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1.
After extensive experiments aimed at determining the free volatile fatty acids (C2 to C6) in organically highly polluted percolation water of household refuse dumping places there proved optimum a column packed with 10% Carbowax 20 M on Chromatron N-AW-DMCS after having been conditioned for five days at 270°C and subsequently covered with 10% hard wax. On short retention times the investigated isomeric column pairs are completely separated. Equally favourable results were obtained also for liquid manure and silage extracts. The detection limits lie between 10 and 20 mg/l, the relative standard deviation is 20 … 30% in the range of the lower detection limit and 2 … 3% at 200 mg/l in the upper range. In the investigation of percolation waters with concentrations between 235 and 4300 mg/l reproducibility lies at a mean relative standard deviation of 0.5 … 2.8%. The technique is well suited for routine checking. 相似文献
2.
Soil water repellency (hydrophobicity) is a naturally occurring phenomenon that can be intensified by soil heating during fires. Fire‐induced water repellency, together with the loss of plant cover, is reportedly the principal source of increased surface runoff and accelerated erosion in burned soils. In this study, the surface water repellency of several soils affected by summer forest fires in northwest Spain was studied and compared with that of adjacent unburned soils. Soil water repellency was determined using the ethanol percentage test (MED). Most of the unburned soil samples exhibited water repellency that ranged from strong to very strong; only four of the unburned soil samples were non‐repellent. Water repellency in the unburned soils was significantly correlated with the organic carbon content (r = 0·64, p < 0·05). Overall, fires increased the surface water repellency in soils with previously low degrees of water repellency and caused little change in that of originally strongly hydrophobic soils. In order to examine in detail the changes in water repellency with temperature, three unburned soil samples were subjected to a controlled heating program. Water repellency increased between 25 and 220 °C, water repellency peaked between 220 and 240 °C and disappeared above 260–280 °C. Extrapolation of the results of the heating tests to field conditions suggested that the intensity of fire (temperature and time of residence) reached by most soils during fires is not too high. Based on the results, the determination of water repellency could be used as a simple test for the indirect estimation of the intensity levels reached on the soil surface during a fire. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
3.
Steam-Solid Chromatography Assay of Phthalates in Water Using Detection of Their Hydrolytic Products
P. Kov&#x; 《洁净——土壤、空气、水》1982,10(5):449-457
A method for the chromatographic analysis of small amounts of phthalates in water was developed. The reaction conditions for the quantitative alkaline hydrolysis of phthalates in water samples to corresponding alcohols are described. The procedure enables us to determine water samples in concentrations of 0.045 … 45 mg/l of di-i-octyl phthalate. The final determination is carried out by the direct injection of otherwise unprepared hydrolytic products into the column of a steam-solid chromatograph. The individual alcohols have been separated according to their boiling points (alcohols C4? C9 are eluated under the five-min retention time). The quantitative hydrolysis course was verified on the natural samples of ground water contaminated by ca. 10 thousand kg of di-i-octyl phthalate by a standard addition method. The accuracy of this determination was 97.5% (variation coefficient ? cx = 1.5%). The stability of di-i-octyl phthalate in water at 20°C and various pH values were also tested. 相似文献
4.
Artefact-free Determination of Trihalomethanes in Chlorinated Swimming-pool Water Using Headspace Solid-phase Microextraction and Gas Chromatography Headspace solid-phase microextraction (headspace SPME) is a rather new technique for the solvent-free extraction and concentration of volatile substances from water into an organic polymer layer covering a fused-silica fiber. In combination with gas chromatography, the method represents a powerful tool for sensitive headspace investigations. As the adsorption of low boiling substances is favoured at low temperatures, the method can be operated at ambient temperature without formation of artefacts. Therefore, the method is ideally suited for the analysis of volatile disinfection by-products in water including several thermolabile THM-precursors. For the artefact-free determination of trihalomethanes it is superior to headspace gas chromatography under the conditions of the German standard method DIN 38407-F5. Compared to gas chromatography after pentane extraction (DIN 38407-F4), headspace SPME is simpler, less- laborious, better reproducible, and, especially for polar, easily water-soluble components, much more sensitive. In addition, it operates solvent-free and can be automated. Using a 100-μ polydimethylsiloxane-coated fiber, the method is linear over at least 2 orders of magnitude and has a relative standard deviation of 2… 7% in the upper ng/L range. With a 65-μ polydimethylsiloxane/divinylbenzene-coating on the fiber, the sensitivity of the method can be extended to limits of quantitation in the low ng/L range. However, this fiber, shows an increased susceptibility to matrix effects as observed in the presence of diisopentyl ether, which can only be compensated by using the method of standard addition. 相似文献
5.
Gas-chromatographic Determination of Polychlorinated Biphenyls in Water after Headspace Solid-phase Microextraction Headspace-analytical techniques are usually applied to the determination of easily volatile substances in water, whereas semivolatiles are generally isolated by liquid-liquid or solid-phase extraction. In the present paper, a method is presented for isolating high boiling polychlorinated biphenyls (PCB) using headspace solid-phase microextraction at elevated temperature. In spite of their low vapor pressure, the analytes are adsorbed very efficiently on a poly-dimethylsiloxane-coated fiber. Thus, in combination with GC/ECD, a very simple and sensitive solventless determination of PCB is accomplished. Using the simplest possible standard conditions, limits of determination in the lowest nanogram-per-liter range are achieved. Further increased sensitivity down to the ppq (parts per quadrillion) range is possible by stirring and increasing the sample volume and adsorption time. Moderate matrix effects have been observed in some surface and groundwaters. 相似文献
6.
Zeolites have been used for a long time for purification and catalytical purposes. Recently, first products appeared on the market using zeolites also for improving the indoor air quality so far volatile organic compounds (VOC) are concerned. However, porous compounds like zeolites can be found also in plaster material. Therefore, it was manifest to evaluate the capability of plaster with regard to air cleaning. In this article, the contribution of plaster compounds toward adsorption and catalytical decomposition of VOCs is evaluated using α‐pinene, chlorobenzene, 2‐ethoxyethylacetate, and pentanal as target substances under standard conditions (23°C, 50% r.H.). These compounds were chosen because of their VOC typical physicochemical properties like molecular dimensions, density, boiling point, vapor pressure, and octanol–water distribution coefficient (logkow). Hydrated lime and metakaolin were found out to have good adsorption properties under these circumstances. Also natural zeolites showed good results especially on pentanal. By investigations in environmental chambers the reduction potential of test plasters on chlorobenzene and 2‐ethoxyethylacetate concentrations could be shown. Application of coatings had no or only temporary influence on the performance of the plaster. Additional tests in small chambers demonstrated the possibility to improve the properties of plasters with help of FAU‐ or MFI‐type zeolites but the experiments also showed that α‐pinene and pentanal undergo chemical reactions. Further effort should be made on investigations also toward other compounds, especially more volatile ones like formaldehyde. Also additional building materials like insulation material or boards should be taken into account. 相似文献
7.
The relationship between stream water DOC concentrations and soil organic C pools was investigated at a range of spatial scales in subcatchments of the River Dee system in north‐east Scotland. Catchment percentage peat cover and soil C pools, calculated using local, national and international soils databases, were related to mean DOC concentrations in streams draining small‐ (<5 km2), medium‐ (12–38 km2) and large‐scale (56–150 km2) catchments. The results show that, whilst soil C pool is a good predictor of stream water DOC concentration at all three scales, the strongest relationships were found in the small‐scale catchments. In addition, in both the small‐ and large‐scale catchments, percentage peat cover was as a good predictor of stream water DOC concentration as catchment soil C pool. The data also showed that, for a given soil C pool, streams draining lowland (<700 m) catchments had higher DOC concentrations than those draining upland (>700 m) catchments, suggesting that disturbance and land use may have a small effect on DOC concentration. Our results therefore suggest that the relationship between stream water DOC concentration and catchment soil C pools exists at a range of spatial scales and this relationship appears to be sufficiently robust to be used to predict the effects of changes in catchment soil C storage on stream water DOC concentration. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
8.
Water repellency is a widespread property of Pinus pinaster and Eucalyptus globulus forest soils in NW Spain and is particularly severe during the summer dry conditions. The aim of this work was to compare actual water repellency at field‐moist samples with potential water repellency after drying at 25 and 105 °C in samples collected at different times of year under four forest soils. Also, we investigated whether drying at 25 or 105 °C led to repellency values comparable to the highest levels reached under field conditions in the summer with a view to developing an appropriate sampling protocol towards estimating the maximum possible water repellency of a given soil as a key to establishing its environmental effects. The actual and potential water repellency was determined by using the water drop penetration time (WDPT) and molarity of an ethanol drop (MED) tests. Clear seasonal patterns of water repellency were observed from the results for the four forest soils, peaking in the dry period and disappearing after prolonged wet periods. Water repellency lasts longer in sandy loam soils than in more finely textured soils, and also under eucalyptus than under pine forests. Drying soil samples at 25 or 105 °C increased water repellency, as measured with the WDPT method, in the four soils, but especially in the non‐repellent samples collected during the wet period. The increase was more marked in the sandy loam soils than in the more finely textured soils, and also after drying at 105 °C than at 25 °C. MED measurements exposed a common trait in the four soils; thus, the water repellency values obtained under field conditions in summer invariably exceeded those obtained after drying at 25 or 105 °C. In addition, the repellency values for dried samples collected in the wet period were never comparable to the maximum levels observed under field conditions in the summer. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
9.
In this paper we quantitatively test the hypothesis that soil freeze–thaw (FT) processes significantly increase the potential for upland hillslope erosion during run‐off events that follow thaw. We selected a highly frost‐susceptible silt to obtain an upper bound on FT effects, and completed three series of six experiments each to quantify differences in soil erosion and rill development in a bare soil following a single FT cycle. Each series represented a specific soil moisture range: 16–18 per cent, 27–30 per cent and 37–40 per cent by volume, with nominal flow rates of 0·4, 1·2 and 2·4 L/min and slopes of 8° and 15°. Each experiment used two identical soil bins: one a control (C) that remained unfrozen, and another that was frozen and thawed once. Standard soil characterization tests did not detect significant differences between the FT and C bins. We measured cross‐sectional geometry of an imposed straight rectangular rill before each experiment, sediment load during and rill cross‐sections after. Changes in cross section provided detailed measures of erosion at specific locations, while sediment load from time series run‐off samples integrated the rill erosion. Several parameters, including average maximum rill width, average maximum rill depth, rill cross‐section depth measures and sediment load, all followed similar trends. Each was greater in the FT than in the C, with values that generally increased with slope and flow. However, soil moisture was the only parameter that affected the FT/C ratios. Average sediment load grouped by soil moisture provided FT/C ratios of 2·4, 3·0 and 5·0 for low, mid and high moisture, respectively. In contrast, a ‘dry’ experiment at 4–5 per cent soil moisture had FT/C of 1·02 for sediment load. These results show a dramatic increase with soil moisture in the rate and quantity of bare soil eroded due to the FT cycle. As both FT and C results were highly sensitive to initial conditions, minimum differences in soil weight, bulk density and soil moisture through each series of experiments were required to achieve consistent results, indicating that rill erosion may be chaotic. Published in 2005 by John Wiley & Sons, Ltd. 相似文献
10.
Based on an analysis of a large array of meteorological data, we have shown that surface air temperatures differ significantly
in years of sunspot maxima and minima for different months and latitudes and longitudes of observation points. This difference
is the greatest at high latitudes of 60–83°; it is equal to +2.07 ± 0.28°C in February in the longitudinal range of 170 ±
190° and −1.41 ± 0.29°C in November in the longitude range of 150 ± 170°. 相似文献
11.
A miniaturized ultrasonic extraction procedure was developed for the determination of polycyclic aromatic hydrocarbons (PAHs) in soil by gas chromatography‐mass spectrometry. After determination of the most suitable extraction solvent with 5 min sonication time, several other parameters (sample amount, solvent volume and number of extraction times) were optimized using a 23 factorial experimental design. Recoveries of PAHs from spiked soil samples were over 90% for three different fortification levels between 50 and 300 μg/kg, and relative standard deviations of the recoveries were in the range of < 1–15%. The limits of detection ranged from 0.002 to 1.87 μg/kg. The performance of the developed procedure was also compared with other traditional Soxhlet, shake flask and large scale ultrasonic extraction procedures on real soil samples, and extraction methods showed comparable efficiencies. The proposed procedure required small volumes of solvent and sample. It was practicable, rapid and easy to use for analysis of PAHs in soils. 相似文献
12.
Eric J. Martin Kevin G. Mumford Bernard H. Kueper 《Ground Water Monitoring & Remediation》2016,36(1):54-61
Electrical resistance heating (ERH) experiments were performed in a two‐dimensional water‐saturated porous medium comprising an electrically conductive, low‐permeability clay lens embedded within a less electrically conductive, higher permeability silica sand. These were compared to experiments performed in homogeneous silica sand. All experiments were performed in the absence of a non‐aqueous phase liquid (NAPL) or dissolved volatile organic compound (VOC). Temperature monitoring showed preferential heating in the clay lens and higher overall heating rates throughout the test cell compared to the homogeneous case. Gas production was localized around the sand–clay interface due to high temperature and low capillary displacement pressure. Above the clay lens, unexpected temperature plateaus were observed, similar to those observed in previous experiments during NAPL–water co‐boiling. A conceptual model based on the consumption of thermal energy as latent heat of vaporization in the highly localized heating and gas production region adjacent to the clay lens is proposed to explain the temperature plateaus. Supporting data is drawn from images of the gas phase and electric current measurements. These results show that the use of co‐boiling plateaus as an indicator of NAPL–water co‐boiling could be misleading during applications of ERH at sites containing electrically conductive, low‐permeability clay lenses embedded within less electrically conductive, higher‐permeability sands. 相似文献
13.
Prescribed burning is a forest management tool to reduce forest fire hazards. It is largely applied in the USA and is gaining importance worldwide, particularly in Europe. However, its effects on soils still have to be better understood. This study analyses the effects of two types of prescribed burnings (i.e. low and high burn severities of up to 200 °C and at or above 400 °C) on soil hydrophobicity, infiltration, and water storage capacity of top soils. Prescribed burnings were performed on four different plots in southern and western Catalonia, Spain. Soil samples were collected before and after burning to assess water repellency with the water drop penetration time (WDPT). Three rainfall simulations before burning and three after burning were executed on areas of 1 m2, and soil water contents at four to five depths were measured every 4 min during and after rainfall simulations using time domain reflectometry equipment (TDR). Following burning at both severities, water storage capacity of the top soil decreased between 1·7 and 5·4%vol on all four plots. No significant changes in volume flux density and velocity of the wetting fronts were discernible. Water drop penetration times increased moderately at the soil surface of the plots that were exposed to the high burn severity, and decreased slightly when burn severity was low. On two of the four plots the presence of partially moist organic litter prevented the underlying soil from excessive heating. Changes in hydrophobicity and water storage capacity of the top soil did not affect infiltration. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
14.
Experimental determinations of the dry liquidus temperatures of two pantellerite, and two pantelleritic trachyte glasses in the pressure range 0–2 kilobars, show minima in the liquidus curves between 0.1 and 0.2 kb. The pantellerite minima are 830°–850° C; the trachyte minima are 920°–940° C. At pressures below the minima a separate vapour phase co-exists with liquid, at higher pressures the intrinsic volatiles are completely soluble in the liquid and the liquidus curves have a positivedT/dP. Similar results have been obtained from a range of other pantelleritic glasses, and together with consistent alkali feldspar compositions (from a wide range of experimental conditions) are indicative of a close approach to equilibrium. The form of the liquidus curves above the minima, if rellecting natural conditions, offers a ready explanation of the near-or super-liquidus aspect of many peralkaline lavas. The temperatures in these anhydrous experiments are 100°–150° C higher than those for similar compositions in the presence of excess water. (Also, in the presence of excess water, the crystallization sequences in the natural glasses are profoundly modified, with pyroxene appearing on the liquidus). At lower pressures, feldspar is the liquidus phase in the dry pantellerites, but is joined by quartz around 1 kb, and superseded by quartz at higher pressures. As pantellerites with quartz phenocrysts are uncommon, low pressure equilibration is perhaps normal in these magmas. Feidspar is the usual liquidus phase in the trachytes, except at very low pressures where it is preceded by iron oxide. Preliminary studies at 5 kb indicate that the pantelleritic and trachytic liquidus curves are converging (in the range 950°–1000° C). Crystallization sequences, and the forms and positions of the solidus curves are therefore of vital importance. These, together with the vapour-present/vapour-absent conditions, are currently under investigation. 相似文献
15.
This work describes the modification of silica gel with dimethylglyoxime, in order to prepare an effective sorbent for the preconcentration and determination of copper. The sorption capacity of dimethylglyoxime‐modified silica‐gel (DMGMS) was 71.37 mg g–1 and the optimum pH for the quantitative recovery of copper was found to be 5.0. The optimum flow rate, sorbent amount, and sample volume were 1 mL min–1, 300 mg, and 50 mL, respectively. 10 mL of 0.1 mol L–1 HCl was the most suitable eluent. The detection limit of copper was 6.0 ng mL–1. The recommended method, for the determination of copper, is simple and reliable, without any notable matrix effect and can be successfully applied to environmental water samples. Copper recovery in the range from 99–100% was obtained from seawater and thermal spring water using this method. The method was applied to standard reference materials, NIST‐1515 (apple leaves) and NIST‐1643e (simulated fresh water), for the determination of copper and the results were in good agreement with certified values. 相似文献
16.
Stream temperature modelling using artificial neural networks: application on Catamaran Brook,New Brunswick,Canada 总被引：2，自引：0，他引：2
Fish habitat and aquatic life in rivers are highly dependent on water temperature. Therefore, it is important to understand andto be able to predict river water temperatures using models. Such models can increase our knowledge of river thermal regimes as well as provide tools for environmental impact assessments. In this study, artificial neural networks (ANNs) will be used to develop models for predicting both the mean and maximum daily water temperature. The study was conducted within Catamaran Brook, a small drainage basin tributary to the Miramichi River (New Brunswick, Canada). In total, eight ANN models were investigated using a variety of input parameters. Of these models, four predicted mean daily water temperature and four predicted maximum daily water temperature. The best model for mean daily temperature had eight input parameters: minimum, maximum and mean air temperatures of the current day and those of the preceding day, the day of year and the water level. This model had an overall root‐mean‐square error (RMSE) of 0·96 °C, a bias of 0·26 °C and a coefficient of determination R2 = 0·971. The model that best predicted maximum daily water temperature was similar to the first model but excluded mean daily air temperature. Good results were obtained for maximum water temperatures with an overall RMSE of 1·18 °C, a bias of 0·15 °C and R2 = 0·961. The results of ANN models were similar to and/or better than those observed from the literature. The advantages of artificial neural networks models in modelling river water temperature lie in their simplicity of use, their low data requirement and their good performance, as well as their flexibility in allowing many input and output parameters. Copyright © 2008 Crown in the right of Canada and John Wiley & Sons, Ltd. 相似文献
17.
Yui Kouketsu Tomoyuki Mizukami Hiroshi Mori Shunsuke Endo Mutsuki Aoya Hidetoshi Hara Daisuke Nakamura Simon Wallis 《Island Arc》2014,23(1):33-50
The Raman spectra of carbonaceous material (CM) from 19 metasediment samples collected from six widely separated areas of Southwest Japan and metamorphosed at temperatures from 165 to 655°C show systematic changes with metamorphic temperature that can be classified into four types: low‐grade CM (c. 150–280°C), medium‐grade CM (c. 280–400°C), high‐grade CM (c. 400–650°C), and well‐crystallized graphite (> c. 650°C). The Raman spectra of low‐grade CM exhibit features typical of amorphous carbon, in which several disordered bands (D‐band) appear in the first‐order region. In the Raman spectra of medium‐grade CM, the graphite band (G‐band) can be recognized and several abrupt changes occur in the trends for several band parameters. The observed changes indicate that CM starts to transform from amorphous carbon to crystallized graphite at around 280°C, and this transformation continues until 400°C. The G‐band becomes the most prominent peak at high‐grade CM suggesting that the CM structure is close to that of well‐crystallized graphite. In the highest temperature sample of 655°C, the Raman spectra of CM show a strong G‐band with almost no recognizable D‐band, implying the CM grain is well‐crystallized graphite. In the Raman spectra of low‐ to medium‐grade CM, comparisons of several band parameters with the known metamorphic temperature show inverse correlations between metamorphic temperature and the full width at half maximum (FWHM) of the D1‐ and D2‐bands. These correlations are calibrated as new Raman CM geothermometers, applicable in the range of c. 150–400°C. Details of the methodology for peak decomposition of Raman spectra from the low to medium temperature range are also discussed with the aim of establishing a robust and user‐friendly geothermometer. 相似文献
18.
Ice‐ and snow‐melted water flow over partially thawed frozen soil of cultivated slopes causes serious soil erosion, which results in soil degradation and affects productivity in Northeast China. Water flow velocity over frozen and nonfrozen soil shows importance in understanding meltwater erosion. In this work, a series of laboratory experiments were conducted to measure water flow velocity over frozen and nonfrozen soil slopes. Experiments were performed using the electrolyte trace method under the pulse boundary model, under conditions of 4 slope gradients (5°, 10°, 15°, and 20°), 3 flow rates (1, 2, and 4 L/min), and 7 sensors positioned at 0.1, 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0 m away from the electrolyte injection point. Results showed that velocities over frozen soil slopes increased with flow rate and slope gradient. Flow velocities over nonfrozen soil slopes increased with flow rate and slope gradients from 5° to 15° and stabilized at 15°. Flow velocities over frozen soil slopes were 30%, 54%, 71%, and 91% higher than those over nonfrozen ones at slope gradients of 5°, 10°, 15°, and 20°. Flow velocities over frozen soil slopes under different flow rates of 1, 2, and 4 L/min were approximately 52%, 59%, and 79% higher than those over nonfrozen soil, respectively. This study can help in assessing the erosion of partially thawed frozen soil by meltwater flow. 相似文献
19.
Formation of Artefacts and its Suppression during the Determination of Volatile Halogenated Hydrocarbons in Water by Means of Headspace Gas Chromatography under the Standard Conditions of DIN 38407-F5. Part I: Formation of Dehydrohalogenation Products from Saturated Halogenated Hydrocarbons Under the conditions recommended by DIN 38407-F5 for the headspace gas-chromatographic determination of volatile halogenated organic substances in water (equilibration at 60…80°C for a least 60 min) several halocarbons are degraded by dehydrohalogenation resulting in the formation of unsaturated artefacts with one halogen atom less. Thus pentachloroethane and 1,1,2,2-tetrachloroethane are decomposed to form tetrachloroethylene and trichloroethylene, respectively. This leads to low results of the analytes and to false-positive detection of the reaction products. The unwanted degradation reactions can be reduced by decreasing the temperature and duration of equilibration, and they are completely suppressed by acidification of the samples. 相似文献
20.
Ellen E. Moyer David W. Ostendorf Don H. Kampbell Yuefeng Xie 《Ground Water Monitoring & Remediation》1994,14(1):110-119
Soil gas samples from intact soil cores were collected on adsorbents at a field site, then thermally desorbed and analyzed by laboratory gas chromatography (GC). Vertical concentration profiles of predominant vapor phase petroleum hydrocarbons under ambient conditions were obtained for the zone directly above the capillary fringe. Water and residual phase weathered aviation gasoline were present in this region of the profile.
The sampling, trapping, and GC methodology was effective in most respects. Reproducibility, trapping, and desorption efficiency were generally satisfactory, and different sorbent tubes gave similar results. A minor shortcoming of the method occurred with the most volatile compound, 2,3-dimcthylbutane, which was poorly retained during several weeks of storage lime and was also poorly desorbed.
Vapor phase concentrations of predominant hydrocarbon compounds all increased with depth at one sampling location. At a more highly contaminated location, concentrations of highly volatile compounds increased with depth while concentrations of less volatile compounds remained constant or decreased, possibly indicating distillation effects. Scatier in the data was attributed to heterogeneities in water and residual phase distribution. 相似文献
The sampling, trapping, and GC methodology was effective in most respects. Reproducibility, trapping, and desorption efficiency were generally satisfactory, and different sorbent tubes gave similar results. A minor shortcoming of the method occurred with the most volatile compound, 2,3-dimcthylbutane, which was poorly retained during several weeks of storage lime and was also poorly desorbed.
Vapor phase concentrations of predominant hydrocarbon compounds all increased with depth at one sampling location. At a more highly contaminated location, concentrations of highly volatile compounds increased with depth while concentrations of less volatile compounds remained constant or decreased, possibly indicating distillation effects. Scatier in the data was attributed to heterogeneities in water and residual phase distribution. 相似文献