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The hydrological role of biological topsoil crusts and water repellency in sandy dry-land areas

Yair A., Almog R., Arbel Y.

Landform Analysis

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2018

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Vol. 36

33--44

EN

Dryland areas are regarded as highly sensitive to climatic changes. A positive relationship between rainfall and environmental factors is often assumed for areas with an average annual rainfall of 100–300 mm. This assumption disregards the fact that a climate change in arid areas is not limited to climatic factors. It is often accompanied by a pronounced spatial variability in surface characteristics. The present work deals with the complex relationships among average annual rainfall, surface properties and the spatial redistribution of water resources in sandy areas located in the Northern Negev Desert. Two case studies are considered. The first deals with the hydrological effects of biological topsoil crusts on the water regime, along a rainfall gradient (86–170 mm). This study is based on five monitoring sites. Data obtained show a decrease in water availability with increasing annual rainfall. The findings are attributed to the decisive role played by the non-uniform properties of the topsoil crust along the rainfall gradient. The second case refers to the non-uniform development, and survival, of planted trees. Trees planted on steep dunes are well developed, with a high survival rate, whereas trees planted on low angle dunes are small. This study focused on the role of a water repellent layer on the water regime. Data obtained show a striking difference between steep and low dunes in all aspects studied, namely the degree of water repellency, frequency and magnitude of runoff events, infiltration depth and soil moisture. All variables monitored were found higher on steep than on low dunes. The large trees shed a substantial amount of leaves, whose decay developed a water repellent layer. Runoff generation over the repellent layer enhanced deep water penetration, through the process of subsurface flow. The lack of a water repellent layer over the low dunes prevented runoff generation, with its positive effects.

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An Effect of Washing on Durability of Hydrophobic Finishes of Membrane Laminates

Kowalski M., Salerno-Kochan R.

Autex Research Journal

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2018

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Vol. 18, no. 2

137--142

EN

The aim of the study is to show how the washing process, while considering the type of washing agent and number of wash cycles, determines the durability of hydrophobic finishes of laminated fabrics. The samples of material were subject to multiple wash cycles in clear water and with the use of two types of washing agents, namely, an ordinary washing powder and a detergent recommended by manufacturers of functional clothing. The washed materials were subject to spray test and its waterproofing and degree of surface wetting were evaluated. The tests have shown that waterproofing of membrane laminates with DWR (durable water repellent) coating become deteriorated during washing treatment and the use of special detergent does not guaranty the maintenance of better coating properties than an ordinary washing agent.

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Ocena niezwilżalności w wybranych glebach organicznych saprowo-murszowych

Hewelke E.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2013

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Vol. 22, No. 3

281--289

PL

Głównym celem badań jest analiza zjawiska hydrofobowości w glebie torfowo-murszowej. Badania zostały przeprowadzone w odwodnionych, użytkowanych łąkowo profilach gleby saprowo-murszowej, zlokalizowanych w środkowym Basenie Biebrzy. Przeprowadzono ocenę zwilżalności gleby, wykorzystując test czasu wsiąkania kropli wody (WDPT) i alkoholu (MT). Badania wykazały silną zależność hydrofobowości od uwilgotnienia gleby. Wartości wyników potencjalnej niezwilżalności są znacznie większe niż dla większości gleb mineralnych.

EN

The main objective of this study is an analysis of the phenomenon of hydrophobicity in peat-moorsh soil. Research took place in the drained Sapric Histosol, used as meadows, soil profiles located in the central basin of Biebrza Valley. The persistence and degree of water repellency were examined in the soil using water drop penetration time (WDPT) and alcohol percentage tests (MT). The research showed the extreme dependence of hydrophobicity on soil water content. The values of potential water repellency of the soils studied are much greater than for most mineral repellent soils.