Caracterización de las vías atmosféricas y mecanismos de exportación de contaminantes y vapor de agua desde la cuenca mediterránea occidental en la época estival

pag. var.

Lignin extraction, purification and depolymerization study

280 p. : il.

The Convective Instabilities in a Liquid-Vapor System with a Non-equilibrium Evaporation Interface

Rayleigh-Marangoni-B,nard instability in a system consisting of a horizontal liquid layer and its own vapor has been investigated. The two layers are separated by a deformable evaporation interface. A linear stability analysis is carried out to study the convective instability during evaporation. In previous works, the interface is assumed to be under equilibrium state. In contrast with previous works, we give up the equilibrium assumption and use Hertz-Knudsen's relation to describe the phase change under non-equilibrium state. The influence of Marangoni effect, gravitational effect, degree of non-equilibrium and the dynamics of the vapor on the instability are discussed.

Two-Dimensional Hillslope Scale Soil Erosion Model

On a hillslope, overland flow first generates sheet erosion and then, with increasing flux, it causes rill erosion. Sheet erosion (interrill erosion) and rill erosion are commonly observed to coexist on hillslopes. Great differences exist between both the intensities and incidences of rill and interrill erosion. In this paper, a two-dimensional rill and interrill erosion model is developed to simulate the details of the soil erosion process on hillslopes. The hillslope is treated as a combination of a two-dimensional interrill area and a one-dimensional rill. The rill process, the interrill process, and the joint occurrence of rill and interrill areas are modeled, respectively. Thus, the process of sheet flow replenishing rill flow with water and sediment can be simulated in detail, which may possibly render more truthful results for rill erosion. The model was verified with two sets of data and the results seem good. Using this model, the characteristics of soil erosion on hillslopes are investigated. Study results indicate that (1) the proposed model is capable of describing the complex process of interrill and rill erosion on hillslopes; (2) the spatial distribution of erosion is simulated on a simplified two-dimensional hillslope, which shows that the distribution of interrill erosion may contribute to rill development; and (3) the quantity of soil eroded increases rapidly with the slope gradient, then declines, and a critical slope gradient exists, which is about 15-20 degrees for the accumulated erosion amount.

Transport of pollutants through the water and subsurface soil using simulated acid rain

The mobility of heavy metals (Zn, Cd, Pb and Ni) was studied in the laboratory acidic leaching two different soils around Ibadan with simulated acid rain. The sampling was carried out from two different sites viz: Orogun and Ilupeju respectively. For Orogun site a depth of 128cm was reached (consisting of four horizons). Different length of polyvinyl chloride (PVC) pipes were cut for different soil horizon depth as observed on the field. The PVC pipes were packed with requires masses of soil. This is then leached using simulated acid rain of different pH of 2.0, 4.0, 6.0 and 8.0 after spiking with known volume of standard solution of metals of interest. It was found that simulated acid rain enhanced the mobility of metals in solution. The pH, Cation Exchange capacity, % clay and organic matter were found to contributed majority to the mobility of metals. Generally as observed, the mobility of metal was to follow the order Zn>Ni>Pb>Cd as the soil is becoming more acidic

Exploitation of soil biota ecosystem services in agriculture: a bioeconomic approach

24 p.