Soils as filter and buffer for pesticides--experimental concepts to understand soil functions.

The turnover of natural organic matter (NOM) in soils results in CO(2) production and the formation of various organic carbon pools of different stabilities. These humification products are reaction partners for binding and remobilisation of pesticides in soil. Research is needed to characterise soil organic carbon pools to interpret the functioning of soils with respect to storage, filter, buffer and degradation potentials. The experimental set ups must be embedded in a time and space perspective of organic carbon dynamics and anthropogenic impact and must deal with mechanisms taking place at the molecular level (structure activity relationships) and the system level (pool characteristics and reactivities). The sound prediction of these mechanisms is still a matter of scientific debate because the structure of NOM and its reaction potential is still not understood.