Archives of Environmental Contamination and Toxicology最新文献

Studies on temporal variation of metal concentrations and their relationship with metal-binding proteins in crocodilians remain scarce. This study aimed to assess interannual changes in physiological (Cu and Zn) and xenobiotic (Hg and Cd) metals, as well as metallothioneins (MTs) levels in blood plasma of 17 semicaptive Morelet’s crocodiles (Crocodylus moreletii) sampled twice (n = 34 samples) in 2016 and 2018. Metal concentrations were quantified in plasma samples, and MTs were measured as biomarkers of metal exposure. Results showed a 1.4-fold increase in Hg and 3.5-fold increase in Cd concentrations over time, possibly reflecting dietary exposure or other unmonitored environmental factors. In contrast, Cu concentrations decreased, while Zn remained stable. MTs levels did not differ significantly between years; however, linear models suggested associations between MTs and both Cu and Cd, highlighting their potential role in homeostasis and detoxification. Although based on a small sample size and limited to plasma, these findings offer insights into metal dynamics under semicaptive conditions and support the value of MTs as candidate biomarkers for future monitoring. Improved temporal frameworks and direct environmental or dietary data are needed to better interpret these trends and support conservation strategies for this endangered species.

Gadolinium (Gd) and Lanthanum (La) are rare earth elements (REEs) widely employed in contemporary technologies due to their unique physicochemical properties. However, their increasing release into aquatic environments has raised concerns about potential ecotoxicological effects. This study assessed the acute biochemical and molecular response of fourth-instar Chironomus sancticaroli larvae exposed to Gd and La at 0.03, 0.30, 3.00, and 30 μg L⁻¹. Exposure to La at 0.03 and 3.00 μg L⁻¹ induced a significant increase in acetylcholinesterase (AChE) activity, suggesting potential neurotoxic effects that may alter synaptic transmission and behavioral responses in larvae, whereas Gd did not affect AChE activity. Furthermore, La inhibited esterase-α activity, while Gd inhibited esterase-β activity in larvae exposed to 0.30, 3.00, and 30 μg L⁻¹, suggesting specific alterations in detoxification and metabolic processing pathways. Both REEs triggered oxidative stress, as evidenced by the increase in catalase and glutathione S-transferase activities at specific concentrations, which may reflect a compensatory response to increased reactive oxygen species. Lipid peroxidation was detected only at the highest La concentration (30 μg L⁻¹), indicating membrane damage and potential impairment of cellular integrity. Gene expression analysis showed downregulation of hemoglobin D across all La concentrations and hemoglobin E across all Gd concentrations, potentially compromising oxygen transport and respiratory efficiency of larvae. These sublethal alterations suggested that C. sancticaroli larvae are sensitive to both elements, with La exerting broader physiological disruption, in addition, these findings rise concern about the ecological risk of REE contamination in freshwater ecosystems.

This study provides comprehensive information on the abundance of microplastics (MPs) in wastewater effluents, sand, and seawater samples collected from areas in Northern Greece. Sampling was conducted over a one-year period to account for seasonal variations in MP abundance. The collected samples were analyzed using microscopic and spectroscopic techniques, yielding valuable insights into the physicochemical characteristics of MPs. MPs concentrations in sand samples ranged from 15.5 ± 6.2 to 174.7 ± 17.3 items kg⁻¹ of dry sand, while the highest concentrations were recorded in winter. Among aqueous matrices, the highest MP concentrations were found in wastewater effluents, ranging from 0.43 ± 0.17 to 1.72 ± 0.45 items L⁻¹, with greater loads detected during wet seasons. In seawater samples, MP abundance ranged from 0.078 ± 0.011 to 0.989 ± 0.35 items m⁻³, with the highest concentrations recorded during the summer season. Regarding polymer identification, the analysis of MPs was conducted using micro-FTIR instrumentation, and the most frequently detected polymers in the examined samples were PE (poly(ethylene), PP (polypropylene), PET (poly(ethylene terephthalate)), and PA (polyamide). Morphological analysis revealed that fibers were the dominant MP shape across all matrices. Size distribution analysis indicated that most MPs particles were small-sized (< 1 mm). The morphological and chemical characteristics of MPs indicate strong links among matrices. SEM-EDX analysis revealed metals on MPs from sand samples, reinforcing these connections. This study investigates MP abundance across environments, uncovering their sources, inter-matrix relationships, and interactions with pollutants, offering insights into patterns of environmental contamination.

This study introduces a non-invasive method for monitoring environmental pollution by analysing metal(loid)s in the faeces of sentinel species. We measured the concentrations of four metal(loid)s, arsenic (As), chromium (Cr), cadmium (Cd), and lead (Pb), in the droppings of four large wading bird species (Little Egret, Great Egret, Reef Heron, and Striated Heron) from 2020 to 2024 in the wetland ecosystem of the Eastern Province of Saudi Arabia, a part of the Central Asian Flyway. Our results revealed significant level of the metal(loid)s in the bird droppings, indicating environmental pollution likely linked to industrial activities, agricultural runoff, and urban expansion. All metal(loid)s exhibited significant temporal variation, with increasing concentrations observed across species. Pb and Cd also showed rising trends but exhibited species-specific effects. While the metal(loid)s analysis confirms exposure and accumulation, it does not by itself allow definitive identification of pollutant sources. Based on previous environmental assessments and land-use data, the studied wetlands are known to be influenced by anthropogenic activities, suggesting that the metal(loid)s in bird faeces predominantly originate from local pollution. However, we acknowledge that further source-tracing analyses would strengthen this inference. This study highlights the need for continuous monitoring of metal(loid)s pollution to safeguard wildlife health and maintain ecological stability. Given the study area’s proximity to industrial zones, these findings advocate for enhanced pollution control measures and targeted management strategies to mitigate risks and conserve wetland habitats.

Invasive aquatic plants threaten the health of aquatic ecosystems, and demand for chemical control is likely to increase as nuisance levels are reached. Diquat is a contact herbicide registered in many countries to control invasive aquatic plants. The objective of our study was to assess the effects of the aquatic herbicide diquat (Reward®) on North American native and non-native plants, algal communities, an amphipod and an amphibian using outdoor mesocosms to simulate natural systems. Our experimental design included a control and five nominal concentrations of diquat ranging from 100% (18.3 L/ha; 1153 µg/L) to 6.4% (1.2 L/ha; 74 µg/L) of the label rate of a single diquat application. Effects of diquat were found to vary among study organisms. All four plant species were negatively affected at all concentrations, exhibiting either mortality or severe reductions in dry biomass (< 1% the biomass of the controls). In contrast, phytoplankton biomass increased 7 d following diquat application concomitant with significant changes in algal community structure. A concentration–response relationship was observed for amphipod survival (LC₅₀ at 6 weeks = 155 µg/L) with 100% mortality in the highest treatment after two weeks. In contrast, diquat had a significant positive effect on tadpole survival, growth and development, possibly because of the higher algal biomass and decaying plant tissues. A lower label rate than currently recommended, at least in waterbodies with low turbidity, could provide effective control of target species while reducing effects on non-target biota.

Microplastics have been found in every part of the planet and in almost every tissue type that has been tested. They are a complex class of pollutants with multiple direct and indirect effects. There is an urgent and growing need to understand their toxicological impacts. Here we measured the effects of two size classes (13.2 µm ± 8.1 and 595.7 µm ± 187.3) of aged polyethylene microplastics, in the presence or absence of copper (10 μg/L), on the behavior of zebrafish and on their ability to respond to a conspecific alarm cue. Additionally, we measured the effects of the microplastics and copper on metal bioaccumulation and induction of metallothionein. Exposure to microplastics decreased the swimming speed of the zebrafish but may have reduced some of the effects of copper. Fish exposed to copper and microplastics had higher swimming velocities than fish exposed to copper alone. However, large microplastics also increased copper bioaccumulation and metallothionein production. Fish that were not exposed to copper decreased their swimming speed after addition of the alarm cue, but there was also an interaction with microplastics. Multivariate analysis of swimming behavior showed that fish exposed to small microplastics and copper formed a distinctive group after addition of the alarm, suggesting that it altered their behavioral responses. Our results show complex interactions between microplastics and copper and highlight the need for comprehensive risk assessment under different environmental scenarios. Fish rely on olfaction to find food and avoid predators. It is well established that metals can inhibit olfaction in fish. Microplastics may interact with metallic pollutants to increase their impact.

Urban freshwater streams across northern latitudes are undergoing increasing salinization due, in part, to road salt inputs during winter months. Road salt contamination has been monitored across Canada for over 40 years; however, the scale of contamination in the Pacific Northwest, which experiences relatively mild and rainy winters, is not well understood. A network of almost 40 water quality loggers in the Lower Mainland of Vancouver, B.C., Canada (VLM) was leveraged to better understand the scale of road salt inputs to local streams and identify factors that influence the magnitude and occurrence of these contamination events. Specific conductance data from these loggers indicate that road salt is entering creeks, resulting in brief salt pulses that typically last 1 day or less. Road salt pulses occur as frequently as three times per week in winter months and can attain maximum chloride concentrations above British Columbia’s acute guideline for chloride (600 mg/L Cl⁻) by as much as 11-fold in streams. The amount of road salt entering creeks is influenced by the extent of impervious surface in the surrounding catchment basin, with more urbanized creeks receiving higher inputs. Interestingly, cumulative salt inputs do not correlate with winter severity and remain consistent even during mild winters. Acute pulses of road salt occur in VLM streams between November and March, coinciding with the spawning and incubation period of locally important Pacific salmon species such as coho and chum salmon. This timing poses a direct risk to developing salmonids, and the benthic invertebrates which sustain them later in development.

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Lead (Pb) poisoning poses a significant threat to wildlife. A primary cause of Pb poisoning is the unintentional ingestion of Pb ammunition and fishing weights, which are still used for hunting and fishing in numerous regions globally. While the effects of Pb poisoning on birds and mammals are well established, impacts on reptiles are less well documented and difficult to assess under field conditions. In this study, we investigated the effects of extreme Pb exposure on captive sub-adult Nile crocodiles (Crocodylus niloticus; n = 18). We administered Pb dosages in the form of fishing weights (54–215 g) and monitored changes in blood lead concentrations, packed cell volumes, urine Pb concentrations, growth, and body condition over a 48-week period. Crocodiles exhibited a remarkable tolerance to exceptionally high Pb exposure over the duration of the study. Despite the lack of obvious clinical signs of Pb toxicity, elevated BPb concentrations were linked to lower PCVs, indicating anaemia across all treatment groups by week eight. However, crocodiles showed a sustained erythropoietic response which may be contributing to their resilience to acute Pb toxicity. While Pb exposure did not significantly affect body condition, it was associated with a discernible reduction in weight gain over the duration of the study. Our estimation of a 5.8–7.3-year timeframe for complete dissolution of the Pb fishing weights in the experimental crocodiles’ stomachs carries significant implications for wild populations, which are likely to be exposed to Pb for far longer than 48-week duration of this study.

This study utilized the methodology of digital soil mapping (DSM) to investigate the spatial prediction of toxic metals and their environmental covariates in the Ghorveh Plain, western Iran. The environmental covariates are defined as the factors that control the distribution of toxic metals at the geographical scale under investigation. They could be used for predicting the sources and monitoring of pollution. A total of 150 soil samples (0–30 cm) were analyzed for toxic metal concentrations and some soil properties. A comprehensive set of environmental variables was obtained from remote sensing imagery, DEM, and ancillary data, which were identified as likely to control the spatial distributions of toxic metals. The genetic algorithm was utilized to identify “all-relevant” environmental covariates for each toxic metal. Three machine learning algorithms, namely random forests (RF), cubist, and regression trees (RT), were employed to establish the statistical relationships between toxic metals and the environmental covariates. The RF model exhibited the most optimal prediction performance. All three models, particularly the RF, demonstrated robust performance, exhibiting minimal impact on the model’s functionality when confronted with alterations in the training and testing data. Consequently, the optimal model, RF, was integrated with a bootstrapping method to generate prediction and uncertainty maps. The soil properties and hydrologic factors were the primary variables influencing the spatial distribution of each toxic metal. This study indicates that the integration of DSM techniques with machine learning models and supplementary datasets offers a viable approach to the generation of maps for monitoring and prioritizing remediation measures in areas contaminated by toxic metals.

Karst water bodies are vital groundwater resources particularly vulnerable to pollution. Protecting their water quality requires documenting contaminants traditionally associated with anthropogenic activities (metals, nutrients, and fecal indicator bacteria) as well as emerging contaminants, such as antibiotic-resistant organisms (AROs) and perfluoroalkyl substances (PFAS). This study detected contaminants in karst-associated water bodies on the Yucatán Peninsula, including 10 sinkholes (cenotes) and one submarine groundwater discharge (SGD) site. The concentrations of metals (strontium, cadmium, nickel, lead), nutrients (phosphate, silicate, ammonium, nitrate, and nitrite), and fecal indicator bacteria (fecal coliforms, Escherichia coli) were consistent with previous reports, sometimes exceeding recommended standards for groundwater or the protection of aquatic life. This included elevated lead (80.3 µg/L) and nitrate (413 μmol/L) concentrations at two cenotes, and elevated E. coli levels (167 – 1800 CFU/100 mL) in five cenotes. Additionally, 34 antibiotic-resistant E. coli strains were identified in nine cenotes and most strains were multidrug-resistant. Perfluorooctanesulfonic acid (PFOS) and perfluorohexanoic acid (PFHxA) were also detected in eight cenotes and the SGD, with total PFAS concentrations from 0.68 to 10.71 ng/L. The absence of associations between contaminants and urban cover suggests karst hydrology influences contaminant cycling—stable isotope signatures (δ¹⁸O, δ²H) confirming that most systems are interconnected to regional groundwater flows, that could allow contaminants to travel long distances. The Yucatán Peninsula’s karst is an important freshwater reservoir used for consumption and recreation; the presence of contaminants and the karst’s vulnerability to their spread raises concerns and highlights the need for continued monitoring and conservation.