Search results for "infiltration"
showing 10 items of 291 documents
I beni confiscati come nuovo spazio pubblico
2014
Nel territorio a nord-est di Palermo la criminalità organizzata, in molte occasioni, ha condizionato il potere politico e amministrativo e inciso su valori e abitudini collettive, esercitando unʼinfluenza determinante nellʼespansione periurbana e nella conseguente trasformazione del paesaggio agrario. Alcuni dei principali centri oggetto della ricerca hanno governato il territorio sotto il controllo sistematico della mafia rendendo necessario lʼintervento dello Stato. Esaminare i rapporti tra amministrazioni locali e Cosa nostra in quei luoghi permette di individuare ricorrenze criminali nella gestione dei beni collettivi e di concentrare lʼattenzione sulle proprietà confiscate. In the nort…
Clientelismo e metodo mafioso: network Criminali e pubblica amministrazione in Sicilia
2011
Quale relazione lega clientelismo e mafia? Quali elementi accomunano crimine dei potenti e metodo mafioso? Come si strutturano i sistemi criminali nelle realtà locali? Il saggio presenta una selezione ragionata di studi sulle relazioni tra clientelismo e mafia (par. 1) e sulle reti che si configurano nell’interconnessione tra sistemi criminali e pubblica amministrazione (par. 2). Tali studi permettono di leggere tanto fenomeni storici, come i comitati d’affari che asservivano i poteri pubblici nella Palermo degli anni Cinquanta (par. 3), tanto fenomeni più recenti, come quelli che, dal 1991 in poi, rientrano nella fattispecie dei Comuni e degli enti locali commissariati per infiltrazioni ma…
An assessment of the Beerkan method for determining the hydraulic properties of a sandy loam soil
2014
Abstract Establishing the ability of the Beerkan Estimation of Soil Transfer parameters (BEST) procedure to reproduce soil properties is necessary for specific soil types. In this investigation, the BEST predictions for a sandy loam soil were compared with water retention data obtained by a standard laboratory method and with the saturated soil hydraulic conductivity, K s , obtained by both the Wu et al. (1999) method, applied to the BEST infiltration data, and the Simplified Falling Head (SFH) technique. When the original BEST-slope algorithm with the infiltration constants fixed at β = 1.9 and γ = 0.79 was applied, the agreement between the predicted and the measured retention data was sa…
A test of the Beerkan Estimation of Soil Transfer parameters (BEST) procedure
2014
Abstract The Beerkan Estimation of Soil Transfer parameters (BEST) procedure is attractive for a simple soil hydraulic characterization but testing the ability of this procedure to estimate soil properties is necessary. The BEST predictions were compared with soil water retention and hydraulic conductivity data measured in the laboratory and the field, respectively, at ten Sicilian field sites. Provided that BEST yielded physically possible scale parameters of the soil characteristic curves in most of the four replicated infiltration runs at a site, the measured water retention was satisfactorily predicted (i.e., not statistically significant differences between measurements and predictions…
Testing steady-state analysis of single-ring and square pressure infiltrometer data
2016
Testing reliability of the saturated soil hydraulic conductivity, Ks, estimated by applying the steady-state single-ring (SR) model to the quasi steady-state infiltration rates obtained with a single-ring pressure infiltrometer (PI) increases confidence in the estimated Ks values. Determining a means to estimate Ks from infiltration data collected with a square infiltrometer allows the use of sources of different shapes. Using numerically simulated infiltration rates for six homogeneous soils ranging in texture from sand to silty clay loam, this investigation suggested an overall good performance of the SR model, with estimated Ks values differing by not more than 25% from the true values f…
ASSESSMENT OF THE SIMPLIFIED FALLING HEAD TECHNIQUE TO MEASURE THE FIELD SATURATED SOIL HYDRAULIC CONDUCTIVITY
2013
The Simplified Falling Head (SFH) technique to measure field saturated soil hydraulic conductivity, Kfs, has received little testing or comparison with other techniques. Different experiments were carried out to i) determine the effect of ring size on the measured conductivity; ii) compare the SFH and Pressure Infiltrometer (PI) techniques in a clay loam soil; and iii) assess the indirect approach to estimate the * parameter used in the SFH methodology. Sampling a relatively large number of sites allowed to detect a statistically significant relationship between the Kfs values obtained with rings differing in diameter (0.15 and 0.30 m, respectively). This relationship suggested that a meas…
An Evaluation of the Single-test Tension Infiltrometer Method for determining the Hydraulic Conductivity of Lateral Capillarity Domain Soils
2004
Abstract The transient and the steady-state single-test tension infiltrometer methods are expected to provide poor hydraulic conductivity K0 estimates in soils situated in the lateral capillarity domain. To evaluate the best strategy for conducting a single-test experiment in these soils, infiltration experiments were numerically simulated for a sandy loam and a clay soil by using two initial pressure heads (−1 and −100 m), four pressure heads at the soil surface (from −0·15 m to −0·01 m), and a maximum duration of 4 h (sandy loam soil) and 12 h (clay soil). The most accurate predictions of K0, differing by a factor of between 0·9 and 1·1 from the true value, were obtained in wet conditions…
Field and laboratory approaches for determining sodicity effects on saturated soil hydraulic conductivity
2006
Abstract Dilution of high-sodicity soil water by low-sodicity rainfall or irrigation water can cause declining soil hydraulic conductivity (K) by inducing swelling, aggregate slaking and clay particle dispersion. Investigations of sodicity-induced reduction in K are generally restricted to repacked laboratory cores of air-dried and sieved soil that are saturated and equilibrated with sodic solution before tests are conducted. This approach may not yield a complete picture of sodicity effects in the field, however, because of loss of antecedent soil structure, small sample size, detachment of the sample from the soil profile, reliance on chemical equilibrium, and differing time scales betwee…
A laboratory analysis of falling head infiltration procedures for estimating the hydraulic conductivity of soils
2006
Abstract Falling head (FH) infiltration procedures can give rapid estimates of the field saturated hydraulic conductivity ( K fs ) of soils. The objectives of this investigation were to develop a procedure for estimating both the K fs and the α ⁎ parameter of the exponential hydraulic conductivity function from a FH experiment, and to compare FH procedures differing by experimental and computational demands. A total of 33 FH experiments were carried out on repacked, sandy loam and loam soil cores. A two level (TL) analysis was applied to determine a value of α ⁎ for each soil core. K fs was then calculated by three different approaches, ranging from the fitting approach (FA) that used the m…
Nitrogen losses in vineyards under different types of soil groundcover. A field runoff simulator approach in central Spain
2017
The soils of Mediterranean vineyards are usually managed with continuous tillage, resulting in bare soil, low infiltration and high soil erosion rates. Soil nutrients, such as nitrogen, could be lost dissolved in the runoff, causing a decrease in soil fertility on such degraded soils and producing eutrophication downstream. The influences of groundcover on the soil erosion processes and sediment yields in Mediterranean vineyards have been widely addressed. However, the runoff process itself, excluding the effect of raindrop impacts, has barely been studied. Thus, a field runoff simulator was built to assess runoff and nutrient losses under different soil management strategies in Central Spa…