), BB (20%), and traffic emission (19%) were the major contributors to OPv. For OPm, industrial emission dominated at Endoume, while natural sources such as sea salt and dust were the primary contributors at Banyuls; secondary formation processes contributed substantially to OPm at both sites. Overall, this study demonstrates strong spatial and seasonal source dependence of PM oxidative toxicity in the northwestern Mediterranean coastal region, providing important constraints for health-oriented air pollution assessments.

Plastic waste in the environment gradually degrades into microplastics, while organic additives within these plastics, can leach out over time during plastic aging. Each year, approximately 5.4 trillion cigarettes are produced, leading to the disposal of 4.5 trillion of cigarette butts worldwide. Similarly, with mask production potentially reaching 34.5 billion units annually, as observed in 2022 during the pandemic, and 10-20% of plastic waste being inadequately managed globally—whether left uncollected, improperly disposed of, or released into natural environments—it’s estimated that between 0.69 and 1.04 billion masks may end up in marine ecosystems each year. Yet, the environmental impact of these plastics, especially in marine ecosystems covering over 70% of the Earth’s surface, is still poorly understood.In this study cigarette butts and face masks, were incubated in natural seawater under laboratory-controlled conditions for 80 days. The generation of microplastics and the leaching of toxic organic additives, such as phthalates (PAEs) and organophosphate esters (OPEs), from these plastic items into the dissolved phase were closely monitored. Changes were tracked using LDIR for microplastics and GC/MS for additives, with bacterial conditions (biotic and abiotic) varied throughout the experiment. Our results showed that polypropylene (98.5%) was the primary polymer released from face masks, while modified cellulose acetate (91.5%) was predominant in cigarette butts. We found that that a single cigarette butt releases approximately 590 ± 310 microplastic particles (n = 6) per litter, while a single face mask contributes around 1 500 ± 1 000 particles into seawater (n = 6). Additionally, our findings revealed that these microplastic debris types (cigarette butts and masks) were composed of around 20% fibers and 80% fragments.Our results also indicated that both cigarette butts and face masks released significant amounts of PAEs followed by OPEs into the surrounding seawater during the first month. Di-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DnBP) were the primary PAEs leached from face masks, accounting for 31% and 21%, respectively, of the total PAEs released. In cigarette butts, diethyl phthalate (DEP) was the dominant PAE at 57%, followed by di-isobutyl phthalate (DiBP) at 11%. In both materials, 2-ethylhexyl diphenyl phosphate (EHDP) was the main OPE detected, contributing 19% and 18%, respectively. Finally, our results demonstrated that bacterial exposure had minimal impact on the average concentrations of additives released.

Phosphorus is a critical nutrient affecting primary productivity across all ecosystems. Many regions worldwide are limited or co-limited by phosphorus availability, which can be alleviated through atmospheric deposition. Dust is known to be a key external source of phosphorus in ecosystems, assumed to be in the form of various insoluble inorganic minerals. We show that this view is largely incomplete and here we present conclusive evidence, that organic phosphorus as diesters, primarily associated with biological materials. Phosphate diesters significantly correlated with soil bacteria found in dust, implying a direct link with microbial soil communities, without excluding the eukaryotic cells. Phosphate diesters in dust, along with abundant alkaline phosphatase, may contribute 70% to daily primary productivity in the eastern Mediterranean, highlighting the potential of organic phosphorus substrates present in dust as airborne microorganisms to impact the biogeochemistry of oligotrophic environments via atmospheric deposition.

Atmospheric particulate matter (PM) significantly impacts Earth's climate, air quality, visibility, and public health. PM influences the carbon cycle, ocean-atmosphere interactions, and global dynamics. The Mediterranean Sea, a highly climate-sensitive ecosystem, faces growing vulnerability from rising demographic and economic pressures. As part of the FIRETRAC project, we monitored total suspended particles (TSP) for two years at two Northwestern Mediterranean sites: urban Marseille and rural Banyuls-sur-Mer, both in the Gulf of Lions. Chemical analyses (metals, ions, organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and water-soluble total nitrogen (WSTN)), and isotopic techniques (δ¹³C and Δ¹⁴C) along with statistical methods were used to detect TSP composition, sources, and dynamics.TSP particles from Banyuls (-26.31 ± 0.52 ‰) and Marseille (-26.23 ± 0.51 ‰) showed comparable δ¹³C values, indicating a predominantly terrestrial origin. Apparent radiocarbon ages (Δ¹⁴C) ranged from 940 to 5000 years, pointing to a complex mixture of sources with varying reactivities. Additionally, HYSPLIT modeling revealed long-range transport from diverse regions, including the Sahara Desert, Eastern European industrial zones, and Northern Europe, contributing to the particulate matter in the Northwestern Mediterranean Sea. These findings suggest that TSP at both sites likely represent a mixture comprising both anthropogenic and natural sources which is further supported by the analysis of other chemical constituents.Thus at the Marseille site, the Fe-Al correlation reached 0.94 (p < 0.0001, n=59), and during periods of higher concentrations, the HYSPLIT back-trajectory model confirmed its origin from natural source: Saharan dust. Conversely, at both sites, the strong correlation of Mn-Pb (r = 0.88 in Banyuls, 0.97 in Marseille, p < 0.0001, n=60), along with evidence from the HYSPLIT and PCA analysis, indicates shared sources, including industrial emissions and long-range pollution (via routes crossing the Atlantic Ocean, the industrial regions of southern Spain, and southern France). The OC and EC concentrations were relatively similar between the two sites (12.34 ± 5.56 µg·m-³ in Banyuls versus 9.59 ± 4.91 µg·m-³ in Marseille). Banyuls exhibited higher OC/EC ratios, indicating more secondary organic carbon, while Marseille showed stronger primary emissions. Seasonal variations in WSOC and WSTN concentrations suggest their dependence on local emissions and atmospheric seasonal processes. The higher WSTN/WSOC ratio observed in Marseille (0.51 ± 0.34 µg·m-³ compared to 0.36 ± 0.18 µg·m-³ in Banyuls) highlights greater nitrogen contributions, likely attributed to urban pollution.Prncipal component analysis (PCA) showed that PC1 (41.9% variance) is dominated by OC, EC, WSOC, WSTN, and heavy metals (e.g., Pb, Zn, Cu), indicating anthropogenic influences like combustion and industrial emissions. In contrast, PC2 (15.4% variance) was driven by Na, Mg, Sr, and K, representing natural sources such as marine aerosols and soil dust. These findings suggest that regional pollution is largely driven by human activities but moderated by natural background sources, offering key insights for pollution source analysis.Overall, this study reveals that TSP in the Northwestern Mediterranean Sea originates from a complex interplay of anthropogenic and natural sources, influenced by both local emissions and long-range transport and ongoing research in our lab focuses on specific BB tracers of TSP including anhydrosugars and PAHs.

Atmospheric aerosols (AAs) significantly influence the global radiative balance, air quality, biogeochemical cycles, and human health. While their climate and health impacts are well-studied, their biogeochemical role, including contributions of phosphorus (P), nitrogen (N), and organic matter (OM) to oligotrophic regions like the Mediterranean basin, is less explored. Recent studies suggest variable atmospheric deposition of trace metals and nutrients associated with both natural (i.e. recurring Saharan dust storms, biomass burning episodes) and anthropogenic origin (i.e. polluted air masses from northern and central Europe) with atmospheric OM inputs comparable to rivers. However, the detailed composition of atmospheric organic aerosols in the region remains poorly understood.Ultrahigh-resolution mass spectrometry (UHRMS) offers unparalleled resolving power and enables detailed characterization of complex natural and anthropogenic organic matter (OM) mixtures. It also provides stoichiometric insights into organic nitrogen (N) or phosphorus (P) molecules that are often undetectable by methods like NMR spectroscopy or lower-resolution mass spectrometers. Here, we present advanced analysis of the chemical composition of aerosol particles collected in the Western Mediterranean basin. We combined atmospheric pressure photoionization (APPI) and electrospray ionization (ESI), two complementary techniques, to achieve comprehensive coverage of both polar and nonpolar molecular components through UHRMS. Electrospray ionization (+ESI) was paired with a 21-Tesla (T) Fourier-transform ion cyclotron resonance mass spectrometer (FT-ICR MS), delivering exceptional resolving power, sensitivity, acquisition speed, mass accuracy, and dynamic range. Meanwhile, APPI (+ /-) was coupled to an Orbitrap Fusion Lumos 1M to target condensed, polyaromatic, nonpolar compounds that are challenging or impossible to detect by ESI alone.Approximately 28,000 distinct CcHhNnOoPpSs molecular formulas were assigned across all 30 samples collected in the Western Mediterranean basin to ESI(+) 21-T FT-ICR MS spectra after a solid phase extraction to isolate and desalt the samples, revealing an astonishing molecular chemodiversity mainly driven by nitrogen-containing compounds (CHNO) and oxygenated compound (CHO) with minor contribution of sulphur-containing (CHOS) and phosphorus-containing (CHOP) compounds, despite their inherent poor ionisation efficiency in complex mixture. APPI(+/-) / Orbitrap Lumos 1M proved to be a powerful approach for characterizing the molecular composition of highly condensed hydrocarbons, especially the large molecular species that cannot be eluted from gas chromatography columns.We will explore the key factors driving the molecular composition of atmospheric aerosols (AAs) and their influence on variations and potential formation pathways. Our findings aim to improve understanding of their composition and sources with a focus on biogeochemical processes in the nutrient-limited, stratified open waters of the Mediterranean Sea.

Phosphorus (P) is a vital element for all living organisms and is one of the most essential nutrients in both aquatic and terrestrial ecosystems. As a fundamental component of DNA and RNA, it plays a structural role in cell membranes (e.g., as part of phospholipids) and is crucial for various biological processes, such as energy transfer through ATP. In the environment, phosphorus exists in both inorganic forms (e.g., orthophosphate or PO43−) and organic forms. In environmental studies, organic phosphorus (P) is not measured directly but is estimated by subtracting the concentration of inorganic phosphorus species from total phosphorus. This process involves converting all forms of phosphorus into orthophosphate, typically through UV or persulfate oxidation, followed by colorimetric analysis. However, inefficiencies in this transformation can introduce errors and biases, leading to underestimation or overestimation of the organic phosphorus content.Solid-state 31P NMR is a powerful technique that identifies phosphorus chemical species, organic or inorganic, without any previous sample treatment. This technique was widely used in the 2000s in marine chemistry in samples comprised of concentrated dissolved organic matter, fast-sinking particles, marine planktons, and sediments, revealing important features of organic P compounds such as phosphonates. A notable characteristic of P in concentrated dissolved organic matter is that P-esters and phosphonates consistently exhibit a nearly constant ratio of 75:25, regardless of the depth or location where the sample was collected. 31P-NMR, however, has not yet been used for atmospheric samples, and is the primary focus of this study. Here, we analyzed total suspended atmospheric particles collected during dust events, as well as ash produced from the biomass burning of olive trees. We find that the functional groups associated with phosphorus included orthophosphate and monophosphate esters, which shared the same chemical shift (H₃PO₄ and RH₂-PO₄), phosphate diesters (R₁R₂HPO₄), and pyrophosphate (H₄P₂O₇). P in our samples consisted of phosphate diesters (72–88%), followed by orthophosphate (10–19%) and pyrophosphate (1–8%). Unlike marine samples, phosphonates were absent, suggesting the absence of compounds containing carbon-phosphorus (C–P) bonds. Phosphate diesters are primarily found in naturally occurring organic compounds, such as nucleotides and their derivatives (e.g., DNA, RNA, AMP, ADP, ATP), including phospholipids, and thus constitute the majority of atmospheric organic phosphorus. As these compounds have C-O-P bonds they are readily hydrolyzed in the marine environment by the alkaline phosphatase enzyme, providing an important source of P in aquatic/marine ecosystems. Overall, our results suggest that organic-P, as estimated by 31P NMR, can account for up to 80% of total P in dust and burning biomass samples. Thus, the organic-P fraction of external inputs is likely as significant for marine primary productivity as inorganic inorganic-P.

Lipidomics, a subfield of metabolomics, is an emerging field where hundreds to thousands of lipid species are simultaneously identified. Given the ubiquity and diverse biological roles of lipids, lipidomics offers valuable insights into mechanisms and the discovery of biomarkers related to environmental stressors that affect the cellular physiology and their numerous biochemical pathways. The major source of lipids in the atmosphere are the biogenic particles (bioaerosols) e.g., bacteria, fungi, pollen, plant fragments and viruses. Specifically, the terrestrial ecosystems including deserts, are the major sources of the atmospheric bioaerosols with urban environments and areas with agricultural and industrial activity being particularly important. The desert dust aerosols contain high concentrations of bioaerosols mainly composed of soil microorganisms and plant detritus. Agricultural dust can contain significantly more amounts of biological material, which subsequently can be enriched with additional biogenic particles when they are transported across terrestrial and aquatic environment through their coagulation with other airborne bioaerosols. The lipidome of airborne biogenic particles is unexplored to date, yet it can provide unique insights on bioaerosols, their stress state and oxidant exposure history. During this study we used lipidomics as a novel tool for the atmospheric research, to study the lipid changes in bioaerosols systems induced by their exposure to air pollutants and other atmospheric aging factors.To achieve this, Saharan dust aerosols (n= 15) were sampled from East Mediterranean (Crete, Greece) using a high-volume (85 m3 h−1) TSPs sampler (TISCH). Dust atmospheric particles were collected on precombusted (450 °C for 5 h) 20 × 25 cm quartz filters (Pall, 2500QAT-UP). A reliable analytical protocol was established for lipidomics analysis of Saharan dust aerosols, which allowed us to identify approximately 60 lipid species, primarily phosphatidylcholines (PC), phosphatidylethanolamines (PE), triglycerides (TG), and their oxidation products, ceramides (Cer), and monogalactosyldiacylglycerols (MGDG). In addition to lipid analysis, biological identification and chemical analysis, including metals, major ions, and sugars, was also performed and will be discussed in detail.Each dust event has a distinct signature, reflecting not only the chemical composition of the Saharan soil but also the atmospheric processing during its long-range transport. Preliminary results indicate a higher percentage contribution from the oxidation products of TG (OxTG, 33%) and PCs (OxPC, 22%) to the total identified lipids. The significant correlation between PCs and mannitol indicates a fungal contribution to airborne cholines. Furthermore, the correlation between anthropogenic metals (e.g., V, Ni, As, Cr, Pb) and galactolipids (MGDG), which are common plant membrane lipids, indicates a complex mixture of anthropogenic emissions and plant material in the dust aerosols due to long range transport of Saharan soil.