煤中氟的研究进展   总被引：3，自引：0，他引：3  

徐立荣  雒昆利  王五一  冯福建  谭见安 《地球科学进展》2004,19(1):95-099

在全面综合国内外研究文献的基础上,分析了煤中氟的含量、分布规律、赋存状态以及燃烧释放规律等方面的研究进展和存在的问题。我国煤中氟的研究总体上说滞后于煤中其它某些微量元素（如砷、硒、汞等）的研究。进一步深入研究煤中氟+K313的分布规律、赋存状态、来源及迁移转化规律,是今后煤中氟研究的重点。  相似文献   

Elimination of Zinc from Roof Runoff through Geotextile and Clinoptilolite Filters     

Konstantinos Athanasiadis  Brigitte Helmreich  Peter A. Wilderer 《洁净——土壤、空气、水》2004,32(6):419-428

Direct infiltration of roof runoff into the ground may pose a potential risk of soil and groundwater contamination. The performance of two different barrier materials for the retention of zinc from roof runoff of an eleven year old zinc roof was examined in a field study. As barrier materials geotextile and clinoptilolite were applied. Automatic samplers were used to take samples both at the inlet and at the outlet of the retention facility. Samples of twenty rain events were examined. Zinc was detected in the roof runoff in concentrations of up to 25 mg/L, and lead which originates from the tin‐solder was present in concentrations of up to 84 μg/L. Under most circumstances, a first flush could be observed for the analysed substances. No retention of heavy metals was observed, where only geotextile was used as a barrier material. The clinoptilolite filter was able to adsorb up to 97 % of zinc from the roof runoff.  相似文献   

An infiltration model based on flow variability in macropores: development, sensitivity analysis and applications   总被引：1，自引：0，他引：1  

Markus Weiler   《Journal of Hydrology》2005,310(1-4):294-315

Simulating infiltration in soils containing macropores still provides unsatisfactory results, as existing models seem not to capture all relevant processes. Recent studies of macropore flow initiation in natural soils containing earthworm channels revealed a distinct flow rate variability in the macropores depending on the initiation process. When macropore flow was initiated at the soil surface, most of the macropores received very little water while a few macropores received a large proportion of the total inflow. In contrast, when macropore flow was initiated from a saturated or nearly saturated soil layer, macropore flow rate variation was much lower. The objective of this study was to develop, evaluate, and test a model, which combines macropore flow variability with several established approaches to model dual permeability soils. We then evaluate the INfiltration–INitiation–INteraction Model (IN³M) to explore the influence of macropore flow variability on infiltration behavior by performing a sensitivity analysis and applying IN³M to sprinkling and dye tracer experiments at three field sites with different macropore and soil matrix properties. The sensitivity analysis showed that the flow variability in macropores reduces interaction between the macropores and the surrounding soil matrix and thus increases bypass flow, especially for surface initiation of macropore flow and at higher rainfall intensities. The model application shows reasonable agreement between IN³M simulations and field data in terms of water balance, water content change, and dye patterns. The influence of macropore flow variability on the hydrological response of the soil was considerable and especially pronounced for soils where initiation occurs at the soil surface. In future, the model could be applied to explore other types of preferential flow and hence to get a generally better understanding of macropore flow.  相似文献   

Nonlinear mixed effect modelling for improved estimation of water retention and infiltration parameters     

T.C. Omuto  B. Minasny  A.B. McBratney  E.K. Biamah 《Journal of Hydrology》2006,330(3-4):748-758

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Influence of rainfall-induced wetting on the stability of slopes in weathered soils   总被引：13，自引：0，他引：13  

Jaehong Kim  Sangseom Jeong  Seongwan Park  Jitendra Sharma 《Engineering Geology》2004,75(3-4):251-262

Shallow failures of slopes in weathered soil are caused by infiltration due to prolonged rainfall. These failures are mainly triggered by the deepening of the wetting band accompanied by a decrease in matric suction induced by the water infiltration. This paper reports trends of rainfall-induced wetting band depth in two types of weathered soils that are commonly found in Korea. Both theoretical and numerical analyses for wetting band depth are presented based on the soil–water characteristic curve obtained using filter paper as well as tensiometer tests. It is found that the magnitude of wetting front suction plays a key role in the stability of slopes in weathered soils. Theoretical analysis based on modified Green and Ampt model tends to underestimate the wetting band depth for typical Korean weathered soils. It was also deduced that for Korean weathered soils, the factor of safety drops rapidly once the wetting band depth of 1.2 m reached.  相似文献   

Measurement and prediction of water movement in a field soil: The matrix-macropore dichotomy     

K. R. J. Smettem  P. J. Ross 《水文研究》1992,6(1):1-10

The saturated and unsaturated flow properties of a field soil under two tillage treatments were obtained with ponded rings and disc permeameters of dissimilar radii. No difference was observed between tillage treatments but the flow properties displayed a distinct macropore-matrix dichotomy, with K changing by an order of magnitude as ψ₀ went from just - 30 mm to zero. Accurate prediction of time to incipient ponding was achieved using both numerical and analytical models calibrated with field hydraulic properties that were characteristic of the soil matrix. However, extension of the numerical model to the prediction of the wetting front development under non-ponded conditions was less accurate due to localized preferred wetting It is hypothesized that at this site, localized concentration of rainfall and hence, preferred wetting, May, occur by interception and stemflow associated with lines of standing stubble present in the original seeding slots.  相似文献   

Analysis of the landslide triggering mechanism during the storm of 20th–21st November 2000, in Northern Tuscany     

N. Casagli  S. Dapporto  M. L. Ibsen  V. Tofani  P. Vannocci 《Landslides》2006,3(1):13-21

A severe rainstorm of high intensity occurred on 20th–21st November 2000, in the region of Pistoia, Tuscany, Italy, which triggered, within the entire province, over 50 landslides. These landslides can be broadly defined as complex earth slides—earth flows, originating as rotational slides that develop downslope into a flow. In this paper, two such landslides have been investigated by modelling the process of rainwater infiltration, the variations in both the positive and negative pore water pressures and their effect on slope stability during the storm. For both sites, results from morphometric and geotechnical analyses were used as a direct input to the numerical modelling. A modified Chu, 1978 approach was used to estimate the surface infiltration rate by adapting the original Green and Ampt, 1911 equations for unsteady rainfall intensity in conjunction with the surficial water balance. For transient conditions, a finite element analysis was used to model the fluctuations in pore water pressure during the storm, with the computed surface infiltration rate as the surface boundary condition. This was then followed by the application of the limit equilibrium Morgenstern and Price, 1965 slope-stability method, using the temporal pore water pressure distributions derived from the seepage analysis. From this methodology, a trend for the factor of safety was produced for both landslide sites. These results indicate that the most critical time step for failure was a few hours following the rainfall peak.  相似文献   

Inverse upscaling of hydraulic parameters during constant flux infiltration using borehole radar     

Dale F. Rucker 《Advances in water resources》2011,34(2):215-226

Modeling unsaturated flow in porous media requires constitutive relations that describe the soil water retention and soil hydraulic conductivity as a function of either potential or water content. Often, the hydraulic parameters that describe these relations are directly measured on small soil cores, and many cores are needed to upscale to the entire heterogeneous flow field. An alternative to the forward upscaling method using small samples are inverse upscaling methods that incorporate soft data from geophysical measurements observed directly on the larger flow field. In this paper, we demonstrate that the hydraulic parameters can be obtained from cross borehole ground penetrating radar by measuring the first arrival travel time of electromagnetic waves (represented by raypaths) from stationary antennae during a constant flux infiltration experiment. The formulation and coupling of the hydrological and geophysical models rely on a constant velocity wetting front that causes critical refraction at the edge of the front as it passes by the antennae. During this critical refraction period, the slope of the first arrival data can be used to calculate (1) the wetting velocity and (2) the hydraulic conductivity of the wet (or saturated) soil. If the soil is undersaturated during infiltration, then an estimate of the saturated water content is needed before calculating the saturated hydraulic conductivity. The hydraulic conductivity value is then used in a nonlinear global optimization scheme to estimate the remaining two parameters of a Broadbridge and White soil.  相似文献   

Effects of soil degradation on infiltration rates in grazed semiarid rangelands of northeastern Patagonia, Argentina     

M.P. Chartier  C.M. Rostagno 《Journal of Arid Environments》2011,75(7):656-661

In grazed semiarid ecosystems, considerable spatial variability in soil infiltration exists as a result of vegetation and soil patchiness. Despite widespread recognition that important interactions and feedbacks occur between vegetation, runoff and erosion, currently there is only limited quantitative information on the control mechanisms that lead to differences in infiltration from different vegetation types. In this paper, we determine (i) the relationship between vegetation and soil surface characteristics and (ii) the soil infiltration rate by using rainfall simulations on runoff plots (0.60 × 1.67 m) in three plant communities of northeastern Patagonia: grass (GS), degraded grass with scattered shrubs (DGS), and degraded shrub steppes (DSS). Our results clearly indicate that vegetation and soil infiltration are closely coupled. Total infiltration was significantly higher in the GS (69.6 mm) compared with the DGS and DSS (42.9 and 28.5 mm, respectively). In the GS, soil infiltration rate declined more slowly than the others communities, reaching a terminal infiltration rate significantly greater (57.7 mm) than those of DGS and DSS (25.7 and 12.9 mm, respectively). The high rate of water losses via overland-flow may limit the possibilities for grass seedling emergence and establishment and favor the persistent dominance of shrubs.  相似文献   

Seasonal soil water dynamics in the jarrah forest,Western Australia. II: Results from a site with fine-textured soil profiles     

J. K. Ruprecht  N. J. Schofield 《水文研究》1990,4(3):259-267

Seasonal soil water dynamics were measured at a fine-textured, upslope site within the jarrah forest of southwest Western Australia and compared to the results from a coarse-textured hillslope transect. Gravity drainage dominated during winter and early spring. This reversed in early summer and an upward potential gradient was observed to 7 m depth. A shallow ephemeral saturation zone was observed above a clay pan at 1.5 m depth. This saturation zone persisted through late winter and early spring, contrasting with the short-lived saturation in the duricrust on the hillslope transect. The annual maximum to minimum unsaturated soil water storage was about 530 mm, 50 mm greater than the hillslope transect and higher than most values reported elsewhere in Australia. Significant soil water content changes following winter rain were generally restricted to 6 m but at one site occurred to 9 m. These depths were significantly less than the coarser-textured hillslope transect. Soil water drying rates averaged 5 mm day^?1 during extended dry periods compared to 3.5 mm day^?1 on the hillslope transect. The drying rate occurred uniformly through the profile until late summer when a significant decrease in the upper 3 m was observed.  相似文献