Formation, characterization and release of non-extractable residues of [14C]-labeled organic xenobiotics in soils.

The amount of non-extractable residues (NER) of organic xenobiotics in the soil can considerably exceed the amount of extractable residues which are accessible to normal residue analysis. The NER therefore present a burden to the soil, the toxicological and ecotoxicological potential of which is largely unknown. For the characterization of bound residues and their binding type, special solubilization methods such as supercritical fluid extraction are applied and experiments with radiolabeled model polymers are performed.

Formation and release of residues of the 14C-labelled herbicide isoproturon and its metabolites bound in model polymers and in soil.

The humic monomer catechol was reacted with (14)C-isoproturon and some of its metabolites, including (14)C-4-isopropylaniline, in aqueous solution under a stream of oxygen. Only in the case of (14)C-4-isopropylaniline, incorporation in oligomers, in fulvic acid-like polymers, and in humic acid-like polymers by covalent bonds was observed. The main oligomer was identified by mass spectrometry as a trimer, 4,5-bis-(4-isopropylphenylamino)-3,5-cyclohexadiene-1,2-dione.

A model for the formation and degradation of bound residues of the herbicide 14C-isoproturon in soil.

The humic monomer catechol was reacted with 14C-isoproturon and some of its metabolites, including 14C-4-isopropylaniline, in aqueous solution under a stream of oxygen. Only in the case of 14C-4-isopropylaniline, incorporation in oligomers, in fulvic acid-like polymers, and in humic acid-like polymers was observed. The main oligomer was identified by mass spectrometry as 4,5-bis-(4-isopropylphenylamino)-3,5-cyclohexadiene-1,2-dione.

S-triazine residues in groundwater.

In the last years, the occurrence of pesticides and other chemicals in groundwater has been confirmed. The herbicide atrazine is among the pesticides most frequently detected in groundwater. In groundwater samples from the United States atrazine concentrations reached levels up to 10 micrograms/1.