Soil monitoring in Switzerland by the NABO- network: objectives, experiences and
problems
This contribution presents major problems and gaps of current longterm soil monitoring concepts related to pollution as seen from the experience of the NABO-network in the light of three main objectives:
1. The assessment of soil pollution and related ecotoxicological risks rises the problems of separating anthropogenic pollution from natural background levels for inorganic
compounds. The different rating standards (e.g. guide levels, "frequent contents, assumed natural background levels) give different results of the pollution level in the same soil. The assessment of soil pollution depends therefore very much on the
definiton of adequate standards of reference and will therefore always remain a more or less accurate approximation.
2. The assessment of soil pollution through space has to cope with spatial representativity of observation points in a very heterogeneous medium. The 102 NABO observation sites spread over Switzerland are too few to be treated by geostatistical procedures. The grouping of the laboratory results by functional criteria, especially land use and parent material, may possibly lead to statements related to space.
3. The temporal evolution of topsoil concentrations of pollutants was studied so far on 20 selected sites for a period of 5 years. The fact that significant increases but also
decreases could be measured, suggests that the temporal changes are a complex result not only of inputs and outputs, but also of processes of residual enrichments and dilution by pedoturbation, especially ploughing and earthworm activity.
Further recognized problems of longterm soil monitoring related to pollutants are the restrictions of biomonitoring due to the poor reproducibility and the difficulty of general risk assessment because of the great heterogeneity and buffer capacity in soils compared to air and water.
