Laserfiche WebLink
Lysimeter testing: <br /> It is recommended to clean the lysimeters before installation. This is done <br /> submerging the porous part of the lysimeter for several hours in 70% isopropyl <br /> alcohol or denatured alcohol, followed by a rinse with distilled or de-ionized <br /> water. <br /> For a more thorough cleaning it is recommended to draw the isopropyl alcohol <br /> through the porous steel. This can be done by submerging the porous part of the <br /> lysimeter in the alcohol, then close one outlet and apply a vacuum to the other <br /> outlet. Keep the porous part of the lysimeter submerged in isopropyl alcohol. <br /> After 30 minutes remove the lysimeter from the alcohol, remove all alcohol from <br /> the lysimeter by holding it upside downs and letting the alcohol drain out, and <br /> repeat the latter procedure with distilled water. <br /> Although all lysimeters are thoroughly tested for air leaks before shipment, it is <br /> recommended that they be tested again before installation in the borehole. <br /> Submerge the lysimeter with its porous part for up to 15 minutes in distilled <br /> water. Then remove the lysimeter from the water and hold it upside down to let <br /> the water drain out. Now close the shortest two outlet tubes, and apply a positive <br /> pressure of about 4 to 6 psi (0.3 to 0.4 bar)to the other outlet. Place the lysimeter <br /> back in the water so that the upper part is submerged first (use a long shallow <br /> container, if available or a bucket), and then submerge the lower part. There <br /> should be no consistent air bubbles coming from the pressurized lysimeter. <br /> It is important to test the lysimeter assembly in the field once the vacuum/ <br /> pressure tubes and the fluid return tubes are attached to the lysimeter with <br /> stainless steel unions. This needs to be done before lowering the lysimeters in the <br /> boreholes.After soaking the lysimeters in distilled water, and/or drawing <br /> distilled water through the porous parts of the lysimeters, apply air pressure <br /> (about 0.4 bar or 6 psi)to the assembly, and check for air leaks by holding the <br /> various parts (unions etc.)under water. This test should be done on all tubing <br /> connections. If there are leaks at some of these connections tighten the nuts on <br /> the unions. <br /> Connecting and protecting the tubing: <br /> Each lysimeter has three 1/4 inch stainless steel tubes protruding from the top of <br /> the lysimeter. The longer tube needs to connect to the vacuum/pressure tube, <br /> and the middle tube to the sample collection tube. The shortest tube is either <br />