Wetlands are recognized for the importance of their hydrological function and biodiversity, and there is now a consensus to protect and restore them as well as to complete the knowledge on their functioning. Here, we studied the dissolved organic matter (DOM) of a wetland composed of the Auzon cut-off meander, the Allier River, the alluvial fluvial flow, and watershed aquifer. Water was sampled at different locations, in spring, summer, and autumn. For each sample, DOM was characterized for its chemical and optical properties and its photooxidant capacity through its ability to generate DOM triplet excited states (³DOM*) and singlet oxygen upon simulated solar light exposure. UV-visible and fluorescence indices revealed that DOM was mainly microbial-derived whatever the sampling sites with spatial and temporal variations in terms of aromaticity (5.5–22%), specific UV absorbance at 254 nm (0.28–2.82 L m⁻¹mgC⁻¹), ratio of the absorbance at 254 and 365 nm (4.6–10.8), fluorescence index (1.35–166), and biological index (0.812–2.25). All the samples generated ³DOM* and singlet oxygen, rates of formation of which showed parallel variations. Using principal component analysis (PCA), we found positive correlations between the sensitizing properties of DOM samples and parameters associated to the abundance of low molecular weight and low absorbing chromophores. Moreover, the parameter variation across the wetland reinforced the hydrological movements observed in a previous study, suggesting that these parameters could be used as water connection tracers.

Removal of arsenic from water is of utmost priorities on a global scenario due to its ill effects. Therefore, in the present study, aluminium oxide nano-particles (nano-alumina) were synthesised via solution combustion method, which is self-propagating and eco-friendly in nature. Synthesised nano-alumina was further employed for arsenate removal from water. Usually, pre-oxidation of arsenite is performed for better removal of arsenic in its pentavalent form. Thus, arsenate removal as a function of influencing parameters such as initial concentration, dose, pH, temperature, and competing anions was the prime objective of the present study. The speciation analysis showed that H₂AsO4– and HAsO₄²⁻ were co-existing anions between pH 6 and 8, as a result of which higher removal was observed. Freundlich isotherm model was well suited for data on adsorption. At optimal temperature of 298 K, maximum monolayer adsorption capacity was found as 1401.90 μg/g. The kinetic data showed film diffusion step was the controlling mechanism. In addition, competing anions like nitrate, bicarbonate, and chloride had no major effect on arsenate removal efficiency, while phosphate and sulphate significantly reduced the removal efficiency. The negative values of thermodynamic parameters ΔH° (− 23.15 kJ/mol) established the exothermic nature of adsorption, whereas the negative values of ΔG° (− 7.05, − 6.51, − 5.97, and − 5.43 kJ/mol at 298, 308, 318, and 328 K respectively) indicated the spontaneous nature of the process. The best-fitted isotherm was used to design a batch adsorber to estimate the required amount of aluminium oxide nano-particles for achieving the desired equilibrium arsenate concentration. Nano-alumina was also applied to treat the collected arsenic-contaminated groundwater from actual field. Experimental data were used to develop a neural network–based model for the effective prediction of removal efficiency without carrying out any extra experimentation.

Effects of surface modification by carboxyl group on Pb²⁺ adsorption performances and stability of peanut shell and its extracts (cellulose, lignin, and hemicellulose) were investigated. Stability of the biosorbents was measured by determining organic compound release amount (TOC). Results showed that adsorption capacity of peanut shell and the extract was poor and stability of them was not good enough. Amount of organic compound released from the unmodified sorbents followed the order: cellulose > lignin > peanut shell > hemicellulose. Hemicellulose was the main organic compound release resource for the raw peanut shell. Due to the poor stability of the raw materials, peanut and its extract could not be used directly in the practical waste water treatment. After modification, adsorption capacity of peanut shell, cellulose, lignin, and hemicellulose increased by 4- to 6-folds. Stability of the modified sorbents also increased significantly, and TOC determined for the modified peanut shell, cellulose, and hemicellulose was lower than 4.0 mg L⁻¹ in the optimum pH range from 4.0 to 6.0 even using for 30 days, which was lower than the drinking water standard in China. Modified peanut shell and its extract except for lignin could be used safely in pH ranged from 4.0 to 6.0. Surface modification could improve the adsorption performances and stability of the biosorbents.

Proton adsorption behavior on the surface of Al-substituted goethites as a function of pH and ionic strength was investigated and simulated with the multisite surface complexation (MUSIC) model. In addition, X-ray diffraction, X-ray photoelectron spectroscopy, and field emission scanning electron microscope were used to characterize the crystal structure, chemical composition, micromorphology, and surface properties of the Al-substituted goethite. Al substitution was found to affect the crystal structure and micromorphology of goethite. The morphological differences did not result in significant differences in PZC value but largely affected the surface charge values. Goethite surface charge capacity increased progressively with increasing amount of Al substitution, which was attributed to increases in the density of surface coordinated sites due to the increase in (021)/(110) face ratio. The optimization calculations enabled a satisfactory fitting of the titration data of both pure goethite and Al-substituted goethite, and the MUSIC model facilitated a more specific understanding of the charging behavior of Al-substituted goethite. The singly (≡FeOH⁻⁰.⁵ + ≡AlOH⁻⁰.⁵) and triply coordinated (≡Fe₃O⁻⁰.⁵ + ≡AlFe₂O⁻⁰.⁵) surface groups were most likely responsible for the basic charging behavior of goethite in the pH range of 4–10. All results indicate that the MUSIC model has excellent performance in characterizing Al-substituted goethite, and the model has promising application prospect in other substituted metal (hydr)oxides.

The uncontrolled discharge of organic and inorganic substances causes overenrichment of water bodies by nutrients resulting in eutrophication which disturbs the flora and fauna balance of the lake ecosystem affecting its water quality. Therefore, it is necessary to remove excess nutrients from contaminated lake water. The present investigation was attempted to reduce high organic content and excess nutrients from the sewage-contaminated lake water using microalgae and bacteria in the form of activated sludge. Comparative analyses in three different setups state that maximum efficient removal of nutrients and organic matter (chemical oxygen demand [COD]) was achieved by the symbiotic co-culture than stand-alone cultures of microalgae and activated sludge. The highest removal of nitrates (NO₃⁻) and phosphates (PO₄⁻) was 93% and 99% with maximum removal of COD by 73% in the case of co-culture. The maximum biomass obtained was 7.8 g/L in the co-culture system. Fourier transform infrared spectroscopy confirms the presence of fatty acids and lipids in the microalgae biomass. The effect of cultivation time and pH was studied in optimization for simultaneous biomass production, organic matter reduction and for removal of nutrients using central composite design (CCD) under response surface methodology (RSM). The optimized results were in good agreement with the experimental results. Graphical Abstract

Trace elements’ concentration in the ocean is fast growing and is a source of major concern. Being charismatic and at the top of food chains, seabirds are often used as biological monitors of contaminants. We studied the concentration of trace elements in blood of black-browed albatross from the Falklands Islands, which we here show, by tracking with geolocators, forage over most of the Patagonian Shelf. Levels of trace elements were measured in males and females from two different islands. Blood concentrations of trace elements were not significantly different between islands, which is consistent with observations from foraging behavior revealing that birds from both islands foraged in broadly the same areas in the months before sampling. Arsenic and selenium concentrations in females were higher than in males. Sex-related differences in the concentration of these elements may be related to unknown slight differences in diet or to differences in assimilation between sexes. These results provide reference values for monitoring elemental contamination in the Patagonian Shelf Large Marine Ecosystem using black-browed albatrosses, one of the most abundant top predators and a suitable sentinel for the region’s environmental health.

Scale-up and commercialization of biodiesel is often delimited by costly feedstock that adds up to the process costs. These underlying issues demand the exploration of unconventional cheap feed to improve the process economics. Conversion of waste cooking oil (WCO) into biodiesel could reduce the process costs by 60–70%. However, the continuous exposure to heat during frying leads to oxidation as well increase in the free fatty acid (FFA) content which intensifies the time and energy required for transesterification. The present study analyzes the effect of parameters over the conversion of WCO (with 8.17% FFA) into biodiesel via two-step acid-alkali-based microwave-assisted transesterification. Response surface methodology (RSM) was used to optimize the oil:methanol volume ratio, microwave power, and reaction time during the acid-catalyzed esterification to bring down the FFA below 1%. Microwave irradiation of 250 W, with methanol:oil molar ratio of 19.57:1 [oil:methanol volume ratio of 1.31 (expressed as decimal)] and reaction time of 35 s, resulted in 0.082% of FFA. Alkali-catalyzed transesterification with methanol:oil molar ratio of 5:1 with 2% sodium hydroxide at 65 °C thereby produced fatty acid methyl esters (FAMEs) with the volumetric biodiesel yield of 94.6% in 30 min. Physiochemical properties of the transesterified WCO were well comparable with the biodiesel standards. The study highlights the essentiality of multivariate optimization for the esterification process that could aid in understanding the interactive effects of variables over FFA content. Such studies would benefit in scaling up of the transesterification process at industrial level by improving the economics of the overall bioprocess.

Fertilization with animal manure is one of the main routes responsible for the introduction of antibiotic residues, antibiotic resistance genes, and zoonotic bacteria into the environment. The aim of this study was to assess the effect of the use of pig (swine) manure as a fertilizer on the presence and fate of six antibiotic residues, nine antibiotic resistance genes, and bacteria (zoonotic bacteria Salmonella spp. and Campylobacter spp. and E. coli as indicator for Gram-negative bacterial species of the microbiota of livestock) on five fields. To the best of our knowledge, the present study is the first to assess a multitude of antibiotic residues and resistance to several classes of antibiotics in pig manure and in fertilized soil over time in a region with an intensive pig industry (Flanders, Belgium). The fields were sampled at five consecutive time points, starting before fertilization up to harvest. Low concentrations of antibiotic residues could be observed in the soils until harvest. The antibiotic resistance genes studied were already present at background levels in the soil environment prior to fertilization, but after fertilization with pig manure, an increase in relative abundance was observed for most of them, followed by a decline back to background levels by harvest-time on all of the fields studied. No apparent differences regarding the presence of antibiotic resistance genes in soils were observed between those fertilized with manure that either contained antibiotic residues or not. With regard to dissemination of resistance, the results presented in this study confirm that fertilization with animal manure directly adds resistance genes to the soil. In addition, it shows that this direct mechanism may be more important than possible selective pressure in soil-dwelling bacteria exerted by antibiotic residues present in the manure. These results also indicate that zoonotic bacteria detected in the manure could be detected in the soil environment directly after fertilization, but not after 1 month. In conclusion, although some antibiotic residues may be present in both manure and soil at concentrations to exert selective pressure, it seems that antibiotic resistance is mostly introduced directly to soil through fertilization with animal manure.

This panel study aimed to evaluate the associations between short-term exposure to indoor and outdoor PM₂.₅ and anxiety in schoolchildren. During 3 waves in March, July, and November 2018 with 7 days per wave, 52 children aged 10 years were recruited from two schools in a city in Korea. To assess outdoor exposure, we used PM₂.₅ concentration measures for every hour at the national measurement station (NMS) closest to the two participating schools. To assess indoor exposure, we measured PM₂.₅ concentration at the children’s homes and in classrooms, based on 30-min average. Based on time-activity logs, personal average daily exposure values were calculated for each participant, according to exposure values assessed at 30-min intervals by location. Children’s anxiety was assessed via the Korean version of the State Anxiety Inventory for children every day during each wave. Linear mixed effects model was conducted to analyze the association between PM₂.₅ exposure and anxiety using repeated measurements. Personal exposure to PM₂.₅ by time-activity log was the highest in March and at home. A low correlation coefficient was observed between PM₂.₅ concentrations at home and at the NMS (ρ = 0.36, p < 0.0001) whereas a high correlation coefficient was observed between PM₂.₅ concentrations in classrooms and at the NMS (ρ = 0.64, p < 0.0001). There was no association between PM₂.₅ exposure and anxiety in children based on the analysis of repeated measurements during the study period. Since previous studies reported controversial results, long-term follow-up studies are needed in various regions to further investigate the associations between PM₂.₅ exposure and children’s mental health.

The mining sector has great importance to the economic activity in Brazil. However, it is also responsible for several environmental impacts such as the rupture of the Fundão dam (Mariana, Brazil) that resulted in the spillage of 50 million m³ of mining tailings in the Doce River Basin. This study evaluated the acute and chronic effects of Fundão tailings on growth, development, respiration rates, swimming performance, and avoidance behavior of Lithobates catesbeianus tadpoles. Results showed that 96-h exposure to different dilutions (10, 25, 50, 75, and 100%) of a stock solution containing mining tailings (50 g/L) caused no mortality of tadpoles; however, the most concentrated solution decreased the swimming speed of the animals. After 16 days, tadpoles exposed to 25, 50, and 100% treatments had both swimming speed and distance traveled reduced. Oxygen consumption was also decreased in tadpoles exposed to the 100% solution after 20 days. Avoidance test indicated that tadpoles avoided lower tailing concentrations, but a reduced avoidance response was attested to the higher concentrations, probably due to the toxic effects of the residues that prevented animals’ displacement. Chemical analysis confirmed the occurrence of cadmium (Cd), lead (Pb), iron (Fe), manganese (Mn), zinc (Zn), and aluminum (Al) in Fundão tailings and its presence in the mouth and inside the intestine of treated tadpoles indicated the ingestion of metals by these organisms. This study showed that even presenting low lethal toxicity, long-term exposure to mining tailings from Fundão dam caused morphophysiological and behavioral damage in tadpoles.