1,721,348 research outputs found
Sistema lisimetrico a suzione e metodo per rilevare flussi idrici in un terreno (BREVETTO ITALIANO)
No full textL’invenzione concerne un sistema lisimetrico a suzione comprendente due dispositivi di captazione 10 e 20 definenti ciascuno una superficie di captazione S’ e S”. I due dispositivi sono sovrapposti tra loro con le due superfici di captazione in posizioni opposte. In condizione d’uso i due dispositivi sovrapposti tra loro sono collocati nel terreno a differenti profondità in modo tale che una prima superficie S’ sia rivolta verso la superficie T del suolo per intercettare i flussi di percolazione, e la seconda superficie S” sia rivolta verso la falda F per intercettare i flussi di risalita. Il sistema 1 comprende mezzi di suzione 30 idraulicamente collegati ad entrambi i dispositivi 10 e 20 per prelevare i fluidi da essi intercettati applicando una depressione.
Preferibilmente, il sistema 1 comprende: - mezzi 40 per rilevare il potenziale idrico del suolo in due o più punti del terreno in prossimità dei due dispositivi di captazione 10 e 20; e - una centralina elettronica di controllo 60 che regola il funzionamento e/o l’attivazione dei dispositivi in funzione dei valori del potenziale idrico rilevato, determinando la direzione del flusso idrico rilevato nel suolo
THE SOILS OF ITALY, E. Costantini, C. Dazzi (eds). Springer: Dordrecht, Heidelberg, New York, London, 2013. ISBN: 978-94-007-5641-0 (hardcover), € 176.75, ISBN-1 978-94-007-5642-7 (eBook), € 142.79, x + 354 pp.
No full textDrainage flux measurement and errors associated with automatic tension-controlled suction plates
No full textAutomatic control of high tension soil solution samplers (suction
lysimeters) in response to the surrounding soil matric potential has
been proposed as a new method to reduce the convergence and divergence
fluxes around the lysimeters. It is important to evaluate the
instruments’ performance with automatically regulated suction because
the efficiency of the control and its effects on the flux volumes
could vary with the surrounding soil matric potential. An automatic
equilibrium tension lysimeter (AETL) system was developed composed
of 16 small-area (572 cm2) ceramic suction plates that were
continuously kept in equilibrium by an automated control device. The
automated control device consisted of a datalogger connected to electronic
tensiometers and to an electric vacuum pump that was activated
to regulate the ceramic plate suction. The system was evaluated
by simulating its performance with the HYDRUS-2D finite-element
model. The AETL system continuously kept the lysimeters’ suction
in equilibrium with the surrounding soil when the soil water matric
potential head ranged from 2306 to 0 cm H2O. Suction control was
less effective during low drainage conditions (soil matric potential
head less than 250 cm H2O), when it took more time to re-equilibrate
the pressure heads. However analysis of the variability of drainage and
model simulations showed that incorrect suction control in drier conditions
had a limited effect on the collected volumes. Suction was much
better controlled when drainage flux was high, allowing a correct estimate
of drainage. Automatic control of suction plates is a valuable
tool for estimating drainage fluxes. Fine control of suction is needed
when drainage flux is high because even the slight overapplication of
suction, which is typically done during field experiments to overcome
porous plate resistance and ensure that a sample is collected, could
produce marked overestimation of water drainage (.30%)
Monitoring desertification in a Savannah region in Sudan using Landsat imagesand spectral mixture analysis
No full textTwo Landsat images, acquired in 1987 and 2008, were analyzed to evaluate desertification processes in
central North Kurdufan State (Sudan). Spectral Mixture Analysis (SMA) and multitemporal comparison
techniques (change vector analysis) were applied to estimate the long-term desertification/re-growing of
vegetation cover over time and in space.
Site-specific interactions between natural processes and human activity played a pivotal role in
desertification. Over the last 21 years, desertification significantly prevailed over vegetation re-growth,
particularly in areas around rural villages. Changes in land use and mismanagement of natural
resources were the main driving factors affecting degradation. More than 120,000 km2 were estimated as
being subjected to a medium-high desertification rate. Conversely, the reforestation measures, adopted
by the Government in the last decade and sustained by higher rainfall, resulted in low-medium regrowth
conditions over an area of about 20,000 km2.
Site-specific strategies which take into account the interactions of the driving factors at local scale are
thus necessary to combat desertification, avoiding any implementation of untargeted measures. In order
to identify the soundest strategies, high-resolution tools must be applied. In this study the application of
spectral mixture analysis to Landsat data appeared to be a consistent, accurate and low-cost technique to
identify risk areas
Municipal wastewater treatment with vertical flow constructed wetlands for irrigation reuse
No full textThe treatment effect of two pilot-scale vertical flow constructed wetlands (VFCWs) on municipal wastewaters and their suitability for irrigation reuse were evaluated in a 2-year (2002-2003) experiment. One VFCW was planted with Typha latifolia and the other with Phragmites australis. VFCW efficiency was evaluated in terms of both mass removal and water quality improvement, considering the following parameters: pH, electrical conductivity (EC(w)), total suspended solids (TSS), chemical oxygen demand (COD) and biochemical oxygen demand (BOD), total nitrogen (TN) and nitrate (NO(3)(-)), total phosphorus (TP) and orthophosphate (PO(4)(3-)), sodium (Na), potassium (K), magnesium (Mg) and calcium (Ca). The accumulation of the elements in the plant organs and VFCW sandy surface layer and their offtake with the macrophyte harvest were also measured. In quantitative terms the established VFCWs showed higher removal efficiencies (>86%) for COD, BOD, N and K, while lower efficiencies (65%) due to the massive growth, The results were less favourable in terms of water quality, because the high evapotranspiration losses counteracted the depuration process by concentrating the elements in the outflow water. Higher concentrations were found in outflow than inflow, especially of Na (relative increase of 89%) and Mg (relative increase of 74%). Only parameters with high removal efficiencies fulfilled the Italian guidelines for irrigation reuse whereas parameters with lower efficiencies (e.g., TSS, TP) limited the potential water reuse. Efficient pre-cleaning systems or innovative integrated systems are thus necessary to obtain high removal efficiencies that reduce the effect of ET on water qualit
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