In the present study, electrospun nanofiber membranes (ENMs) of polyacrylonitrile (PAN) were modified by dispersing α-Fe₂O₃ nanoparticles, synthesized using a thermal solvent process, in a PAN solution. The morphology and physiochemical properties of the prepared ENMs and the α-Fe₂O₃ were characterized using FESEM, EDX, BET, XRD, FTIR, porosity, and contact angle measurement. XPS was used to investigate the interaction of ENM with arsenate (As(V)) during the adsorption. Moreover, the effect of pH, the equilibrium isotherm, and the kinetics were investigated in batch experiments. The Langmuir isotherm best correlated the experimental results, indicating monolayer adsorption on ENMs, and the kinetics was best fitted, R² > 0.99, by the pseudo-second-order model. In addition, the effects of certain conditions on the filtration performance were examined, such as feed concentration and transmembrane pressure (TMP). By passing sodium hydroxide (0.1 M) for 20 min, the membrane was regenerated. The increase in TMP, along with the presence of co-ions including chloride, nitrate, and sulfate, had negative impacts on the removal of As(V). The results show that the modified ENMs with α-Fe₂O₃ nanoparticles are applicable for As(V) ion removal and possibly for eliminating other heavy metals from aqueous media.

The selection of shade trees with appropriate spacing is important for minimising their impact on nutrient accumulation by understorey cash crops in agroforestry systems. Cocoa trees may be intercropped with overstorey legume or non-legume shade trees. A legume tree and/or a non-legume timber tree with edible kernels (Gliricidia sepium and Canarium indicum, respectively) are used as shade trees in cocoa plantations particularly in Papua New Guinea. This study explored the nutrient concentrations of cocoa beans in response to both tree-shade species and shade-tree spacing regime. The study also investigated the extent to which C. indicum tree spacing altered the nutrient concentrations of canarium kernels. G. sepium trees in the study had a final spacing of 12 m × 12 m while the spacing regimes of either 8 m × 8 m or 8 m × 16 m used for C. indicum. The calcium (Ca) concentrations of cocoa beans did not differ significantly between plants located next to G. sepium and plants located next to C. indicum. Cocoa beans next to C. indicum trees with spacing of 8 m × 16 m had higher potassium (K) concentrations than those next to G. sepium trees. However, phosphorus (P) concentrations of cocoa beans next to C. indicum trees with spacing of 8 m × 8 m or next to G. sepium trees were significantly higher than those next to C. indicum trees with spacing of 8 m × 16 m. The K concentrations in cocoa beans and soil were not correlated nor were the P concentrations in cocoa beans and soil. Correlations between nutrients in leaves and cocoa beans, or between leaves and canarium kernels, were not strong. Our results suggest that cocoa and canarium trees can be intercropped successfully, and that they do not compete for soil nutrients.

Freshwater aquatic environment close to cities and industrial areas is more sensitive than marine environment. The freshwater shellfish Semisulcospira cancellate was introduced as a bioindicator to monitor the heavy metal contamination in the river through ionomic profiles and arsenic speciation. The shellfish samples were collected near four cities along the Xiang River in China. The concentrations of elements including Mg, Al, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Sr, Cd, Sn, Sb, Ba, and Pb were determined using ICP-MS. Multivariate statistical analyses such as Pearson’s correlation analysis and principle component analysis (PCA) were employed to identify the possible sources of the elements in the shellfish samples. Three principle components were extracted from the ionomic matrix and were associated with natural existence, biological pathways, and mining and smelting activities, respectively. The ionomic profiles of the shellfish samples were evaluated through hierarchical cluster analysis (HCA) which was exhibited in the form of heatmap. The shellfish samples were categorized according to the sampling sites with different contamination levels. Six As species including arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), and arsenocholine (AsC) were separated and quantified using HPLC-ICP-MS. The concentrations of As(III) and As(V) were linearly increased with total As concentration increasing. However, the proportion of AsB was decreased with total As while the AsB concentration was irrelevant to total As.

The non-steroidal anti-inflammatory drug (NSAID) diclofenac is one of the most frequently studied as well as controversially discussed pharmaceutically active drug on the subject of its relevance to the environment. This study was conducted to assess the bioconcentration potential of diclofenac and its behavioral and biochemical effects in Daphnia magna. The bioconcentration factors of diclofenac determined after 48 h of aqueous exposure in Daphnia magna were 70.94 and 8.02 for the nominal exposure concentrations of 5 and 100 μg/L, respectively. Diclofenac exposure obviously decreased the filtration and ingestion rates of the daphnids. A significant increase of the acetylcholinesterase activity that was observed in this study indicates that diclofenac might not have neurobehavioral toxicity in Daphnia magna. Significant induction of malondialdehyde content is an indication of overproduction of reactive oxygen species leading to oxidative damage in daphnids after diclofenac exposure. Moreover, significant inhibition of the superoxide dismutase, catalase, and glutathione reductase activities implies that the antioxidant defense system of Daphnia magna was overwhelmed. Also, significant inhibition of glutathione s-transferase activity might point to the fact that the enzyme was not capable to detoxify diclofenac in Daphnia magna. These findings indicate that diclofenac can accumulate and consequently stimulate behavioral and biochemical disturbances in Daphnia magna.

Mercury is a global neurotoxic pollutant, which can be globally transported and bioaccumulated in the food chain. Iron–steel production is one of the most significant sources of anthropogenic atmospheric mercury emission, while information on this source is scarce. Hourly gaseous elemental mercury (GEM) and particle bound mercury (PBM) were studied inside (IP) and at the boundary (BP) of a typical iron–steel plant in the Yangtze River Delta (YRD), China from September 2016 to August 2017. The GEM concentrations were 0.97–503.1 and 0.05–112.6 ng/m³ at the IP and BP sites, respectively, while PBM concentrations were one to four orders of magnitude higher than urban and suburban ambient levels. Several lines of evidences indicated that PBM was mainly originated from the iron–steel manufacturing process, especially from sintering and coke-making processes in this iron–steel plant. However, a combined emission effect contributed to GEM variation. The receptor model of positive matrix factorization (PMF) showed that local direct emissions (coal combustion, industrial activity, vehicle exhaust, and secondary evaporation from polluted soil) contributed 51.3% of the total GEM concentration variation. Potential source contribution function (PSCF) and concentration weighted trajectory (CWT) models clearly showed that air masses moving from areas surrounding YRD had the highest concentrations of atmospheric mercury. These results provided evidence that iron–steel manufacturing emissions have a considerable effect on regional atmospheric mercury concentrations, especially PBM.

Eisenia fetida earthworms were exposed to sub-lethal levels of imidacloprid for 48 h via contact filter paper tests and soil tests. After the exposure, ¹H nuclear magnetic resonance (NMR) metabolomics was used to measure earthworm sub-lethal responses by analyzing the changes in the polar metabolite profile. Maltose, glucose, malate, lactate/threonine, myo-inositol, glutamate, arginine, lysine, tyrosine, leucine, and phenylalanine relative concentrations were altered with imidacloprid exposure in soil. In addition to these metabolites (excluding leucine and phenylalanine), fumarate, ATP, inosine, betaine, scyllo-inositol, glutamine, valine, tryptophan, alanine, tyrosine, and isoleucine relative concentrations shifted with imidacloprid exposure during contact tests. Metabolite changes in E. fetida earthworms exposed to imidacloprid showed a non-linear concentration response and an upregulation in gluconeogenesis. Overall, imidacloprid exposure in soil induces a less pronounced response in metabolites glucose, maltose, fumarate, adenosine-5′-triphosphate (ATP), inosine, scyllo-inositol, lactate/threonine, and tyrosine in comparison to the response observed via contact tests. Thus, our study highlights that tests in soil can result in a different metabolic response in E. fetida and demonstrates the importance of different modes of exposure and the extent of metabolic perturbation in earthworms. Our study also emphasizes the underlying metabolic disruption of earthworms after acute sub-lethal exposure to imidacloprid. These observations should be further examined in different soil types to assess the sub-lethal toxicity of imidacloprid to soil-dwelling earthworms.

The successful phytoextraction of potentially toxic elements (PTEs) from polluted soils can be achieved by growing non-food and industrial crops. Tobacco (Nicotiana tabacum L.) is one of the main industrial crops and is widely grown in many countries. Tobacco can uptake high concentrations of PTEs especially in aboveground biomass without suffering from toxicity. This review highlighted the potential of tobacco for the phytoextraction of heavy metals and tolerance mechanisms under metal stress. Different management practices have been discussed which can enhance the potential of this plant for metal extraction. Finally, suitable options for the management/disposal of biomass enriched in excess metal have been elaborated to prevent secondary pollution.

DDT transformation to DDD in soil is the most commonly reported pathway under anaerobic conditions. A few instances of DDT conversion to products other than DDD/DDE have been reported under aerobic conditions and hardly any under anaerobic conditions. In particular, few reports exist on the anaerobic degradation of DDT in African tropical soils, despite DDT contamination arising from obsolete pesticide stockpiles in the continent as well as new contamination from DDT use for mosquito and tsetse fly control. Moreover, the development of possible remediation strategies for contaminated sites demands adequate understanding of different soil processes and their effect on DDT persistence, hence necessitating the study. The aim of this work was to study the effect of simulated anaerobic conditions and slow-release carbon sources (compost) on the dissipation of DDT in two tropical clay soils (paddy soil and field soil) amenable to periodic flooding. The results showed faster DDT dissipation in the field soil but higher metabolite formation in the paddy soil. To explain this paradox, the levels of dissolved organic carbon and carbon mineralization (CH₄ and CO₂) were correlated with p,p-DDT and p,p-DDD concentrations. It was concluded that DDT underwent reductive degradation (DDD pathway) in the paddy soil and both reductive (DDD pathway) and oxidative degradation (non-DDD pathway) in the field soil.

Oxytetracycline (OTC), a type of tetracycline, was used widely as feeding additive to promote animal growth in breeding industry in the world. Its residue has been found in soils. Based on potted maize experiments, the influences of OTC on soil enzyme activity, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and soil fertility were investigated during the growth stages of maize receiving different fertilizers (spent mushroom substrate, worm manure, and biochar, among others, with single applications and combined applications with their cooperating microbial inoculants). The results showed that OTC negatively affected the soil enzyme activity, MBC, MBN, and cation exchange capacity (CEC). Enzyme activity, MBC, and MBN were more sensitive to OTC than soil fertility. The significant negative correlations were found between OTC concentrations and catalase, MBC, and CEC (p < 0.05). This indicated that the effects of OTC on soil can be alleviated by different fertilizers, and the effects of T6 (microbial inoculants), T7 (microbial inoculants + worm manure), T8 (microbial inoculants + SMS), and T9 (microbial inoculants + biochar) were the best among those of all treatments. During the mature stage of maize, the content of OTC in the soil of T7 was the lowest compared with other treatments. The results provide a good basis for the development of methods to remediate OTC-contaminated soils.

The Environmental Kuznets Curve hypothesis is a theoretical proposition explicating the link between a locality’s income level and environmental degradation. Previous studies estimated the current relationship with an unchanging parameter. However, due to changes in global conomic and political conditions, natural disasters, technological shocks, and implemented policies, the link between income and environmental degradation is about to change. The study investigates the income-pollution nexus for G7 countries—Canada, France, Germany, Italy, Japan, the UK, and the USA—from 1970 to 2014 using a novel methodology: bootstrap panel rolling window causality. In this context, this approach is advantageous for determining the link between income and pollution level in sub-sample periods, rather than assuming an unchanging parameter, and captures the hidden causal linkages between income and environmental pollution. The results confirm the validity of the EKC hypothesis in Japan and the USA, whereas in the other countries, the relationship between EF and GDP exhibits no evidence for an inverted U-shaped pattern.