Dilution versus pollution in watercourses affected by acid mine drainage: a graphic model for the Iberian Pyrite Belt (SW Spain)

The aim of this study was to chemically characterize the water quality impacts of the 88 acid mine drainage (AMD) generating mines in the Spanish sector of the Iberian Pyrite Belt (IPB). This was necessary because the Water Framework Directive of the European Union and the hydrological plans of the Tinto, Odiel, and Piedras river basins require that water quality be improved enough to allow at least some of the rivers in the IPB to sustain healthy fish populations by 2027. The results indicate a clear decrease in metals, arsenic, and sulfate concentrations and increased pH between the AMD-sources and the river channels.info:eu-repo/semantics/publishedVersio

Effects of aeration and organic loading rates on degradation of trichloroethylene in a methanogenic-methanotrophic coupled reactor

The effects of four aeration and four organic loading (OLR) rates on trichloroethylene (TCE) degradation in methanogenic-methanotrophic coupled reactors were studied using ethanol as the carbon source for the methanogens. Microcosm and PCR studies demonstrated that methanotrophs capable of mineralizing TCE and methanogens were present in the biomass throughout the study. The gene for the particulate form of methane monooxygenase (pMMO) was detected by PCR, but not that for the soluble form (sMMO). TCE mineralization by methanotrophs was therefore due primarily to pMMO activity. Low TCE concentrations were measured in effluent and off-gas samples in all cases. Volatilization losses were 0-5%. Dichloroethylene (DCE) was also observed, but vinyl chloride and ethylene were never detected. Changes in the aeration rate had no effect on TCE removal, but did influence DCE degradation. Reductive dechlorination of TCE to DCE was favored at low and no-aeration conditions, and DCE accumulation occurred due to slow DCE degradation. Low DCE levels were observed at the higher aeration rates, which indicated that conditions in these reactors were amenable to the aerobic co-metabolism of TCE and DCE. The OLR did have an effect on TCE removal. TCE and DCE removal were negatively affected when the OLR was increased. An OLR of 0.3 g COD lrx\u443day\u443 or lower with an aeration rate of 3 lO2 lrx\u443day\u443 and higher is the recommended operating condition of a coupled reactor for removal of TCE.NRC publication: Ye

Transmembrane permeability channels across the outer membrane of Haemophilus influenzae type b

Outer membranes of Haemophilus influenzae type b were fractionated to yield Triton X-100-insoluble material and lipopolysaccharide and phospholipids. Liposomes reconstituted from lipopolysaccharide and phospholipids were impermeable to sucrose (Mr, 342) and to a high-molecular-weight dextran (average Mr, 6,600). When the Triton X-100-insoluble material was introduced into the reconstituted liposomes, the vesicles became permeable to sucrose, raffinose (Mr, 504), and stachyose (Mr, 666) and fully retained dextrans of Mr greater than 1,500. Inulin (average Mr, 1,400) was tested for its efflux from the reconstituted outer membrane vesicles; 62% of the added inulin was trapped. The molecular weight exclusion limit for the outer membrane of H. influenzae type b was therefore estimated at approximately 1,400. A protein responsible for the transmembrane diffusion of solutes was purified from H. influenzae type b by extraction of whole cells with cetyl trimethyl ammonium bromide. When this extract was passed over DEAE-Sepharose, three protein-containing peaks (I, II, and III) were eluted. Peaks I and II contained mixtures of proteins as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis; when tested for their pore-forming properties, these proteins were unable to render liposomes of lipopolysaccharide and phospholipid permeable to sucrose. Peak III contained only one molecular species of protein of molecular weight 40,000; this protein acted as a porin in reconstituted vesicles. The molecular weight exclusion limit for 40,000-molecular-weight protein matched the estimate of approximately 1,400 which was determined for outer membranes. A series of homologous saccharides of increasing degree of polymerization was prepared from agarose by hydrolysis with beta-agarase and fractionation on gel filtration chromatography. These oligosaccharides of Mr, 936, 1,242, 1,548, and 1,854 were assayed for retention by the complete vesicles containing 40-kilodalton protein and lipopolysaccharide and phospholipids. All of these oligosaccharides were lost by efflux through the porin. Since the molecular conformation of the largest oligosaccharide is an elongated semirigid helix, it is suggested that the pore formed by the 40-kilodalton protein does not act as a barrier to the diffusion of this compound.</jats:p

A microcosm test for potential mineralization of chlorinated compounds under coupled aerobic/anaerobic conditions

In this study, the feasibility of using a mineralization test under coupled aerobic/anaerobic conditions was demonstrated. The coupling of anaerobic methanogenic and aerobic methanotrophic conditions in a microcosm required the presence of both a carbon source for anaerobic metabolism and oxygen for aerobic metabolism. These requirements were fulfilled by using a slow hydrolyzing organic matter along with intermittent addition of oxygen to the bottle headspace. Perchloroethylene (PCE) mineralization tests confirmed the effectiveness of the proposed methodology as well as PCE mineralization under coupled conditions.NRC publication: Ye

Microwave-assisted retting and optimization of the process through chemical composition analysis of the matrix

Pre-soaked flax stems were subjected to microwave assisted retting at different power levels and the effectiveness of microwave assisted retting was studied through the analysis of chemical compounds presented in the retted flax fibers processed from the stems. Response surface statistical design was used for this study with JMP\uae 10 software. Chemical analyses were performed by gravimetric methods to find out percentage of compounds. Cellulose, hemicellulose, lignin and pectin concentrations and the sugar content in the solution obtained after the treatment were subjected to analysis. Cellulose percentage in the fiber was increased significantly (p<0.0001) with the increase of microwave power at various soaking levels, which proved the release of cellulosic fiber with the application of microwave energy during retting. Hemicellulose, lignin and pectin concentrations decreased significantly after microwave-assisted retting which explained higher degree of retting after the treatment. This study noted change in chemical composition of the fibers, which can be used as a tool to estimate the effectiveness of microwave-assisted retting and the results could lead to optimization of the process. \ua9 2013 Elsevier B.V.Peer reviewed: YesNRC publication: Ye