ABSTRACT
Virtually any of the plethora of reactions in organic chemistry may be exploited for the abiotic degradation of xenobiotics. These include nucleophilic displacement, oxidation, reduction, thermal reactions, and halogenation. Hydrolytic reactions may convert compounds such as esters, amides or nitriles into the corresponding carboxylic acids, or ureas and carbamides into the amines. These abiotic reactions may therefore be the rst step in the degradation of such compounds. The transformation products may, however, be resistant to further chemical transformation so that their ultimate fate is dependent upon subsequent microbial reactions. For example, for some urea herbicides, the limiting factor is the rate of microbial degradation of the chlorinated anilines that are the initial products of hydrolysis. The role of abiotic reactions should therefore always be taken into consideration, and should be carefully evaluated in laboratory experiments on biodegradation and biotransformation. The results of experiments directed to microbial degradation are probably discarded if they show substantial interference from abiotic reactions. A good illustration of the complementary roles of abiotic and biotic processes is offered by the degradation of tributyltin compounds. Earlier experiments (Seligman et al. 1986) had demonstrated the degradation of tributyltin to dibutyltin primarily by microbial processes. It was subsequently shown, however, that an important abiotic reaction mediated by ne-grained sediments resulted in the formation of monobutyltin and inorganic tin also (Stang et al. 1992). It was therefore concluded that both processes were important in determining the fate of tributyltin in the marine environment.
