Past mining activities have left a legacy of abandoned mine tailing deposits whose metal contaminants poses serious risks to ecosystems and human health. While the development of a vegetated cover in mine tailings can help in mitigating these risks, the local factors limiting plant establishment in these sites are not well understood, restricting phytostabilization efforts. Here, we explore some of the barriers that limit seedling establishment of two species (Vachellia farnesiana and Prosopis velutina) in a mine tailing deposit located in Nacozari, Sonora, Mexico, and assess whether compost addition can help in overcoming these barriers in pot and field experiments. Our field observations found 20 times more carbon and at least 4 times more nitrogen concentration in areas under vegetated patches than in non-vegetated areas, while a previous study found no difference in metal concentrations and other physicochemical parameters. This suggests that organic matter and nutrients are a major limitation for plant establishment. In agreement with this, species failed to establish without compost addition in the field experiment. Compost addition also had a positive effect on biomass accumulation, pH and microbial activity, but increased the substrate soluble concentration of As, Cu, and Zn. Nonetheless, only Cu, K, and Mo in P. velutina accumulated in tissues at levels considered toxic for animal consumption. Our study documents that compost addition facilitated plant establishment for the phytostabilization of mine tailings and help to prevent the dispersion of most metal contaminants via animal consumption. We encourage the use of complementary strategies to minimize the risk of dispersion of metal contaminants.

This work aimed to remove sulfate and acidity from mine-impacted water (MIW) via electrocoagulation (EC), a technique which stands as an advanced alternative to chemical coagulation in pollutant removal from wastewaters. The multiple electrochemical reactions occurring in the aluminum anode and the stainless steel cathode surfaces can form unstable flakes of metal hydroxysulfate complexes, causing coagulation, flocculation, and floatation; or, adsorption of sulfate on sorbents originated from the electrochemical process can occur, depending on pH value. Batch experiments in the continuous mode of exposition using different current densities (35, 50, and 65 A m⁻²) were tested, and a statistical difference between their sulfate removals was detected. Furthermore, the intermittent mode of exposure was also tested by performing a 2²-factorial design to verify the combination with different current densities, concluding that better efficiencies of sulfate removal were obtained in the continuous mode of exposition, even with lower current densities. After 5 h of electrocoagulation, sulfate could be removed from MIW with a mean efficiency of 70.95% (in continuous mode of exposition and 65 A m⁻² current density), and this sulfate removal follows probable third-order decay kinetics in accordance with the quick drop in sulfate concentration until 3 h of exposure time, remaining virtually constant at longer times. Graphical abstract

Paraquat dichloride is a broad-spectrum herbicide used worldwide. It is very fast acting and used to kill a wide range of grasses and broad-leaved weeds. Paraquat dichloride gets run off to aquatic water bodies, and its presence has been reported by various researchers, where its effect is certain on aquatic organisms. Fish are vulnerable to aquatic pollutants as they are in direct contact with their environment. Therefore, our study was designed to evaluate the effects of herbicide paraquat dichloride on histology of vital organs (gills, liver, and kidney) of the fresh water fish Channa punctatus (Bloch). Toxicity effects are evaluated under static renewal test conditions, and histological alterations were detected microscopically. Fish were exposed to acute dose (96hLC₅₀/₂ = 32.93 mg/L) for 96 h of paraquat dichloride. Simultaneous control was also maintained. Principal histopathological alterations in gills during acute exposure showed curling of secondary lamellae, aneurysm, gill bridging, and enlargement of the cartilaginous core. The tissue damages like melanomacrophage centers, pyknotic nucleus, large sinusoidal congestion, and cell fusion are some histological alterations observed in the liver after acute exposure. The changes in histoarchitecture observed in the kidney include an increase in Bowman’s space, necrosis of glomeruli, and damage to collecting duct at acute exposure. The histopathological changes were more prominent with the duration of exposure in the experimental groups. The present study demonstrated that the vital organs exhibited significant damage, among all gill histology specifically got altered being directly exposed to paraquat dichloride. Paraquat dichloride exposure affects the histology of gills, liver, and kidney, thus impairing the vital functions like respiration, excretion, and metabolic regulation which in turn will affect the fish health and is a serious threat. Histopathological alteration in gills, liver, and kidney can be regarded as sensitive biomarkers of paraquat dichloride toxicological manifestations and thus can be utilized for ecotoxicological biomonitoring of aquatic bodies. Graphical abstract

The use of wastewater for agricultural irrigation is a common practice worldwide; long-term use of wastewater can have adverse effects, such as the migration of the anthropogenic dissolved organic matter into the aquifer. Three-dimensional fluorescence spectroscopy (EEM) was used to investigate the characteristics of dissolved organic matter (DOM) in groundwater and irrigation wastewater, to establish the effect of intensive irrigation on the water quality from the aquifer that underlies the area. The fluorescence spectra showed the presence of humic and fulvic acids and anthropogenic organic compounds similar to aromatic proteins and soluble microbial products in wastewater resources. The significant fraction of DOM in groundwater samples are aromatic proteins and soluble microbial products, identical to wastewater. Chlorides and nitrate ion concentrations suggest a local flow system. High levels of TDS are associated with intensive irrigation with residual water and the return irrigation associated with a gradual increase in salts of CO₃²⁻, NO₃⁻, HCO₃⁻, Cl⁻, and SO₄²⁻. The anthropogenic DOM is a useful indicator of water quality management in groundwater based on origin tracking of DOM and changes in organic pollutants. Fluorescence spectroscopy can be used to investigate groundwater pollution characteristics and monitor DOM dynamics in groundwater.

Exposure to suboptimal ambient temperature during pregnancy has been reported as a potential teratogen of fetal development. However, limited animal evidence is available regarding the impact of extreme temperatures on maternal pregnancy and the subsequent adverse pregnancy outcomes. Our objective in this study is to investigate the relationship between temperature and maternal stress during pregnancy in mice. This study used the Naval Medical Research Institute (NMRI) mice during the second and third pregnant weeks with the gestational day (GD) (GD 6.5–14.5 and GD 14.5–17.5). Mice were exposed to suboptimal ambient temperature (1 °C, 5 °C, 10 °C, 15 °C, 40 °C, 42 °C, 44 °C, 46 °C, and 48 °C for the experimental group and 23 °C for the control group) 1 h per day, 7 days a weekin each trimester. Measurements of placental development (placental weight [PW] and placental diameter [PD]) and fetal growth (fetal weight [FW] and crown-to-rump length [CRL]) between experimental and control groups were compared using analysis of variance (ANOVA). Data on the occurrence of preterm birth (PTB) and abnormalities were also collected. The results showed that exposure to both cold and heat stress in the second and third weeks of pregnancy caused significant decreases in measurements of placental development (PW and PD) and fetal growth (FW and CRL). For all temperature exposures, 15 °C was identified as the optimal temperature in the development of the embryo. Most PTB occurrences were observed in high-temperature stress groups, with the highest PTB number seen in the exposure group at 48 °C, whereas PTB occurred only at 1 °C among cold stress groups. In the selected exposure experiments, an approximate U-shaped relation was observed between temperature and number of abnormality occurrence. The highest percentage of these anomalies occurred at temperatures of 1 °C and 48 °C, while no abnormalities were observed at 15 °C and in the control group. Our findings strengthened the evidence that exposure to suboptimal ambient temperatures may trigger adverse pregnancy outcomes and worsen embryo and fetal development in mice.

Heavy metal–contaminated sediment is a common environmental problem. In situ stabilization is an effective and low-cost method to remediate heavy metal–contaminated sediment. In this study, a red mud-based low-cost composite (RMM) was used to stabilize heavy metal–contaminated sediment. RMM was mixed with heavy metal–contaminated sediment at the doses of 0%, 1%, 3% and 5%. The CaCl₂-extractable, DTPA-extractable, leachability (TCLP) and heavy metal fractions were analysed to evaluate the stabilization efficiency of RMM for heavy metals. The selected properties and microbial activities of the sediment were analysed to verify the safety of RMM to sediment. The results showed that RMM reduced the DTPA-, CaCl₂- and TCLP-extractable heavy metals in sediment. At an RMM dose of 5%, DTPA-, CaCl₂- and TCLP- extractable heavy metals were reduced by 7.60%, 72.34% and 69.24% for Pb; 18.20%, 76.7% and 23.57% for Cd; 32.7%, 96.50% and 49.64% for Zn; and 35.0%, 61.20% and 55.27% for Ni, respectively. TCLP- and DTPA-extractable Cu was reduced by 71.15% and 12.90%, respectively. In contrast, CaCl₂-extractable Cu increased obviously after the application of RMM. RMM reduced the acid-soluble fraction of Zn by 6.99% and increased the residual fraction of Ni by 4.28%. However, the influence of RMM on the fractions of Pb, Cd and Cu was nonsignificant. In addition, the application of RMM increased the pH values of the sediment, and the microbial activity in the sediment was also obviously enhanced. These results indicated that RMM has great potential in the remediation of heavy metal–contaminated sediment.

Oil pollution caused by heavy shipping traffic in the Baltic Sea could be removed by the help of highly porous aerogels made from the waste. These could be produced from environmentally friendly cellulose, e.g., from paper waste, but would have to be hydrophobized for oil sorption. Such a cellulose aerogel was investigated in this research work. Six types of aerogel with 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 wt% cellulose with porosities in the range of 96–98% stabilized by unsaturated polyester as cross-linker have been produced. Aerogel’s sorption capacity as well as its regeneration for sorption of crude oil, marine diesel oil, and biodiesel sorption from water surface and mechanical strength has been estimated. It was found out that crude oil sorption capacity reach 29.67 ± 0.39 g g⁻¹, biodiesel—29.07 ± 0.26 g g⁻¹, while marine diesel oil—26.26 ± 0.39 g g⁻¹. The aerogel with 0.5 wt% cellulose shows the best sorption properties after 10 cycles of the sorption.

A heterotrophic nitrification-aerobic denitrification (HN-AD) mixed culture was established as a simulated aquatic ecosystem to investigate the simultaneous removal of aniline and ammonium, as well as the succession of bacterial community. Aniline and ammonium were found to be simultaneously transformed, with maximum removal efficiencies of 99.98% and 89.87%, respectively. The presence of aniline at lower concentrations (0 to 100 mg/L) slightly inhibited ammonium oxidation, whereas further increasing the aniline concentration (from 100 to 500 mg/L) yielded an apparent enhancement effect, increasing the ammonium-N removal rate from 0.33 to 1.26 mg/L/day. In contrast, ammonium-N concentrations of 100 mg/L were able to facilitate aniline removal. Ammonium was the preferred nitrogen source for aniline removal when compared with nitrification metabolites such as nitrate or nitrite. The analysis of microbial community succession using high-throughput sequencing revealed that the microbial diversity generally decreased throughout the aniline and ammonium removal process. Proteobacteria is observed to increase at the climax stage, and the average relative abundances of Pseudomonas, Massilia, and Bacillus were highest at the climax stage and were positively related to the removal rate of aniline and ammonium-N. Surprisingly, the abundance of these microbes at the end stage was almost equal to that observed at the initial stage. This study demonstrated that polluted aquatic ecosystems hold potential for simultaneous removal of pollutants (hazardous organic carbon and ammonium), and have excellent self-rehabilitation abilities.

Chloramination of drinking water and wastewater can generate carcinogenic nitrosamines, among which, nitrosodipropylamine (NDPA) with large molecular weight and weak polarity has been commonly found. However, knowledge on the formation of NDPA remains highly limited. Laboratory tests were conducted to quantify NDPA formation during chloramination of nitrogenous precursors, including dipropylamine and methyldipropylamine, and pesticides such as trifluralin, oryzalin, and vernolat. Results showed that all precursors exhibited > 10.0% NDPA yields after 24 h. Oryzalin and trifluralin accomplished the highest (13.63%) and lowest (11.31%) yield, respectively. Maximal yields of all precursors were observed at pH 9.0 and temperature 288 K. Maximums of NDPA yield from oryzalin (18.27%) and vernolat (19.54%) were formed at Cl:N of 0.7:1.0, but maximal yields of dipropylamine (18.44%), methyldipropylamine (22.98%), and trifluralin (33.06%) were achieved at Cl:N of 1.2:1.0. Maximal NDPA yields of dipropylamine (37.14%), methyldipropylamine (32.84%), and vernolat (49.02%) were observed at [NH₂Cl]₀:[precursor]₀ = 500, but highest yields of trifluralin (30.24%) and oryzalin (25.53%) were accomplished at [NH₂Cl]₀:[precursor]₀ = 50. Bromide and organic contents in tap and raw water reduced NDPA due to competition for NH₂Cl. Chloramination of water impacted by amines and pesticides should be careful of NDPA formation.

In the search for alternatives to bioremediation of soils, this research aimed to analyze the effects of lime, cement, and asphalt as stabilizers on clayey gravel and sand soil contaminated with gasoline in the laboratory. Concentrations of 10–20% of lime, cement, and asphalt were added to the soil. A standard sample was chosen to compare the results obtained in the modified Proctor compaction, California bearing ratio (CBR), direct shear, and consolidation tests. It was found that the presence of more than 10% liquid low–density hydrocarbon affects plasticity, void ratio, friction angle, moisture content, dry density, and cohesion. According to the tests carried out, soils contaminated with concentrations lower than 10% of gasoline are recommended to construct the subgrade and sub-base layers in pavements. Finally, it was found that cement is the stabilizer that presented overall higher enhancements of the mechanical properties of the clayey gravel and sand soil among the three stabilizers. However, the results also show that depending on the soil use and specific parameter requirements, other stabilizers can be used.