首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Lymph node and spleen tissues involved in malignant lymphomas were analysed for iron, manganese, copper, zinc and magnesium by atomic absorption spectrophotometry. The levels of iron are found to be significantly lower in the case of Hodgkin's lymphoma compared with non-Hodgkin's lymphoma and normal lymph nodes. However, they are elevated in Hodgkin's lymphoma when compared with the normal value for spleen tissues. Magnesium is significantly higher in lymph nodes of non-Hodgkin's lymphoma compared with Hodgkin's lymphoma and normal values, but is not altered significantly in spleen tissues. The distribution of the other elements examined is not altered significantly in malignant lymphomas. The importance of the in situ levels of these elements to NMR imaging is discussed.  相似文献   

2.
The distillation technique has been investigated as a means of concentrating in the distillate the low-molecular-weight volatile polar organic compounds such as alcohols, ketones, and aldehydes in aqueous solution. The volatility of these compounds relative to that of water was found to be a useful parameter in determining the concentration of the respective compounds in the distillate. By directly injecting the distillate onto a gas chromatographic column, low-molecular-weight volatile polar organics can be determined quantitatively at the ppb level. The relative standard deviation for the distillation technique is approximately 5% based on triplicate runs using an internal standard. This study shows that the distillation technique is a simple, unique, and efficient method of concentrating low-molecular-weight volatile polar organics at the ppb level for subsequent gas chromatographic analysis.  相似文献   

3.
The 226Ra and 228Ra content of the lichens Umbilicaria cylindrica, U. deusta, U. murina and U. hirsuta has been determined as a function of the growth altitude above sea level, based on data derived from material collected from localities in southwest Poland. These data are interpreted as graphs and formulae to show the influence of environmental factors, particularly altitude, on the concentration of 226Ra and 228Ra, and the coefficients of accumulation calculated.  相似文献   

4.
C.P. Huang  M.H. Wu   《Water research》1977,11(8):673-679
The removal of chromium(VI) by activated carbon, filtrasorb 400, is brought by two major interfacial reactions: adsorption and reduction. Chemical factors such as pH and total Cr(VI) that affect the magnitude of Cr(VI) adsorption were investigated. The adsorption of Cr(VI) exhibits a peak value at pH 5–6. The particle size of carbon and the presence of cyanide species do not change the magnitude of chromium removal. The reduced Cr(VI), e.g. Cr(III) is less adsorbable than Cr(VI).The free energy of specific chemical interaction, ΔGchem was computed by the Gouy-Chapman-Stern-Grahame model. The average values of ΔGchem are −5.57 RT and −5.81RT, respectively, for Cr(VI) and CN. These values are significant enough to influence the overall magnitude of Cr(VI) and CN adsorption. Results also indicate that HCrO4 and Cr2O2−7 are the major Cr(VI) species involved in surface association.  相似文献   

5.
One of the chemicals most clearly exemplifying scientific and political controversy concerning efforts to control its discharge to surface waters is phosphorus and its complexes. These materials are discharged as natural components of domestic wastewaters and include phosphorus from human waste and food waste as well as residual detergent phosphorus. Significant amounts of phosphorus also reach surface waters from non-point sources such as agricultural and urban runoff. This paper presents results of several field and laboratory investigations designed to position the impact of detergent phosphorus contributions to surface water quality. In a number of areas where legislation banned the sale of phosphorus detergents, limnological investigations were carried out to assess the impact of the ban upon receiving water quality. Field studies in natural lakes demonstrate that reductions of phosphorus in wastewaters, even up to 50%, may not substantially improve the trophic status of lakes. The consistent conclusion emerging from these studies is that the elimination of detergent phosphorus has not measurably improved lake water quality.  相似文献   

6.
Ozone-sparged vessels for the oxidation of a model organic compound, methanol, was studied. The parameters under study included superficial gas velocity, the gas phase ozone concentration, the rate of ozonation of methanol and its oxidative products, the residence time, etc. The scale-up method based on the mathematical model developed in this study accurately predicts the superficial gas velocity and the gas phase ozone concentration required for two larger geometrically similar vessels to achieve the same level of total organic carbon removal obtained in a small vessel.  相似文献   

7.
A scheme for the speciation of metals in freshwaters has been applied to the analysis of the final effluent from a sewage treatment plant and to the receiving river upstream and downstream of the effluent outfall. The treatment plant was selected because of the high influent and effluent concentrations of Cd. The metal speciation patterns in the effluent are interpreted primarily in terms of organic interactions, which appear to be exerting a solubilizing effect on Cd and Cu, but not on the Pb and Fe which are principally associated with the particulate size fraction (> 12 μm). The influx of metals with the sewage effluent alters the speciation pattern in the river. A large part of the Cd is added to the smallest size fraction (< 0.015 μm). However, the major part of each metal, with the exception of Mn, is associated with the colloidal and particulate size fractions, thus minimising the immediate toxic significance to aquatic life.  相似文献   

8.
A scheme for the speciation of metals in freshwaters has been applied to the metals Pb, Cd, Cu, Fe and Mn in the treated effluent of a lead-acid battery manufacturer and the receiving river upstream and downstream of the effluent outfall. The speciation is inferred from measurements of the size-associations of the metals, the lability with respect to anodic stripping voltammetry and Chelex resin and by u.v. irradiation to destroy organic complexing agents. The results are related to chemical and physical interactions within the waters and are discussed in terms of the impact of the effluent discharge upon the receiving river.  相似文献   

9.
Various approaches, such as bioassays, computer-assisted modelling and direct measurement following physical separation are currently being used to investigate the speciation of trace metals in sea water. The electrochemical techniques used successfully as a necessary prerequisite for the experiments involved include conventional polarography, anodic stripping voltammetry (ASV) and potentiometry. Differential pulse anodic stripping voltammetry (DPASV) using mercury film electrodes enables direct studies in ultratrace levels present in non-contaminated ocean waters.By varying the conditions of the sample chemistry and electroanalysis it is possible to characterize metal-organic interactions. This is demonstrated in the case of natural sea water samples subjected to ASV diagnosis. Differences in the Pb and Cu values yielded for Baltic waters by two methods based on DPASV and AAS are discussed with regard to speciation.An analysis of the existing literature is used to briefly summarize the needs of future research. Important problems requiring a more precise quantitative analysis include the adsorption of organics on electrodes and the kinetics and thermodynamic constants of chelates with special regard to the physico-chemical nature of metal-humic substances. The introduction of new and improved electroanalytical techniques and equipment for speciation studies is strongly recommended.  相似文献   

10.
An improved method has been developed for the analysis of the adenosinetriphosphate (ATP) content of environmental samples with the luciferin-luciferase assay. Factors affecting the recovery and stability of the ATP as well as the enzymatic reaction were optimized. The most versitile method utilizes procedure which can be used for natural waters, sediments and sludges. This involves homogenization at room temperature in 10−2 M trisodium phosphate, pH 11.7, containing 23% chloroform. This method is more effective than other methods tested and results in minimal interference with the enzymatic reaction. It also provides improved ATP recovery and long term stability of extracted ATP. Another method that can be used on natural waters and sludges is by boiling for 5 min in 10−2 M glycine buffer, 5 × 10−3 M Mg-EDTA, pH 10, which resulted in complete extraction and no hydrolytic loss of ATP. However, it is not satisfactory for sediments containing high humic acid substances as well as high metal loadings.In addition to the direct comparison of endogenous ATP extraction by various methods, actual recoveries of spiked radioactive ATP was measured. ATP adsorption, hydrolysis and recoveries in each method were determined by the use of [8-14C] ATP and [γ-32P] ATP.  相似文献   

11.
Male pathogen free CFE albino Sprague Dawley rats were exposed 8 h per day, 5 days per week, for three years to a 1/1000 dilution of automotive exhaust gas, containing 58 ppm carbon monoxide, 0.37% carbon dioxide, 23 ppm nitrogen oxides, 2 ppm aldehydes, less than 5 mg/l hydrocarbons and 8.5 micrograms/m3 lead. Lead, cadmium, iron, zinc, calcium and magnesium were measured by atomic absorption in the femurs and tibias of the rats which died during the experiment. A comparison with two control groups revealed that the only significant difference in the elements measured in the bones was a 500% increase in lead concentration. The calculations of the correlations between the percentages of the elements in bones, the ages and the body weights of the rats, as well as cluster analysis, did not show consistent variations of the water, calcium, magnesium concentrations nor of the other studied metals related to this increase in lead concentration. Moreover, longevity was the same in the 3 groups of rats, but the body weight was statistically smaller (4%) in the group exposed to the auto exhaust dilution.  相似文献   

12.
Sulfur dioxide is a reduced compound which acts as a positive interference in the chemical oxygen demand (COD) analysis. Significant amounts of sulfur dioxide present in industrial waste samples may therefore result in erroneously high COD values, compared to that of a sample with only the organic portion of the waste. By adding 65 mg l−1 Mn2+ to a secondary wastewater sample spiked with 500 mg l−1 sulfur dioxide, and oxygenating the sample for 6 min, sulfur dioxide was oxidized completely to sulfate. This oxidation procedure provides a statistically valid means of removing SO2 interference in the COD analysis. The procedure provides an efficient means of investigating the organic COD of industrial effluents laden with SO2 or its dissociation products.  相似文献   

13.
A nonlinear finite strip method of analysis is described for the post-local buckling of geometrically imperfect plate assemblies. The method is used to provide an accurate alternative to the Winter effective width formula for obtaining the effective section of a simply supported I-beam in the post-local buckling range of structural response. The effective section of a locally buckled beam with thin flange outstands is used to investigate the resistance of the beam to flexural-torsional buckling. The analytical methods developed to assess the nonlinear interaction of local and lateral buckling are compared with experimental tests performed by Cherry.  相似文献   

14.
Cooling water at coastal and estuarine power stations is chlorinated to inhibit mussel growth in the intakes to the condensers and a means of automatically monitoring the free residual chlorine concentration is desired so that the dosage can be precisely maintained at 0.2 μg ml−1 Cl2. The Delta Scientific model 82124 amperometric membrane probe has been tested in the laboratory for its suitability for this application. The probe had a linear response to hypochlorous acid over the range 0–5 μg ml−1, but was not specific for free residual chlorine, as chloramines also produced a response. The main product of the chlorination of sea water is bromine, to which the probe is about five times more sensitive than to hypochlorous acid. Although the probe can be calibrated with bromine, its response is then much noisier than that obtained with hypochlorous acid. The salinity of the sample influences the reading obtained at a given concentration of oxidant: increasing the salinity increases the reading obtained with hypochlorous acid but decreases that obtained with bromine.  相似文献   

15.
The copper binding capacity was used to follow physico-chemical changes in the mixing of sewage effluent and seawater. In laboratory experiments dilute aliquots of filtered and unfiltered effluents were mixed with artificial seawater to give saline concentrations of between 0 and 40‰. The copper binding capacity of the filtered sample decreased rapidly from 22.8 to 0 μg l−1 in the salinity range 5–10‰. The difference between the unfiltered and filtered binding capacity, defined as the adsorption capacity, varied from 28.5 to 0 μg l−1 in the salinity range 15–22‰. These results were interpreted in terms of destabilisation of copper associations with humates, colloids and particulate matter with increasing salinity. The behaviour of unfiltered binding capacity in the effluent plume was measured and the results showed reasonable agreement with results from the laboratory experiments.  相似文献   

16.
Differential pulse polarography and differential pulse anodic stripping voltammetry were used to determine copper, lead, cadmium and zinc complexes of relevance to environmental conditions. The dependency of peak current on pH and alkalinity was interpreted in terms of the variation in the metal species present. Stability constants of copper and lead complexes with carbonate were determined from the magnitude of the shift of peak potential using the method of Lingane. Inclusion of the transfer coefficient, calculated from the peak half-width for electrochemically irreversible systems, was used to determine the stability constant. By using both electroanalytical techniques, the investigator validates the correctness of his results without needing to rely on prior determinations of the stability constant for verification.  相似文献   

17.
The effect of a mixture of calcium alginate, iron(III)ferrocyanide and potassium iodide added to rat diet on 85Sr, 137Cs and 131I metabolism and health was investigated in female rats after four weeks of treatment. The retention of these radioisotopes was determined in the whole body and critical organs six days after 85Sr and 137Cs and one day after 131I oral administration. The health effect of the mixture was evaluated by measuring body weights, haematological parameters, concentrations of iron, zinc and manganese in the kidneys, liver and femur, bone parameters (femur composition and morphometry) and by a histopathological examination.The mixture reduced 85Sr retention in the femur 11 times, 137Cs retention in the thigh muscle 102 times and 131I retention in the thyroid 134 times. Treated animals were in good health and the only differences found between the control and experimental rats were slightly lower haemoglobin values in the blood and a slightly lower iron concentration in the liver.It is concluded that the mixture was very efficient for decreasing body retention of three important fission products and that it can be used over long periods without causing adverse health effects.  相似文献   

18.
The effects of pH, inorganic suspended solids and organic suspended solids on the adsorption of organics by activated carbon were investigated using sewage effluents and selected organic compounds of varying size, structure, molecular weight and properties in model solutions. It was found that suspended solids, and in particular organic suspended solids, could interfere with the adsorption process, both in terms of adsorption capacity and adsorption rate; the effect of the solids diminished as the size of the adsorbate increased. The effect of pH variation became more significant as the acidity or basicity of the adsorbate in solution increased. Adsorption of organics from biologically treated sewage effluents was somewhat more effective in the acid and alkaline pH regions than in the neutral pH region.  相似文献   

19.
The application of flameless atomic absorption analysis to the determination of cadmium, copper and lead in sewage sludges is described. The technique is sensitive and very rapid, since the normal lengthy sample pre-treatment has been virtually eliminated. The method can be potentially extended to a large range of metals in all types of sludges.  相似文献   

20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号