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Prenatal monitoring of three pregnancies at risk of Morquio's disease type A by determination of N-acetylgalactosamine 6-sulphate sulphatase activity in cultured amniotic cells is reported. In one pregnancy prenatal diagnosis of one affected fetus was made. Enzyme determinations in tissues of the aborted fetus confirmed the prenatal diagnosis. 相似文献
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Electrochemical remediation of copper contaminated kaolinite by conditioning anolyte and catholyte pH simultaneously 总被引:9,自引:0,他引:9
This report examined electrochemical remediation of copper contaminated kaojinite by controlling electrolytes‘ pH for both of anolyte and catholyte simultaneously.Results showed the electrokinetic process and remediation efficiency varied obviously when different buffer systems,including citric acid(test 1),nitric acid EDTA(test 2)and nitric acid(test 3),were used to control catholyte pH AND Na2CO3 was used at the same time to control all anolyte one.It was found that under such pH condition soil‘s pH in soil column kept at 3.0-7.0 successfully,and correspondingly no copper precipitation and decrease of soil electroconductivity appeared.which are usually observed in electrokinetic process due to OH^- introduction into soil cojumn by electrochemical reaction occurred in cathode.Electroosmosis flow rates were almost equal for these three tests,indicating that these buffers did not affect Zeta-potential of kaolinite within the examined duration.More acid and basic solution was added into electrokinetic cell when nitric acid was used as buffer than when nitric acid EDTA and then citric acid were used.Due to introduction of large amounts of ions into soil column,significant higher current was observed for test 3 than other two.Analysis of copper speciation and total quantity in kaolinite indicated that 22.5%,23.74%and 55.65% Cu were removed from kaolinite for test 1,test 2 and test 3 respectively after only 10 days‘ electrokinetic remediation. 相似文献
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Rathfelder KM Abriola LM Singletary MA Pennell KD 《Journal of contaminant hydrology》2003,64(3-4):227-252
The ability of a multiphase flow model to capture the migration behavior of chlorinated solvents under conditions of surfactant-facilitated interfacial tension (IFT) reduction is assessed through comparison of model predictions with observations from controlled laboratory experiments. Tetrachloroethene (PCE) was released in two-dimensional saturated systems, packed with sandy media that incorporated rectangular lenses of capillary contrast. Spatially uniform interfacial tension conditions were created in the tanks by pre-flushing the porous medium with either Milli Q water or an aqueous surfactant solution. Experimental observations showed that surfactant-facilitated IFT reductions substantially lowered capillary resistance to the vertical downward migration of PCE and enabled PCE to enter finer grained, less permeable lenses that were not penetrated in the absence of surfactant. An immiscible flow model was used to simulate the conditions of the laboratory experiments. Under higher IFT conditions (47.5 and 5 dyn/cm), the model could successfully predict the general migration behavior of the organic liquid. Model predictions, however, exhibited poorer agreement with observed migration pathways under low IFT conditions (0.5 dyn/cm). In all cases, the predicted PCE distributions were influenced by selection of the parametric model for capillary retention and relative permeability. Simulated migration rates were more consistent with observed behavior when the Brooks-Corey/Burdine model was employed. For low interfacial tensions, improved predictions of migration pathways were obtained through grid refinement and incorporation of small-scale packing variability. Simulations highlight the substantial sensitivity of model predictions to the capillary pressure-scaling factor, grid resolution, and small-scale porosity variations at interfaces of permeability contrast under reduced IFT conditions. 相似文献
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A novel method to remediate dense nonaqueous phase liquid (DNAPL) source zones that incorporates in situ density conversion of DNAPL via alcohol partitioning followed by displacement with a low interfacial tension (IFT) surfactant flood has been developed. Previous studies demonstrated the ability of the density-modified displacement (DMD) method to recover chlorobenzene (CB) and trichloroethene (TCE) from heterogeneous porous media without downward migration of the dissolved plume or free product. However, the extent of alcohol (n-butanol) partitioning required for in situ density conversion of high-density NAPLs, such as tetrachloroethene (PCE), could limit the utility of the DMD method. Hence, the objective of this study was to compare the efficacy of two n-butanol delivery approaches: an aqueous solution of 6% (wt) n-butanol and a surfactant-stabilized macroemulsion containing 15% (vol) n-butanol in water, to achieve density reduction of PCE-NAPL in two-dimensional (2-D) aquifer cells. Results of liquid-liquid equilibrium studies indicated that density conversion of PCE relative to water occurred at an n-butanol mole fraction of 0.56, equivalent to approximately 5 ml n-butanol per 1 ml of PCE when in equilibrium with an aqueous solution. In 2-D aquifer cell studies, density conversion of PCE was realized using both n-butanol preflood solutions, with effluent NAPL samples exhibiting density reductions ranging from 0.51 to 0.70 g/ml. Although the overall PCE mass recoveries were similar (91% and 93%) regardless of the n-butanol delivery method, the surfactant-stabilized macroemulsion preflood removed approximately 50% of the PCE mass. In addition, only 1.2 pore volumes of the macroemulsion solution were required to achieve in situ density conversion of PCE, compared to 6.4 pore volumes of the 6% (wt) n-butanol solution. These findings demonstrate that use of the DMD method with a surfactant-stabilized macroemulsion containing n-butanol holds promise as an effective source zone remediation technology, allowing for efficient recovery of PCE-DNAPL while mitigating downward migration of the dissolved plume and free product. 相似文献