In order to determine if soil hydraulic properties present a direction-dependent behavior, undisturbed samples were collected at different horizons and orientations (vertical, diagonal [45°], and horizontal) in structured soils in the Weichselian moraine region in northern Germany. The water-retention curve (WRC), the saturated hydraulic conductivity (k f ), and the air permeability (k a ) were measured. The air-filled porosity (e a ) was determined, and pore-continuity indices (k a /e a , k a / e a 2 , N) and blocked porosities (e b ) were derived from the relationship between k a and e a . The development of soil structures with defined forms and dimensions (e.g., platy by soil compaction or prismatic up to subangular-blocky by swelling-shrinkage processes) and the presence of biopores can induce a direction-dependent behavior of pore functions. Although the pore volume as a scalar is isotropic, the saturated hydraulic conductivity and air permeability (as a function of air-filled porosity) can be anisotropic. This behavior was observed in pore-continuity indices showing that the identification of soil structure can be used as a first parameter to estimate if hydraulic properties present a direction-dependent behavior at the scale of the soil horizon.
Andisols present exceptional physical properties, making up < 1% of the world's soils. While there is a lot of information about non-volcanic soil properties, research about soils of volcanic origin is limited. Specifically, no major studies have been carried out to improve our knowledge of these soils' hydrological behavior, which is relevant due to the impact of climate change on water resources and to the soil's role in the hydrological cycle. Thus, the aim of this work was to analyze the water content dynamics of a soil slope derived from volcanic ashes under different land covers. We hypothesized that land cover, rainfall, and air temperature, in addition to the hydraulic properties of the volcanic ash soil, regulate the slope's water content dynamics. Our study was conducted in S Chile, in a fluvial terrace covered by pastures in the uplands, a native forest in the adjacent slope, and a hygrophilous forest in the floodplain at the base of the slope, surrounding a stream. Soil physical properties, such as bulk density (Db), volume of macropores (wCP), plant available water (PAW) and saturated hydraulic conductivity (Ks) were studied. Rainfall, air temperature, volumetric water content ( Field ) and soil temperature were continuously measured with data loggers. The groundwater level was also measured. Water content dynamics reflect the behavior of rainfall and air/soil temperatures under different land covers, as well as, revealing the specific behavior of volcanic soil's pore system (e.g., Db < 0.9 Mg m -3 ). Soil depths exposed to more intensive and dynamic wetting and drying cycles presented well-defined water release ranges as compared to the pore system of deeper soil horizons. Soils present large water holding capacities (PAW > 24%), however, during summer they can reach volumetric water contents near to the permanent wilting point quickly at a depth of 5 cm. The water table altitude was directly related to the temporal changes of Field measured at a depth of 50 cm, highlighting the fact that the saturated and unsaturated zones are connected.
Retention of D in neutron-irradiated W and desorption were examined after plasma exposure at 773 K. Deuterium was accumulated at a relatively high concentration up to a large depth of 50-100 m due to the trapping effects of defects uniformly induced in the bulk. A
The effects of neutron and ion irradiations on deuterium (D) retention in tungsten (W) were investigated. Specimens of pure W were irradiated with neutrons to 0.3 dpa at around 323 K and then exposed to high-flux D plasma at 473 and 773 K. The concentration of D significantly increased by neutron irradiation and reached 0.8 at% at 473K and 0.4 at% at 773 K. Annealing tests for the specimens irradiated with 20 MeV W ions showed that the defects which play a dominant role in the trapping at high temperature were stable at least up to 973 K, while the density decreased at temperatures equal to or above 1123 K. These observations of the thermal stability of traps and the activation energy for D detrapping examined in a previous study (≈1.8 eV) indicated that the defects which contribute predominantly to trapping at 773 K were small voids. The higher concentration of trapped D at 473 K was explained by additional contributions of weaker traps. The release of trapped D was clearly enhanced by the exposure to atomic hydrogen at 473 K, though higher temperatures are more effective for using this effect for tritium removal in fusion reactors.2
Volcanic soils in southern Chile cover approximately 60% of the arable land in the country. These soils are under a wide range of land uses from pristine systems to intensively used ones. The objective of this study was to determine the effect of the land use change on: i) the structural stability after external and internal forces, ii) the hydraulic conductivity and iii) its functional resilience. Disturbed and undisturbed soil samples were collected at 5, 20 and 40 cm depths in an Andisol (Typic Hapludand) under native forest (NF), 50 year old pasture (P50) and 1 year old pasture (P1). The water retention, shrinkage and consolidation curves, hydraulic conductivity (Ks), air permeability (Ka), organic carbon content (CO), soil texture and allophane contents were determined. The unsaturated hydraulic conductivity (Ku) was estimated according to van Genuchten (1980). Soil deformation indexes as a consequence of mechanical (COLEm) and hydraulic (COLE h ) stresses were calculated. The studied soil is subject to continuous changes in their structure as a consequence of mechanical and hydraulic stresses affecting the pore size distribution and its functionality. The magnitude of these changes decreased with the increasing intensity of the land use. The great shrinkage capacity of the soil may have consequences on its hydraulic behaviour depending on the drying intensity through the formation of cracks and preferential path flows. Finally, the soil pores are able to recover its functional integrity after compaction, which is strongly related to the presence of organic matter contents.Keywords: Andisol, structural properties, pore functions
RESUMENLos suelos volcánicos del sur de Chile constituyen cerca del 60% del suelo arable del país. Estos suelos se encuentran bajo un amplio rango de usos desde sistemas prístinos hasta otros con un uso intensivo. El objetivo de este trabajo fue determinar el efecto del cambio de uso de suelo sobre: i) la estabilidad del suelo frente a presiones externas e internas; ii) la conductividad hidráulica y iii) su resiliencia funcional. Muestras disturbadas y no disturbadas de suelo fueron recolectadas a 5, 20, 40 cm de profundidad 190 Rev. Cienc. Suelo Nutr. / J. Soil. Sci. Plant Nutr. 9(3): 190-209 (2009)
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