Polycyclic aromatic hydrocarbon (PAH) concentrations were determined in four dated sediment cores collected in mud depocenters of the southern Brazilian continental shelf. Core dating results covered the interval between 1925 and 2017. The total PAH concentrations (ΣPAHs) ranged from 44.69 ng g⁻¹ to 305.43 ng g⁻¹ and were similar between the analysed cores. Fine-grained sediments and total organic carbon (TOC) results did not correlate with the ΣPAHs, indicating that the variations in PAH concentrations are mostly related to variations in sources and emissions. PAH source appointment indicated a high input of a natural compound (perylene) and the predominance of anthropogenic PAHs from coal, biomass, and fuel combustion. Alkylated PAHs presented high contributions throughout all cores. The historical deposition of PAHs was associated with different periods of the socio-economic and industrial development of near coastal cities and reflected very well the history of coal production and consumption in the southern region of Brazil. The low levels of ΣPAHs before 1945 in all analysed cores may be related to the beginning of the industrialization process and the lower urbanization degree in the region. Between 1945 and 1965, the gradual ΣPAHs increase reflects the establishment and enlargement of the southern Brazilian industrial sector. The interval between 1965 and 1990 corresponded to the highest ΣPAHs in three of the four analysed cores. After 1990, a relative decrease in the ΣPAHs was observed in most cores and may be related the multiple cuts of incentives to the industrial usage of coal, as well as to Brazil's efforts in environmental regulation for coal extraction and consumption.

The decline of shark populations in the world ocean is affecting ecosystem structure and function in an unpredictable way and new ecological information is today needed to better understand the role of sharks in their habitats. In particular, the characterization of foraging patterns is crucial to understand and foresee the evolution of dynamics between sharks and their prey. Many shark species use the mesopelagic area as a major foraging ground but the degree to which different pelagic sharks rely on this habitat remains overlooked. In order to depict the vertical dimension of their trophic ecology, we used mercury stable isotopes in the muscle of three pelagic shark species (the blue shark Prionace glauca, the shortfin mako shark Isurus oxyrinchus and the smooth hammerhead shark Sphyrna zygaena) from the northeastern Pacific region. The Δ¹⁹⁹Hg values, ranging from 1.40 to 2.13‰ in sharks, suggested a diet mostly based on mesopelagic prey in oceanic habitats. We additionally used carbon and nitrogen stable isotopes (δ¹³C, δ¹⁵N) alone or in combination with Δ¹⁹⁹Hg values, to assess resource partitioning between the three shark species. Adding Δ¹⁹⁹Hg resulted in a decrease in trophic overlap estimates compared to those based on δ¹³C/δ¹⁵N alone, demonstrating that multi-isotope modeling is needed for accurate trophic description of the three species. Mainly, it reveals that they forage at different average depths and that resource partitioning is mostly expressed through the vertical dimension within pelagic shark assemblages. Concomitantly, muscle total mercury concentration (THg) differed between species and increased with feeding depth. Overall, this study highlights the key role of the mesopelagic zone for shark species foraging among important depth gradients and reports new ecological information on trophic competition using mercury isotopes. It also suggests that foraging depth may play a pivotal role in the differences between muscle THg from co-occurring high trophic level shark species.

Atmospheric warming and increasing tropospheric ozone (O₃) concentrations often co-occur in many cities of the world including China, adversely affecting the health status of urban trees. However, little information is known about the combined and interactive effects from increased air temperature (IT) and elevated O₃ (EO) exposures on urban tree species. Here, Ginkgo biloba and Populus alba ‘Berolinensis’ seedlings were subjected to IT (+2 °C of ambient air temperature) and/or EO (+2-fold ambient air O₃ concentrations) for one growing season by using open-top chambers. IT alone had no significant effect on physiological metabolisms at the early growing stage, but significantly increased photosynthetic parameters, antioxidative enzyme activities (P < 0.05). EO alone decreased physiological parameters except for increased oxidative stress. Compared to EO exposure alone, plants grown under IT and EO combined showed higher antioxidative and photosynthetic activity. There was a significant interactive effect between IT and EO on net photosynthetic rate, stomatal conductance, water use efficiency, the maximum quantum efficiency of PSII photochemistry, the actual quantum efficiency of PSII, enzyme activities, aboveground biomass and root/shoot ratio (P < 0.05), respectively. These results suggested that during one growing season, IT mitigated the adverse effect of EO on the tested plants. In addition, we found that G. biloba was more sensitive than P. alba ‘Berolinensis’ to both IT and EO, suggesting that G. biloba may be a good indicator species for climate warming and air pollution, particularly under environmental conditions as they co-occur in urban areas.

With the widespread use of plastics and nanotechnology products, nanoplastics (NPs) have become a potential threat to human health. It is of great practical significance to study and evaluate the distribution of NPs in mice as mammal models and their entry, transport, and cytotoxicity in human cell lines. In this study, we detected the tissue distribution of fluorescent polystyrene nanoplastics (PS-NPs) in mice and assessed their endocytosis, transport pathways, and cytotoxic effects in GES-1 cells. We found that PS-NPs were clearly visible in gastric, intestine, and liver tissues of mice and in GES-1 cells treated with PS-NPs. Entry of PS-NPs into GES-1 cells decreased with the inhibition of caveolae-mediated endocytosis (nystatin), clathrin-mediated endocytosis (chlorpromazine HCl), micropinocytosis (ethyl-isopropyl amiloride), RhoA (CCG-1423), and F-actin polymerization (lantrunculin A). Rac1 inhibitors (NSC 23766) had no significant effect on PS-NPs entering GES-1 cells. F-actin levels significantly decreased in CCG-1423-pretreated GES-1 cells exposed to PS-NPs. GES-1 cell ultrastructural features indicated that internalized PS-NPs can be encapsulated in vesicles, autophagosomes, lysosomes, and lysosomal residues. RhoA, F-actin, RAB7, and LAMP1 levels in PS-NPs-treated GES-1 cells were remarkably up-regulated and the Rab5 level was significantly down-regulated compared to levels in untreated cells. PS-NPs treatment decreased cell proliferation rates and increased cell apoptosis. The formation of autophagosomes and autolysosomes and levels of LC3II increased with the length of PS-NPs treatment. The results indicated that cells regulated endocytosis in response to PS-NPs through the RhoA/F-actin signaling pathway and internalized PS-NPs in the cytoplasm, autophagosomes, or lysosomes produced cytotoxicity. These results illustrate the potential threat of NPs pollution to human health.

Detailed, high resolution time-series observations were performed to investigate sources, diel cycling, natural attenuation, and loadings of dissolved trace metals/metalloids in a subtropical headwater stream draining intensive horticulture in Australia. A transect of ∼3 km away from the source (farms) showed >75% reduction in concentration and loads of most trace elements. Mercury and arsenic had elevated loads downstream relative to other elements. Hourly time-series sampling revealed elevated creek discharge at night, accompanied by elevated nickel, selenium, copper, and mercury loads. Inputs from groundwater or treated sewage used for irrigation within the catchment are likely sources. Groundwater bore and treated sewage samples were highly contaminated with either zinc, copper, or mercury. Comparisons of daily and hourly samples indicated common sampling strategies can underestimate horticultural contaminant loadings. Load estimates for mercury and copper derived from hourly samples were 1.6- to 7- fold greater than loads from daily sample data collected over 79 days with varying rainfall. These high contaminant concentrations and loads are of concern to food products receiving irrigation and protected waterbodies downstream.

Microplastic pollution is a growing concern worldwide. Despite numerous studies showing the occurrence of microplastics in low-trophic level aquatic organisms, microplastic ingestion and contamination in cetaceans, especially those from Asian waters, has been rarely recorded. Here, we investigated stomach microplastic pollution in twelve Indo-Pacific humpback dolphins stranded along the Pearl River Estuary (PRE), China. We also compared microplastic abundances in dolphins stranded near populated urban areas (ZH, n = 6) with those stranded near rural areas (JM, n = 6). Microplastics were detected in all samples, with abundance ranging widely from 11 to 145 items individual⁻¹ (mean ± SD, 53 ± 35.2). Major microplastics were polypropylene and polyethylene fibers, with the size mostly ranging from 1 to 5 mm and the dominant colors of white or transparent. Humpback dolphins from ZH (73 ± 36.8 items individual⁻¹) exhibited a significantly higher average microplastic abundance than those from JM (33 ± 18.3 items individual⁻¹, p < 0.05). In particular, the highest microplastic concentration was identified in the dolphin (SC-ZH01) stranded near the mouth of the Pearl River, whereas the dolphin (SC-JM04) collected at the rural site contained the lowest concentration of microplastics, suggesting the important influence of land-based human activities on the accumulation of microplastics in the PRE. The identification of varied microplastic polymers indicated their complex source scenarios. This study suggests that, as one of top predators in the potential microplastic food chains, this cetacean species could likely serve as an endpoint biomonitoring species of microplastic pollution in the PRE or other similar estuarine ecosystems. Our results highlight the need for more studies towards better understanding the potential impacts of microplastics on this endangered species.

Arsenic (As) is a toxic metalloid and its widespread contamination in agricultural soils along with soil salinization has become a serious concern for human health and food security. In the present study, the effect of cotton shell biochar (CSBC) in decreasing As-induced phytotoxicity and human health risks in quinoa (Chenopodium quinoa Willd.) grown on As-spiked saline and non-saline soils was evaluated. Quinoa plants were grown on As contaminated (0, 15 and 30 mg kg⁻¹) saline and non-saline soils amended with 0, 1 and 2% CSBC. Results showed that plant growth, grain yield, stomatal conductance and chlorophyll contents of quinoa showed more decline on As contaminated saline soil than non-saline soil. The application of 2% CSBC particularly enhanced plant growth, leaf relative water contents, stomatal conductance, pigment contents and limited the uptake of As and Na as compared to soil without CSBC. Salinity in combination with As trigged the production of H₂O₂ and caused lipid peroxidation of cell membranes. Biochar ameliorated the oxidative stress by increasing the activities of antioxidant enzymes (SOD, POD, CAT). Carcinogenic and non-carcinogenic human health risks were greatly decreased in the presence of biochar. Application of 2% CSBC showed promising results in reducing human health risks and As toxicity in quinoa grown on As contaminated non-saline and saline soils. Further research is needed to evaluate the role of biochar in minimizing As accumulation in other crops on normal as well as salt affected soils under field conditions.

As the ubiquitous active components in aquatic environments, low molecular weight organic acids (LMWOAs) have a large influence on the environmental behaviors of contaminants. This research was focused on the effect of different LMWOAs including 11 aliphatic acids and 7 aromatic acids on the photodegradation kinetics of tetracycline (TC), and the development of quantitative structure-activity relationship (QSAR) model. Results showed that TC photodegradation in the presence of LMWOAs fitted pseudo-first-order photolysis kinetics, and the observed photolysis rate constant (kobs) varied from 0.077 to 0.331 h⁻¹. The QSAR model was developed by partial-least-squares (PLS) with using a sequential approach with 25 theoretical molecular descriptors. Four descriptors including ELUMO-EHOMO, ELUMO, CCR and Qmax were found to mechanistically and statistically affect kobs.The high cross validated regression coefficient (Qcum2, 0.898) and high correlation coefficient (R², 0.908) indicated significantly goodness-of-fit and high robustness of the model. The predicted and observed values with high agreement in the defined applicability domain featured accuracy and feasibility of model. This work provided a robust predictive method for estimating the TC photodegradation in the presence of different structures of LMWOAs.

The emergence of clinically relevant β-lactam-resistant bacteria poses a serious threat to human health and presents a major challenge for medical treatment. How opportunistic pathogenic bacteria acquire antibiotic resistance and the prevalence of antibiotic-resistant opportunistic pathogenic bacteria in the environment are still unclear. In this study, we further confirmed that the selective pressure of heavy metals contributes to the increase in ampicillin-resistant opportunistic pathogens in the Xiangjiang River. Four ampicillin-resistant opportunistic pathogenic bacteria (Pseudomonas monteilii, Aeromonas hydrophila, Acinetobacter baumannii, and Staphylococcus epidermidis) were isolated on Luria-Bertani (LB) agar plates and identified by 16S rRNA sequencing. The abundance of these opportunistic pathogenic bacteria significantly increased in the sites downstream of the Xiangjiang River that were heavily influenced by metal mining activities. A microcosm experiment showed that the abundance of β-lactam resistance genes carried by opportunistic pathogenic bacteria in the heavy metal (Cu²⁺ and Zn²⁺) treatment group was 2–10 times higher than that in the control. Moreover, heavy metals (Cu²⁺ and Zn²⁺) significantly increased the horizontal transfer of plasmids in pathogenic bacteria. Of particular interest is that heavy metals facilitated the horizontal transfer of conjugative plasmids, which may lead to the prevalence of multidrug-resistant pathogenic bacteria in the Xiangjiang River.

Ammonia (NH₃) emitted into the atmosphere from agricultural sources may affect nearby sensitive ecosystems due to high dry deposition fluxes on vegetation and soil surfaces, contributing to critical load exceedances. Ammonia fluxes near sources are simulated by either short-range atmospheric models or regional models using large grid cell sizes. However, studies are missing on the comparison of the results simulated by these two types of models. This paper presents the effect of model formalism, input factors, especially grid cell size and wind speed and the choice of deposition threshold on the spatial patterns of NH₃ dry deposition fluxes and deposition threshold exceedances. We used the Eulerian chemistry-transport model CHIMERE and the Gaussian plume model OPS-ST on two study domains characterised by contrasting land use. We showed that the average annual NH₃ dry deposition fluxes over each whole domain are similar for both models. By contrast, NH₃ dry deposition fluxes near sources are higher when simulated with OPS-ST that provides analytical solutions that can be sampled with small grid cell sizes (i.e., from 25 to 1600 m in this study), than with CHIMERE, which uses large grid cell sizes (i.e., 800 and 1600 m). As a result, the spatial patterns of deposition threshold exceedance were very different between both models. These patterns depend mainly on grid cell size, the input factors and the choice of the deposition threshold value. We show that the model formalism has a relatively small effect on the results and that the differences result mainly from the spatial resolutions to which they can be applied. Simulation results must therefore be interpreted carefully, taking into account the simulation conditions.