Classification and modelling of non-extractable residue (NER) formation of xenobiotics in soil - a synthesis

This review provides a comprehensive overview about NER formation and attempts to classify the various types. Xenobiotic NER derived from parent pesticides (or other environmental contaminants) and primary metabolites sorbed or entrapped within the soil organic matter (type I) or covalently bound (type II), are pose a considerably higher risk than those derived from productive biodegradation. However, bioNER (type III) resulting from conversion of carbon (or nitrogen) from the compounds into microbial biomass molecules do not pose any risk. Experimental approaches to clearly distinguish between the types are provided and a model to prospectively estimate bioNER formation in soil is proposed.