The anaerobic digestion of wastewater rich in volatile fatty acids (VFAs) provides a sustainable approach for methane production whilst reducing environmental pollution. However, the anaerobic digestion of VFAs may not be stable during long-term operation under a short hydraulic retention time. In this study, conductive carbon cloth was supplemented to investigate the impacts on the anaerobic digestion of VFAs in wastewater sourced from dark fermentation. The results demonstrated that the failure of anaerobic digestion could be avoided when carbon cloth was supplemented. In the stable stage, the methane production rate with carbon cloth supplementation was improved by 200–260%, and the chemical oxygen demand (COD) removal efficiency was significantly enhanced compared with that in the control without carbon cloth. The relative abundance of potential exoelectrogens on the carbon cloth was increased by up to 8-fold compared with that in the suspension. Electrotrophic methanogens on the carbon cloth were enriched by 4.2–17.2% compared with those in the suspension. The genera Ercella and Petrimonas along with the methanogenic archaea Methanosaeta and Methanosarcina on the carbon cloth may facilitate direct interspecies electron transfer, thereby enhancing methane production.

Acid deposition has been regarded as a serious factor in the deteriorative water environment and ecosystems. Despite the powerful acid emission control measures have been implemented by the Chinese government, many areas (especially Southeast China) are still suffering from acid deposition. The chemical and isotopic (δ³⁴S and ⁸⁷Sr/⁸⁶Sr) compositions of rainwater in Hangzhou, a typical megacity in Southeast China with serious acid rain problem, for one year were studied with the aim to better constrain potential sources and explore the causes of rainwater acidification. Most rainwater samples were acidic, with a VWM pH value of 4.65. SO₄²⁻ was the dominant anion and the main acid ion in rainwater. Sulfur isotope and the quantity equilibrium model revealed that sea salt, crustal, biogenic, and anthropogenic sulfur represented 2.3%, 0.1%, 16.7%, and 80.8% of the SO₄²⁻ source in rainwater, respectively. The back trajectory and strontium isotopes indicated that the base cations (BCs) in rainwater originated mainly from anthropogenic sources. The relatively low neutralizing capacity caused by limited BCs input and emission control measures undermines some efforts to reduce rainwater acidity. This case study demonstrated that a valuable tool to probe the source of acid rain and unravel the mechanism of rainwater acidification can be provided by multiple lines of evidence, including rainwater chemical compositions, stable sulfur isotopes, and stable strontium isotopes.

In this study, heterojunction photocatalysts, XAg@C-TCZ, based on MOF-derived C–TiO₂ and Cd₀.₅Zn₀.₅S decorated with Ag nanoparticles (Ag NPs) were successfully synthesized through hydrothermal and calcination methods. The catalytic effectiveness of XAg@C-TCZ was evaluated by simultaneous photocatalytic degradation of rhodamine B (RhB) and reduction of Cr(VI) under simulated sunlight irradiation. The presence of the Z-scheme heterojunction was demonstrated through trapping experiments, X-ray photoelectron spectroscopy (XPS), time-resolved photoluminescence (PL) investigations, and electron spin resonance (ESR) spectroscopy. With an initial RhB and Cr(VI) concentration of 7 mg L⁻¹ and 5 mg L⁻¹, the catalyst 10Ag@C-TCZ achieved a simultaneous removal of 95.2% and 95.5% within 120 min, respectively. With the same catalyst, the degradation rate of RhB was 2.75 times higher and the reduction rate of Cr(VI) was 9.3 times higher compared to pure Cd₀.₅Zn₀.₅S. Total organic carbon (TOC) analysis confirmed the extent of mineralization of RhB, while the reduction of Cr(VI) was corroborated by XPS. Compared to pure RhB and Cr(VI) solutions, the reaction rates are smaller in the solution containing both contaminants, which is attributed to the competition for ·O₂⁻. 10Ag@C-TCZ also exhibited a stable catalytic performance in tap water and lake water. This work provides a new perspective on the construction of heterojunctions with doped MOF derivatives for the purification of complex pollutant systems.

The wide range of industrial applications of chromium (Cr) has led to an increasing risk of water contamination by Cr(Ⅵ). However, efficient methods to remove or decrease the toxicity of Cr(Ⅵ) in situ are lacking. The main aim of this study was to investigate the mechanisms by which selenite alleviates chromium(Ⅵ)-induced toxicity in Chlamydomonas reinhardtii. Our results showed that K₂Cr₂O₇ had toxic effects on both the structure and physiology of C. reinhardtii in a dose-dependent manner. Adding selenite significantly alleviated chromium accumulation and toxicity in cells. RNA-seq data showed that the expression level of selenoproteins such as SELENOH was significantly increased. Both SELENOH-amiRNA knockdown mutants and selenoh insertional mutant produced more reactive oxygen species (ROS) and grew slower than the wild type, suggesting that SELENOH can reduce chromium toxicity by decreasing the levels of ROS produced by Cr(Ⅵ). We also demonstrated that selenite can reduce the absorption of Cr(Ⅵ) by cells but does not affect the process of Cr(Ⅵ) adsorption and efflux. This information on the molecular mechanism by which selenite alleviates Cr(Ⅵ) toxicity can be used to increase the bioremediation capacity of algae and reduce the human health risks associated with Cr(Ⅵ) toxicity.

Investigating environmental pollution is important to understand its impact on endangered species such as green turtles (Chelonia mydas). In this study, we investigated the accumulation and potential toxicity of selected persistent organic pollutants (POPs) and naturally occurring MeO-PBDEs in liver, fat, kidney and muscle of turtles (n = 30) of different gender, size, year of death, location and health status. Overall, POP concentrations were low and accumulation was highest in liver and lowest in fat which is likely due to the poor health of several animals, causing a remobilization of lipids and associated compounds. PCBs and p,p’-DDE dominated the POP profiles, and relatively high MeO-PBDE concentrations (2′-MeO-BDE 68 up to 192 ng/g lw, 6-MeO-BDE 47 up to 79 ng/g lw) were detected in all tissues. Only few influences of factors such as age, gender and location were found. While concentrations were low compared to other marine wildlife, biological toxicity equivalences obtained by screening the tissue extracts using the micro-EROD assay ranged from 2.8 to 356 pg/g and the highest values were observed in muscle, followed by kidney and liver. This emphazises that pollutant mixtures found in the turtles have the potential to cause dioxin-like effects in these animals and that dioxin-like compounds should not be overlooked in future studies.

Most chemical plant wastewater contains both organic and inorganic pollutants, which are easy to diffuse along with surface runoff. The combined pollution of nonylphenol (NP) and cadmium (Cd) in soil is a serious problem that has not attracted enough attention. Based on the effects of selenium (Se) and Pseudomonas aeruginosa (P. aeruginosa) on plant and soil microbial communities, we speculated that the application of Se and P. aeruginosa in soil could improve the phytoremediation efficiency of ryegrass on contaminated soil. In this study, pot experiments with Cd and NP co-contaminated soil were conducted, and the results showed that application of P. aeruinosa alone could improve the removal rates of NP and Cd by ryegrass, and the supplementary of Se further enhanced the effect of micro-phyto remediation, with the highest removal rates of NP and Cd were 79.6% and 49.4%, respectively. The application of P. aeruginosa plus Se reduced the adsorption of Cd and NP through C–O and Si–O–Fe of the soil, changed the enzyme activity, and also affected the changing trend of the microbial community in soil. Pseudomonas, Sphingomonadales, Nitrospira, and other beneficial bacteria were enriched after a 60-day period with P. aeruginosa and Se treatment, thus promoting the removal of NP and Cd. In light of the above results, we suggest that P. aeruginosa application can efficiently facilitate the phytoremediation of ryegrass on Cd-NP co-contaminated soil, and Se supplementation in soil showed the synergistic effect on the remediation.

Agricultural use of organochlorine pesticides (OCPs) increased during the twentieth century but many of them have been progressively banned several decades after their introduction. Nevertheless, these lipophilic chemical compounds may persist in soils and sediments. From sediment deposits, it is possible to reconstruct the chronology of OCP releases in relation to former applications through time. Nevertheless, long-term fate of OCPs i.e. source, transfer, and storage through the watershed, is also related to the OCPs-sediment characteristics interactions, and our study showed the significant links between OCPs and labile or refractory organic matter. From sediment cores collected in a mainly agricultural watershed, the Eure River watershed (France), aldrin and lindane widespread applications during the 1950s–1970s have been recorded. While lindane applications declined after that date, according to the temporal trend of the stable isomer of hexachlorocyclohexane (β-HCH), α-, and γ-HCH have been recorded at significant levels in the 2000s, suggesting first local post-ban applications. Nevertheless, the relationships between these OCPs and labile organic matter resulted in an overestimation of the post-ban releases. Also, the detection of stable metabolites of dichlorodiphenyltrichloroethane (DDT) (i.e. 4,4′-DDE) and heptachlor (i.e. heptachlor epoxide) several decades after their ban, revealed the role of old deep soils erosion in the chronology of OCP releases and thus the reemergence of stable transformation products from historical OCPs.

Recent epidemiological studies have explored effects of light at night (LAN) exposure on breast cancer, but reported inconsistent findings. We performed a systematic review and meta-analysis of available evidence regarding the association of LAN assessed by satellite data with breast cancer. We conducted a systematic PubMed, Web of Science, and EMBASE database literature search until August 2020. Random-effects meta-analysis was applied to synthesis risk estimates. Heterogeneity was measured using statistics of Cochran’s Q, I², and Tau² (τ²). We assessed publication bias through funnel plot and Egger’s test. Moreover, subgroup analyses according to study design and menopausal status were performed. Risk of bias (RoB) of each included study was assessed using a domain-based RoB assessment tool. The confidence in the body of evidence was appraised using the GRADE approach for level-of-evidence translation. A total of 1157 studies were identified referring to LAN and breast cancer, from which 6 were included for quantitative synthesis. We found a significantly higher odds of breast cancer in the highest versus the lowest category of LAN exposure (OR = 1.11, 95% CI: 1.06, 1.16; I² = 0.0%). In the subgroup analyses stratified by menopausal status and study design, significant association was found in postmenopausal women (OR = 1.07, 95% CI = 1.00, 1.13) and cohort studies (OR = 1.11, 95% CI = 1.05, 1.18), while the summary estimates of premenopausal women and case-control studies showed no significance. The level of evidence for the association of LAN exposure and breast cancer risk was graded as “moderate” with “probably low” RoB according to the NTP/OHAT framework. In conclusion, this study suggests a link of LAN exposure with risk of breast cancer. Further high-quality prospective studies, especially performed in low-to middle-income countries with improvement in the area of LAN exposure assessment are needed to advance this field.

Biodiesel side stream waste glycerol was identified as a cheap carbon source for rhamnolipids (RLs) production which at the same time could improve the management of waste. The present study aimed to produce RLs by using Pseudomonas aeruginosa RS6 utilizing waste glycerol as a substrate and to evaluate their physico-chemicals properties. Fermentation conditions such as temperature, initial medium pH, waste glycerol concentration, nitrogen sources and concentrations resulted in different compositions of the mono- and di-RLs produced. The maximum RLs production of 2.73 g/L was obtained when P. aeruginosa RS6 was grown in a basal salt medium supplemented with 1% waste glycerol and 0.2 M sodium nitrate at 35 °C and pH 6.5. At optimal fermentation conditions, the emulsification index (E₂₄) values of cooking oil, diesel oil, benzene, olive oil, petroleum, and kerosene were all above E₂₄₌50%. The surface tension reduction obtained from 72.13 mN/m to 29.4–30.4 mN/m was better than the surface activity of some chemical-based surfactants. The RLs produced possessed antimicrobial activities against Gram-negative and Gram-positive bacteria with values ranging from 37% to 77% of growth inhibition when 1 mg/mL of RLs was used. Concentrations of RLs below 1500 μg/mL did not induce phytotoxicity effects on the tested seeds (Vigna radiata) compared to the chemical-based- surfactant, SDS. Furthermore, RLs tested on zebrafish (Danio rerio) embryos only exhibited low acute toxicity with an LC₅₀ value of 72.97 μg/mL at 48 h of exposure suggesting a green and eco-biochemical worthy of future applications to replace chemical-based surfactants.

A large amount of tetracycline (TC) persists in water, soil, food, and feed due to the overuse of antibiotics, causing serious environmental problems such as damage to ecosystems and posing risks to human health. Thus, there is an urgent need to find a method to detect TC that is practical, rapid, sensitive, and offers ready visualization of TC levels so that adequate remediation measures can be immediately implemented. Herein, we report a fluorescent and colorimetric dual-mode nanosensor for the detection of TC based on reduced state carbon dots (r-CDs). In the presence of TC, the emission fluorescence of r-CDs was quenched by the Förster resonance energy transfer mechanism to achieve high-sensitivity detection of TC with a low limit of detection (LOD) of 1.73 nM. Moreover, TC was also detected by r-CDs via a noticeable color change of the solution (from colorless to red) with the naked eye, having an LOD of 0.46 μM. Furthermore, r-CDs have excellent selectivity and sensitivity in detecting TC in wastewater, and therefore, have practical applications in wastewater treatment. The fluorescent and colorimetric dual-mode proposed in this work may offer a unique idea for the detection of TC, with great prospects for environmental wastewater applications.