Similar results are obtained for iron. At Eh -300 mV (Figure ), representative of soil solutions under anoxic conditions, iron is mainly present in its reduced form M for Cu II and Fe II /Fe III and 10 -5 M for PDMA. Different type of lines represents different ionic strength. Mn II , is also redox sensitive, but it does not form strong complexes with PDMA, due to its low logK value, and for that reason it is not included in the figure.