Bioaccumulation and metabolic fate of sewage sludge derived organic xenobiotics in plants

Sewage sludges will always contain a very complex mixture of organic contaminants. Therefore, information is needed to provide data on the persistence of these sludge derived organics in soils and their uptake by food crops. The results of this study demonstrate that all compounds, even non-polar ones, are assimilated by intact plants and different in vitro systems. Uptake depended on the plant species and on the physico-chemical properties of the chemicals. The main metabolites being formed are polar conjugates with carbohydrates and amino acids. Polycyclic aromatic hydrocarbons (PAHs) are partly converted to oxygenated derivatives which are known to be even more toxic. Depending on the plant species, and especially in monocots, large amounts of the chemicals and/or their metabolites, are frequently incorporated into non-extractable residues. The association, and type of binding to cell wall components, enable conclusions to be made about the bioavailability of these bound residues.