The dynamics of the coastal aquifers are well-expressed by geochemical and isotopic signatures. Coastal regions often exhibit complex groundwater recharge pattern due to the influence of depression in the Bay of Bengal, tidal variations on surface waters, saline water intrusion and agricultural return flows. In this research, groundwater recharge processes occurring in coastal Tamil Nadu, South India were evaluated using major ion chemistry and environmental isotopes. A total of 170 groundwater samples were collected from shallow and deep aquifers during both post-monsoon (POM) and pre-monsoon (PRM) seasons. The isotopic results showed a wide variation in the shallow groundwater, suggesting contribution from multiple recharge sources. But, the deeper groundwater recharge is mainly from precipitation. The northern part of the study area showed more depleted isotopic values, which rapidly changed towards south from −6.8 to −4.4‰. Alternatively, central and southern parts exhibited relatively enriched isotopic content with variation from −0.58 to −2.7‰. Groundwater was discerned to be brackish to saline with chloride content, 600–2060 mgL⁻¹ and δ¹⁸O ranging from −5.8 to −4.5‰, suggesting influence of the saline water sources. A minor influence of anthropogenic activities was also observed in the deeper groundwater during PRM, which was confirmed by tritium and Cl⁻ trends. The old groundwater with depleted isotopic content infer recharged by distant sources while modern groundwater with enriched isotopes points to the influence of evaporated recharge.

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) are highly toxic organic compounds, and very few studies on their presence in polar environments have been conducted. This study assessed the concentration and distribution of PCDD/Fs, dioxin-like polychlorinated biphenyls (DL-PCBs), and non-dioxin-like polychlorinated biphenyls in selected fjords of the Svalbard archipelago in Norway. The ∑PCDD/Fs observed for Raudfjorden, Smeerenburgfjorden, Magdalenefjorden, and Kongsfjorden were 22.80 pg/g, 25.65 pg/g, 18.27 pg/g, 33.50 pg/g, and 21.69 pg/g, respectively. The WHO's toxic equivalents values of both ∑PCDD/Fs and ∑DL-PCBs were comparatively higher than those reported in other polar regions. Of the four fjords studied, the sediments from Kongsfjorden exhibited the presence of the most toxic materials, including PCB-126 and PCB-169, of DL-PCBs. More than 80% of the total analysed PCDD/Fs were comprised of highly chlorinated congeners (hexa-to-octa forms). More studies are required to understand the destination and transport of these hazardous pollutants in high Arctic sediments.

Coastal plastic pollution is a global problem, it affects local ecosystems, and can have economic and social implications. Plastic pollution is pervasive at high latitudes but there is a lack of data on the spatial and temporal amount of marine litter entering coastal systems. In this study, a seasonal accumulation survey of anthropogenic debris and beach wrack was conducted for the first time in Iceland. One hundred data collections were performed on a coast in the Snæfellsnes peninsula throughout one year. Of all the debris retrieved, over 9000 items (0.2 to 50 cm), 78.5 % were plastics. Beach wrack correlated strongly with the quantities of plastic debris entering the coastal environment (R² > 0.9; p < 10⁻¹¹), with a different slope for each season. The presence of beach wrack informed important daily and spatial fluctuations in the quantities of plastic debris, while seasonal fluctuations demonstrated higher arrival rate of plastic in autumn and winter.

Trace elements are pollutants of both natural and anthropogenic origin which can influence negatively on ecosystem and wildlife health. We evaluated trace element in blood samples of gray seal (Halichoerus grypus) stranded in the Gulf of Riga and their influence on their health status through hematological and biochemical profiles. Zn showed the highest levels followed by Cu > Se > Pb > THg > As. Cr and Cd were not detected. Most trace element levels were generally comparable to those reported in seal species; however, high Pb values were observed in those sample showing detectable concentrations (<0.046–257.6 μg/kg ww). Significant positive correlations were found between trace elements concentrations and various biochemical parameters, including Se-ASAT, Se:Hg-ASAT, Cu-TP, Cu-ALB, CuCa, Zn-ALAT, ZN-LDH, ZnP, Zn-Segment neutrophils, and Pb-CK. Nevertheless, most relationships were not strong enough (p > 0.04) to assume a toxicological implication. Despite its limitations, this information could serve as the baseline for future research.

Southeast Brazilian bays have been increasingly degraded by untreated organic loads. Therefore, to assess fecal contamination status, sediment quality regarding polycyclic aromatic hydrocarbons (PAHs), and sources of organic matter (OM), we have determined fine-grained and total organic carbon (TOC) content and concentrations of PAHs and sterols in twenty-six surface sediment samples in Sepetiba Bay. The fine-grained (1–26 %), TOC (0.20–3.45 %), PAHs (<LQ – 78.27 ng g⁻¹) and sterols (0.10–21.58 μg g⁻¹) results showed a decreasing trend from the internal to the external sector of the study area. The diagnostic ratios of selected PAHs and sterols indicated a mixture with significant contribution from continental and pyrolytic OM in all stations. The fecal contamination is significant to the internal sector of Sepetiba Bay. Considering a site-specific sediment quality guidelines (SQGs) the PAHs levels with more restricted benchmark values indicate the harbor and the internal sector as contaminated.

An unusual coastward expansion of the toxic dinoflagellate species Margalefidinium polykrikoides was observed in 2020 summer after a tropical storm passing Chesapeake Bay. Such coastward expansion was only recorded in 2007. A newly developed coupled Lagrangian particle tracking and harmful algal bloom model driven by environmental variables was used to investigate the underlying mechanisms and successfully reproduced the expansion patterns. Persistent pre-storm southerly winds favored the delivery of bloom source water originated inside the bay to the coast. Storm-induced strong upwelling of denser subsurface water interacted with the after-storm outflow plume (steered southward as the storm's impacts waned), forming a transport barrier to accumulate algae and delineate the coastwide bloom extent. Algal diel vertical migrations and transport barrier enable algae to stay in the nearshore regions. The storm-induced coastward expansion of M. polykrikoides might increase future bloom possibility in the coastal area.

Nanoplastics (NPs) are widely found in the environment and can act as a vector for various toxic substances and promote their diffusion and bioenrichment, but the underlying mechanisms are largely unknown. Here, the adsorption characteristics of bisphenol A (BPA) onto NPs were explored. The results show that the adsorption of BPA on NPs was dominated by saturated single-layer adsorption and affected by both intra-particle diffusion and liquid film diffusion. Electrostatic interaction, π–π interaction, and hydrophobic effects played key roles in adsorption. In addition, the introduction of electrolytes inhibited the adsorption of BPA onto NPs. Interestingly, the introduction of suspended sediment promoted the formation of heterogeneous aggregates of NPs-SS, thereby reducing the adsorption capacity, indicating that aggregation may play an important role in the adsorption behavior of NPs. Overall, our results provide new insights into the adsorption behavior of BPA on NPs and the underlying mechanisms under different environmental conditions.

Horseshoe crabs (HSCs) are a group of ancient chelicerates with great ecological and biomedical importance. Food poisonings caused by the consumption of Asian HSCs have significant impacts on public health and safety. This study measured tetrodotoxin (TTX) concentrations in two HSC species across various life stages in May 2020 from the northern Beibu Gulf, their most important spawning and nursery habitats in China. The average TTX contents in both Carcinoscorpius rotundicauda and Tachypleus tridentatus ranged 6.2–8.0 μg/kg and 3.8–8.4 μg/kg, respectively. While sampling location, growth and molt stages have little influence on TTX distribution in both species, significantly higher levels of TTX were detected in hemolymph, but lower in pooled tissues of early-instar juvenile T. tridentatus. These results provide a regional view of TTX occurrence and distribution in HSCs during their spawning season, which are critical for future studies to enhance understanding of TTX dynamics and formation in HSCs.