Use of Large Lysimeters to Monitor Unsaturated Hydraulic Properties of Amended Soils

Abstract

The design and construction of large ~ diameter lysimeters has been implemented to monitor the soil water retention behaviour and permeability characteristics of contaminated soils under remediation. The work was carried out as part of a larger project focussing on the sustainable remediation of low value brownfield land. Three lysimeters have been filled with lead contaminated soil: one control; one with a amendment; and one with a and compost amendment. A new software system was built to control the point water content measurement and irrigation system, which could log data to an online unified data repository; provided an interface for connectivity to any serial port device; deal with templating for simplified setup; and realtime feedback for the end user. High capacity tensiometers were used in conjunction with the point water content measurement system to read volumetric water contents and suctions in the large control lysimeter over a series of wetting and drying cycles, each lasting several months. The results demonstrate that there was a difference between small scale laboratory tests and the data obtained from the lysimeters, particularly in the near surface soil due to cracking. Where cracking was not present, the agreement was stronger, but differences suggested that the drying curves in the lysimeter was predominantly scanning behaviour whereas the element tests were likely more representative of primary drying behaviour.