The aquifer in Tondiarpet, Chennai, had been severely contaminated with petroleum fuels due to an underground pipeline leakage. Groundwater samples were analyzed quarterly for priority pollutants such as benzene, toluene, ethylbenzene, xylenes, and naphthalene (BTEXN) using purge and trap gas chromatography and mass spectrometer from 2016 to 2018. The maximum concentrations of BTEXN in groundwater at the site were found to be greater than the permissible limits significantly. Among the five sampling locations (MW1, MW2, MW3, MW4, and MW5), mean BTEXN levels were found to be higher near MW2, confirming the source location of petroleum leakage. Human health risk assessment was carried out using deterministic and probabilistic methods for exposure to BTEXN by oral and dermal exposure pathways. Risk analysis indicated that mean cancer and non-cancer risks were many times higher than the allowable limits of 1E-06 and 1 respectively in all age groups (children, teens, and adults), implying the adverse health effects. Oral exposure is predominately contributing (60–80%) to the total health risk in comparison to the dermal exposure route. Variability and uncertainty were addressed using the Monte Carlo simulations and the resultant minimum, maximum, 5th, 95th, and mean percentile risks were predicted. Under the random exposure conditions to BTEXN, it was estimated that the risk would become unacceptable for >98.7% of the exposed population. Based on the sensitivity analysis, exposure duration, and ingestion rate are the crucial variables contributing significantly to the health risk. As part of the risk management, preliminary remediation goals for the study site were estimated, which require >99% removal of the BTEXN contamination for risk-free exposures. It is suggested that the residents of Tondiarpet shouldn’t utilize the contaminated groundwater mainly for oral ingestion to lower the cancer incidence related to exposure to BTEXN.

Compared to marine microplastics research, few studies have bio-monitored microplastics in inland waters. It is also important to understand the microplastics’ uptake and their potential risks to freshwater species. The Australian glass shrimp Paratya australiensis (Family: Atyidae) is commonly found in fresh waterbodies in eastern Australia, and are sensitive to anthropogenic stressors but have a wide tolerance range to the natural environmental conditions. This study aimed to understand the microplastics’ occurrence and types in water samples and the shrimp P. australiensis, and identify if the shrimp could be a suitable bioindicator for microplastic pollution. Surface water and P. australiensis across ten urban and rural freshwater sites in Victoria were sampled. In total, 30 water samples and 100 shrimp were analysed for microplastic content, and shrimp body weights and sizes were also recorded. Microplastics were picked, photographed and identified using FT-IR microscopy: in water samples, 57.9% of items including suspect items were selected to identify; all microplastics found in shrimp samples were identified. Microplastics were present in the surface waters of all sites, with an average abundance of 0.40 ± 0.27 items/L. A total of 36% of shrimp contained microplastics with an average of 0.52 ± 0.55 items/ind (24 ± 31 items/g). Fibre was the most common shape, and blue was the most frequent colour in both water and shrimp samples. The dominant plastic types were polyester in water samples, and rayon in shrimp samples. Even though results from this study show a relatively low concentration of microplastics in water samples in comparison with global studies, it is worth noticing that microplastics were regularly detected in fresh waterbodies in Victoria, Australia. Compared with water samples, shrimp contained a wider variety of plastic types, suggesting they may potentially behave as passive samplers of microplastics pollution in freshwater environments.

The traditional incremental lifetime cancer risk (ILCR) model of urban soil polycyclic aromatic hydrocarbon (PAH) health risk assessment has a large spatial scale and commonly calculates relevant statistics by regarding the whole area as a geographic unit but fails to consider the high heterogeneity of the PAH distribution and differences in population susceptibility and density in an area. Therefore, the risk assessment spatial performance is insufficient and does not reflect the characteristics of cities, which are centered on human activities and serve the needs of humans, thus making it difficult to effectively support PAH prevention and treatment measures in cities. Here, the random forest model combined with the kriging residual model (RFerr-K) is used to estimate high-precision PAH distributions, separately considering the exposure characteristics of children and adults with different susceptibilities, and kindergarten point-of-interest (POI) and population density index (PDI) data were used to estimate the distributions of the kindergarten children and adults in the study area. Through the refined expression of these three dimensions, a new spatially explicit model of the incremental lifetime cancer-causing population distribution (MapPILCR) was constructed, and the risk threshold range delineation method was proposed to accurately identify regional risk levels. The results showed that the RFerr-K model significantly improves the accuracy of PAH prediction. The susceptibility index (SI) of children is 45% higher than that of adults, and POI and PDI data can be used effectively in population distribution estimation. The MapPILCR model provides a useful method for the spatially explicit assessment of the cancer risk of urban populations to inspire urban pollution grid management.

Following the 16TAN Husky oil spill along the North Saskatchewan River (NSR), the occurrence and natural attenuation of the petroleum hydrocarbons were assessed by analyzing the littoral zone sediments/oil debris collected from July 2016 to October 2017. Husky oil-free, mixed sediment-Husky oil, and Husky oil debris samples were identified for all the collected samples. Shoreline sediments were contaminated by mixed biogenic, pyrogenic and petrogenic inputs prior to the spill. Oil stranded on the shoreline of NSR was moved or buried due to the very dynamic conditions of the shoreline, or cleaned through a series of cleanup activities after the spill. Most normal alkanes were naturally weathered, whereas most of the branched alkanes and all of the saturated petroleum biomarkers remained. Some lighter molecular weight (e.g., 2 to 3-ring) polycyclic aromatic hydrocarbons (PAHs) were lost rapidly after the spill, whereas sulfur containing components, e.g., dibenzothiophenes and benzonaphthothiiophenes, and those having a heavier molecular weight did not change markedly even 15 months post-spill. Similarly, some light hydrocarbons (e.g., <C₁₀) were lost over the first kilometers from the point of entry (POE), while heavier hydrocarbons did not show any major differences away from the POE. Very large inter-site and inter-survey discrepancies were found for samples. Evaporation into the air and dissolution into water, combined with biodegradation, were together or independently the main contributors to the loss of the light molecular hydrocarbons.

Perfluorobutanesulfonate (PFBS), an aquatic pollutant of emerging concern, is found to disturb the neural signaling along gut-brain axis, whereas probiotic additives have been applied to improve neuroendocrine function of teleosts. Both PFBS and probiotics can commonly target nervous system. However, whether and how probiotic bacteria can modulate the neurotoxicities of PFBS remain not explored. It is thus necessary to elucidate the probiotic modulation of PFBS neurotoxicity, which can provide implications to the application of probiotic bacteria in aquaculture industry. In the present study, adult zebrafish were exposed to 0, 10 and 100 μg/L PFBS with or without dietary administration of probiotic Lactobacillus rhamnosus. Interaction between PFBS and probiotic along gut-brain axis was examined, covering three dominant pathways (i.e., neurotransmission, immune response and hypothalamic-pituitary-adrenal (HPA) axis). The results showed that, compared to the single effects, PFBS and probiotic coexposure significantly altered the acetylcholinesterase activity and neurotransmitter profiles in gut and brain of zebrafish, with mild effects on neuronal integrity. Neurotransmitters closely correlated reciprocally in intestines, which, however, was distinct from the correlation profile in brains. In addition, PFBS and probiotic were combined to impact brain health through absorption of bacterial lipopolysaccharides and production of inflammatory cytokines. Relative to neurotransmission and immune signaling, HPA axis was not involved in the neurotoxicological interaction between PFBS and probiotic. Furthermore, it needs to point out that interactive modes between PFBS and probiotic varied a lot, depending on exposure concentrations, sex and toxic indices. Overall, the present study provided the first evidence that probiotic supplement could dynamically modulate the neurotoxicities of PFBS in teleost.

Ionic liquids (ILs) are considered as extracting solvents in soil remediation. However, they can be pollutants themselves, and their own toxicities are of concerns. Notably, organisms were exposed to pollutants at random life stages in actual environmental exposure scenario, which is different from the set-up of one uniform life stage in usual experiment designs. The influence of life stages on ILs toxicities will provide essential information on their actual environmental risks. In the present study, effects of 1-ethyl-3-methylimidazolium bromide ([C₂mim]Br) were measured on C. elegans with egg exposure and adult exposure. In egg exposure, [C₂mim]Br increased the lifespan, stimulated initial reproduction and inhibited the total reproduction. Biochemical indices including oxidative stress, antioxidant responses and oxidative damage were further measured to explore the toxicity mechanisms. Results showed that [C₂mim]Br significantly stimulated O₂⁻· as the oxidative stress and superoxide dismutase (SOD) as the antioxidant defense. In adult exposure, [C₂mim]Br inhibited initial reproduction, total reproduction and lifespan. Biochemical results showed that [C₂mim]Br significantly stimulated H₂O₂ and oxidized glutathione (GSSG). The overall findings demonstrated that [C₂mim]Br caused life stage-dependent toxicities on C. elegans. Future studies are still needed for the detailed mechanisms.

The effective mineral absorption and bioreduction were considered as two preferred processes to alleviate the bioavailability and toxicity of toxic trace metals. In this study, the bioreduction of hexavalent chromium (Cr(VI)) on goethite (FeOOH) in the presence of Pseudomonas aeruginosa (P. aeruginosa) was investigated with different environmental factors, including carbon source concentrations, pH, temperature and initial Cr(VI) concentrations. The characterization of FeOOH–P. aeruginosa indicated that P. aeruginosa was surrounded by FeOOH, which could provide the essential iron for bacterial growth and reduce Cr(VI) to Cr(III). The optimal experimental conditions for Cr(VI) (initial concentration: 35 mg L⁻¹) absorption (∼46%) and bioreduction (∼54%) involved a temperature of 45 °C and pH of 5.5. Meanwhile, extracellular polymeric substances (EPS) secreted by P. aeruginosa and its functional groups played important roles in the reduction of Cr(VI). They could reduce Cr(VI) to Cr(III) and transform to Cr(OH)₃ or Feₓ-Cr₍₁₋ₓ₎(OH)₃ precipitation. These results of this study are of significant importance to better understand the environmental geochemical behavior of Cr(VI) with the interactions between soil minerals and microorganisms.

Polycyclic aromatic compounds (PACs) are ubiquitous in the environment. Wildlife (including fish) are chronically exposed to PACs through air, water, sediment, soil, and/or dietary routes. Exposures are highest near industrial or urban sites, such as aluminum smelters and oil sands mines, or near natural sources such as forest fires. This review assesses the exposure and toxicity of PACs to wildlife, with a focus on the Canadian environment. Most published field studies measured PAC concentrations in tissues of invertebrates, fish, and birds, with fewer studies of amphibians and mammals. In general, PAC concentrations measured in Canadian wildlife tissues were under the benzo[a]pyrene (BaP) guideline for human consumption. Health effects of PAC exposure include embryotoxicity, deformities, cardiotoxicity, DNA damage, changes to DNA methylation, oxidative stress, endocrine disruption, and impaired reproduction. Much of the toxicity of PACs can be attributed to their bioavailability, and the extent to which certain PACs are transformed into more toxic metabolites by cytochrome P450 enzymes. As most mechanistic studies are limited to individual polycyclic aromatic hydrocarbons (PAHs), particularly BaP, research on other PACs and PAC-containing complex mixtures is required to understand the environmental significance of PAC exposure and toxicity. Additional work on responses to PACs in amphibians, reptiles, and semi-aquatic mammals, and development of molecular markers for early detection of biological responses to PACs would provide a stronger biological and ecological justification for regulating PAC emissions to protect Canadian wildlife.

Black carbon (BC) as the main component of pollutants in the Arctic plays an important role on regional climate change. In this study, we applied the regional climate-chemistry model, WRF-Chem, to investigate the spatial distribution, transportation, and impact factors of BC in the Arctic. Compared with reanalysis data and observations, the WRF-Chem performed well in terms of the seasonal variations of meteorological parameters and BC concentrations, indicating the applicability of this model on Arctic BC simulation works. Our results showed that the BC concentrations in the Arctic had an obviously seasonalvariation pattern. Surface BC concentrations peaked during winter and spring seasons, while the minimum occurred during summer and autumn seasons. For the vertical distribution, BC aerosols mainly concentrated in the Arctic lower troposphere, and most of BC distributed near the surface during winter and spring seasons and in the higher altitude during other seasons. The seasonality of BC was associated with the seasonal change of meteorological field. During winter, the significant northward airflow prevailing in northern Eurasia caused the transport of accumulated pollutants from this region into the Arctic. The similar but weakened northward airflow pattern and the anticyclone activity during spring can allow pollutants to be transported to the Arctic lower troposphere. Moreover, the more stable atmosphere during winter and spring seasons made BC accumulated mainly near the surface. During summer and autumn seasons, the less stable boundary layer and the cyclone activity in the Arctic facilitated the diffusion of pollutants into the higher altitude. Meanwhile, the higher relative humidity can promote the wet removal process and lead to the relatively lower BC concentrations near the surface. Compared with the seasonal change of emission, our analysis showed that the seasonal variation of meteorological field was the main contributor for the seasonality of BC in the Arctic.

Phosphorus (P) plays a critical role in eutrophication and algal growth; therefore, improving our understanding of the impact of P is essential to control harmful algal blooms. In this study, Microcystis aeruginosa was treated with 5-h ambient irradiation in the medium with different dissolved inorganic P (DIP) concentrations, DIP-free, moderate-DIP, and high-DIP, to explore its growth and other physiological responses. Compared to photosynthetically active radiation (PAR), UV-A (320–400 nm) and UV-B (280–320 nm) radiation had inhibitive effects on the photosynthesis and growth of M. aeruginosa, while high P availability could alleviate or eliminate the negative effects of UV radiation. The photosynthetic parameters had a minimum reduction and quickly recovered after re-inoculation under high-DIP conditions. Confirmed by SEM, photosynthetic pigments, the generation of reactive oxygen species (ROS), superoxide dismutase (SOD) activity and other methods, ambient UV radiation exerted oxidative stresses rather than direct lethal effects on M. aeruginosa. Photosynthetic parameters indicated that algal UV-adaptation processes could include decreasing photo-induced damages and increasing self-repair efficiency. The P acquired by M. aeruginosa cells can have two function, which included alleviating UV-induced negative effects and sustaining algal growth. Consequently, UV-adaptation processes of M. aeruginosa resulted in an elevated demand for DIP, which resulted to increased P uptake rates and cellular P quota under moderate and high-DIP conditions. Therefore, the production of carotenoid and phycocyanin, and SOD activity increased under UV stress, leading to a better adaptation capability of M. aeruginosa and decreased negative effects of UV radiation on its growth. Overall, our findings demonstrated the significant interactive effects of P enrichment and irradiation on typical cyanobacteria, and the strong adaptation capability of M. aeruginosa in the eutrophic UV-radiated waters.