The study investigates the effect of aluminium oxide nanoparticles as an additive to Madhuca Indica (mahua) methyl ester blends on performance, emission analysis of a single-cylinder direct injection diesel engine operated at a constant speed at different operating conditions. The test fuels are indicated as B10A0.2, B10A0.4, B20A0.2, B20A0.4 and diesel respectively. The results indicate that the brake thermal efficiency for aluminium oxide nanoparticles blended biodiesel increases slightly when compared to the mineral diesel. The carbon monoxide (CO), unburnt hydrocarbon (HC) and smoke emission marginally decrease as compared to mineral diesel. Oxides of nitrogen (NOx) emissions are minimum for the aluminium oxide nanoparticles blended mahua methyl esters. Higher cylinder gas pressure and heat release rate were observed for aluminium oxide nanoparticles blended mahua methyl ester. From the study, the blending of aluminium oxide nanoparticles in biodiesel blends produces a most promising results in engine performance and also reduces the harmful emission from the engines.

The biogeochemical cycling of sulfur in soil is closely associated with the mobility and bioavailability of heavy metals; however the influence of sulfur on the behavior of metal-based nanoparticles has not yet been studied. The influence of S fertilizer (S⁰ and Na₂SO₄) applied in paddy soils on CuO NPs behavior in soil pore water was explored in the present study. Synchrotron-based techniques were applied to investigate the migration and speciation transformation of CuO NPs in soil pore water colloids. The application of sulfur fertilizer increased the zeta potential of soil colloids from the rice rhizosphere region and reduced the size of the colloids. Sulfur fertilization decreased the concentration of Cu in soil pore water in the rice rhizosphere region. S⁰ fertilizer reduced the Cu concentration in soil colloids (by 55.8%–73.5%), while Na₂SO₄ increased the Cu concentration in soil colloids (by 173.8%–265.1%). Sulfur fertilization changed the spatial distribution of Fe³⁺ and Cu²⁺ in colloids, making these ions more likely to be aggregated on the edges of soil colloids. Speciation transformation of CuO NPs happened during the process of migration. The main Cu speciation in the soil colloids were CuO NPs, Cu-Cysteine, Cu₂S and Cu-Citrate. Sulfur fertilization increased the proportion of Cu₂S (by 40.5%) in soil pore water colloids from the rice rhizosphere region, while the proportion of CuO NPs was reduced (by 18.4%). Sulfur fertilization changed the morphology and elementary composition of colloids in soil pore water, thus influencing the migration of CuO NPs in the soil column through soil colloids.

ZnO nanoparticles (NPs) have been detected in various wastewater treatment plants. It is widely assumed that size has a crucial effect on the NPs toxicity. Concerns have been raised over probable size-dependent toxicity of ZnO NPs to activated sludge, which could eventually affect the treatment efficiencies of wastewater treatment facilities. The size-dependent influences of ZnO NPs on performance, microbial activities, and extracellular polymeric substances (EPS) from activated sludge were examined in sequencing batch reactor (SBR) in present study. Three different sizes (15, 50, and 90 nm) and five concentrations (2, 5, 10, 30, and 60 mg L⁻¹) were trialled. The inhibitions on COD and nitrogen removal were determined by the particle size, and smaller ZnO NPs (15 nm) showed higher inhibition effect than those of 50 and 90 nm, whereas the ZnO NPs with size of 50 nm showed maximum inhibition effect on phosphorus removal among three sizes of ZnO NPs. After exposure to different sized ZnO NPs, microbial enzymatic activities and removal rates of activated sludge represented the same trend, consistent with the nitrogen and phosphorus removal efficiency. In addition, apparent size- and concentration-dependent effects on EPS contents and components were also observed. Compared with the absence of ZnO NPs, 60 mg L⁻¹ ZnO NPs with sizes of 15, 50, and 90 nm increased the EPS contents from 92.5, 92.4, and 92.0 mg g⁻¹ VSS to 277.5, 196.8, and 178.2 mg g⁻¹ VSS (p < 0.05), respectively. The protein and polysaccharide contents increased with the decreasing particle sizes and increasing ZnO NPs concentrations, and the content of protein was always higher than that of polysaccharide.

Iron nanoparticles (Fe NPs) have often been used for in situ remediation of both groundwater and soil. However, the impact of Fe NPs on the distribution and transformation of As species in contaminated soil is still largely unknown. In this study, green iron oxide nanoparticles synthesized using a euphorbia cochinchinensis leaf extract (GION) were used to stabilize As in a contaminated soil. GION exhibited excellent As stabilization effects, where As in non-specifically-bound and specifically-bound fractions decreased by 27.1% and 67.3% after 120 days incubation. While both arsenate (As (V)) and arsenite (As (III)) decreased after GION application, As (V) remained the dominant species in soil. X-ray photoelectron spectroscopy (XPS) confirmed that As (V) was the dominant species in specifically-bound fractions, while As (III) was the dominant species in amorphous and poorly-crystalline hydrous oxides of Fe and Al. Correlation analysis showed that while highly available As fractions were negatively correlated to oxalate and DCB extractable Fe, they were positively correlated to Fe²⁺ content, which indicated that Fe cycling was the main process influencing changes in As availability. X-ray fluorescence (XRF) spectroscopy also showed that the Fe₂O₃ content increased by 47.9% following GION soil treatments. Overall, this work indicated that As would be transformed to more stable fractions during the cycling of Fe following GION application and that the application of GION, even in small doses, provides a low-cost and ecofriendly method for the stabilization of As in soil.

Smoke from plastic waste incineration in an open air travels worldwide and is a major source of air pollution particulate matter (PM) that is very withstand to degradation and hazard to human health. Suspension of smoke aerosol components in water occurs during rains and fire extinguishing. Here, water-suspended plastic smoke aerosol (WPS) preparations suitable for biotesting were synthesized. It has been revealed using dynamic light scattering that WPS contained major nano-sized (∼30 nm) PM fraction, and this result was confirmed by electron microscopy. Optical absorption of WPS was in the UV region and an increase in λₑₓ led to a red-shift in fluorescence emission with a corresponding decrease in fluorescence intensity. WPS was analyzed in neurotoxicity studies in vitro using presynaptic rat cortex nerve terminals (synaptosomes). Generation of spontaneous reactive oxygen species (ROS) detected using fluorescent dye 2′,7-dichlorofluorescein in nerve terminals was decreased by WPS (10–50 μg/ml) in a dose-dependent manner. WPS also reduced the H₂O₂-evoked ROS production in synaptosomes, thereby influencing cellular oxidative processes and this effect was similar to that for carbon nanodots. WPS (0.1 mg/ml) decreased the synaptosomal membrane potential and synaptic vesicle acidification in fluorimetric experiments. WPS (1.0 mg/ml) attenuated the synaptosomal transporter-mediated uptake of excitatory and inhibitory neurotransmitters, L-[¹⁴C]glutamate and [³H]GABA, respectively. This can lead to an excessive increase in the glutamate concentration in the synaptic cleft and neurotoxicity via over activation of ionotropic glutamate receptors. Therefore, WPS was neurotoxic and provoked presynaptic malfunction through changes of oxidative activity, reduction of the membrane potential, synaptic vesicle acidification, and transporter-mediated uptake of excitatory and inhibitory neurotransmitters in nerve terminals. In summary, synthesis and emission to the environment of ultrafine PM occur during combustion of plastics, thereby polluting air and water resources, and possibly triggering development of neuropathologies.

To compare aquatic organisms’ responses to the toxicity of copper oxide (CuO) nanoparticles (NPs) with those of CuO microparticles (MPs) and copper (Cu) ions, a global metabolomics approach was employed to investigate the changes of both polar and nonpolar metabolites in microalga Chlorella vulgaris after 5-day exposure to CuO NPs and MPs (1 and 10 mg/L), as well as the corresponding dissolved Cu ions (0.08 and 0.8 mg/L). Unchanged growth, slight reactive oxygen species production, and significant membrane damage (at 10 mg/L CuO particles) in C. vulgaris were demonstrated. A total of 75 differentiated metabolites were identified. Most metabolic pathways perturbed after CuO NPs exposure were shared by those after CuO MPs and Cu ions exposure, including accumulation of chlorophyll intermediates (max. 2.4–5.2 fold), membrane lipids remodeling for membrane protection (decrease of phosphatidylethanolamines (min. 0.6 fold) and phosphatidylcholines (min. 0.2–0.7 fold), as well as increase of phosphatidic acids (max. 1.5–2.9 fold), phosphatidylglycerols (max. 2.2–2.3 fold), monogalactosyldiacylglycerols (max. 1.2–1.4 fold), digalactosylmonoacylglycerols (max. 1.9–3.8 fold), diacylglycerols (max. 1.4 fold), lysophospholipids (max. 1.8–3.0 fold), and fatty acids (max. 3.0–6.2 fold)), perturbation of glutathione metabolism induced by oxidative stress, and accumulation of osmoregulants (max. 1.3–2.6 fold) to counteract osmotic stress. The only difference between metabolic responses to particles and those to ions was the accumulation of fatty acids oxidation products: particles caused higher fold changes (particles/ions ratio 1.9–3.0) at 1 mg/L and lower fold changes (particles/ions ratio 0.4–0.7) at 10 mg/L compared with ions. Compared with microparticles, there was no nanoparticle-specific pathway perturbed. These results confirm the predominant role of dissolved Cu ions on the toxicity of CuO NPs and MPs, and also reveal particle-specific toxicity from a metabolomics perspective.

Addressing the presence of rutile nanoparticles (NPs) in the air is a work in progress, and the development of methodologies for the identification of NPs in atmospheric dust is essential for the assessment of its toxicological effects. To address this issue, we selected the fast growing desertic city of Hermosillo in northern Mexico. Road dust (n = 266) and soils (n = 10) were sampled and bulk Ti-contents were tested by portable X-ray fluorescence. NPs were extracted from atmospheric dust by PM₁.₀-PTFE filters and further characterized by Confocal Raman Microscopy, Energy-dispersive X-ray spectroscopy (EDS) coupled to Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). Results showed (i) the average concentration of Ti in road dust (3447 mg kg⁻¹) was similar to natural values and worldwide urban dusts; (ii) the bulk geochemistry was not satisfactory for Ti-NPs identification; (iii) 76% of the total extracted PM₁.₀ sample corresponded to NPs; (iv) mono-microaggregates of rutile NPs were identified; (v) ubiquitous polycyclic aromatic hydrocarbons (PAHs) were linked to NPs. The genotoxicity of rutile and PAHs, in connection with NPs content, make us aware of a crucial emerging environmental issue of significant health concern, justifying further research in this field.

Although nanoscale surface roughness has been theoretically demonstrated to be a crucial factor in the interaction of colloids and surfaces, little experimental research has investigated the influence of roughness on colloid or silver nanoparticle (AgNP) retention and release in porous media. This study experimentally examined AgNP retention and release using two sands with very different surface roughness properties over a range of solution pH and/or ionic strength (IS). AgNP transport was greatly enhanced on the relatively smooth sand in comparison to the rougher sand, at higher pH, and lower IS and fitted model parameters showed systematic changes with these physicochemical factors. Complete release of the retained AgNPs was observed from the relatively smooth sand when the solution IS was decreased from 40 mM NaCl to deionized (DI) water and then the solution pH was increased from 6.5 to 10. Conversely, less than 40% of the retained AgNPs was released in similar processes from the rougher sand. These observations were explained by differences in the surface roughness of the two sands which altered the energy barrier height and the depth of the primary minimum with solution chemistry. Limited numbers of AgNPs apparently interacted in reversible, shallow primary minima on the smoother sand, which is consistent with the predicted influence of a small roughness fraction (e.g., pillar) on interaction energies. Conversely, larger numbers of AgNPs interacted in deeper primary minima on the rougher sand, which is consistent with the predicted influence at concave locations. These findings highlight the importance of surface roughness and indicate that variations in sand surface roughness can greatly change the sensitivity of nanoparticle transport to physicochemical factors such as IS and pH due to the alteration of interaction energy and thus can strongly influence nanoparticle mobility in the environment.

The co-precipitation method was used to synthesize nano-magnetic adsorbent MnFe₂O₄ (nMFO), characterized through XRD, SEM, EDS, and BET techniques. The synthesized nMFO was used for hexavalent and trivalent chromium ions elimination from the aqueous phase. The optimum pH for the adsorption of Cr (VI) and Cr (III) was determined as 2 and 5, respectively. The chromium ions adsorption behavior was well interpreted through the pseudo-second order kinetics model. Furthermore, isotherm studies were conducted, and the obtained results indicated that Langmuir isotherm model could well justify the chromium ions adsorption process. Quick removal (less than 10 min) of both chromium ions and high removal efficiency were occurred using nMFO. The utmost adsorption capacity of trivalent and hexavalent chromium ions were determined as 39.6 and 34.84 mg g⁻¹, respectively. Thermodynamic studies on chromium adsorption revealed positive value for ΔH and negative value for ΔG, representing that chromium ions adsorption was an endothermic and spontaneous process. The multilinearity in the graphs of chromium ions adsorption was observed using intra-particle diffusion model. In this regard, the external mass transfer of chromium ions on synthesized nanoparticles was the important and controlling step in the adsorption process.

Whether toxicity of silver nanoparticles (AgNPs) to organisms originates from the nanoparticles themselves or from the dissolved Ag-ions is still debated, with the majority of studies claiming that extracellular release of Ag-ions is the main cause of toxicity. The objective of this study was to determine the contributions of both particles and dissolved ions to toxic responses, and to better understand the underlying mechanisms of toxicity. In addition, the pathways of AgNPs exposure to plants might play an important role and therefore are explicitly studied as well. We systematically assessed the phytotoxicity, internalization, biodistribution, and antioxidant responses in lettuce (Lactuca sativa) following root or foliar exposure to AgNPs and ionic Ag at various concentrations. For each endpoint the relative contribution of the particle-specific versus the ionic form was quantified. The results reveal particle-specific toxicity and uptake of AgNPs in lettuce as the relative contribution of particulate Ag accounted for more than 65% to the overall toxicity and the Ag accumulation in whole plant tissues. In addition, particle toxicity is shown to originate from the accumulation of Ag in plants by blocking nutrient transport, while ion toxicity is likely due to the induction of excess ROS production. Root exposure induced higher toxicity than foliar exposure at comparable exposure levels. Ag was found to be taken up and subsequently translocated from the exposed parts of plants to other portions regardless of the exposure pathway. These findings suggest particle related toxicity, and demonstrate that the accumulation and translocation of silver nanoparticles need to be considered in assessment of environmental risks and of food safety following consumption of plants exposed to AgNPs by humans.