Understanding of aquaporins (AQPs) facilitating the transport of water and many other small solutes including metalloids like silicon (Si) and arsenic (As) is important to develop stress tolerant cultivars. In the present study, 40 AQPs were identified in the genome of pigeonpea (Cajanus cajan), a pulse crop widely grown in semi-arid region and areas known to affected with heavy metals like As. Conserved domains, variation at NPA motifs, aromatic/arginine (ar/R) selectivity filters, and pore morphology defined here will be crucial in predicting solute specificity of pigeonpea AQPs. The study identified CcNIP2-1 as an AQP predicted to transporter Si (beneficial element) as well as As (hazardous element). Further Si quantification in different tissues showed about 1.66% Si in leaves which confirmed the predictions. Furthermore, scanning electron microscopy showed a higher level of Si accumulation in trichomes on the leaf surface. A significant alleviation in level of As, Sb and Ge stress was also observed when these heavy metals were supplemented with Si. Estimation of relative water content, H₂O₂, lipid peroxidation, proline, total chlorophyll content and other physiological parameters suggested Si derived stress tolerance. Extensive transcriptome profiling under different developmental stages from germination to senescence was performed to understand the tissue-specific regulation of different AQPs. For instance, high expression of TIP3s was observed only in reproductive tissues. Co-expression network developed using transcriptome data from 30 different conditions and tissues, showed interdependency of AQPs. Expression profiling of pigeonpea performed using real time PCR showed differential expression of AQPs after Si supplementation. The information generated about the phylogeny, distribution, molecular evolution, solute specificity, and gene expression dynamics in article will be helpful to better understand the AQP transport system in pigeonpea and other legumes.

Arsenic (As) contamination and bioaccumulation are a serious threat to agricultural plants. To address this issue, we checked the efficacy of As tolerant plant growth promoting bacteria (PGPB), zinc oxide nanoparticles (ZnO NPs) and oxalic acid (OA) in Luffa acutangula grown on As rich soil. The selected most As tolerant PGPB i.e Providencia vermicola exhibited plant growth promoting features i.e solubilzation of phosphate, potassium and siderophores production. Innovatively, we observed the synergistic effects of P. vermicola, ZnO NPs (10 ppm) and OA (100 ppm) in L. acutangula grown on As enriched soil (150 ppm). Our treatments both as alone and in combination alleviated As toxicity exhibited by better plant growth and metabolism. Results revealed significantly enhanced photosynthetic pigments, proline, relative water content, total sugars, proteins and indole acetic acid along with As amelioration in L. acutangula. Furthermore, upregulated plant resistance was manifested with marked reduction in the lipid peroxidation and electrolyte leakage and pronounced antagonism of As and zinc content in leaves under toxic conditions. These treatments also improved level of nutrients, abscisic acid and antioxidants to mitigate As toxicity. This marked improvement in plants’ defense mechanism of treated plants under As stress is confirmed by less damaged leaves cell structures observed through the scanning electron micrographs. We also found substantial decrease in the As bioaccumulation in the L. acutangula shoots and roots by 40 and 58% respectively under the co-application of P. vermicola, ZnO NPs and OA in comparison with control. Moreover, the better activity of soil phosphatase and invertase was assessed under the effect of our application. These results cast a new light on the application of P. vermicola, ZnO NPs and OA in both separate and combined form as a feasible and ecofriendly tool to alleviate As stress in L. acutangula.

Microbial degradation of polycyclic aromatic hydrocarbons (PAHs) is the major channel for their decontamination from different environments. Aerobic and anaerobic biodegradations of PAHs in batch reactors with single or multiple bacterial strains have been intensively studied, but the cooperative mechanism of functional PAH-degrading populations at the community level under field conditions remains to be explored. We determined the composition of PAH-degrading populations in the bacterial community and PAHs in farmland and wasteland soils contaminated by coking plants using high-throughput sequencing and high-performance liquid chromatography (HPLC), respectively. The results indicated that the PAH content of farmland was significantly lower than that of wasteland, which was attributed to the lower content of low molecular weight (LMW) PAHs and benzo [k]fluoranthene. The soil physicochemical properties were significantly different between farmland and wasteland. The naphthalene content was related to the soil organic carbon (SOC) and pH, while phenanthrene was related to the nitrate nitrogen (NO₃⁻-N) and water content (WC). The pH, nitrite (NO₂⁻-N), SOC, NO₃⁻-N and WC were correlated with the content of high molecular weight (HMW) PAHs and total PAHs. The relative abundances of the phyla Actinobacteria, Chloroflexi, Acidobacteria, and Firmicutes and the genera Nocardioides, Bacillus, Lysobacter, Mycobacterium, Streptomyces, and Steroidobacter in farmland soil were higher than those in wasteland soil. The soil physicochemical characteristics of farmland increased the diversities of the PAH degrader and total bacterial communities, which were significantly negatively related to the total PAHs and LMW PAHs. Subsequently, the connectivity and complexity of the network in farmland were lower than those in wasteland, while the module containing a module hub capable of degrading PAHs was identified in the network of farmland soil. Structural equation modelling (SEM) analysis showed that the soil characteristics and optimized abundance and diversity of the bacterial community in farmland were beneficial for the dissipation efficiency of PAHs.

Nowadays, microplastics represent emergent pollutants in terrestrial ecosystems that exert impacts on soil properties, affecting key soil ecological functions. In agroecosystems, plastic mulching is one of the main sources of plastic residues in soils. The present research aimed to evaluate the effects of two types of plastic sheets (un-biodegradable and biodegradable) on soil abiotic (pH, water content, concentrations of organic and total carbon, and total nitrogen) and biotic (respiration, and activities of hydrolase, dehydrogenase, β-glucosidase and urease) properties, and on phytotoxicity (germination index of Sorghum saccharatum L. and Lepidium sativum L.). Results revealed that soil properties were mostly affected by exposure time to plastics rather than the kind (un-biodegradable and biodegradable) of plastics. After six months since mesocosm setting up, the presence of un-biodegradable plastic sheets significantly decreased soil pH, respiration and dehydrogenase activity and increased total and organic carbon concentrations, and toxicity highlighted by S. saccharatum L. Instead, the presence of biodegradable plastic sheets significantly decreased dehydrogenase activity and increased organic carbon concentrations. An overall temporal improvement of the investigated properties in soils covered by biodegradable plastic sheets occurred.

A biological treatment method was tested in laboratory conditions for the removal of hydrocarbons contained in a waste disposal soil sample consisting of excavated sandy soil from a former fueling station. Two fractions of hydrocarbons were quantified by GC-FID: diesel (C₁₀–C₂₁) and lubricant oil (C₂₂–C₄₀). Meat and bone meal (MBM, 1% w/w) was used as a bio-stimulant agent for soil organisms. Cyclodextrin, an oligosaccharide produced from starch by enzymatic conversion, was also used to assess its ability to improve the bioavailability/biodegradability of hydrocarbons in the soil. Parameters such as temperature, pH, water content and aeration (O₂ availability) were monitored and optimized to favor degradation processes. Two different experimental tests were prepared: one to measure the degradation of hydrocarbons; the other to monitor the mobility of some elements in the soil and in the leachate produced by watering with tap water. Soil samples treated with MBM and cyclodextrin showed, over time, a greater removal of the more persistent hydrocarbon fraction (lubricant oil). MBM-treated soils underwent a faster hydrocarbon removal kinetic, especially in the first treatment period. However, the final hydrocarbon concentrations are comparable in all treatments, including control. Over time, the effect of cyclodextrin on hydrocarbon degradation seemed to be relevant. MBM-treated soils sequestered lead in the very first weeks. These results highlight the intrinsic capacity of soil, and its indigenous microbial communities, to degrade petroleum hydrocarbons and suggest that MBM-induced bioremediation is a promising, environmentally friendly technology which should be considered when dealing with hydrocarbon/heavy metal co-contaminated soils.

Contribution of liquid water content (LWC) to the levels of the carcinogenic particulate nitro(so) compounds and the chemistry affecting LWC were investigated based on the observation of seven nitrosamines and two nitramines in rural (Seosan) and urban (Seoul) area in South Korea during October 2019 and a model simulation. The concentrations of both the total nitrosamines and nitramines were higher in Seosan (12.48 ± 16.12 ng/m³ and 0.65 ± 0.71 ng/m³, respectively) than Seoul (7.41 ± 13.59 ng/m³ and 0.24 ± 0.15 ng/m³, respectively). The estimated LWC using a thermodynamic model in Seosan (12.92 ± 9.77 μg/m³) was higher than that in Seoul (6.20 ± 5.35 μg/m³) mainly due to higher relative humidity (75 ± 9% (Seosan); 62 ± 10% (Seoul)) and higher concentrations of free ammonia (0.13 ± 0.09 μmol/m³ (Seosan); 0.08 ± 0.01 μmol/m³ (Seoul)) and total nitric acid (0.09 ± 0.07 μmol/m³ (Seosan); 0.04 ± 0.02 μmol/m³ (Seoul)) in Seosan while neither fog nor rain occurred during the sampling period. The relatively high concentrations of the particulate nitrosamines (>30 ng/m³) only observed probably due to the higher LWC (>10 μg/m³) in Seosan. It implies that aqueous phase reactions involving NO₂ and/or uptake from the gas phase enhanced by LWC could be promoted in Seosan. Strong correlation between the concentrations of nitrosodi-methylamine (NDMA), an example of nitrosamines, simulated by a kinetic box model including the aqueous phase reactions and the measured concentration of NDMA in Seosan (R = 0.77; 0.37 (Seoul)) indicates that the aqueous phase reactions dominantly enhanced the NDMA concentrations in Seosan. On the other hand, it is estimated that the formation of nitrosamines by aqueous phase reaction was not significant due to the relatively lower LWC in Seoul compared to that in Seosan. Furthermore, it is presumed that nitramines are mostly emitted from the primary emission sources. This study implies that the concentration of the particulate nitrosamines can be promoted by aqueous phase reaction enhanced by LWC.

Arsenite [As(III)] toxicity causes impeded growth, inadequate productivity of plants and toxicity through the food chain. Using various chemical residues for priming is one of the approaches in conferring arsenic tolerance in crops. We investigated the mechanism of abscisic acid (ABA)-induced As(III) tolerance in rice genotypes (cv. Swarna and Swarna Sub1) pretreated with 10 μM of ABA for 24 h and transferred into 0, 25 and 50 μM arsenic for 10 days. Plants showed a dose-dependent bioaccumulation of As(III), oxidative stress indicators like superoxide, hydrogen peroxide, thiobarbituric acid reactive substances and the activity of lipoxygenase. As(III) had disrupted cellular redox that reflecting growth indices like net assimilation rate, relative growth rate, specific leaf weight, leaf mass ratio, relative water content, proline, delta-1-pyrroline-5-carboxylate synthetase and electrolyte leakage. ABA priming was more protective in cv. Swarna Sub1 than Swarna for retrieval of total glutathione pool, non-protein thiols, cysteine, phytochelatin and glutathione reductase. Phosphate metabolisms were significantly curtailed irrespective of genotypes where ABA had moderated phosphate uptake and its metabolizing enzymes like acid phosphatase, alkaline phosphatase and H⁺/ATPase. Rice seedlings had regulated antioxidative potential with the varied polymorphic expression of those enzymes markedly with antioxidative enzymes. The results have given the possible cellular and physiological traits those may interact with ABA priming in the establishment of plant tolerance with As(III) over accumulation and, thereby, its amelioration for oxidative damages. Finally, cv. Swarna Sub1 was identified as a rice genotype as a candidate for breeding program for sustainability against As(III) stress with cellular and physiological traits serving better for selection pressure.

Oil-contaminated soils resulted from drilling activities can cause significant damages to the environment, especially for living organisms. Treatment and management of these soils are the necessity for environmental protection. The present study investigates the field study of seven oil-contaminated soils treated by different stabilization/solidification (S/S) methods, and the selection of the best treated site and treatment method. In this study, first, the ratios of consumed binders to the contaminated soils (w/w) and the treatment times for each unit of treated soils were evaluated. The ratios of consumed binders to the contaminated soils were between 6 and 10% and the treatment times for each unit of treated soils were between 4.1 and 18.5 min/m³. Physicochemical characteristics of treated soils were also determined. Although S/S methods didn’t change the water content of treated soils, they increased the porosity of soils. Unexpectedly, the cement-based S/S methods didn’t increase the pH of the treated soils. The highest and the lowest leaching of petroleum hydrocarbons was belonging to S/S using diatomaceous earth (DE) and the combination of Portland cement, sodium silicate and DE (CS-DE), respectively. The best acid neutralization capacity was obtained for soils treated using the combination of Portland cement and sodium silicate (CS). Based on the best-worst multi-criteria decision-making method (BWM-MCDM), the soils treated using CS-DE was select as the best. The BWM-MCDM can be used as an effective tool for the selection of the best alternative in all areas of environmental decontamination.

Understanding the subsurface transport of perfluorooctanoic acid (PFOA) is of considerable interest for evaluating its potential risks to humans and ecosystems. In this study, packed-column experiments were conducted to examine the influence of surface roughness on PFOA transport in unsaturated glass beads, quartz sand and limestone porous media. Results showed decreasing moisture content significantly increased the air-water interfacial adsorption of PFOA and led to greater retardation in all three types of porous media. Particularly, rougher surface (limestone > quartz sand > glass beads) and smaller grain size (i.e. a larger solid specific surface area, SSSA) significantly enhanced PFOA retardation under unsaturated conditions. These results were further supported by bubble column experiments and SSSA analysis of porous media, which demonstrate that except for the factors affecting PFOA transport in solid-water interface (e.g. surface charge and chemical heterogeneity), the greater retardation of PFOA during transport is attributed to the larger air-water interfacial areas associated with rougher surface and smaller grain size and hence greater interfacial adsorption of PFOA. Our results indicated the importance of surface roughness on the retention and transport of PFOA in the unsaturated zone.

Livestock manure is a reservoir of antibiotic resistance genes (ARGs), posing a potential risk to environment and human health. However, there has been no optimization study about the comprehensive composting treatment for livestock manure ARGs based on multiple operation factors. In this study, anaerobic composting of swine manure in light was conducted under different combined conditions of composting time, temperature, water content, pH, heavy metal passivators and wheat straw. The diversity and relative abundance of ARGs in the compost were detected using high throughput quantitative real-time PCR, and the concentrations of antibiotics and heavy metals were determined. The results showed that under the optimized conditions (composting time, 30 d; temperature, 50 °C; water content, 50%; pH 9.0; heavy metal passivators and wheat straw), compared with the control, the detected number of ARGs and mobile genetic elements in the compost was reduced by 45% and 27.3%, and their relative abundance decreased by 33.9% and 36.9%, respectively. Moreover, the exchangeable heavy metal content of the compost declined by 34.7–57.1%, and the antibiotic level decreased by 28.8–77.8%. This study proposes that synergistic effects of key parameters can effectively mitigate the combined contamination of ARGs, antibiotics, and heavy metals in swine manure.Optimized parameters (anaerobic composting time 30 d, temperature 50 °C, water content 50%, pH 9.0) effectively mitigated the combined pollution of ARGs, antibiotics, and heavy metals in swine manure.