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Several studies indicate that experimental determination of porous medium permeability by a gas flow method may be influenced by gas properties and ambient temperature. In order to explain these influences, a very simple model is developed based on the idea that the flow in the porous medium may results from both pressure-driven and free molecular flows. Measurements of the permeability of sand and a woven fibrous material performed with air and helium flows seem to corroborate this view. Based on the approach developed, we also study the phenomenon known as slip, and a methodology to quantify the slip length is presented.

Amendments with the potential to reduce phosphorus (P) losses from agricultural grassland arising from the land application of dairy-soiled water (DSW) were investigated. Optimal application rates were studied, and associated costs and feasibility were estimated. First, batch tests were carried out to identify appropriate chemicals or phosphorus sorbing materials to control P in runoff from DSW. Then, the best four treatments were examined in an agitator test. In this test, soil-placed in a beaker-was loaded with DSW or amended DSW at a rate equivalent to 5 mm ha −1 (the maximum permissible application rate of DSW allowable in a 42-day period in Ireland). The soil was overlain with continuously stirred water to simulate runoff on land-applied DSW. Optimum application rates were selected based on percentage removal of dissolved reactive phosphorus in overlying water and the estimated cost of amendment. The costs of the amendments, per cubic metre of DSW, increased in the order: bottom ash (1.55 €), alum (1.67 to 1.92 €), FeCl 2 ·4H 2 O (3.55 to 8.15 €), and lime (20.31 to 88.65 €). The feasibility of the amendments, taking into account their cost, potential adverse effects, public perception, and their performance, decreased in the order: alum>FeCl 2 ·4H 2 O> bottom ash>lime. Amendments to DSW could be introduced in critical source areas-areas where high soil test P and direct migration pathways to a receptor overlap.

Effect of chemical amendments to dairy soiled water and time between application and rainfall on phosphorus and sediment losses in runoff. Science of the Total Environment 430: 1-7. DOI: 10.1016430: 1-7. DOI: 10. /j.scitotenv.2012 This article is provided by the author(s) and Teagasc T-Stór in accordance with publisher policies.Please cite the published version.The correct citation is available in the T-Stór record for this article.