Three types of labeled silica nanoparticles were used in transport experiments in saturated sand. The goal of this study was to evaluate both the efficiency of labeling techniques (fluorescence (FITC), metal (Ag(0) core) and radioactivity (110mAg(0) core)) in realistic transport conditions and the reactive transport of silica nanocolloids of variable size and concentration in porous media. Experimental results obtained under contrasted experimental conditions revealed that deposition in sand is controlled by nanoparticles size and ionic strength of the solution. A mathematical model is proposed to quantitatively describe colloid transport. Fluorescent labeling is widely used to study fate of colloids in soils but was the less sensitive one. Ag(0) labeling with ICP-MS detection was found to be very sensitive to measure deposition profiles. Radiolabeled (110mAg(0)) nanoparticles permitted in situ detection. Results obtained with radiolabeled nanoparticles are wholly original and might be used for improving the modeling of deposition and release dynamics.

Organic complexing agents, such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA) and picolinic acid, have been widely used at nuclear sites and are therefore found as common co-contaminants in radioactive contaminated land. This study has explored the mechanisms by which these three complexing agents affect the sorption of Th(IV) to pure silica and a natural sand. EDTA, NTA and, to a lesser extent, picolinic acid decreased the sorption of Th to silica, demonstrating the formation and solubility of Th complexes. However, Th sorption to sand was kinetically controlled and complexation enhanced the rate of Th sorption. EDTA and NTA did not sorb significantly to the sand, and metal desorption indicated that the mechanism involved exchange with sand-associated metals. At equilibrium, however, Th sorption was not affected by the presence of the ligands, and modelling suggested that the interaction between Th and the surface binding sites controlled Th sorption thermodynamically.

Simulation procedure integrated with multi-scale in horizontally regional–urban-point levels and in vertically atmosphere–surface–unsaturated–saturated layers, was newly developed in order to predict the effect of urban geometry and anthropogenic exhaustion on the hydrothermal changes in the atmospheric/land and the interfacial areas of the Japanese megalopolis. The simulated results suggested that the latent heat flux in new water-holding pavement (consisting of porous asphalt and water-holding filler made of steel by-products based on silica compound) has a strong impact on hydrologic cycle and cooling temperature in comparison with the observed heat budget. We evaluated the relationship between the effect of groundwater use as a heat sink to tackle the heat island and the effect of infiltration on the water cycle in the urban area. The result indicates that effective management of water resources would be powerful for ameliorating the heat island and recovering sound hydrologic cycle there.

Marine invertebrates inhabiting estuaries and coastal areas are exposed to natural suspended particulate matter (SPM) like clay or diatom shells but also to anthropogenic particles like microplastics. SPM concentrations may reach 1 g per liter and more, comprising hundreds of millions of items in the size range of less than 100 μm. Suspension feeders and deposit feeders involuntarily ingest these particles along with their food. We investigated whether natural and anthropogenic microparticles at concentrations of 20 mg L⁻¹, which correspond to natural environmental SPM concentrations in coastal marine waters, are ingested by the brown shrimp Crangon crangon and whether these particles induce an oxidative stress response in digestive gland tissue. Shrimp were exposed to clay, silica, TiO₂, polyvinyl chloride (PVC), or polylactide microplastics (PLA) for 6, 12, 24, and 48 h, respectively. The activities of the anti-oxidative enzymes superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR) were measured. All five particle types were ingested by the shrimp along with food. The presence of the particles in the shrimp stomach was verified by scanning electron microscopy. The activities of the anti-oxidative enzymes did not vary between animals exposed to different types of microparticles and control animals that did not receive particles. The temporal activity differed between the three enzymes. The lack of a specific biochemical response may reflect an adaptation of C. crangon to life in an environment where frequent ingestion of non-digestible microparticles is unavoidable and continuous maintenance of inducible biochemical defense would be energetically costly. Habitat characteristics as well as natural feeding habits may be important factors to consider in the interpretation of hazard and species-specific risk assessment.

Asphalt-surfaced areas such as roads have been reported as major non-combustion sources of reactive organic compounds in urban areas. Emission of latter compounds from asphalt is exacerbated due to exposure to sunlight and high temperature, contributing to negative human and environmental health outcomes. Furthermore, loss of asphalt components over time is linked to bitumen's aging that reduces service life of roads. Here, we introduce a designed bio-grafted-silica nano-filler derived from wood pellet as a sink for latter volatile compounds in an asphalt mixture. Molecular modeling calculations showed the remarkable adsorptive activity of the bio-grafted silica for trapping select asphalt volatiles, especially for the sulfur-containing aromatics and the oxygen-containing aromatics. Laboratory experiment revealed that the bitumen modified with bio-grafted silica exhibited up to 23% lower signs of aging. Thermogravimetric analysis proved that the modified bitumen exhibited a 16% reduction in mass loss compared to neat bitumen. Dynamic vapor sorption analysis also showed bio-grafted silica adsorbed higher amounts of a candidate volatile than pristine silica. The study outcomes highlights the advantages of a bio-derived modifier in asphalt to address concerns associated with the loss of hazardous compounds.

The excessive arsenic (As) accumulation in plant tissues enforced toxic impacts on growth indices. So, the utilization of As-contaminated food leads to risks associated with human health. For the reduction of As concentrations in foods, it is obligatory to fully apprehend the take up, accretion, transportation and toxicity mechanisms of As within plant parts. This metalloid impairs the plant functions by disturbing the metabolic pathways at physio-biochemical, cellular and molecular levels. Though several approaches were utilized to reduce the As-accumulation and toxicity in soil-plant systems. Recently, engineered nanoparticles (ENPs) such a zinc oxide (ZnO), silicon dioxide or silica (SiO₂), iron oxide (FeO) and copper oxide (CuO) have emerged new technology to reduce the As-accumulation or phytotoxicity. But, the mechanistic approaches with systematic explanation are missing. By knowing these facts, our prime focus was to disclose the mechanisms behind the As toxicity and its mitigation by ENPs in higher plants. ENPs relives As toxicity and its oxidative damages by regulating the transporter or defense genes, modifying the cell wall composition, stimulating the antioxidants defense, phytochelatins biosynthesis, nutrients uptake, regulating the metabolic processes, growth improvement, and thus reduction in As-accumulation or toxicity. Yet, As-detoxification by ENPs depends upon the type and dose of ENPs or As, exposure method, plant species and experimental conditions. We have discussed the recent advances and highlight the knowledge or research gaps in earlier studies along with recommendations. This review may help scientific community to develop strategies such as applications of nano-based fertilizers to limit the As-accumulation and toxicity, thus healthy food production. These outcomes may govern sustainable application of ENPs in agriculture.

The catalytic hydrogenolysis of a typical model compound of mulching film waste, polyethylene, was investigated as a potential way to improve economic efficiency of mulching film recycling. Nickel-based heterogeneous catalysts are proposed for polyethylene hydrogenolysis to produce liquid hydrocarbons. Among catalysts supported on various carriers, Ni/SiO₂ catalyst shows the highest activity which may due to the interactions between nickel and silica with the formation of nickel phyllosilicate. As high as 81.18% total gasoline and diesel range hydrocarbon was obtained from the polyethylene hydrogenolysis at relatively mild condition of 280 °C, and 3 MPa cold hydrogen pressure. The result is comparable to what have been reported in previous studies using noble metal catalysts. The gasoline and diesel range hydrocarbon are n-alkanes with a distribution at a range of C₄–C₂₂. The gas products are primarily CH₄ along with a small amount of C₂H₆ and C₃H₈. High yield of CH₄ as much as 9.68% was observed for the cleavage of molecule occurs along the alkane chain.

In recent decades, nanotechnology has rapidly developed. Therefore, there is growing concern about the potential environmental risks of nanoparticles (NPs). Caenorhabditis elegans (C. elegans) has been used as a powerful tool for studying the potential ecotoxicological impacts of nanomaterials from the whole animal level to single cell level, especially in the area of reproduction. In this review, we discuss the reproductive toxicity of common nanomaterials in C. elegans, such as metal-based nanomaterial (silver nanoparticles (NPs), gold NPs, zinc oxide NPs, copper oxide NPs), carbon-based nanomaterial (graphene oxide, multi-walled carbon nanotubes, fullerene nanoparticles), polymeric NPs, silica NPs, quantum dots, and the potential mechanisms involved. This insights into the toxic effects of existing nanomaterials on the human reproductive system. In addition, we summarize how the physicochemical properties (e.g., size, charge, surface modification, shape) of nanomaterials influence their reproductive toxicity. Overall, using C. elegans as a platform to develop rapid detection techniques and prediction methods for nanomaterial reproductive toxicity is expected to reduce the gap between biosafety evaluation of nanomaterials and their application.

The tannery industries utilize environmentally hazardous chemicals to achieve dehairing of animal hides, which causes enormous waterbed pollution & high TDS load. Alkaline protease enzyme for dehairing can be an effective solution to resolve the environmental problems of the tannery industry waste. However, stable, cost-efficient and eco-benign formulations of alkaline protease need to be developed for commercial applications in the tannery industry. This works aimed at development of a nano-formulation of the enzyme alkaline protease (AKP) as a bioconjugate nano silica-alkaline protease enzyme (BC–SiNP-AKP). This work reports one pot green synthesis of the BC-SiNP-AKP bionanoconjugate complex which included both biotemplating and immobilization of the AKP on to the synthesized silica nanoparticles from cell-free extracts of Bacillus circulans grown in potato peel based medium. Among the cell free crude, acetone concentrated and purified sols of the enzyme AKP, acetone precipitated enzyme sol was found to be best for the biological SiNP synthesis and formation of BC-SiNP-AKP conjugate. The BC-SiNP-AKP had size ranging from 100 to 200 nm with crystalline morphologies varying from spherical, tubular to laminated crystallites. The developed bioconjugate formulation displayed 1.7-fold increase in the enzyme activity post nano-conjugation with superlative dehairing potential on goat skin. The optimized parameters for dehairing were found to be as temperature 37 °C for 24 h of incubation and with enzyme to buffer ratio (2: 50 mL). Thereafter, the dehaired skin was assessed for its histopathological effects, which were found to be safe without any deteriorative changes. The developed formulation is environmentally congenial for its use as depilating agent for animal hides in terms of being green, single pot and cost effective synthesis.

Soil and groundwater contamination with potentially toxic elements (PTEs) including cadmium (Cd) and copper (Cu) has become a serious problem for ecosystem functioning. Silicon (Si) may precipitate these metals as silicates, and may also form, at undersaturation of silicates, ‘Si-contaminant compounds’, i.e. particles of polymerized silica with PTEs incorporated or adsorbed by inner-sphere complexes. While the formation of these compounds in aqueous solution has been proven, their formation in soil remains unclear yet. Therefore, we conducted column experiments with a topsoil horizon artificially contaminated with Cd or Cu solutions (10 mM) in the presence (10 mM) and absence of monomeric Si, and monitored the elemental composition of the eluates during 12 irrigation steps with artificial rainwater by microwave-plasma atomic emission spectrometry, the size and charge of the particles eluted by dynamic light scattering and phase analysis light scattering, and determined the spatial distribution of total and exchangeable Cd and Cu in soil after the experiments. When Si was previously applied to soil, significantly larger particles (up to > 200 nm) in the eluates indicated Si polymerization and formation of Si-contaminant compounds. However, Cd and Cu concentrations were very low (<0.4 μM), pointing to efficient retardation in soil. In any variant, the particles formed were slightly negatively charged (−11 mV). The molar metal:Si ratios in the eluates and significant correlations between the amounts of Si and metals in soil extracted by NH₄NO₃ pointed to the formation of Si-contaminant compounds, too. More Cu than Cd was retained in soil, and significantly more in the presence of Si, but less Cu than Cd was in exchangeable form. While particularly Cu formed Si-contaminant compounds, which reduced the concentration of Cu ions, the Si-contaminant-compound particles in the eluates remained very small, thus potentially susceptible to particulate export from soil into the groundwater.