Graphene oxide (GO) and nano-sized zero-valent iron-reduced graphene oxide (nZVI-rGO) composite were prepared. The GO and nZVI-rGO composite were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR), energy-dispersive spectroscopy (EDS), and Raman spectroscopy. The size of nZVI was about 6 nm as observed by TEM. The system of nZVI-rGO and persulfate (PS) was used for the degradation of trichloroethylene (TCE) in water, and showed 26.5 % more efficiency as compared to nZVI/PS system. The different parameters were studied to determine the efficiency of nZVI-rGO to activate the PS system for the TCE degradation. By increasing the PS amount, TCE removal was also improved while no obvious effect was observed by varying the catalyst loading. Degradation was decreased as the TCE initial concentration was increased from 20 to 100 mg/L. Moreover, when initial solution pH was increased, efficiency deteriorated to 80 %. Bicarbonate showed more negative effect on TCE removal among the solution matrix. To better understand the effects of radical species in the system, the scavenger tests were performed. The •SO₄ ⁻ and •O₂ ⁻ were predominant species responsible for TCE removal. The nZVI-rGO-activated PS process shows potential applications in remediation of highly toxic organic contaminants such as TCE present in the groundwater. Graphical abstract Persulfate activated by reduced graphene oxide and nano-sized zero-valent iron composite can be used for efficient degradation of trichloroethylene (TCE) in water.

Several studies have reported that the chewing habit of smokeless tobacco (SLT) has been associated with oral cancer. The aim of the present study was to evaluate the trace levels of lead (Pb) in biological samples (blood, scalp hair) of oral cancer patients and referents of the same age group (range 30–60 years). As the concentrations of Pb are very low in biological samples, so a simple and efficient ionic liquid-based microextraction in a single syringe system has been developed, as a prior step to determination by flame atomic absorption spectrometry. In this procedure, the hydrophobic chelates of Pb with ammonium pyrrolidinedithiocarbamate (APDC) were extracted into fine droplets of 1-butyl-3-methylimidazolium hexafluorophosphate [C₄MIM][PF₆] within a syringe while using Triton X-114 as a dispersant. Factors influencing the microextraction efficiency and determination, such as pH of the sample, volume of [C₄MIM][PF₆] and Triton X-114, ligand concentration, and incubation time, were studied. To validate the proposed method, certified reference materials were analyzed and the results of Pb²⁺ were in good agreement with certified values. At optimum experimental values of significant variables, detection limit and enhancement factor were found to be 0.412 μg/L and 80, respectively. The coexisting ions showed no obvious negative outcome on Pb preconcentration. The proposed method was applied satisfactorily for the preconcentration of Pb²⁺ in acid-digested SLT and biological samples of the study population. It was observed that oral cancer patients who consumed different SLT products have 2–3-fold higher levels of Pb in scalp hair and blood samples as compared to healthy referents (p < 0.001). While 31.4–50.8 % higher levels of Pb were observed in referents chewing different SLT products as compared to nonconsumers (p < 0.01).

The sensitivity of two tomato (Solanum lycopersicum L.) cultivars, Rechaiga II and De Colgar, to 50, 80, and 100 ppb ozone (O₃) exposures was assessed in fumigation chamber, during 4 h per day over a period of 7 days. The Rechaiga II variety was shown to be sensitive to the dose of 50 ppb, showing chlorotic spots on the adaxial leaf surface and alterations of some physiological parameters. During 1-week fumigation, ozone caused a decrease in stomatal conductance, chlorophylls a and b, total chlorophylls, and carotenoids, although soluble sugars and membrane integrity were significantly increased in fumigated plants compared to controls. This trend was similar for the three pollutant doses used in fumigation. The De Colgar tomato remained asymptomatic.

Fusarium wilt of cucumber caused by Fusarium oxysporum f. sp. cucumerinum J. H. Owen is one of the major destructive soilborne diseases and results in considerable yield losses. Methyl bromide was once the most effective disease control method but has been confirmed as harmful to the environment. Using suppressive media as biological controls to assist crop growth is becoming popular. In this study, Fusarium wilt of cucumber was successfully controlled by a newly identified suppressive media: vinegar residue compost-amended media (vinegar residue compost mixed with peat and vermiculite in a 6:3:1 ratio (v/v) vinegar residue substrate (VRS). Greenhouse experiments were carried out to evaluate the effect of VRS on the growth of cucumber seedlings and disease suppression. The control was peat/vermiculite (2:1, v/v). To identify the mixed media most suitable for the growth of plants and their suppressiveness indicators, we evaluated the biological characteristics of cucumber, the physicochemical and biochemical properties of the growth media, and the enzyme activities. Total organic C (Cₒᵣg), microbial biomass C (Cₘᵢc), basal respiration (Rₘᵢc), and enzyme (catalase, invertase, urease, proteinase, phosphatase, β-glucosidase, and hydrolysis of fluorescein diacetate) activities increased significantly after vinegar waste compost amendment. The compost media also showed a significantly positive effect on the growth of cucumber seedlings and the suppression of the disease severity index (DSI, 38 % reduction). The cucumber rhizosphere population of F. oxysporum f. sp. cucumerinum (FOC) was significantly lower in VRS than in the control. These results demonstrate convincingly that vinegar residue compost-amended media has a beneficial effect on cucumber growth and could be applied as a method for biological control of cucumber Fusarium wilt.

Among 348 microbial strains isolated from petroleum hydrocarbon-contaminated soil, five were selected for their ability to produce biosurfactant based on battery of screening assay including hemolytic activity, surface tension reduction, drop collapse assay, emulsification activity, and cell surface hydrophobicity studies. Of these, bacterial isolate DSVP20 was identified as Pseudomonas aeruginosa (NCBI GenBank accession no. GQ865644) based on biochemical characterization and the 16S rDNA analysis, and it was found to be a potential candidate for biosurfactant production. Maximum biosurfactant production recorded by P. aeruginosa DSVP20 was 6.7 g/l after 72 h at 150 rpm and at a temperature of 30 °C. Chromatographic analysis and high-performance liquid chromatography-mass spectrometry (HPLC-MS) revealed that it was a glycolipid in nature which was further confirmed by nuclear magnetic resonance (NMR) spectroscopy. Bioremediation studies using purified biosurfactant showed that P. aeruginosa DSVP20 has the ability to degrade eicosane (97 %), pristane (75 %), and fluoranthene (47 %) when studied at different time intervals for a total of 7 days. The results of this study showed that the P. aeruginosa DSVP20 and/or biosurfactant produced by this isolate have the potential role in bioremediation of petroleum hydrocarbon-contaminated soil.

Southern Tuscany (Italy) is characterized by extensive arsenic (As) anomalies, with concentrations of up to 2000 mg kg soil⁻¹. Samples from the location of Scarlino, containing about 200 mg kg⁻¹of As, were used to study the influence of the inoculation of an arbuscular mycorrhizal (AM) fungus (Rhizophagus irregularis, previously known as Glomus intraradices) and of phosphorus (P) application, separately and in combination, on As speciation in the rhizosphere of Zea mays on plant growth and As accumulation. Also, P distribution in plant parts was investigated. Each treatment produced a moderate rise of As(III) in the rhizosphere, increased As(III) and lowered As(V) concentration in shoots. P treatment, alone or in combination with AM, augmented the plant biomass. The treatments did not affect total As concentration in the shoots (with all the values <1 mg kg⁻¹dry weight), while in the roots it was lowered by P treatment alone. Such decrease was probably a consequence of the competition between P and As(V) for the same transport systems, interestingly nullified by the combination with AM treatment. P concentration was higher with AM only in both shoots and roots. Therefore, the obtained results can be extremely encouraging for maize cultivation on a marginal land, like the one studied.

In recent decades, free-living protozoa (FLP) have gained prominence as the focus of research studies due to their pathogenicity to humans and their close relationship with the survival and growth of pathogenic amoeba-resisting bacteria. In the present work, we studied the presence of FLP in operational man-made water systems, i.e. cooling towers (CT) and hot sanitary water systems (HSWS), related to a high risk of Legionella spp. outbreaks, as well as the effect of the biocides used, i.e. chlorine in CT and high temperature in HSWS, on FLP. In CT samples, high-chlorine concentrations (7.5 ± 1.5 mg chlorine L⁻¹) reduced the presence of FLP by 63.8 % compared to samples with low-chlorine concentrations (0.04 ± 0.08 mg chlorine L⁻¹). Flagellates and amoebae were observed in samples collected with a level of 8 mg chlorine L⁻¹, which would indicate that some FLP, including the free-living amoeba (FLA) Acanthamoeba spp., are resistant to the discontinuous chlorine disinfection method used in the CT studied. Regarding HSWS samples, the amount of FLP detected in high-temperatures samples (53.1 ± 5.7 °C) was 38 % lower than in low-temperature samples (27.8 ± 5.8 °C). The effect of high temperature on FLP was chiefly observed in the results obtained by the culture method, in which there was a clear reduction in the presence of FLP at temperatures higher than 50 °C, but not in those obtained by PCR. The findings presented here show that the presence of FLP in operational man-made water systems should be taken into account in future regulations.

In former coal transformation plants (coking and gas ones), the major organic contamination of soils is coal tar, mainly composed of polycyclic aromatic compounds (PACs). Air oxidation of a fresh coal tar was chosen to simulate the abiotic natural attenuation impact on PAC-contaminated soils. Water-leaching experiments were subsequently performed on fresh and oxidized coal tars to study the influence of oxidation on dissolved organic matter (DOM) quality and quantity. The characterization of the DOM was performed using a combination of molecular and spectroscopic techniques (high-performance liquid chromatography–size-exclusion chromatography (HPLC-SEC), 3D fluorescence, and gas chromatography coupled with mass spectrometry (GC–MS)) and compared with the DOM from contaminated soils sampled on the field exposed to natural attenuation for several decades. An increase in the oxygenated polycyclic aromatic compound concentrations was observed with abiotic oxidation both in the coal tar and the associated DOM. Polycyclic aromatic hydrocarbon concentrations in the leachates exceeded pure water solubility limits, suggesting that co-solvation with other soluble organic compounds occurred. Furthermore, emission excitation matrix analysis combined with synchronous fluorescence spectra interpretation and size-exclusion chromatography suggests that oxidation induced condensation reactions which were responsible for the formation of higher-molecular weight compounds and potentially mobilized by water. Thus, the current composition of the DOM in aged soils may at least partly result from (1) a depletion in lower-molecular weight compounds of the initial contamination stock and (2) an oxidative condensation leading to the formation of a higher-molecular weight fraction. Abiotic oxidation and water leaching may therefore be a significant combination contributing to the evolution of coal tar-contaminated soils under natural attenuation.

The objective of this work was to study the degradation and mineralization of ethylenethiourea (ETU) in water by ozonation at different pH values and in the presence of hydrogen peroxide. Degradation experiments were performed using an initial ETU concentration of 50 ppm for 180 min with a gas flux of 0.25 dm³ min⁻¹and an O₃production rate of 12.1 mg min⁻¹. Degradation of by-products was monitored by direct injection electrospray ionization mass spectrometry (ESI-MS), ETU concentration was determined by HPLC-UV, and its mineralization was detected by total organic carbon (TOC) analysis. Optimum degradation of ETU in water was observed at pH = 11, whereas at pH = 3, the degradation of ETU was slowest, indicating that the reaction occurred through different mechanisms. The additional effects of hydroxyl radicals formed at the highest pH can be used to explain the results obtained in this study. Peroxone experiments were carried out in the presence of 400 and 800 mg L⁻¹H₂O₂; the degradation of ETU was faster at 400 mg L⁻¹H₂O₂. This was attributed to the scavenging effect of the excess H₂O₂. ETU treatment by ozonation produced several by-products of degradation such as ethylene urea and 2-imidazoline.

This study investigates carbon dioxide (CO₂) and methane (CH₄) emissions and carbon (C) budgets in a horizontal subsurface flow pilot-plant constructed wetland (CW) with beds vegetated with Cyperus papyrus L., Chrysopogon zizanioides (L.) Roberty, and Mischantus × giganteus Greef et Deu in the Mediterranean basin (Sicily) during the 1st year of plant growing season. At the end of the vegetative season, M. giganteus showed the higher biomass accumulation (7.4 kg m⁻²) followed by C. zizanioides (5.3 kg m⁻²) and C. papyrus (1.8 kg m⁻²). Significantly higher emissions of CO₂were detected in the summer, while CH₄emissions were maximum during spring. Cumulative CO₂emissions by C. papyrus and C. zizanioides during the monitoring period showed similar trends with final values of about 775 and 1,074 g m⁻², respectively, whereas M. giganteus emitted 3,395 g m⁻². Cumulative CH₄bed emission showed different trends for the three C4 plant species in which total gas release during the study period was for C. papyrus 12.0 g m⁻²and ten times higher for M. giganteus, while C. zizanioides bed showed the greatest CH₄cumulative emission with 240.3 g m⁻². The wastewater organic carbon abatement determined different C flux in the atmosphere. Gas fluxes were influenced both by plant species and monitored months with an average C-emitted-to-C-removed ratio for C. zizanioides, C. papyrus, and M. giganteus of 0.3, 0.5, and 0.9, respectively. The growing season C balances were positive for all vegetated beds with the highest C sequestered in the bed with M. giganteus (4.26 kg m⁻²) followed by C. zizanioides (3.78 kg m⁻²) and C. papyrus (1.89 kg m⁻²). To our knowledge, this is the first paper that presents preliminary results on CO₂and CH₄emissions from CWs vegetated with C4 plant species in Mediterranean basin during vegetative growth.