PLANT BIOAVAILABILITY OF NATURAL AND MODEL HUMIC ACID-BOUND [14C] ATRAZINE RESIDUES

The release of bound [14C] atrazine residues and their uptake by maize plants was investigated. “Natural” humic acids, extracted from a brown soil, and “model” humic acids, prepared from catechol, both containing bound [14C] atrazine residues were incubated with plants in soil. After 21 days, the maize plants contained 0,7% (plants grown in soil mixed with “natural” humic acids) to 1.7% (plants grown in soil mixed with “model” humic acids) of the radioactivity originally introduced. The roots contained 55 to 70% of the [14C] residues whereas the remainder was present in the shoots. A significant amount of the total [14C] residues (29 to 53%) became again bound in plant tissues, whereas the, majority of extractable [14C] residues was present in the form of conjugates. The behaviour of “model” humic acid-bound residues was comparable to that of “natural” humic acid-bound residues or soil-bound residues. © 1990, Taylor & Francis Group, LLC. All rights reserved.