Generalized gene expression programming models for estimating reference evapotranspiration through cross-station assessment and exogenous data supply

Environmental Science and Pollution Research - Adopting methodologies utilizing exogenous data from ancillary stations for determining crop water requirement is a suitable approach to exempt local...     

Antimony induces oxidative stress and cell death in normal hepatocytes

Antimony (Sb) accumulates in the liver which is one of the target organs for metal-mediated toxicity. Although toxicity of Sb was previously investigated, the precise mechanism of Sb-induced hepatotoxicity remains to be determined. The aim of this study was to examine the role of oxidative stress, and mitochondria in the induction of cell death by Sb. Our results showed that liver cell lysis induced by Sb is mediated by reactive oxygen species (ROS) formation, lipid peroxidation and decline of mitochondrial membrane potential (MMP). Antimony-induced ROS formation, lipid peroxidation and reduction of MMP were significantly diminished by antioxidants and ROS scavengers such as dimethyl sulfoxide and mannitol; mitochondrial permeability transition (MPT) pore sealing agents such as carnitine and trifluoperazine; and adenosine triphosphate (ATP) generator, L-glutamine. Antimony-induced ROS formation, lipid peroxidation and fall in MMP were potentiated by glutathione (GSH) depletion via n-bromoheptane. MPT pore sealing agents and ATP generator inhibited hepatotoxicity, indicating Sb-activated cell death via mitochondrial pathway. Pretreatment of hepatocytes with antioxidants and ROS scavengers also blocked cell death induced by Sb, whereas GSH depletion enhances Sb-induced cell death, suggesting that oxidative stress may be directly involved in the reduction of MMP. These findings contribute to a better understanding of the mechanisms that mediate Sb-induced cell death in isolated rat hepatocytes.     

Extraction of ultra traces of polychlorinated biphenyls in aqueous samples using suspended liquid-phase microextraction and gas chromatography-electron capture detection

This study reports the feasibility of applying directly suspended liquid-phase microextraction (DSLPME)-gas chromatography detection for the pre-concentration and determination of low levels of eight polychlorinated biphenyls (PCBs) in aqueous samples. The technique requires minimal sample preparation, analysis time and solvent consumption and represents significant advantages over conventional analytical methods. The experimental parameters such as salt content, sample temperature, stirring rate, extraction time, micro-drop volume and breakthrough volume were investigated and found to have significant influences on DSLPME. Under the optimal experimental conditions, the enrichment factor ranged from 578 to 729, and the recovery was above 93 %. Calibration curves possessed good linearity (R ²?>?0.99) over a wide concentration range of 0.1–10.0 μg L^?1 with limits of detection ranging from 0.01 to 0.07 μg L^?1. The relative standard deviations for 1.0 μg L^?1 of PCBs in water by using internal standard were in the range 2–14 % (n?=?3). The proposed simple, accurate and sensitive analytical method was applied successfully to the determination of trace amounts of PCBs in water samples.     

Degradation of CL-20 by white-rot fungi

In previous studies, we found that the emerging energetic chemical, CL-20 (C6H6N12O12, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane), can be degraded following its initial denitration using both aerobic and anaerobic bacteria. The C and N mass balances were not determined due to the absence of labeled starting compounds. The present study describes the degradation of the emerging contaminant by Phanerochaete chrysosporium using ring-labeled [15N]-CL-20 and [14C]-CL-20. Ligninolytic cultures degraded CL-20 with the release of nitrous oxide (N2O) in amounts corresponding to 45% of the nitrogen content of CL-20. When ring-labeled [15N]-CL-20 was used, both 14N14NO and 15N14NO were observed, likely produced from -NO2 and N-NO2, respectively. The incubation of uniformly labeled [14C]-CL-20 with fungi led to the production of 14CO2 (> 80%). Another ligninolytic fungus, Irpex lacteus, was also able to degrade CL-20, but as for P. chrysosporium, no early intermediates were observed. When CL-20 was incubated with manganese peroxidase (MnP), we detected an intermediate with a [M-H]- mass ion at 345 Da (or 351 and 349 Da when using ring-labeled and nitro-labeled [15N]-CL-20, respectively) matching a molecular formula of C6H6N10O8. The intermediate was thus tentatively identified as a doubly denitrated CL-20 product. The concomitant release of nitrite ions (NO2-) with CL-20 degradation by MnP also supported the occurrence of an initial denitration prior to cleavage and decomposition.     

Preliminary ecotoxicological characterization of a new energetic substance, CL-20

A new energetic substance hexanitrohexaazaisowurtzitane (or CL-20) was tested for its toxicities to various ecological receptors. CL-20 (epsilon-polymorph) was amended to soil or deionized water to construct concentration gradients. Results of Microtox (15-min contact) and 96-h algae growth inhibition tests indicate that CL-20 showed no adverse effects on the bioluminescence of marine bacteria Vibrio fischeri and the cell density of freshwater green algae Selenastrum capricornutum respectively, up to its water solubility (ca. 3.6 mg l(-1)). CL-20 and its possible biotransformation products did not inhibit seed germination and early seedling (16-19 d) growth of alfalfa (Medicago sativa) and perennial ryegrass (Lolium perenne) up to 10,000 mg kg(-1) in a Sassafras sandy loam soil (SSL). Indigenous soil microorganisms in SSL and a garden soil were exposed to CL-20 for one or two weeks before dehydrogenase activity (DHA) or potential nitrification activity (PNA) were assayed. Results indicate that up to 10,000 mg kg(-1) soil of CL-20 had no statistically significant effects on microbial communities measured as DHA or on the ammonium oxidizing bacteria determined as PNA in both soils. Data indicates that CL-20 was not acutely toxic to the species or microbial communities tested and that further studies are required to address the potential long-term environmental impact of CL-20 and its possible degradation products.     

Extended geometric method: a simple approach to derive adsorption rate constants of Langmuir-Freundlich kinetics

A new and simple equation has been presented here for calculation of adsorption and desorption rate constants of Langmuir-Freundlich kinetic equation. The derivation of new equation is on the basis of extension and correction to the geometric method which has been presented by Kuan et al. [Kuan, W.-H., Lo, S.-L., Chang, C.M., Wang, M.K., 2000. A geometric approach to determine adsorption and desorption kinetic constants. Chemosphere 41, 1741-1747] for the kinetics of adsorption/desorption in aqueous solutions. The correction is to consider that the concentration of solute is not constant and changes as adsorption proceeds. The extension is that we applied Langmuir-Freundlich kinetic model instead of Langmuir kinetic model to consider the heterogeneity and therefore it is more applicable to the real systems. For solving Langmuir-Freundlich kinetic model, some geometric methods and also Taylor expansion were used and finally a simple and novel equation was derived (Eq. (20)) for calculation of adsorption rate constant. This new method was named "extended geometric method". The input data of the obtained equation can be simply derived from initial data of adsorption kinetics. Finally the adsorption of methyl orange onto granular activated carbon was carried out at dynamic and equilibrium conditions and the capabilities of extended geometric method were examined by the experimental data.     

Fractal approach in expansive clay-based materials with special focus on compacted GMZ bentonite in nuclear waste disposal: a systematic review

Environmental Science and Pollution Research - Knowledge of the behavior of highly compacted expansive clays, as an engineered barrier, in disposal of high-level nuclear waste (HLW) systems to...