APPARATUS FOR CONSTANT-HEAD SOLUTE TRANSPORT AND SOIL-WATER CHARACTERISTIC DETERMINATION

We developed a system to impose, maintain, and monitor constant matric head (h) and water content (theta) within large soil cores during sat urated or unsaturated now. Critical elements include: (i) delivery of water and chemicals to the column inlet using a modified disk permeame ter; (ii) paired time domain reflectometry (TDR) and transducer tensio meter sensors; and (iii) solenoid valves at the outlet for uninterrupt ed negative pressure and simultaneous collection of large effluent vol umes. Use of TDR and tensiometry provides detailed water retention dat a and allows hydraulic conditions within the soil to be continuously m onitored during single or multiple experiments using the same soil col umn. Our experiences have emphasized the need to measure soil column h rather than infer its status based on applied pressure.