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91.
Mean growing season soil PCO2 data were obtained for 19 regions of the world in nine countries. Bivariate and multiple linear regression analysis with soil log(PCO2) as the dependent variable and TEMP, PRECIP, log(AET), and log(PET) as the four climatic independent variables demonstrated that AET was the best independent predictor of soil PCO2. An improved soil PCO2-AET model was developed by assuming (1) that as AET approaches zero, soil PCO2 approaches the atmospheric value and (2) that there is an upper limit to soil PCO2 at very high AET. This model has the form log(PCO2) = ?3·47 + 2·09 (1 ?e?0·0172 AET) where AET is in mm. It explains 67 per cent of the initial variation in the soil PCO2 data, predicts a soil log(PCO2) of ? 3·47 at AET = 0, and an upper limit of 3·5 per cent (log(PCO2) = ? 1·45) for mean growing season soil PCO2 at AET values of 2000 mm and above. The results of this study suggest that soil PCO2 levels in tropical areas are, on average, higher than those in temperate, alpine, and arctic regions. 相似文献
92.
93.
本文根据影响岩溶水位的因素,利用改进的BP神经网络建立一个能够反映济南市泉域岩溶地下水动态变化的随机模型,并进行检验,与运用多元回归模型预测的结果相比较,结果表明:BP神经网络模型进行岩溶地下水动态变化预测是可行的,该模型具有较强的学习、容错和联想功能,对岩溶地下水动态变化的预测精度大大的提高。最后在模拟的基础上,又对泉水喷涌的宏观趋势作了进一步的预测和分析。 相似文献
94.
A. P. Dykes 《Landslides》2007,4(3):279-290
The West Mouth of the Great Cave at Niah in Sarawak, northwest Borneo and the North Passage that leads to the West Mouth contain
large deposits of guano. The main deposit, several metres thick in places, forms the sloping floor of the entire North Passage.
A mass movement deposit identified in the West Mouth, having a volume of 600 m3, originated as a guano mudflow up the North Passage in the order of 40,000 years ago. This failure of the guano slope was
investigated to determine whether particular conditions or events could be identified as the most likely causes. The physical,
hydrological and geotechnical properties of samples of the material were determined so that the stability of the slope could
be assessed. Stability analyses showed that shearing failure of the slope would require inputs of water to the slope in quantities
for which no feasible explanation can be suggested. However, the properties of the guano are similar to those of loess, indicating
a high susceptibility to ‘hydrocollapse’. Very shallow failure of the slope, possibly as several smaller mudflows, could therefore
have occurred due to additional water in quantities that could realistically be supplied as rainwater spray, possibly with
a seismic trigger. The climate must therefore have been wetter than it is at present. These findings have implications for
the interpretation of sediment deposits in other relict caves. 相似文献
95.
Igor Jemcov 《Environmental Geology》2007,51(5):767-773
The management of groundwater flow systems in karst regions appears, at present, to be the most important procedure for solving
water deficiency problems during periods of low rainfall. Faced with a lack of data for characterizing the water supply potential
of karst aquifers, analyses of spring hydrographs may provide valuable indirect information regarding the structure of karst
hydrogeological systems. To estimate the optimal exploitation capacities of karstic sources, a stochastic-conceptual approach
was applied in case studies from the Serbian karst. Water supply potentials were initially evaluated on the basis of groundwater
budgets. Further steps towards defining optimal “exploitable” regimes included analyses of storage changes in karst water
reservoirs under natural conditions and calculation of the potential expansion of currently tapped sources. The results obtained
through these analyses are a significant contribution to feasibility studies and aid in the avoidance of problems of overexploitation. 相似文献
96.
Jan Šafanda Philipp Heidinger Helmut Wilhelm Vladimír Čermák 《Hydrogeology Journal》2007,15(2):423-428
As part of the International Continental Scientific Drilling Program (ICDP), the 1.5-km-deep borehole Yaxcopoil-1, located in the Chixculub meteor impact structure in Mexico, has undergone further study after drilling operations ceased. Temperature logs were repeated ten times at intervals 0.3–0.8, 15, 24 and 34 months after borehole shut-in. The logs bear a distinct signature of transient heat transfer by groundwater flow manifested by a gradual distortion of the linear temperature profile when a cold wave of 0.8–1.6°C amplitude was detected propagating downward from 145 to 312 m at a rate of 4–6 m/month. To understand the nature of this moving anomaly, a 20-day monitoring of the cold wave was carried out at a depth of 307 m that showed further cooling of 0.6°C during the first 16 days of the passage followed by temperature stabilisation. As an explanation of this unusual phenomenon, a theory is proposed, whereby the drilling mud has accumulated within the overlying and cooler highly porous and permeable karstic rocks during the drilling and migrates downward. The observed migration rate suggests a permeability higher than 10?11 m2. This indicates a high vulnerability to contamination of the only freshwater aquifer in the Yucatan region. 相似文献
97.
Spatial pattern of Karst rock desertification in the Middle of Guizhou Province,Southwestern China 总被引:13,自引:0,他引:13
Karst rocky desertification is a typical type of land degradation in the Southwestern China. It has great ecological and economical
implications for the local people. Landsat images from the middle of Guizhou Province collected in 1974, 1993 and 2001 were
used for change detection of the pattern of Karst rocky desertification. The results show the following findings: (1) Desertification
area expanded drastically in 27 years, at an increasing rate about 116.2 km2/year. (2) High areas (900–1,500 m) are the most affected. (3) Areas with the slope <5° or >25° are also easily tend to be
Karst rocky deserted. (4) The process of Karst rocky desertification is nearly irreversible. Few areas of Karst rocky desertification
could be meliorated to non-desertification land. (5) Most of the degraded lands are located in the south and the central of
the study region, and the meliorated land areas are sparsely located in the east and the west part of the region. All these
findings would provide bases for the decision-making of the local government to improve the Karst rocky desertification 相似文献
98.
Oscar Escolero Luis E. Marin Eloisa Domínguez-Mariani Sandra Torres-Onofre 《Environmental Geology》2007,51(5):719-723
A hydraulic analysis of the interface between freshwater–saltwater behavior was done in the Merida Yucatan zone, two machines
that constantly register the groundwater levels were installed, and three electric conductivity logs were taken from wells.
When comparing the measured results with the ones obtained using theoretical equations developed to calculate the freshwater–saltwater
interface position, it was proved that in some cases these equations can be applied, and in others not. Two effects that rule
the behavior of karst aquifers in extraordinary conditions were found. 相似文献
99.
Sokrat Amataj Todor Anovski Ralf Benischke Romeo Eftimi Laurence L. Gourcy Liliana Kola Ioannis Leontiadis Eftim Micevski Alqiviadis Stamos Jovan Zoto 《Environmental Geology》2007,51(5):749-753
Prespa Lake and Ohrid Lake constitute a hydraulic system shared between Albania, FYR of Macedonia and Greece. Karst rocks
separate both lakes. The elevation of Prespa Lake is about 150 m higher than that of Ohrid Lake. Considering these facts,
Cvijić formulated in 1906 the hypothesis that Prespa Lake recharges the St. Naum and Tushemisht springs at Ohrid lakeside.
Environmental isotopes demonstrated that Prespa Lake recharges about 37–42 and 52–54% of water emerging in St. Naum, and Tushemisht
springs, respectively. An artificial tracer experiment carried out in 2002 physically demonstrated the underground connection
between both lakes. This experiment confirmed the supposed underground connection and brought important information about
the groundwater velocity, transit time, and karst water conduits development. 相似文献
100.
Branka Trček 《Environmental Geology》2007,51(5):761-765
The role of an epikarst zone in the karst aquifer hydraulic behaviour was brought into focus in our studies referring to the
catchment area of the Hubelj spring (SW Slovenia). This study points out the significance of effects of the fast preferential
flow—epiflow, which is the main factor controlling solute/contaminant transport towards the aquifer saturated zone. The so-called
epikarstic hypothesis is verified on the basis of the most significant research results that are supported by the most important
findings from the literature. 相似文献