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421.
Maria Clementina Caputo Lorenzo De Carlo Costantino Masciopinto John Robert Nimmo 《Environmental Earth Sciences》2010,60(3):583-590
Up to now, field studies set up to measure field-saturated hydraulic conductivity to evaluate contamination risks, have employed
small cylinders that may not be representative of the scale of measurements in heterogeneous media. In this study, a large
adjustable ring infiltrometer was designed to be installed on-site directly on rock to measure its field-saturated hydraulic
conductivity. The proposed device is inexpensive and simple to implement, yet also very versatile, due to its large adjustable
diameter that can be fixed on-site. It thus allows an improved representation of the natural system’s heterogeneity, while
also taking into consideration irregularities in the soil/rock surface. The new apparatus was tested on an outcrop of karstic
fractured limestone overlying the deep Murge aquifer in the South of Italy, which has recently been affected by untreated
sludge disposal, derived from municipal and industrial wastewater treatment plants. The quasi-steady vertical flow into the
unsaturated fractures was investigated by measuring water levels during infiltrometer tests. Simultaneously, subsurface electrical
resistivity measurements were used to visualize the infiltration of water in the subsoil, due to unsaturated water flow in
the fractures. The proposed experimental apparatus works well on rock outcrops, and allows the repetition of infiltration
tests at many locations in order to reduce model uncertainties in heterogeneous media. 相似文献
422.
Mapping and monitoring net primary productivity with AVHRR NDVI time-series: statistical equivalence of cumulative vegetation indices 总被引:1,自引:0,他引:1
Carlo Ricotta Giancarlo Avena Alessandra De Palma 《ISPRS Journal of Photogrammetry and Remote Sensing》1999,54(5-6)
In the last two decades, numerous investigators have proposed cumulative vegetation indices (i.e., functions which encode the cumulative effect of NDVI maximum value composite time-series into a single variable) for net primary productivity (NPP) mapping and monitoring on a regional to continental basis. In this paper, we investigate the relationships among three of the most commonly used cumulative vegetation indices, expanding on the definition of equivalence of remotely sensed vegetation indices for decision making. We consider two cumulative vegetation indices as equivalent, if the value of one index is statistically predictable from the value of the other index. Using an annual time-series of broad-scale AVHRR NDVI monthly maximum value composites of the island of Corsica (France), we show that the pairwise linear association among the analysed cumulative vegetation indices shows coefficients of determination (R2) higher than 0.99. That is, knowing the value of one index is statistically equivalent to knowing the value of the other indices for application purposes. 相似文献