John Selvamony Armstrong-Altrin

Microplastic pollution has become a growing concern in coastal ecosystems, due to its persistence and potential ecological impacts. This study evaluates the seasonal differences in microplastic abundance in the Coatzacoalcos beach sediments, Veracruz, Gulf of Mexico. Sediment samples were collected from the foreshore zone during the dry (April 2019) and rainy (October 2022) seasons. Microplastics were extracted by density separation and analyzed using Stereomicroscopy, Scanning Electron Microscope (SEM), and Fourier-Transform Infrared Spectroscopy (FTIR). The microplastic abundance estimation was higher in the rainy season (1210 MPs kg⁻¹) compared to the dry season (690 MPs kg⁻¹). Polymers detected during the rainy season were acrylonitrile–butadiene–styrene (ABS), poly(ethyl acrylate) (PEA), and cellophane (CE). The surface features of microplastics in the rainy season exhibited smooth surfaces, physical weathering features, adhered silica globules, and fragments of diatom frustules, indicating biological colonization and recent deposition after a long marine transport. In the dry season, the identified polymers were styrene–acrylonitrile (SAN), ABS, PEA, and CE, with surface features dominated by chemical weathering, such as flaking, dissolution pits, and grooves due to photo-oxidation. Seasonal variability in microplastic distribution was influenced by precipitation, river discharge, and sea currents. These findings highlight the role of climatic factors in controlling microplastic abundance, and highlight the need for improved waste management strategies in the coastal regions.

Sediment geochemistry and 165 detrital zircon grains U–Pb ages are analyzed from the Ventosa beach sediments in the Gulf of Tehuantepec, Mexican Pacific. The objective is to investigate the sediment weathering condition, compositional variations, and to locate the source areas delivering sediments to the coast. Weathering indices reveal a moderate chemical weathering, indicating that the sediments are chemically immature. The SiO2 content (~72–78 wt. %) and the trace element concentrations indicate that the beach sediments are dominantly derived from the felsic igneous rocks. The rare earth element (REE) patterns of the Ventosa sediments are homogeneous and are depleted relative to the average upper continental crust (UCC) values. The environmental indices reveal a “moderately severe enrichment” for Cu content (Enrichment Factor EF = 5.62–8.87; and Geo Accumulation Index Igeo = 1.41–1.98). Anthropogenic enrichment in Pb, Ba, and Zn contents with the possibility of adverse aquatic biota effect is also observed. Th/U ratios in zircon grains are >0.3, indicate an igneous origin. Two major U–Pb age groups are identified i.e. (1) Miocene (~23–12.9 Ma) and (2) Proterozoic (Neoproterozoic: ~999–545 Ma; Mesoproterozoic: ~2549–1006 Ma). These ages suggest that the zircon grains were originated from the nearby source terranes, most likely from the Cenozoic plutons exposed along the southern Oaxaca coastal region, as well as the volcanic and sedimentary rocks of the Todos Santos Formation.

This study investigates the textural characteristics, mineral composition, and U–Pb ages of detrital zircon grains from the Playa Norte (PN) and Playa Tamiahua (PT) beach sediments along the Gulf of Mexico (GoM). The objective is to trace the sediment origin and to identify the possible environmental impacts in the coastal ecosystem. This work represents the first integrated provenance and geochemical analysis performed in these beaches, contributing to a broader regional sedimentological and geochronological database for the GoM. The results reveal distinct compositional and provenance signatures: PN sediments are rich in quartz (57.7% avg.), feldspars (15.7% avg.), and carbonate minerals (8.6% avg.), with zircon populations dominated by Proterozoic ages (~820–2200 Ma) and minor anthropogenic enrichment. In contrast, PT exhibits higher contents of quartz (78.6% avg.), andesine (9.6% avg.), and anorthite (8.5% avg.), with zircons mainly of Oligocene age (~32 Ma) and minimal contamination. Comparison with potential source regions indicates that PN sediments were derived primarily from the Sierra Madre Oriental, while PT sediments were originated from the Mesa Central and Eastern Mexican Alkaline Provinces. Overall, the findings demonstrate that, beyond littoral mixing and sediment recycling, the composition of GoM coastal sediments reflects the region’s complex tectono-sedimentary evolution and variable natural versus anthropogenic influences. PN is enriched in arsenic content, which is associated with agricultural activities and oil industries, while PT exhibits low values with no evidence of contamination. Meanwhile, Cr in PN suggests an anthropogenic input, which is linked to oil exploration activities in the GoM.