The understanding and interpretation of leaching processes have improved significantly during the past two decades and several Nordic countries have implemented the use of leaching tests in recent or pending legislation on utilisation and landfilling of waste and contaminated soil. This progress is based mainly on experience from laboratory experiments in combination with modelling work but also on the use of field lysimeters.
Unlike laboratory experiments, which are mostly performed under very controlled conditions (e.g. homogeneous, uniform packing of pre-treated test material, saturated steady-state flow conditions, and controlled uniform hydraulic conditions), lysimeter experiments generally simulate actual field conditions. Lysimeter experiments are suitable for verification of results obtained in the laboratory and for demonstrating similarities and differences between field experiments and laboratory experiments. Lysimeter tests therefore play an important role in the interpretation of laboratory test results with respect to field conditions.
Lysimeter experiments are mostly used for scientific studies of the fate and movement of water, pesticides, salts/nutrients, tracers, trace elements and heavy metals. Lysimeters have been used to study water percolation through and evaporation from soil and waste, and more recently to evaluate solute transport models and monitor the fate and mobility of contaminants.
Lysimeters are designed and adjusted to suit individual research requirements and lysimeter tests are therefore not suited for standardisation. However, many studies involving lysimeters can be found in literature, and each study provides useful information about the use, design and operation of lysimeters. In this report some of this information has been collected and discussed. Much of the experience with lysimeter tests have been associated with soil science, and in order to benefit from this, essential work on soil science aspects has been included in the report together with work experiences performed to study leaching of contaminants from soil and waste materials. The report describes the general principles of lysimeter tests, and various aspects of the design and operation of lysimeters are discussed based on selected international publications. A detailed discussion of the comparison of the results of lysimeter leaching tests to the results of laboratory leaching is included in the report.
Finally, some guidelines for selection, design and operation of lysimeters for various specific purposes are presented. For each type of lysimeter advantages and limitations are listed and tables with information on lysimeter studies on soil and waste, respectively, provide the possibility to find a few references that might be helpful in designing a lysimeter test. Hopefully, this may help a user find the most appropriate lysimeter test methodology for a given purpose.