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71.
Measurements of topsoil magnetic susceptibility are often used for quick assessment of soil contamination of anthropogenic
origin, with heavy metals or other pollutants. However, because of complicated correlations between low-field magnetic susceptibility
(shortened to magnetic susceptibility) of topsoil and soil pollution, the outcome of a field magnetometry survey can not be
related directly to soil pollution. For each case study, the results should be interpreted on their own taking into account
not only the type of pollution but also pedogenic, biogenic and environmental factors. In practice, it is very difficult to
measure and consider all these factors. Here we illustrate the merit of geostatistical methods, which are focused on the spatial
variability of a phenomenon, in the interpretation of soil magnetometry results.
This article presents the analysis of spatial variability of top soil layers magnetic susceptibility-within the Upper Silesia
Industrial Region (USIR)-using semivariance analysis. It also explains how to adjust the sampling density of field magnetometry
measurements to spatial variability of the soil pollution as well as to the spatial scale of the investigated area. For this
purpose, the values of magnetic susceptibility have been measured by using various sampling densities at areas of different
size located within USIR. This enabled to determine the main scales of magnetic susceptibility spatial variability of soils
within USIR using semivariance. A few distinct scales of variability were found from the site scale to a more regional scale.
Variability ranges of 30 km, 12 km, and 5 km refer to the large regional scale, whereas smaller ranges of few hundreds down
to a few tens of meters, can be attributed to the local (site) scale. In addition, the precision of the measuring campaigns,
performed within USIR with different sampling densities, was compared through the analysis of the spatial variability of the
soil magnetic susceptibility signal by using ordinary kriging.
jarek97@yahoo.com, piotr.fabijanczyk@is.pw.edu.pl 相似文献
72.
土体饱和度确定的两个问题 总被引:6,自引:0,他引:6
本文探讨了有关土饱和度确定的两个问题,由于试验技术手段的限制,土堆栈 饱和度只能通过其它物理性质指标之间的关系来求取,这样换算得到的饱和度往往偏大,并且,根据实验分析,地下水位以下的粘性土并不都是饱和的,因此,在岩土工程中,非饱和土工力学亟待深入研究。 相似文献
73.
74.
从土的各向异怀角度对土的可恢复剪胀现象进行了解释。基于各向异性情况下的土体弹性本构关系理论分析,认为土的可恢复剪胀现象可部分归因于土的各向异性引起的弹性剪胀。借助有关土体弹性参数实验结果,研究了应力诱导各迥异性对土体弹性剪胀的影响,结果表明:随土体应力诱导各向异性的增大,土体的弹性剪胀也增大。从土体弹性剪胀角度研究了土的卸荷体缩条件,认为土体卸荷体缩取决于加载应力路径的应力增量比,给出了土体出现卸荷体缩的区域。 相似文献
75.
The value of a physically based model versus an empirical approach in the prediction of ephemeral gully erosion for loess-derived soils 总被引:3,自引:0,他引:3
Jeroen Nachtergaele J. Poesen A. Steegen I. Takken L. Beuselinck L. Vandekerckhove G. Govers 《Geomorphology》2001,40(3-4)
A data set on soil losses and controlling factors for 58 ephemeral gullies has been collected in the Belgian loess belt from March 1997 to March 1999. Of the observed ephemeral gullies, 32 developed at the end of winter or in early spring (winter gullies) and 26 ephemeral gullies developed during summer (summer gullies). The assessed data have been used to test the physically based Ephemeral Gully Erosion Model (EGEM) and to compare its performance with the value of simple topographical and morphological indices in the prediction of ephemeral gully erosion.Analysis shows that EGEM is not capable of predicting ephemeral gully cross-sections well. Although conditions for input parameter assessment were ideal, some parameters such as channel erodibility, critical flow shear stress and local rainfall depth showed great uncertainty. Rather than revealing EGEM's inability of predicting ephemeral gully erosion, this analysis stresses the problematic nature of physically based models, since they often require input parameters that are not available or can hardly be obtained.With respect to the value of simple topographical and morphological indices in predicting ephemeral gully erosion, this study shows that for winter gullies and summer gullies, respectively, over 80% and about 75% of the variation in ephemeral gully volume can be explained when ephemeral gully length is known. Moreover, when previously collected data for ephemeral gullies in two Mediterranean study areas and the data for summer gullies formed in the Belgian loess belt are pooled, it appears that one single length (L)–volume (V) relation exists (V=0.048 L1.29; R2=0.91). These findings imply that predicting ephemeral gully length is a valuable alternative for the prediction of ephemeral gully volume. A simple procedure to predict ephemeral gully length based on topographical thresholds is presented here. Secondly, the empirical length–volume relation can also be used to convert ephemeral gully length data extracted from aerial photos into ephemeral gully volumes. 相似文献
76.
77.
膨胀土是具有较大胀缩变形能力的特殊性粘土,膨胀土斜坡地区极易发生滑坡等地质灾害,本文根据安康汉江二号桥南侧滑坡勘察资料,较全面地介绍了该膨胀土滑坡特征,为滑坡根治提供了充分的地质依据。 相似文献
78.
Trace metals in acid sediments and waters, Pimpama catchment, southeast Queensland, Australia 总被引:2,自引:1,他引:2
The Pimpama River floodplain has developed over the last several thousand years as a result of sea-level fluctuations that
shaped the lower catchment and enabled the formation of sedimentary pyrite. The subsequent production of sulfuric acid due
to the oxidation of this pyrite enhances the breakdown of metal-bearing sediments and can lead to leaching of major and trace
metals into the waters of the region. The seasonal pattern of rainfall and current land-use activities are important aspects
that intensify the natural production of acid and influence the release and distribution of metals. To identify the source
and migration of metals in the Pimpama catchment and to understand the impact of pyrite oxidation on the distribution of metals
in sediments and waters, several components of the drainage system were analyzed: bedrock, sediments from river bed and bank,
and water. The elements analyzed in this study (V, Cr, Co, Ni, Cu, Zn and Pb) are all present in the bedrock material which
explains their occurrence in the unconsolidated sediments of the floodplain. These metals concentrate in the upper section
of the sedimentary sequence and their presence is related to clay minerals such as smectite, organic matter and iron phases.
However, Zn, Mo and Co occur in higher amounts than the local background and within standard shale. This comparison suggests
that the diagenetic processes alone cannot explain the higher concentrations and it is concluded that these metals also have
an anthropogenic source. The formation of sulfuric acid creates conditions for higher mobility of some metals, such as Cr,
Co, Ni, Cu, Zn, but does not affect less mobile ones such as Mo and Pb. Over the longterm, the production of acid influences
the breakdown of mineral phases and enhances the process of weathering. Over the short term, every rain event leaches acid
from sediments and mobilizes metals resulting in a substantial reduction in the quality of river water.
Received: 2 October 1998 · Accepted: 16 February 1999 相似文献
79.
高围压下冻土强度弱化的机理分析 总被引:7,自引:5,他引:2
围压作用下,影响冻结砂土强度弱化的主要原因是孔隙冰的压融,矿物颗粒细化的微裂隙的发育。影响冻结粉质粘土强度弱化的主要原因是孔隙冰的压融和微裂隙的发育,这些过程是不独立存在的,而是共同影响,共同作用,从而导致了冻土强度的弱化。 相似文献
80.
渭干河灌区的水土环境及水文地质条件在克孜尔水库建成后发生了一定的变化,本文结合灌区12年来的水盐监测资料,对灌区地下水的埋深变化规律、水质演变趋势、灌区的排水效果及目前存在的问题进行了分析与探讨,并为今后灌区排水措施和保持水土环境的良性发展提出了建议. 相似文献