A laboratory experimental set-up for the study of organic compounds transport through unsaturated soils

The presence of pollutants in soils is one of the major problems for the use of the groundwater and also for future use of the land. The contamination from reactive pollutants can derive from use of fertiliser in agriculture, from industrial processes as well as from illegal landfill. The remediation of these sites is still an open problem due to the different opinion of scientists, and to the different technologies now available on the environmental market. One of the main reason for the uncertainties in the correct choice of the remediation technique is surely that the behaviour of transport and dispersion of pollutants in soil is still not well known. Particularly, the adsorption/desorption phenomena are strictly related to the specific soil and to the specific contaminant. So it can be worth carrying out laboratory experiments (with low costs and with controlled conditions) to evaluate the parameters suitable for the understanding of the involved processes and for the eventual use of models. In the present paper an experimental study of phenol transport and dispersion in soil is proposed. It can be considered as a test on the suitability of laboratory reconstruction of a real situations The aim is to build a low costs methodology that can give information in controlled situations on the soil response to a contamination. A careful research of sampling instrumentation has enabled us to build a test section larger than those generally described in the literature, in this way it was possible to have a heterogeneous and realistic soil structure. This last aspect can be considered as a step towards "in situ" conditions. A tracer is used to characterise the fluidodynamic part and a solution containing phenol is added to the soil. The aim is to reproduce the circumstances where contaminants in the upper part of the soil are transported by rainfall and add to the pollutant in the deeper part. The soil is completely characterised from the physical and chemical point of view. A soil moisture meter is used to evaluate the wet front in time and space and a tensiometer furnishes the value of the matrix potential in the section. A series of nine micro-lysimeters are used to sample to solution in time. © 2000 Elsevier Ltd. All rights reserved.