Triple oxygen isotope values of xylem water were measured along the length of smooth horsetail stems ( Equisetum laevigatum ). Extreme isotope enrichment is observed moving from base to stem tip. δ ¹⁸ O values range from −8.3‰ at the base to 82.6‰ at the tip. Δ′ ¹⁷ O values range from 0 to −1,797 per meg. The δ ¹⁸ O and Δ′ ¹⁷ O values are the most extreme measured for any terrestrial material and expand the known range of Δ′ ¹⁷ O values by fivefold for mass-dependent fractionation on Earth. The extreme isotope enrichments are explained using a hybrid evaporation/chain-of-lakes model, allowing us to refine the leaf respiration coefficient to θ _k = 0.511 ± 0.001. This new value is required to explain the low Δ′ ¹⁷ O values previously measured in desert plants and animals and is critical when using fossil samples for paleoclimate reconstruction. Coexisting phytoliths and stem water were also measured. The 1000 ln ¹⁸ α _silica-water value at the plant base (35.89‰) appears to be in isotopic equilibrium, with far smaller fractionations of 10.3‰ near the tip. The smaller fractionations at higher levels are explained by continual silica deposition as the plant elongates and the δ ¹⁸ O values of each segment become higher. The overall integrated phytolith value is a combination of early and late silica growth. The Δ′ ¹⁷ O _silica − Δ′ ¹⁷ O _water values are not in equilibrium, explained by a kinetic isotope effect, with a λ value of 0.5205 vs. 0.5244 for equilibrium. Phytolith isotope values may lead to erroneous interpretations for paleoclimate reconstruction.

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals widely used for their thermal and chemical resistance but are now of major environmental concern due to their persistence, bioaccumulation, and adverse health effects. Regulatory actions have been implemented globally, yet efforts to identify sources and degradation processes remain hindered by analytical limitations. Compound-Specific Isotope Analysis (CSIA) offers a promising approach for tracing PFAS sources and assessing their environmental transformation, but its application has been limited by the lack of suitable methods. This study presents the development and validation of a CSIA method for selected perfluorocarboxylic acids (PFCAs) and heptadecafluorooctane sulfonic acid (PFOS) using gas chromatography-Isotope Ratio Mass Spectrometry (GC-C-IRMS). An isobutyl-derivatization procedure was optimized to enhance compatibility with GC analysis, enabling successful isotope ratio measurements for perfluoroheptanoic acid (PFHpA), pentadecafluorooctanoic acid (PFOA), and nonadecafluorodecanoic acid (PFDA), with precision below ±0.5 ‰. In contrast, heptadecafluorooctane sulfonic acid (PFOS) could not be analyzed. Preliminary Elemental Analysis-IRMS (EA-IRMS) of standards from multiple suppliers revealed significant isotopic variability (up to 10 ‰), supporting the feasibility of isotopic fingerprinting for source attribution. Solid-phase microextraction (SPME) was employed for sample preparation, minimizing chromatographic interference. The method was successfully tested on real water samples spiked with PFCAs, demonstrating its potential for tracing PFCAs contamination in real-world contexts. This work lays the foundation for broader application of CSIA to PFCAs, providing a novel tool for environmental forensics and improved risk assessment.

Plastic pollution in marine environments has become a global concern, emphasizing the need for innovative analytical approaches to trace sources and assess degradation processes. In this study, an integrated analytical approach, combining carbonyl index (CI) and stable isotope analysis (δ¹³C and δ¹⁸O), was applied to compare polyethylene (PE) pellets retrieved from coastal environments with the corresponding industrial reference material. The study takes advantage of the PE pellet spill from the container ship Toconao, which provided both reference pellets from the original industrial batch and pellets exposed to natural marine conditions for three months, enabling a direct comparison between pristine and environmentally aged material. CI was determined using the SAUB (Specified Area Under Band) method through FTIR-ATR (Fourier Transform InfraRed - Attenuated Total Reflectance) spectroscopy, revealing an average increase of 12.4% after three months of natural exposure, consistent with the formation of new carbonyl groups due to environmental degradation. Carbon isotope analysis showed minimal variation between the standard and exposed samples, indicating preservation of the original isotopic signature during early degradation stages, thus confirming its reliability for tracing plastic sources. In contrast, oxygen isotope analysis report a linkage with CI, highlighting that photooxidative degradation affects the oxygen isotopic composition of the macromolecule, concurrently with the formation of new carbonyl groups. These results demonstrate that the combined spectroscopic-isotopic approach enables simultaneous assessment of source and degradation of plastics in the environment, providing a promising tool for large-scale monitoring of plastic origin and aging processes.

The great white shark (Carcharodon carcharias), a keystone predator vital to marine ecosystem stability, is increasingly exposed to anthropogenic threats, including endocrine-disrupting chemicals (EDCs). This study highlights the use of non-invasive epidermal biopsies to assess physiological and ecological parameters in 28 live specimens sampled from the Dyer Island Nature Reserve, South Africa. Epidermal tissue was analyzed for vitellogenin (Vtg), a biomarker of estrogenic exposure, while dermal tissue was used for stable isotope analyses of carbon and nitrogen, essential for understanding the feeding habitat of white sharks. Vitellogenin, typically restricted to sexually mature females, was unexpectedly detected in males and immature females, indicating significant exposure to estrogenic pollutants. This finding raises concerns about the potential reproductive and population-level impacts on this vulnerable species. Stable isotope analyses confirmed that dermal tissue alone is sufficient for trophic studies, eliminating the need for deeper muscle sampling. By demonstrating that epidermal and dermal tissues provide critical data for both biomarkers and isotopic studies, this research supports the adoption of minimally invasive techniques. Shallower biopsies reduce stress on the animals, making this method a valuable tool for conservation research and management of C. carcharias.

Commercial smooth-hound sharks of the genus Mustelus are commonly landed and consumed in Mediterranean fisheries, raising concerns about potential human exposure to persistent contaminants. This study investigated the occurrence of organochlorine compounds (OCs), including hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (DDT) and its metabolites, and polychlorinated biphenyls (PCBs), together with per- and polyfluoroalkyl substances (PFAS), in muscle and liver tissues of Mustelus mustelus and Mustelus punctulatus collected in the waters of the Egadi Archipelago (central Mediterranean Sea). OCs were detected in all analyzed samples, with total PCB concentrations reaching higher values in liver compared to muscle tissues, reflecting tissue-specific accumulation and detoxification processes. PFAS were detected in all analyzed muscle samples (1.10–58.5 ng/g w.w.), with PFOS, PFOA and PFNA generally below current European regulatory thresholds, although isolated exceedances were observed. Stable isotope analysis (δ¹³C and δ¹⁵N) highlighted differences in trophic ecology between the two species and suggested that feeding habitat and trophic position may influence contaminant exposure patterns, particularly in M. punctulatus. The human health risk assessment, conducted as a screening-level evaluation, indicated potential concern associated with PCB concentrations in liver tissue, while risks associated with muscle consumption were generally lower. Overall, the integration of contaminant analysis and stable isotopes provides insights into organismal exposure pathways and supports the use of smooth-hound sharks as sentinels of contaminant presence in Mediterranean coastal ecosystems.