The behavior of DOC is crucial for our understanding of the transport of many substances through the soil. In the present contribution results will be presented on the effects of pH and Ca on the solubility and molecular size distribution of DOC in the soil solution. The implications of this for the transport of heavy metals (e.g. Cu), hydrophobic organic compounds (e.g. DDT and chlordane), and nutrients (e.g. Fe and P) will be discussed.