Cypermethrin induced alterations in nitrogen metabolism in freshwater fishes

In the present study, two fresh water fishes namely, Channa punctatus and Clarias batrachus, were exposed to three sub-acute concentrations of synthetic pyrethroid, cypermethrin, for 96 h to evaluate the role of amino acids in fulfilling the immediate energy needs of fishes under pyrethroid induced stress as well as to find out the mechanism of ammonia detoxification. The experiments were designed to estimate the levels of free amino acid, urea, ammonia and the activities of aspartate aminotransferase (AAT), alanine aminotransferase (AlAT), glutamate dehydrogenase (GDH), glutamine synthetase (GS) and arginase in some of the vital organs like brain, gills, liver, kidney and muscle of both fish species. The significant decrease in the levels of amino acids concomitant with remarkable increase in the activities of AAT, AlAT and GDH in these vital tissues of fish species elucidated the amino acid catabolism as one of the main mechanism of meeting out the immediate energy demand of the fishes in condition of cypermethrin exposure. The levels of ammonia were significantly increased at 10% of 96 h LC(50) of cypermethrin in the different organs such as brain, gills, liver, kidney and muscle of both fish species while 15% and 20% concentrations of 96 h LC(50) of cypermehrin registered remarkable decline in both fish species. The differential increment in the activities of GDH, GS and arginase and in the level of urea established three different alternative mechanisms of ammonia detoxification. The results indicated that in C. punctatus, the prevalent mode of nitrogen excretion is in the form of conversion of ammonia into glutamine and glutamate while in C. batrachus, the excessive nitrogen is excreted in the form of urea synthesized from ammonia.     

TiO₂ supported over SBA-15: an efficient photocatalyst for the pesticide degradation using solar light

Photocatalytic degradation and mineralization of pesticides are studied over TiO(2) supported mesoporous SBA-15 composite system using solar light. TiO(2) is immobilized over SBA-15 by solid sate dispersion method. The catalysts are characterized by XRD, surface area, UV-Vis diffused reflectance spectra, SEM and TEM. The detailed photocatalytic degradation studies are carried out over TiO(2), SBA-15 and different TiO(2) wt% supported SBA-15. The activity evaluation parameters such as catalyst amount, pH, and pollutant initial concentration are studied taking isoproturon as a model compound and established conditions for pesticide degradation. The optimum degradation is achieved over 10 wt% TiO(2)/SBA-15 within 30 min and the reaction is following pseudo-first order kinetics. The isoproturon mineralization is monitored with TOC reduction and it takes around 9h for disappearance. The commercial pesticide solutions containing imidacloprid and phosphamidon are also successfully degraded over these composites with the established conditions. The data indicates that 10 wt% TiO(2)/SBA-15 composite is an effective and highly active system for the pesticide degradations.     

Photocatalytic degradation of isoproturon herbicide over TiO2/Al-MCM-41 composite systems using solar light

The present investigation covers immobilization of TiO2 using a simple solid state dispersion technique over mesoporous Al-MCM-41 support for the treatment of isoproturon herbicide. Catalysts are characterized by XRD, X-ray photo electron spectroscopy (XPS), surface area, UV-Vis diffused reflectance spectra (DRS), SEM and TEM. A detailed photocatalytic degradation study of isoproturon under solar light in aqueous suspensions is reported. The 10 wt% TiO2/Al-MCM-41 composite system found to be optimum with high degradation activity. The reaction follows pseudo-first order kinetics. The parameters like TiO2 loading over Al-MCM-41, amount of catalyst, concentration of substrate, pH effect, durability of the catalyst, activity comparison of TiO2 and Al-MCM-41 supported system are studied. The mineralization of isoproturon is monitored by TOC. Based on the degradation products detected through LC-MS, a plausible degradation mechanism is proposed. The data indicates that TiO2/Al-MCM-41 composite system is an effective photocatalyst for treatment of isoproturon in contaminated water.     

Bacterial community structure and microorganism inactivation following water treatment with ferrate(VI) or chlorine

Drinking water disinfection plays a critical role in protecting humans from waterborne pathogens. Ferrate(VI) (Fe^VIO₄ ^2?) has also been proposed as a disinfectant. This is the first study investigating the bacterial microbiomes of ferrate(VI)-treated water compared to chlorinated water. Tested water was collected after sand filtration and before disinfection from a drinking water treatment plant at Jiaxing, Zhejiang Province, China. A culture-independent method utilizing propidium monoazide was used with quantitative polymerase chain reaction and pyrosequencing of 16S rRNA genes to distinguish between the viable and nonviable bacterial populations. The operational taxonomic units and α-diversity indexes of the live bacterial phylotypes in the samples were determined. Viable bacteria remained in all samples following chlorination or ferrate treatment. However, the genera Vibrio, Salmonella, Shigella, Escherichia, Campylobacter, Yersinia, Plesiomonas, Legionella, and Helicobacter, which contain important human pathogens, were not present among the 25 dominant genera seen in these samples. The profiles of the bacteria remaining after treatment with either chlorine or ferrate differed. The ferrate-treated samples showed a reduced percent relative abundance of operational taxonomic units of the class Alphaproteobacteria within the total remaining viable bacteria. The genera Flavobacterium and Duganella were relatively resistant to treatment by either chlorine or ferrate(VI). At the highest doses of chlorine and ferrate(VI), the genus Sphingobium represented a greater percentage of live bacteria in the chlorinated sample than in the ferrate(VI)-treated sample. The results suggest that ferrate(VI) and chlorine could inactivate slightly different sets of bacteria and could have different mechanisms of bacterial inactivation.     

Assessment of crude oil biodegradation in arctic seashore sediments: effects of temperature,salinity, and crude oil concentration

The expected increase in offshore oil exploration and production in the Arctic may lead to crude oil spills along arctic shorelines. To evaluate the potential effectiveness of bioremediation to treat such spills, oil spill bioremediation in arctic sediments was simulated in laboratory microcosms containing beach sediments from Barrow (Alaska), spiked with North Slope Crude, and incubated at varying temperatures and salinities. Biodegradation was measured via respiration rates (CO₂ production); volatilization was quantified by gas chromatography/mass spectrophotometry (GC/MS) analysis of hydrocarbons sorbed to activated carbon, and hydrocarbons remaining in the sediment were quantified by GC/flame ionization detector (FID). Higher temperature leads to increased biodegradation by naturally occurring microorganisms, while the release of volatile organic compounds was similar at both temperatures. Increased salinity had a small positive impact on crude oil removal. At higher crude oil dosages, volatilization increased, however CO₂ production did not. While only a small percentage of crude oil was completely biodegraded, a larger percentage was volatilized within 6–9 weeks.     

Enrichment and isolation of endosulfan-degrading microorganism from tropical acid soil

Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,3,4-benzo-dioxathiepin-3-oxide) is a cyclodiene organochlorine currently used as an insecticide all over the world and its residues are posing a serious environmental threat. This study reports the enrichment and isolation of a microbial culture capable of degrading endosulfan with minimal production of endosulfan sulfate, the toxic metabolite of endosulfan, from tropical acid soil. Enrichment was achieved by using the insecticide as sole sulfur source. The enriched microbial culture, SKL-1, later identified as Pseudomonas aeruginosa, degraded up to 50.25 and 69.77 % of α and β endosulfan, respectively in 20 days. Percentage of bioformation of endosulfan sulfate to total formation was 2.12% by the 20th day of incubation. Degradation of the insecticide was concomitant with bacterial growth reaching up to an optical density of 600 nm (OD600) 2.34 and aryl sulfatase activity of the broth reaching up to 23.93 μg pNP/mL/hr. The results of this study suggest that this novel strain is a valuable source of potent endosulfan–degrading enzymes for use in enzymatic bioremediation. Further, the increase in aryl sulfatase activity of the broth with the increase in degradation of endosulfan suggests the probable involvement of the enzyme in the transformation of endosulfan to its metabolites.     

Removal of Cr(VI) onto Ficus carica biosorbent from water

The utilization of sustainable and biodegradable lignocellulosic fiber to detoxify the noxious Cr(VI) from wastewater is considered a versatile approach to clean up a contaminated aquatic environment. The aim of the present research is to assess the proficiency and mechanism of biosorption on Ficus carica bast fiber via isotherm models (Langmuir, Freundlich, Temkin, Harkin’s–Jura, and Dubinin–Radushkevich), kinetic models, and thermodynamic parameters. The biomass extracted from fig plant was characterized by scanning electron microscopy and Fourier-transform infrared spectroscopy. To optimize the maximum removal efficiency, different parameters like effect of initial concentration, effect of temperature, pH, and contact time were studied by batch method. The equilibrium data were best represented by the Langmuir isotherm model, and the maximum adsorption capacity of Cr(VI) onto biosorbent was found to be 19.68 mg/g. The pseudo-second-order kinetic model adequately described the kinetic data. The calculated values of thermodynamic parameters such as enthalpy change (?H ⁰), entropy change (?S ⁰), and free energy change (?G ⁰) were 21.55 kJ/mol, 76.24 J/mol?K, and ?1.55 kJ/mol, respectively, at 30 °C which accounted for spontaneous and endothermic processes. The study of adsorbent capacity for Cr(VI) removal in the presence of Na⁺, Mg²⁺, Ca²⁺, SO ₄ ^2? , HCO ₃ ^? and Cl^? illustrated that the removal of Cr(VI) increased in the presence of HCO^3? ions; the presence of Na⁺, SO ₄ ^2? or Cl^? showed no significant influence on Cr(VI) adsorption, while Ca²⁺ and Mg²⁺ ions led to an insignificant decrease in Cr(VI) adsorption. Further, the desorption studies illustrated that 31.10 % of metal ions can be removed from an aqueous system, out of which 26.63 % of metal ions can be recovered by desorption in first cycle and the adsorbent can be reused. The results of the scale-up study show that the ecofriendly detoxification of Cr(VI) from aqueous systems was technologically feasible.     

Ammonia in the atmosphere: a review on emission sources, atmospheric chemistry and deposition on terrestrial bodies

Gaseous ammonia (NH₃) is the most abundant alkaline gas in the atmosphere. In addition, it is a major component of total reactive nitrogen. The largest source of NH₃ emissions is agriculture, including animal husbandry and NH₃-based fertilizer applications. Other sources of NH₃ include industrial processes, vehicular emissions and volatilization from soils and oceans. Recent studies have indicated that NH₃ emissions have been increasing over the last few decades on a global scale. This is a concern because NH₃ plays a significant role in the formation of atmospheric particulate matter, visibility degradation and atmospheric deposition of nitrogen to sensitive ecosystems. Thus, the increase in NH₃ emissions negatively influences environmental and public health as well as climate change. For these reasons, it is important to have a clear understanding of the sources, deposition and atmospheric behaviour of NH₃. Over the last two decades, a number of research papers have addressed pertinent issues related to NH₃ emissions into the atmosphere at global, regional and local scales. This review article integrates the knowledge available on atmospheric NH₃ from the literature in a systematic manner, describes the environmental implications of unabated NH₃ emissions and provides a scientific basis for developing effective control strategies for NH₃.     

Organ-wise accumulation of fluoride in Prosopis juliflora and its potential for phytoremediation of fluoride contaminated soil

Fluoride (F) contamination is a global environmental problem, as there is no cure of fluorosis available yet. Prosopis juliflora is a leguminous perennial, phreatophyte tree, widely distributed in arid and semi-arid regions of world. It extensively grows in F endemic areas of Rajasthan (India) and has been known as a “green” solution to decontaminate cadmium, chromium and copper contaminated soils. This study aims to check the tolerance potential of P. juliflora to accumulate fluoride. For this work, P. juliflora seedlings were grown for 75 d on soilrite under five different concentrations of F viz., control, 25, 50, 75 and 100 mg NaF kg⁻¹. Organ-wise accumulation of F, bioaccumulation factor (BF), translocation factor (TF), growth ratio (GR) and F tolerance index (TI) were examined. Plant accumulated high amounts of F in roots. The organ-wise distribution showed an accumulation 4.41 mg kg⁻¹dw, 12.97 mg kg⁻¹dw and 16.75 mg kg⁻¹dw F, in stem, leaves and roots respectively. The results indicated significant translocation of F from root into aerial parts. The bioaccumulation and translocation factor values (>1.0) showed high accumulation efficiency and tolerance of P. juliflora to F. It is concluded that P. juliflora is a suitable candidate for phytoremediation purpose and can be explored further for the decontamination of F polluted soils.     

Kinetics of the oxidation of sucralose and related carbohydrates by ferrate(VI)

The kinetics of the oxidation of sucralose, an emerging contaminant, and related monosaccharides and disaccharides by ferrate(VI) (Fe(VI)) were studied as a function of pH (6.5-10.1) at 25°C. Reducing sugars (glucose, fructose, and maltose) reacted faster with Fe(VI) than did the non-reducing sugar sucrose or its chlorinated derivative, sucralose. Second-order rate constants of the reactions of Fe(VI) with sucralose and disaccharides decreased with an increase in pH. The pH dependence was modeled by considering the reactivity of species of Fe(VI), (HFeO(4)(-) and FeO(4)(2-)) with the studied substrates. Second-order rate constants for the reaction of Fe(VI) with monosaccharides displayed an unusual variation with pH and were explained by considering the involvement of hydroxide in catalyzing the ring opening of the cyclic form of the carbohydrate at increased pH. The rate constants for the reactions of carbohydrates with Fe(VI) were compared with those for other oxidant species used in water treatment and were briefly discussed.