Time filter

Source Type

Beit Jann, Israel

Addressed here are bimodal, heterogeneous, variably saturated formations, viewed as mixtures of two populations (background soil and embedded soil) of differing spatial structures. Two distinct cases are considered: In the first case, the texture of the embedded soil is finer than that of the background soil; in the second case, the reverse is true. First-order, Lagrangian- stochastic analysis of vadose-zone transport was used to investigate the combined effect of the texture of the embedded soil and the mean pressure head on solute spread and breakthrough in these formations. The main results of the first-order analysis suggest that features of solute transport associated with the two different formations exhibit a crossover behavior and that the mean pressure head associated with the crossover may be estimated from the asymptotic macrodispersivities associated with the two formations. The applicability of the results of the first-order analysis to more realistic conditions was tested with a series of detailed numerical simulations of the flow and transport in three-dimensional, heterogeneous, bimodal, variably saturated formations; relatively simple, steady state flow and more complicated, transient, nonmonotone flow originating from periodic influx and water uptake by plant roots were considered. For the steady state flows, results of the simulations were in qualitative agreement with the results of the first-order analysis. For the more realistic flow regime, the results of the simulations suggested that the difference between the responses of the two different bimodal formations might decrease substantially, similar to the situation in steady state flow associated with mean pressure head at which a crossover occurs. Copyright © 2010 by the American Geophysical Union. Source

Ben-Hur M.,Institute of Soils
International Water and Irrigation | Year: 2012

Meni Ben-Hur shares his views on some of the changes, challenges and achievements of the water system in the Israeli agriculture. One of the possibilities to dispose of treated wastewater is its reuse in irrigation. This reuse of treated wastewater in Israeli agriculture has increased and expanded over a period of time. The master plan of the Water Authority estimates that the amounts of treated wastewater and freshwater to be allocated to agriculture in the year 2050 will be 909 and 395 mcm. This indicates that the main source of water for irrigation in agriculture in the country is treated wastewater. The challenge being faced is that the irrigation with treated wastewater can lead to leakage of pollution below the roots zone, such as nitrates that have been discovered in orchards with continuous irrigation with secondary treated wastewater at kibbutz Ramat Hakovesh and Mizrah, along with pesticide Atrazine discovered in the fields of kibbutz Maabarot. Source

Zentner E.,Ben - Gurion University of the Negev | Weisbrod N.,Ben - Gurion University of the Negev | Gerstl Z.,Institute of Soils | Gasser G.,Hebrew University of Jerusalem | Ronen D.,Ben - Gurion University of the Negev
Chemosphere | Year: 2015

Spatial heterogeneity in the chemical concentration of interstitial water in the vadose zone was previously observed under apparently homogeneous surface conditions on two leveled fields sprinkler irrigated with treated sewage effluents on the phreatic Coastal Plain aquifer of Israel. This phenomenon greatly hampers the monitoring of groundwater quality. In this study we report on the presence of puddles of different size and shape that were sporadically observed in these fields. Temporal variability noted in the concentration of treated sewage effluents components in the puddles were considered to be related to evapotranspiration and degradation. For example: increases in the electrical conductivity (up to 1.32 mS/cm), and in the concentrations of chloride (up to 521 mg/L), dissolved organic carbon (up to 28.4 mg/L), and carbamazepine (up to 780 ng/L) and decreases in the concentrations of nitrate (up to 20.1 mg/L) and caffeine (3396 ng/L). Variable trends in concentration were observed for sulfamethoxazole, venlafaxine, 10-hydroxy-10,11-dihydrocarbamazepine and o-desmethylvenlafaxine. The presence of puddles was not necessarily related to areas with high irrigation water input. It is postulated that the continuous chemical variability in the puddles, whose location and size are also variable, determine a heterogeneous influx of solutes into the soil and subsequently into the vadose zone. © 2015 Elsevier Ltd. Source

Nasser A.,Institute of Soils | Mingelgrin U.,Institute of Soils
Chemosphere | Year: 2014

DCP (2,4-dichlorophenol) is the key-intermediate in the synthesis of some widely used pesticides and is an EPA priority pollutant. The mechanochemical breakdown of DCP loaded on birnessite (δ-MnO2), montmorillonite saturated with Na+ or Cu2+ and hematite was investigated. Mechanical force was applied by grinding of mixtures of DCP and the minerals, using mortar and pestle. Grinding of DCP for 5min with the montmorillonites or with hematite resulted in negligible degradation during grinding, while grinding with birnessite induced the immediate degradation of 90% of the loaded DCP. Incubation for 24h after grinding did result in up to 30% degradation of the DCP loaded on the other minerals tested.HPLC and LC-MS analysis revealed that the transformation of DCP yielded oligomerization products as well as partial dechlorination. DCP degradation on birnessite was accompanied with a substantial increase in the extractability of manganese from the mineral into an acidic aqueous solution, indicating that Mn(IV) in the mineral transformed into Mn(II) and that birnessite served as an electron acceptor in the transformation. The oligomerization and partial dechlorination brought about by grinding, suggest a reduction in bioavailability and toxicity. © 2013 Elsevier Ltd. Source

Stanhill G.,Institute of Soils | Achiman O.,Institute of Soils
International Journal of Climatology | Year: 2016

Measurements of global radiation Eg↓ made in the first half of the 20th century are reviewed. The thermoelectric pyranometers used to measure Eg↓ in the United States, Western Europe and Russia are described and the published sources of data available up to and including the 1957 International Geophysical Year are documented together with the few analyses of this data which have been reported. Two 100-year-long series measured at Potsdam, Germany and Washington, DC in the United States are presented to illustrate the potential value of the early measurements in understanding the changes in Eg↓ which have occurred in the last 60 years. © 2016 Royal Meteorological Society. Source

Discover hidden collaborations