Studies of the behaviour and fate of the polymer-additives octadecyl-3-(3.5-di-t-butyl-4-hydroxyphenyl)propionate and tri-(2.4-di-t-butylphenyl)phosphite in the environment

Abstract

In order to evaluate the environmental risk potential of the polymer-additives octadecyl-3-(3.5-di-t-butyl-4-hydroxyphenyl)propionate (additive 1) and tri-(2.4-di-t-butylphenyl)phosphite (additive 2) we have studied the degradation of the 14C-labelled single components and their release from a polypropylene matrix in abiotic and biotic test systems as well as their transport behaviour in soil. The biotic degradation in waste compost, activated sludge and in soil was studied. In order to conduct release tests, waste disposal material were used as well. The abiotic degradation was effectuated by photooxidation at a catalytic surface. The highest mineralisation rates were obtained by photooxidative degradation of the two test substances. The maximum content of bounded residues was found for additive 1 in soil and for additive 2 in waste compost. In the extracts of soil and compost, the principal metabolites could be identified in the case of additive 1 as 7.9-di-t-butyl-1-oxaspiro[4.5]deca-6.9-dien-2.8-dion and in activated sludge as the methyl ester of 3-(3.5-di-t-butyl-4-hydroxyphenyl) propionic acid. Additive 2 metabolised in all degradation tests nearly completely under formation of two products. The main component was identified as tri-(2.4-di-t-butylphenyl)phosphate. Both polymer-additives were eluated from the chosen soil types. The transport behaviour of additive 1 was independent from the soil type. In all test matrices additive 1 as well as additive 2 were released from polypropylene. Because the amounts of additive 1 and 2 absorbed onto soil particles were taken into account, the highest liberation rates were found in the soil test.