The effect of free and encapsulated OIT on the biodeterioration of plasticised PVC during burial in soil for 20 months

The incorporation of silica or zeolite encapsulated biocide into plasticised poly vinyl chloride (pPVC) has been used to control biocide delivery rate. Previous in vitro studies have shown that free biocide leached from the plastic more rapidly than from encapsulated formulations. The aim of this study was to determine the long-term effects of free and encapsulated 2-n-octyl-4-isothiazolin-3-one (OIT) incorporation into PVC on properties of the plastic following burial for 20 months in microbially active soil. In general, fewer bacteria and fungi were isolated from samples containing OIT when compared with biocide-free controls. No patterns in fungal colony predominance or range were observed between the pPVC formulations. OIT-containing samples retained more plasticiser than the controls and hence underwent reduced biodegradation by microorganisms.