International audience | Many toxicants are present in water as a mixture. Male infertility is one of the environmental impacts in developed countries. Using our rat seminiferous tubule culture model, we evaluated the effects of waters of different origins, on several parameters of the seminiferous epithelium. Concentrated culture medium was diluted with the waters to be tested (final concentrations of the tested waters were between 8 and 80%). The integrity of the blood-testis barrier was assessed by the trans-epithelial electric resistance (TEER). The levels of mRNAs specific of Sertoli cells, of cellular junctions, of each population of germ cells, of androgen receptor, of estrogen receptor α and of aromatase were also studied. We report, here, the results obtained with ten waters, some of them possessing a negative effect on spermatogenesis. The results showed that according to the tested waters, their effects on the parameters studied might be quite different indicating many different mechanisms of toxicity, including some endocrine disrupting effects. It has been reported that men with impaired semen parameters have an increased mortality rate suggesting semen quality may provide a fundamental biomarker of overall male health. Hence, we have developed a relevant in vitro bioassay allowing to evaluate the potential toxicity of different types of waters on male fertility and to assess some aspects of their mechanism of action. In addition to the TEER measure, the number and/or the identity of the studied mRNAs can be largely increased and/or modified, thus enhancing the possibility of using this model as a "warning system".

International audience

Exposure of females to fine particulate matter ≤2.5 μm in diameter (PM2.5) prior to pregnancy could produce adverse impact on fertility and enhances susceptibility of the offspring to a variety of diseases. In the current study, female C57BL/6 mice (6 weeks of age) were exposed to either concentrated PM2.5 or filtered air (average PM2.5 concentration: 115.60 ± 7.77 vs. 14.07 ± 0.38 μg/m⁻³) using a whole-body exposure device for 12 weeks. Briefly, PM2.5 exposure decreased anti-Müllerian hormone level (613.40 ± 17.36 vs 759.30 ± 21.90 pg mL⁻¹, P＜0.01) and increased reactive oxygen species (ROS) level (45.39 ± 0.82 vs 24.20 ± 0.85 arbitrary unit in fluorescence assay, P＜0.01) in oocytes. The exposure increased oocyte degeneration rate (21.5% vs 5.1%, respectively (P＜0.01) and decreased the 2-cell formation rate (71.9% vs 86.0%, P < 0.01). Transcriptome profiling using RNA sequencing showed wide spectrum of abnormal expression of genes, particularly those involved in regulating the mitochondrial respiratory complex in oocytes and metabolic processes in blastocysts. The exposure decreased litter size (6 ± 0.37 vs 7 ± 0.26, P＜0.05) and weight (1.18 ± 0.02 vs 1.27 ± 0.02 g, P＜0.01). In summary, PM2.5 exposure decreased female fertility, possibly through increased ROS production in oocytes and metabolic disturbances in developing embryos. The cause-effect relationship, however, requires further investigation.

Water pollution is an urgent problem that needs to be controlled via green transformation and the development of the Yangtze River Economic Belt (YREB). Based on the water pollutant discharge and socio-economic database of prefecture-level cities in the YREB from 2011 to 2015, this study explores the spatiotemporal variations in water pollutant discharge in the YREB via two main indicators: chemical oxygen demand (COD) and ammonia nitrogen (NH₃–N). Further, the spatial effects and determinants of water pollutant discharge are quantitatively estimated. The results show that (1) the water pollutant discharge in the YREB has decreased significantly, with the COD and NH₃–N discharge reduced by 10.46% and 10.79%, respectively, and the discharge reduction in the lower reaches was the most prominent; (2) the spatial pattern of water pollutant discharge in the YREB was generally stable and partially improved, and cities with a high rate of water pollutant reduction in the YREB were distributed in the main stream region of the Yangtze River and the intersection of the main stream and tributaries; (3) spatial effects had a significant impact on water pollutant discharge in the YREB, with regional cooperation and economic radiation through environmental management and control initially showing a combined reduction trend in regional water pollutants; and (4) determinants of population size and agricultural economic share declined to varying degrees at the end of the study period, although the urbanization level continued to increase, indicating that urbanization in the YREB occurred too quickly and that water pollutant discharge reduction was limited. However, economic development leading to the deterioration of the water environment was alleviated. In addition, foreign direct investment (FDI) inflows and rapid industrialization processes must be monitored to increase the reduction in characteristic water pollutants.

Spatial variation of the levels of polycyclic aromatic hydrocarbons (PAHs) was evaluated within an urban-industrial district where the main anthropogenic pressures are a 15 MW biomass power plant (BPP) and road traffic. The use of a high-density lichen transplant network and wind quantitative relationships made it possible to perform a hierarchical analysis of contamination. Combined uni-bi and multivariate statistical analyses of the resulting databases revealed a dual pattern. In its surroundings (local scale), the BPP affected the bioaccumulation of fluoranthene, pyrene and total PAHs, although a confounding effect of traffic (mostly petrol/gasoline engines) was evident. Spatial variation of the rate of diesel vehicles showed a significant association with that of acenaphthylene, acenaphthene, fluorene, anthracene and naphthalene. The series of high-speed wind values suggests that wind promotes diffusion rather than dispersion of the monitored PAHs. At the whole study area scale, the BPP was a source of acenaphthylene and acenaphthene, while diesel vehicles were a source of acenaphthylene. PAHs contamination strongly promotes oxidative stress (a threefold increase vs pre-exposure levels) in lichen transplants, suggesting a marked polluting effect of anthropogenic sources especially at the expense of the mycobiont. The proposed monitoring approach could improve the apportionment of the different contributions of point and linear anthropogenic sources of PAHs, mitigating the reciprocal biases affecting their spatial patterns.

The black soldier fly (BSF) Hermetia illucens has a strong tolerance to cadmium stress. This helps to use BSF in entomoremediation of heavy metal pollution. Rich metallothionein (MT) proteins were thought to be important for some insects to endure the toxicity of heavy metal. We identified and characterized three MTs genes in BSF (BSFMTs), including BSFMT1, BSFMT2A, and BSFMT2B. Molecular modeling was used to predict metal binding sites. Phylogenetic analysis was used to identify gene families. Overexpression of the recombinant black soldier fly metallothioneins was found to confer Cd tolerance in Escherichia coli. Finally, functions of BSFMTs in BSF were explored through RNA interference (RNAi). RNAi results of BSFMT2B showed that the larval fresh weight decreased significantly, and the larvae mortality increased significantly. This study suggests that BSFMTs have important properties in Cd detoxification and tolerance in BSF. Further characterization analyses of physiological function about metallothioneins are necessary in BSF and other insects.

When the total ambient PM₂.₅ levels are several-fold higher than the recommended limit, it may be important to study the distributions of different sizes of particulate matter (PM). Here, we assess the distributions of various sizes of total PM₂.₅ for 12 months (on a monthly basis) in New Delhi, India. Importantly, we found that ultrafine particles (i.e., particles <0.5 μm) contribute significantly to total PM₂.₅. PM<₀.₂₅ were the most cytotoxic particles to human lung epithelial cells in all the 12 months. In addition, PM<₀.₂₅ were associated with significantly higher cytotoxicity per unit mass compared to other size fractions constituting PM₂.₅. For any given size of PM, the amount of reactive oxygen species (ROS) generated per unit mass is higher for the month of March as compared to that for the rest of the months in the year. The higher ROS generations for all sizes of PM collected in the month of March was not explained by differences in their metal content values. Our data suggests the lack of correlation between total PM₂.₅ levels and the highly cytotoxic PM<₀.₂₅. In summary, this work establishes the need for policy changes to routinely monitor PM<₀.₂₅ and the necessity to establish exposure limits for PM<₀.₂₅, especially when the total PM₂.₅ levels are breached.

Precious metal mining activities have left complex environmental legacies in lakes around the world, including some sites in climatically sensitive regions of the Canadian sub-Arctic. Here, we examined the long-term impacts of past regional gold mining activities on sub-Arctic lakes near Con Mine (Yellowknife, Northwest Territories) based on sediment core analysis (paleolimnology). In addition to receiving metal(loid)s from roaster stack emissions, the study lakes were also influenced by salt-rich mine drainage from Con Mine tailings. Water samples from these lakes had some of the highest concentrations for salinity-related variables (e.g. Ca²⁺, Cl⁻, Na⁺) and metal(loid)s (e.g. As, Cu, Ni, Sb) in the Yellowknife area. Furthermore, the presence of halophilic diatom (Bacillariophyceae) taxa (Achnanthes thermalis and Navicula incertata) in the recent sediments of Keg and Peg lakes suggest that the extreme saline conditions are strongly influencing the present biota, more than 10 years after the cessation of gold mining activities at Con Mine. The sedimentary metal(loid) profiles (e.g. As, Cu, Ni) of Kam Lake tracked the influence of regional gold mining activities, particularly those at Con Mine, while the algal assemblages recorded the biological responses to salinization and metal(loid) pollution (e.g. marked decreases in diatom species richness, Hill’s N2 diversity, and chrysophyte cyst:diatom valve ratio). At Kam Lake, the algal assemblage changes in the post-mining era were indicative of climate-mediated changes to lake thermal properties (e.g. rise in planktonic diatoms), nutrient enrichment related to urbanization (e.g. increase in eutrophic Stephanodisucs taxa), and/or a combination of both stressors. The lack of biological recovery (i.e. return to pre-mining assemblages) is consistent with investigations of mine-impacted lakes in temperate regions where elevated contaminant levels and emerging stressors (e.g. climate warming, land-use changes) are influencing lake recovery.

Hydrodynamic conditions often affect the eutrophication process and play a key role in algal growth in reservoirs. A promising approach for controlling algal blooms in reservoirs is to create adverse hydrodynamic conditions by implementing reservoir operation strategies. However, research on this method is still nascent and does not support practical applications due to the lack of quantitative hydrodynamic thresholds. In this paper, field observations of algal growth from April 2015 to August 2016 were conducted, and a three-dimensional (3D) model that couples hydrodynamics and water temperatures for the Zipingpu Reservoir was established. Low flow velocities (V) and low Reynolds numbers (Re) in the Longchi tributary are favorable for dinoflagellate growth and accumulation, which can explain why dinoflagellate blooms are more likely to occur in the tributary. A temperature of 18–22 °C is considered a precondition for Peridiniopsis penardii blooms, suggesting that freshwater dinoflagellate species may prefer lower temperatures than marine dinoflagellate species. Shallow mixing layer depth (Zₘᵢₓ) is conducive to Peridiniopsis penardii gathering in the upper water layers and promotes growth. The shallow euphotic layer depth (Zₑᵤ) was speculated to promote the dominance of this species by stimulating its heterotrophy and inhibiting other algal autotrophy. Furthermore, a boundary line analysis was introduced to characterize the relationships between algal biomass and hydrodynamic indicators. Thus, the thresholds for V, Re, and Zₘᵢₓ/Zₑᵤ were determined to be 0.034 m s⁻¹, 6.7 × 10⁴, and 1.7, respectively. Either accelerating horizontal flow to exceed the thresholds of V and Re or facilitating vertical mixing to exceed the threshold of Zₘᵢₓ/Zₑᵤ can prevent dinoflagellate blooms. Therefore, the summarized hydrodynamic threshold system is suggested to be an effective standard for controlling dinoflagellate blooms in the reservoir. Moreover, this study can provide a useful reference for understanding the mechanism of freshwater dinoflagellate blooms.

Anthropogenic activities significantly influence the lake environment and are reflected by the element contents in sediments/soils. The lake fragmentation provides a unique opportunity for comparing the influences of natural/anthropogenic activities of different wetlands systems. In this study, a complex and fragmented lake was investigated, and sediment/soil samples were collected from different systems. The nutrient contents (C, N, and P), stable isotopic compositions (δ¹³C and δ¹⁵N), and trace metal contents (As, Cd, Cr, Cu, Ni, Pb, and Zn) in the sediments/soils were measured to determine the natural and anthropogenic influences and pollution sources. Lake fragmentation was caused by insufficient water input and long-term agricultural and aquacultural activities of local residents. Due to the effect of anthropogenic activities, the enrichment conditions of various elements differed significantly for different wetland systems. Industrial, agricultural, and biological sources significantly influenced the element enrichment in different systems. The results demonstrated that the anthropogenic activities significantly influenced the sediments/soils in wetland systems, and the lake fragmentation reduced the diffusion of the contaminants. These results provide accurate reference information for pollution control, lake management, and ecological restoration.