Hooghly River (HR), the other name used for the lower stretch of River Ganga, is a prime freshwater source in the eastern part of India. However HR has been evidenced with a variety of emerging organic pollutants (EOPs) in the recent past. Given the extensive use of plasticizers and additive in plastic products, we have investigated seven plasticizers and bisphenol A (BPA) in the surface and storm-water of HR up to the tip of the Bay of Bengal. Further using a previously published sediment data we have estimated the fluxes for the aforementioned EOPs. Surface water and storm-water concentrations of seven plasticizers varied between 92.62 and 770 ng/L (176.1 ± 104.8; Avg ± SD) and 120.9–781.5 ng/L (355.2 ± 232.5), respectively. BPA varied between 43 and 8800 ng/L (658.3 ng/L ± 1760) and 117.9–2147 ng/L (459.3 ± 620.2) in surface and storm-water, respectively. With the increase in salinity, a decreasing trend for bis-(2-ethylhexyl) phthalate (DEHP) was evidenced. However, concentration of BPA increased with the increase in salinity. Significant and strong correlation between DEHP and BPA (R² = 0.6; p < 0.01) in the suburban corridor might have resulted from sludge disposal of the scrap recycling activities. Using site-specific principal component analysis, unregulated disposal of plastic waste, particularly from such industrial belts and tourist spots were identified as the possible point sources for plasticizers and BPA in this region. Net diffusive flux based on fugacity fraction showed a trend depending on the pollutant’s aqueous solubility and partition coefficient. However, transfer tendency from water to sediment was noticed in the sites having point source. Estimated ecotoxicological risk posed by BPA was higher for edible fishes and for lower order organisms, PAEs was the major contributor.

Bifenazate is a novel acaricide for selective foliar spraying and is widely used to control mites in agricultural production. However, its toxicity to aquatic organisms is unknown. Here, a zebrafish model was used to study bifenazate toxicity to aquatic organisms. Exposure to bifenazate was found to cause severe cardiotoxicity in zebrafish embryos, along with disorders in the gene expression related to heart development. Bifenazate also caused oxidative stress. Cardiotoxicity caused by bifenazate was partially rescued by astaxanthin (an antioxidant), accompanied by cardiac genes and oxidative stress-related indicators becoming normalized. Our results showed that exposure to bifenazate can significantly change the ATPase activity and gene expression levels of the calcium signaling pathway. These led to heart failure, in which the blood accumulated outside the heart without entering it, eventually leading to death. The results indicated that bifenazate exposure caused cardiotoxicity in zebrafish embryos through the induction of oxidative stress and inhibition of the calcium signaling pathway.

Wetland snakes, as top predators, are becoming globally recognised as bioindicators of wetland contamination. Livers are the traditional test organ for contaminant exposure in organisms, but research is moving towards a preference for non-lethal tissue sampling. Snake scales can be used as an indicator of exposure, as many metals bind to the keratin. We used laser ablation with inductively coupled plasma-atomic emission spectroscopy and mass spectrometry (LA-ICP-MS) to quantify the concentrations of 19 metals and metalloids (collectively referred to ‘metals’ hereafter) in Western tiger snake (Notechis scutatus occidentalis) scales from four wetlands along an urban gradient, and compared them to concentrations measured in captive tiger snake scales. We conducted repeat measures to determine the concentration accuracy of each metal using LA-ICP-MS. Concentrations in wild Western tiger snake scales were significantly higher than in reference tiger snake scales for most metals analysed, suggesting accumulation from environmental exposure. We compared the scale concentrations to sediment concentrations of sampled wetlands, and found inter-site differences between mean concentrations of metals in scales parallel patterns recorded from sediment. Four metals (Mn, As, Se, Sb) had strong positive correlations with liver tissue contents suggesting scale concentrations can be used to infer internal concentrations. By screening for a larger suite of metals than we could using traditional digestive methods, we identified additional metals (Ti, V, Sr, Cs, Tl, Th, U) that may be accumulating to levels of concern in tiger snakes in Perth, Western Australia. This research has progressed the use of LA-ICP-MS for quantifying a suite of metals available in snake scales, and highlights the significance of using wetland snake scales as a non-lethal indicator of environmental contamination.

Chemical pollutants, such as pesticides, often leach into aquatic environments and impact non-target organisms. Marine invertebrates have complex life cycles with multiple life-history stages. Exposure to pesticides during one life-history stage potentially influences subsequent stages; a process known as a carry-over effect. Here, we investigated carry-over effects on the jellyfish Aurelia coerulea. We exposed polyps to individual and combined concentrations of atrazine (2.5 μg/L) and chlorpyrifos (0.04 μg/L) for four weeks, after which they were induced to strobilate. The resultant ephyrae were then redistributed and exposed to either the same conditions as their parent-polyps or to filtered seawater to track potential carry-over effects. The percentage of deformities, ephyrae size, pulsation and respiration rates, as well as the metabolic profile of the ephyrae, were measured. We detected a subtle carry-over effect in two metabolites, acetoacetate and glycerophosphocholine, which are precursors of the neurotransmitter acetylcholine, important for energy metabolism and osmoregulation of the ephyrae. Although these carry-over effects were not reflected in the other response variables in the short-term, a persistent reduction of these two metabolites could have negative physiological consequences on A. coerulea jellyfish in the long-term. Our results highlight the importance of considering more than one life-history stage in ecotoxicology, and measuring a range of variables with different sensitivities to detect sub-lethal effects caused by anthropogenic stressors. Furthermore, since we identified few effects when using pesticides concentrations corresponding to Australian water quality guidelines, we suggest that future studies consider concentrations detected in the environment, which are higher than the water quality guidelines, to obtain a more realistic scenario by possible risk from pesticide exposure.

Enhancing and investigating the photocatalytic activity over composites for new models remains a challenge. Here, an emerging S-scheme photocatalyst composed of 2D/0D g-C₃N₄ nanosheets-assisted SnO₂ nanoparticles (g-C₃N₄/SnO₂) is successfully synthesized and used for degrading nitrogen oxide (NO), which causes negative impacts on the environment. A wide range of characterization techniques confirms the successful synthesis of SnO₂ nanoparticles, g-C₃N₄ nanosheets, and 2D/0D g-C₃N₄/SnO₂ S-scheme photocatalysts via hydrothermal and annealing processes. Besides, the visible-light response is confirmed by optical analysis. The S-scheme charge transfer was elucidated by Density-Functional Theory (DFT) calculation, trapping experiments, and electron spin resonance (ESR). We found that intrinsic oxygen vacancies of SnO₂ nanoparticles and S-scheme charge transfer addressed the limitation of other heterojunction types. It is notable that compared pure SnO₂ nanoparticles and g-C₃N₄, g-C₃N₄/SnO₂ offered the best photocatalytic NO degradation and photostability under visible light with the removal of more than 40% NO at 500 ppb throughout the experiment. Benefiting from the unique structural features, the new generation architectural structure of S-scheme heterojunction exhibited potential photocatalytic activity and it would simultaneously act more promising for environmental treatment in the coming years.

Previous studies have shown that accumulation of perfluoroalkyl acids (PFAAs) in the tissues of aquatic species is highly variable. Movement and migration patterns in these species represent an important consideration when evaluating contaminant accumulation in exposed biota, and may have a large influence on the risk profiles for migratory seafood species. In this study, relationships between PFAA concentrations in muscle and liver tissue, and recent fish migration history (inferred from metals profiles in fish otoliths, otherwise known as otolith chemistry) were evaluated in Sea Mullet (Mugil cephalus). A greater number of PFAAs, and higher concentrations, were found in liver compared to muscle tissue. Perfluorooctane sulfonate (PFOS) was present in highest concentrations in both muscle and liver tissues, and there was strong correlation in concentrations between these two tissues. PFOS was found to decrease and increase alongside recent strontium and barium concentrations (respectively) in the otolith, suggesting higher concentrations of PFAAs in fish recently exposed to comparatively lower salinity environments. This study highlights how otolith chemistry can be employed to examine links between contaminant concentrations in fish, and their recent migration history. This approach shows promise for studying contaminant residues in mobile seafood species within the natural environment.

Aquaculture activities in southern Chile demand floating devices to produce electricity powered by diesel generators. It has been recently proposed to replace this fuel with propane. However, little is known about the behaviour and possible environmental impacts of an accidental release of propane underwater. In this study we evaluated the impact of water temperature and salinity on the saturation and further release of propane under controlled laboratory experiments. Results showed that under extreme environmentally relevant scenarios (high and low temperature and salinity), propane saturated the water more quickly. However, while it is important to consider that saturation times can be similar (∼2 h), the magnitudes of propane dissolved can be different. Experiments showed that cold waters (5 °C) propane is dissolved twice than warm waters (20 °C). Residence time was more affected by water temperature and almost independent of water salinity. Propane may take at least 2 days to be released from waters (around 90% of the initial amount dissolved under laboratory conditions).Additionally, we evaluated the impact on dissolved oxygen displacement and the embryotoxicity of the dissolved fraction by using Zebrafish Embryo Toxicity Assay. Results showed that dissolved oxygen was quickly removed. However, the levels of dissolved oxygen were promptly recovered in the studied systems. We also observed that propane can generate genotoxic effects (3–10% mortality), but after 2 days the system can be almost free of propane and the effects may become much lower. Comparatively with the literature, propane showed to be less toxic than diesel and it is a viable and less environmentally hazardous replacement for diesel.

Microcystin-LR (MC-LR) and glyphosate (GLY) have been classified as a Group 2B and Group 2A carcinogens for humans, respectively, and frequently found in aquatic ecosystems. However, data on the potential hazard of MC-LR and GLY exposure to the fish gut are relatively scarce. In the current study, a subacute toxicity test of zebrafish exposed to MC-LR (35 μg L⁻¹) and GLY (3.5 mg L⁻¹), either alone or in combination was performed for 21 d. The results showed that MC-LR or/and GLY treatment reduced the mRNA levels of tight junction genes (claudin-5, occludin, and zonula occludens-1) and altered the levels of diamine oxidase and D-lactic, indicating increased intestinal permeability in zebrafish. Furthermore, MC-LR and/or GLY treatment remarkably increased the levels of intestinal IL-1β and IL-8 but decreased the levels of IL-10 and TGF-β, indicating that MC-LR and/or GLY exposure induced an inflammatory response in the fish gut. MC-LR and/or GLY exposure also activated superoxide dismutase and catalase, generally upregulated the levels of p53, bax, bcl-2, caspase-3, and caspase-9, downregulated the levels of caspase-8 and caused notable histological injury in the fish gut. Moreover, MC-LR and/or GLY exposure also significantly altered the microbial community in the zebrafish gut and the expression of miRNAs (miR-146a, miR-155, miR-16, miR-21, and miR-223). Chronic exposure to MC-LR and/or GLY can induce intestinal damage in zebrafish, and this study is the first to demonstrate an altered gut microbiome and miRNAs in the zebrafish gut after MC-LR and GLY exposure.

The presence of ultrafine plastics particles and its potential to concentrate and transport organic contaminants in aquatic environments have become a major concern in recent years. Specifically, the uptake of hazardous chemicals by plastics particles may affect the distribution and bioavailability of the chemicals. In this study, the adsorption of tetracycline (TC), an antibiotic frequently found in aquatic environments, on high-density polyethylene (PE) particles with the average size of 45 μm, was investigated. The PE particles were characterized for surface acidity for the first time. Results showed that pH controls the surface charge of PE particles. TC adsorption onto PE particles was rapid as expected following the pseudo-second-order rate law (r² > 0.99). Polar forces in addition to specific chemical interactions, such as hydrogen bonding and hydrophophilicity controlled TC adsorption onto PE particles. Parameters, including pH, dissolved organic matter, ionic strength, major cations and anions affected TC adsorption onto PE micro-particles. Results indicated that PE particles can function as a carrier of antibiotics in the aquatic environment, which potentially imposes ecosystem and human health risks.

Knowledge of the toxic potential of polycyclic aromatic hydrocarbons (PAHs) has increased over time. Much of this knowledge is about the 16 United States - Environmental Protection Agency (US - EPA) priority PAHs; however, there are other US – EPA non-priority PAHs in the environment, whose toxic potential is underestimated. We conducted a systematic review of in vitro, in vivo, and in silico studies to assess the genotoxicity, mutagenicity, and carcinogenicity of 13 US - EPA non-priority parental PAHs present in the environment. Electronic databases, such as Science Direct, PubMed, Scopus, Google Scholar, and Web of Science, were used to search for research with selected terms without time restrictions. After analysis, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol, 249 articles, published between 1946 and 2020, were selected and the quality assessment of these studies was performed. The results showed that 5-methylchrysene (5-MC), 7,12-dimethylbenz[a]anthracene (7,12-DMBA), cyclopenta[cd]pyrene (CPP), and dibenzo[al]pyrene (Db[al]P) were the most studied PAHs. Moreover, 5-MC, 7,12-DMBA, benz[j]aceanthrylene (B[j]A), CPP, anthanthrene (ANT), dibenzo[ae]pyrene (Db[ae]P), and Db[al]P have been reported to cause mutagenic effects and have been being associated with a risk of carcinogenicity. Retene (RET) and benzo[c]fluorene (B[c]F), the least studied compounds, showed evidence of a strong influence on the mutagenicity and carcinogenicity endpoints. Overall, this systematic review provided evidence of the genotoxic, mutagenic, and carcinogenic endpoints of US - EPA non-priority PAHs. However, further studies are needed to improve the future protocols of environmental analysis and risk assessment in severely exposed populations.