In this paper, first the definitions of variability and ergodicity are discussed. This is followed by an overview of variography, and the importance of sequential stochastic simulation is emphasized. The main uncertainties of variograms are discussed, followed by the methods for decreasing this uncertainty. It is stressed that additional geologic information can be obtained from variograms, even beyond the ranges of influence. Possibilities of local evaluation of the gh values and ranges of influence are presented. The main idea of the paper is that the gh values and the ranges of influence are continuous random variables. Up to now variograms were evaluated mainly for geomathematical purposes and their direct geologic evaluation was neglected. The author presents examples of such kinds of evaluation.
The reproducibility, the small scale as well as the large scale variability of137Cs extracted sequentially from the soil by using a modified Tessier procedure was investigated at several grassland sites in Bavaria/Germany and in the Chemobyl area. Because undisturbed grassland soils are never homogeneous with respect to their soil properties, all sequential extractions at the German sites were carried out at each plot separately for different soil layers (e.g., 0–2, 2–5, 5–10, 10–15, 15–20 and 20–30 cm). The results show that the coefficients of variation (CV) for the reproducibility of the extraction procedure for137Cs was (with some exceptions) around 10–20% for all fractions. For the small scale variability of137Cs (samples within an area of 10×10m2) the values for theCV were (again with a few exceptions) in the same range. Compared to that, the large scale variability of extractable137Cs (random soil samples within an area of 100×200 km2) was higher for all fractions, even though only moderately. The implications of these results with respect to a sampling design are discussed.
We analyzed long-term data related to temporal and spatial variation in fish assemblages from five sites along the Suquía River Basin (Córdoba, Argentina). We aimed at determining whether water quality variations generate changes in fish assemblage structure and composition along the river. Despite deterioration of water quality recorded along the basin, fish assemblages were characterized as qualitatively persistent and quantitatively stable, indicating that the specific composition were relatively constant over time. However, on a temporal scale, fish assemblages from the most polluted areas responded to the water quality degradation with a greater variation of species abundance than those from pristine sites. On a spatial scale, changes in fish assemblage structure were related with watershed disturbance gradient and indicated a strong association between fish species distribution and water quality variation. The alterations found in our study suggest a potential imbalance of fish assemblage structure in the long term.
The paper deals with the approaches to the response analysis of large transport and lifeline structures. The background theory for simplified analysis is presented. Seismic inputs represent the cases of explosion impacts and large near field earthquake effects. 3DOF and 6DOF input models are based on surface wave theory and applied for calculations and shaking table experiments. Examples of seismic motion simulations are those obtained during large MASTER shaking table tests in Enel.Hydro-ISMES Seriate, Italy in the framework of EC international projects.
Csillag, F., Kertész, M. & Kummert, Á. , 1996. Sampling and mapping of heterogeneous surfaces: multi-resolution tiling adjusted to spatialvariability. International Journal of Geographical Information Science. 10 .(7) 851
Our data verified the
relationship between meteorological factors and the fluctuation of the
groundwater level. The rate of evaporation dominantly affected the rise and
depth of the groundwater level. It is characteristic for the study site that
there is an inverse relationship between the elevation of the groundwater
observation wells and the depth of groundwater, and the difference between the
levels of groundwater in the separate wells reflected the differences in the
elevation between the wells. Our observations refuted our previous assumptions,
as in the wells not only the concentration of salts changed but also the
chemical type of the water. This can be attributed with great probability to
the lateral flow of the groundwater, which is caused by the vertical
fluctuation, but can be caused by other geological factors as well. We reached
the conclusion that the vertical and sometimes lateral movement of the
groundwater affects the development of soils in a given area. It means that the
reason behind the mosaic-like appearance of the soil cover of a given area can
be searched in the local differences of the chemical composition of the
groundwater, which is a major factor of the spatial variability of the salt
accumulation of soils. The observations and analytical results point to that
the soils of the study site have developed under the effect of fluctuating
groundwater and the elevation is a dominant factor of the spatial variability
of the soil salt accumulation. The level of groundwater, the flow of groundwater
and its composition show relationship with the surface elevation, and their
effect is modified by the geological stratification, which results in a
variable appearance of soil salt accumulation and native vegetation.
The extent of soil erosion in some Spanish semiarid regions has caused great concern regarding the sustainability of soil
resources. Accelerated soil erosion, particularly in some Mediterranean areas, is likely to be one of the main environmental
problems associated with climate change. Fallout 137Cs has been shown to provide a reliable basis for assessing soil erosion rates in different environments around the world.
However, existing information concerning the spatial variation of 137Cs inventories at reference sites has identified a need for further investigation of the factors affecting their spatial variability
in semiarid environments, where stony and skeletal soils are predominant. Reference sites at three locations in the central
Ebro valley were selected to investigate the 137Cs content of several grain size fractions. Each site included both natural vegetated conditions and cultivated land and the
three sites were characterized by different values of mean annual rainfall. The results obtained demonstrate the influence
of lithology, land use and climate on the spatial variability of 137Cs inventories that increase from 1190, to 1500 and 1710 Bq·m−2 with increasing annual rainfall values from 300 to 500 mm at the study sites. The soils on marls at the Valareña site had
the highest proportion of 137Cs in the coarse fractions of cultivated soils (12%) in comparison with soils developed on limestones at Loma Negra (5%),
whereas no 137Cs content was found in the coarse fractions of soils on glacis-terrace materials at Peñaflor. The 137Cs reference inventories are higher in soils on marls and sands at cultivated locations at Valareña and Peñaflor, but have
similar values in soils at cultivated and uncultivated locations on limestones at Loma Negra. Therefore, in absence of level
undisturbed soils with natural vegetation cover, cultivated flat soils on hard rocks could provide reliable reference inventories.