Some microorganisms can produce biotensoactive when in contact with hydrocarbons, which favours micelle formation, allowing microbial cells to metabolise them effectively. In this study, we evaluated the capacity of nitrogen-fixing (NFB) and hydrocarbonoclastic bacterial strains to generate biotensoactive. The sampling site was in a flood plain of the Chico Zapote River, on the low basin of the Tonalá River in Tabasco, Mexico. Rhizospheres and soil contaminated by oil were collected, and the concentration of oil and botanic samples were determined for their taxonomic classification. The collected rhizosphere oil was seeded into Congo red cultures to obtain Azospirillum (NFB) bacteria. The NFB strain was placed in liquid mineral medium with oil as the only carbon source to identify the hydrocarbonoclastic strains. Biochemical and physiological evaluations determined that the species were Azospirillum brasilense and Azospirillum lipoferum. The strains were placed into Kim medium for generating a biosurfactant. The biosurfactant produced by A. brasilense showed an emulsion stability of 229 min, yield of 0.1375 g L⁻¹, emulsion capacity of 80 % and superficial tension of 38 mN m⁻¹, and while the biotensoactive produced by A. lipoferum had an emulsion stability of 260 min, yield of 0.22 g L⁻¹, emulsion capacity of 90 % and superficial tension of 35.5 mN m⁻¹.

A wide variety of application of nanoparticles (NPs) in recent years has raised their possible entrance into the environment so that can affect living components of ecosystems. There is no comparative study on the long-term effects of a wide range of concentrations of NPs, related bulk particles (BPs), and corresponding metal ions on different traits of the plants. The present study has investigated comparative effects of zinc oxide (ZnO) NPs, ZnO BPs, and zinc ions (Zn²⁺) on rapeseed (Brassica napus L.) after long-term exposure to a wide range of concentrations. The inhibitory effects of treatments on the growth of B. napus were in the order Zn²⁺ >> ZnO BPs > ZnO NPs. Results showed the significant changes in the antioxidant enzyme activities, total chlorophyll, soluble proteins, proline, and soluble sugars of the leaves in response to the treatments. However, total phenolic compounds were not affected significantly by any treatment. Overall, in the present study, the toxicity of ZnO NPs on B. napus was lower than those of Zn²⁺ or ZnO BPs. Results indicate that adverse effects of ZnO NPs or BPs on B. napus may be due in part to the toxic effects of Zn²⁺ ions dissolution, probably induced by root exudates, or due o the physical interaction of ZnO particles with roots and induction of structural and functional disorders.

A kinetic study of the photocatalytic degradation of the pharmaceutical clofibric acid is presented. Experiments were carried out under UV radiation employing titanium dioxide in water suspension. The main reaction intermediates were identified and quantified. Intrinsic expressions to represent the kinetics of clofibric acid and the main intermediates were derived. The modeling of the radiation field in the reactor was carried out by Monte Carlo simulation. Experimental runs were performed by varying the catalyst concentration and the incident radiation. Kinetic parameters were estimated from the experiments by applying a non-linear regression procedure. Good agreement was obtained between model predictions and experimental data, with an error of 5.9 % in the estimations of the primary pollutant concentration.

This study aimed to evaluate the removal of polychlorinated biphenyls, with a vermicomposting system, using the following as components: the earthworm Eisenia fetida, peat moss and rabbit excrement and a compound called decachlorobiphenyl, for a period of 91 days under non-sterile conditions. The results obtained were a removal of decachlorobiphenyl 79.6 % with an initial concentration of 100 mg L⁻¹, 89.7 % with 150 mg L⁻¹and 95.38 % with 200 mg L⁻¹; the earthworms bioaccumulated less than 5 mg L⁻¹in all concentrations of decachlorobiphenyl analysed without apparent toxic effect. Weight gain was observed in earthworms that assimilated contaminant during vermicomposting, as the number of cocoons produced in contrast to the control in which both the weight and the number of cocoons were lower. To our knowledge, this is the first study which suggests that vermicomposting may be a suitable mechanism for removal of decachlorobiphenyl with high recalcitrance from contaminated sediment or soils.

Cr interactions with TiO₂were systematically studied using batch and spectroscopic investigations. Sorption of chromium on TiO₂at pH 4.5 increases with increasing Cr concentration. The sorption of Cr(III) is in good agreement with Langmuir isotherm model, whereas that of Cr(VI) is better accounted for by the Freundlich model. At pH 7.0, however, the uptake of Cr(III) by TiO₂is over 95 %, while the extent of Cr(VI) sorption on TiO₂is much less than that of pH 4.5. These results are consistent with SEM observations showing that precipitates of Cr(III) are dominant under neutral pH. The sorption of Cr(VI) on TiO₂decreases with increasing pH. However, Cr(VI) sorption decreases with increasing ionic strength below pH 4.5 whereas the sorption increases with ionic strength above pH 4.5. These observations suggest that Cr(VI) sorption is sensitive to ionic strength, and Cr(VI) could form weakly bound adsorption complexes at the TiO₂–water interface. Phosphate competes with Cr(VI) for TiO₂surface sites during sorption processes, and Cr(VI) desorption accelerates and increases in the presence of phosphate. It is noted that the reduction of Cr(VI) is induced by sunlight on the TiO₂surface, but not detected in acidic solution throughout batch experiments at pH ≥ 4.5 for 24 h.

As rice paddies are widespread sources of water pollution in the agricultural regions of the Asian monsoon area, a mechanistic understanding of nutrient loss from paddies is critical for water quality management. A 2-year experiment was conducted in a typical monsoon-affected rice field to improve our understanding of the impacts of rainfall and agricultural management practice on nitrogen (N) and phosphorus (P) loss. Samples of paddy drainage water were collected during rainfall events (n = 25) and analyzed for total N (T-N) and total P (T-P) concentrations. The impacts of rainfall (amount, duration, and intensity) and agricultural management practice (transplanting and fertilization) on the event mean concentration (EMC) and loss of nutrient were assessed using regression analyses. The results showed that T-N and T-P concentrations were affected by agricultural practice; meanwhile, loss of T-N and T-P was correlated with rainfall characteristics. Specifically, the EMC of T-N but T-P was negatively (p < 0.001) correlated with the number of days after agricultural practice in both years, which likely represents a decrease in nutrient availability in paddy water over time. Loss of T-N and T-P was positively (p < 0.01) correlated with rainfall amount, and this suggests that the rainfall-runoff process is a key driver of nutrient loss in the study area. Our results suggest that rainfall amount and days after transplanting need to be taken into account when estimating nutrient loss from rice paddies in monsoon regions.

Fe₂O₃/γ-Al₂O₃catalysts were prepared using the wet impregnation method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption–desorption. The continuous catalytic wet hydrogen peroxide oxidation of an aqueous phenol solution over Fe₂O₃/γ-Al₂O₃was studied in a fixed-bed reactor. The effects of several factors, such as the weight hourly space velocity (WHSV), particle size, reaction temperature, H₂O₂concentration, and initial pH, were studied to optimize the operation conditions for phenol mineralization. For a 1 g L⁻¹phenolic aqueous solution, the phenol was nearly completely removed and chemical oxygen demand (COD) removal was approximately 92 % at steady-state conditions with a WHSV of 2.4 × 10⁻² gPₕOH h⁻¹ gcₐₜ⁻¹at 80 °C with 5.1 g L⁻¹H₂O₂. The long-term stability of the Fe₂O₃/γ-Al₂O₃catalyst was also investigated for the continuous treatment of phenolic water. The removal of phenol and COD exhibited a slowly decreasing trend, which was primarily due to the complexation of active sites with acid organic compounds and the adsorption of intermediate products. The deposition of organic carbon and Fe leached from the catalyst had a small role in the partial deactivation of the catalyst. The Fe leached from the catalyst partially contributed to the phenol removal during a short run. However, this contribution could be neglected after 36 h because the Fe leached from the catalyst decreased to approximately 5 mg L⁻¹.

Soil thawing can affect the turnover of soil carbon (C) and nitrogen (N) and their release into the atmosphere. However, little has been known about the release of C and N during the thawing of alpine soils in the Qinghai-Tibet Plateau. This study investigated the effects of soil thawing on the release of CO₂, CH₄, and N₂O from alpine peatland soils and alpine meadow soils through an indoor experiment and determined the changes in the dissolved organic C (DOC), dissolved organic N (DON), NO₃ ⁻-N, NH₄ ⁺-N, and NO₂ ⁻-N concentrations in the soils after soil thawing. The freeze–thaw treatments were performed by incubating the soil columns at mild (−5 °C) and severe (−15 °C) for 14 days, and then at 5 °C for 18 days. The control columns were incubated at 5 °C. During thawing, the cumulative CO₂ emissions from the severely frozen alpine peatland soils and alpine meadow soils were 36 and 85 % higher than those from the control soils, and the cumulative N₂O emissions were 3.9 and 5.8 times higher than those from the control soils. However, the thawing after mild freezing produced no significant effects. The two freezing temperatures significantly increased the release of CH₄ from the alpine peatland soils, but the thawing of the severely frozen soils reduced the CH₄ uptake of the alpine meadow soils by 27 %. After the severely frozen alpine peatland soils thawed, the concentrations of DOC, DON, NO₃ ⁻-N, NH₄ ⁺-N, and NO₂ ⁻-N increased significantly, but NO₂ ⁻-N showed no significant changes for the alpine meadow soils. After thawing with mild freezing, DOC in the alpine peatland soils and NH₄ ⁺-N, NO₂ ⁻-N, and DOC in the alpine meadow soils showed no significant changes. This study indicates that the potential for release of C and N from alpine soils during thawing periods strongly depends on the freezing temperature and soil types.

Peatlands serve as important stores of organic matter and regulators of nutrient and metal export to surface waters, yet relatively little is known regarding the impact of more than a century of metal, sulfur, and acid deposition on microbial activity in acidic, nutrient-poor peatlands that are common features around Sudbury, Ontario. In this study, eight peatlands were selected at varying distances from the Copper Cliff Smelter that was once the largest point source of sulfur dioxide and sampled for analysis of nutrient and metal content. Basal microbial respiration, relative response to substrate addition (four synthetic and four natural substrates) assessed as CO₂production rates and microbial biomass were assessed in surface (0–10 cm) peat samples. Bacterial and fungal communities within the peat samples were profiled using terminal restriction fragment length polymorphism analysis. Basal respiration (i.e., carbon mineralization in absence of substrate addition) was lowest and Cu and Ni concentrations and the degree of humification (assessed by the von Post scale) in surface peat samples were highest close to the smelter. Each peatland had a unique bacterial community when assessed using non-metric multidimensional scaling, whereas the fungal community was variable with no consistent patterns across the sites. Despite differences in microbial communities, substrate-induced respiration rates did not differ among peatlands as sites generally responded similarly to carbon substrate additions. Basal respiration rates were related to the humification status of the peat, which was potentially related to environmental degradation in the peatlands or surrounding terrestrial systems closer to the Sudbury smelters.

Arsenic (As) is a ubiquitous metalloid known for its adverse effects to human health. Microorganisms are also impacted by As toxicity, including methanogenic archaea, which can affect the performance of a process in which biological activity is required (i.e., stabilization of activated sludge in wastewater treatment plants). The novel ability of a mixed methanogenic granular sludge consortium to adapt to the inhibitory effect of arsenic As was investigated by exposing the culture to approximately 0.92 mM of arsenite (Asᴵᴵᴵ) for 160 days in an arsenate (Asⱽ)-reducing bioreactor using ethanol as the electron donor. The results of shaken batch bioassays indicated that the original, unexposed sludge was severely inhibited by Asᴵᴵᴵ as evidenced by the low 50 % inhibition concentrations (IC₅₀) determined, i.e., 19 and 90 μM Asᴵᴵᴵ for acetoclastic and hydrogenotrophic methanogenesis, respectively. The tolerance of the acetoclastic and hydrogenotrophic methanogens in the sludge to Asᴵᴵᴵ increased 47-fold (IC₅₀ = 910 μM) and 12-fold (IC₅₀ = 1100 μM), respectively, upon long-term exposure to As. In conclusion, the methanogenic community in the granular sludge demonstrated a considerable ability to adapt to the severe inhibitory effects of As after a prolonged exposure period.