The effect of alginite on the decomposition of the herbicide propisochlor.

The catalytic effect of an oil shale rock "alginite" was studied under laboratory conditions on the decomposition of herbicide propisochlor. The breakdown process was followed in four parallel experiments: buffered solution (pH = 7), in buffer solutions containing alginite or bentonite (a common rock) and also in the solution obtained from the extraction of the alginite (alginite/buffer = 1/10). In the aqueous phase, the decomposition of the herbicide was followed by using HPLC-UV and the metabolites of degradation were identified by GC-MS techniques. For the phenomenological description of the experimental decay curves two parallel reactions with first-order kinetics were taken into account. During the time of experiments, no significant decomposition was observed either in the pure buffer solution or in the presence of bentonite. When, however, alginite was added to the system the degradation of propisochlor was accelerated dramatically: after 5 days, its concentration dropped below 50 % of the initial value. The identified degradation products indicate both reductive as well as oxidative biological mechanisms operating under anoxic conditions. It was proved earlier that the sulfenic and sulfinic acid ester derivatives of the propisochlor appeared in the metabolic pathways of animals and plants but they were not detected yet in the degradation process occurring in the soil environment. Among the degradation products a dehydrochlorinated derivative is a new metabolite identified in our experiments. Our results corroborate the algae-related origin of the alginite rock and forecast its application as a soil ameliorating agent.