Slope and rainfall effects on the volume of sediment yield by gully erosion in the Souar lithologic formation (Tunisia)     

Hajer Bouchnak  Mennoubi Sfar Felfoul  Mohamed Rached Boussema  Mohamed Habib Snane 《CATENA》2009

The Souar lithologic formation in semi-arid Tunisia is undergoing severe gully erosion which is threatening soil and water resources. Soil conservation strategies have focused more on terracing than on gully control techniques, since the contribution of gully sediment yield in the overall soil loss from watersheds is unknown. The paper reports investigations into the sediment yield provided by head-cut as well as sidewall–floor erosion of first order gullies on gentle and steep slope catchments underlined by the Souar lithologic formation. We measured mean field sediment volumes evacuated by different headward reaches of 10 and 9 gullies located on gentle and steep slope catchments, respectively. Two equations between the length of the gully head cutting and the corresponding volume of evacuated sediment were established. The treatment with a Geographic Information System (Arc View) of air photographs of six flights from 1952 to 2000 allowed the calculation of the volume of sediment provided both by head cutting and gully sidewalls–floor erosion through the following up of gully extension in eight catchments during the five periods separating the dates of these flights. Total gully erosion was on average 1.66 m³ ha^− 1 year^− 1 for the gentle slopes and 5.603 m³ ha^− 1 year^− 1 for the steep slopes. Sidewalls–floor contribution in total erosion was on average 81.5% for the gentle slopes and 77.8% for the steep slopes. We found out that the mean annual rainfall resulting from 40 mm daily rainfall threshold explained better the variation of annual head cutting sediment yield for these five periods than any other annual rainfall resulting from lower daily rainfall thresholds. Two equations between these two variables were established both for gentle and steep slope catchments.  相似文献   

Impregnation of ethylcellulose microcapsules containing jojoba oil onto compressive knits developed for high burns     

Fadhel Jaâfar  Mohamed Ali Lassoued  Mahdi Sahnoun  Souad Sfar  Morched Cheikhrouhou 《Fibers and Polymers》2012,13(3):346-351

The medical uses of textile fibers and fabric forms keep on growing. Today, the knits can be used in the medical field. The aim of this present work was to prepare compressive knits, impregnated by ethylcellulose (EC) microcapsules, for the burnt skin. Ethylcellulose microcapsules containing jojoba oil were prepared via the phase separation method. Jojoba oil was chosen because it plays an essential role in skin hydration and avoids the sebum accumulation. Ethylcellulose microcapsules obtained were grafted on two different compressive knit surfaces by impregnation, using the Acrylic Resin (AR) as binder. The prepared microcapsules were analyzed by Scanning Electron Microscopy (SEM). The stability of the microcapsules, the efficiency of the microencapsulation method and the jojoba oil content determination were also investigated. This method of application improved the fabric surface and permitted in maximum the preserving of initial characteristics of knit, such as touch, flexibility and lightness.  相似文献