Laserfiche WebLink
Soil Measurement Systems, LLC <br /> 412 Olive Ave #125 <br /> Huntington Beach CA 92648 <br /> Phone: 520-742-4471 <br /> E-mail: sales@soilmeasurement.com <br /> www.soilmeasurement.com <br /> Vadose Zone Sampling (2" OD, Dual Chamber Lysimeter) <br /> Introduction: <br /> Soils and other geologic materials above the groundwater table are generally <br /> unsaturated, i.e. some of the pore space between soil particles is filled with air, <br /> while the remainder of the pore space is filled with water. Due to capillary action <br /> and other forces, water in the unsaturated or vadose zone is held tightly to the <br /> soil. This means that one has to apply suction on the soil material to extract pore <br /> water for chemical analysis. Unfortunately, one cannot simply insert an open <br /> pipe into unsaturated soil and expect to collect pore water by applying suction <br /> on the pipe. Although sampling of shallow groundwater can be accomplished by <br /> placing an open-ended pipe in the groundwater, for sampling of pore water in <br /> the unsaturated zone, the open end of the pipe has to be closed with a porous <br /> membrane. In moist soil the fine pores in the porous membrane, when in close <br /> contact with the moist soil, fill with pore water by capillary action. When all <br /> pores in the membrane are filled with water air cannot move through when <br /> suction is applied on the pipe. However, water can, and does move through the <br /> porous membrane. By applying suction on the pipe, water from the soil, in <br /> contact with the porous membrane, will flow through the water filled pores in <br /> the membrane. The water collects inside the pipe and can be brought to the soil <br /> surface by vacuuming it up through a tube (may not work for depths greater <br /> than 6—8 meter), or by forcing it up with air pressure. <br /> Note that when air pressure (either positive or negative) applied to SMS <br /> lysimeters is greater than 9 psi (0.6 bars),water held in the pores of the porous <br /> steel tips is forced out and air can move through. This pressure is called <br /> bubbling pressure. Thus at no time should the negative pressure applied to <br />