FORMATION AND BIORELEASE OF BOUND RESIDUES OF PESTICIDES IN 2 BRAZILIAN SOILS .1. [C-14] LINDANE

Soil contamination after pesticide applications is often frequent, and the use of radio-labelled molecules had proved the existence of non e xtractable or bound residues which remain firmly bound to the soil mat rix. The extent of bound residues formation varies according to the ap plied compound, but it may constitute a significant part of residues r emaining in the soil. The extractable and bound residues formation of C-14-lindane were studied immediately and three months after the appli cation. Metabolism, biorelease, and possible bioavailability of bound residues to bean plants were investigated by the use of biometer flask s. The results show that the formation and biorelease of lindane bound residues varied according to the soil type and with the aging time of the compound in the soil. There is a gradual binding because bound re sidues formed immediately after the application were released easier t han the bound residues formed after a time of interaction of lindane w ith the soils. However, although some biorelease had occurred mainly b y the microflora action, some bound residues remained as still bound e ven after the microflora and rhizosphere action, being thus, inactivat ed.