Water vapor transport in soils from a pervaporative

4 A novel method for irrigation with saline water uses a polymer membrane, formed 5 into a tube, to treat and distribute the water simultaneously. The flux of water across 6 the membrane occurs by the process of pervaporation, during which a phase change from 7 liquid to vapor occurs. Thus water arrives in the soil in vapor phase. The experimental 8 results presented in this paper demonstrate that, contrary to previous assumptions, 9 soil vapor flows are a significant transport mechanism during pervaporative irrigation 10 in dry soils. The soil water sorption properties affect the rate of condensation in the 11 soil, which in turn affects both the water distribution in the soil and the loss of water 12 vapor to the atmosphere. The flux from the tube becomes limited by high humidities 13 adjacent to the external surface of the membrane. Thus enhancing condensation in 14 the soil or increasing diffusion through the soil increases flux from the system. These 15 findings highlight the need to consider how plants might interact with water supplied 16 in the vapor phase. 17 PhD Student, Dept. of Civil and Environmental Engrg., Imperial College London, South Kensington, London, SW7 2AZ, UK. E-mail: [email protected] Assistant Professor, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 3H5, Canada Reader, Dept. of Civil and Environmental Engrg., Imperial College London, South Kensington, London, SW7 2AZ, UK. Senior Lecturer, Dept. of Civil and Environmental Engrg., Imperial College London, South Kensington, London, SW7 2AZ, UK. 1