Combined toxicity of graphite-diamond nanoparticles and thiabendazole to Daphnia magna

Carbon-based nanomaterials exhibit unique properties that make them suitable for a wide variety of industrial and biomedical applications. In this work, we studied the acute toxicity of graphite-diamond nanoparticles (GDN) combined with the fungicide thiabendazole (TBZ) to the immobilization of the cladoceran Daphnia magna in the presence and absence of the micro green algae Raphidocelis subcapitata, supplied as food source. The toxicity of GDN to D. magna decreased in the presence of R. subcapitata, while that of TBZ increased, the latter suggesting a carrier effect to TBZ. GDN-TBZ mixtures were fitted to the most common conceptual models applied to mixture toxicity: Concentration Addition (CA), Independent Action (IA) and Combination Index (CI). For GDN-TBZ mixtures in the absence of food the best fit was obtained with dose ratio deviation from CA model, while in the presence of food, dose level deviation from CA gave a better fit. The binary mixtures of GDN and TBZ showed synergistic toxic interactions at low concentrations, which could be attributed to the increased bioavailability of TBZ adsorbed on GDN. For higher concentrations of GDN, the binary mixtures turned antagonistic due to particle agglomeration. Our study provides evidence that deviations from additivity are dose dependent and relevant for the risk assessment of mixtures of nanoparticles with other chemical pollutants.publishe

Microplastic pollution in sublittoral coastal sediments of a North Atlantic island: The case of La Palma (Canary Islands, Spain)

In this work, the microplastic content of sediments collected in July 2020 between 5 and 7 m depth was studied in four locations of La Palma island (Canary Islands, Spain). At each sampling location, three samples were taken parallel to the shoreline. The microplastic content in each sampling corer was studied every 2.5 cm depth after digestion with a H2O2 solution followed by flotation in a saturated NaCl solution. Visualization of the final filtrates under a stereomicroscope revealed that all the sediment samples evaluated contained mostly microfibers (98.3%) which were mainly white/colorless (86.0%) and blue (9.8%), with an average length of 2423 ± 2235 (SD) mm and an average concentration of 2682 ± 827 items per kg of dry weight, being the total number of items found 1,019. Fourier Transform Infrared microscopy analysis of 13.9% (n = 139) of the microfibers also showed that they were mainly cellulosic (81.3%). No significant differences were found between the depths of the sediment. However, significant differences were found between the number of fibers from the sampling sites at the east and west of the island. Such variability could be driven by the winds and ocean mesoscale dynamics in the area. This study confirms the wide distribution of microfibers in sediments from an oceanic island like La Palma, providing their first report in marine sediments of the Canary Islands.En prensa3,20