Edaphic Aspects of the Disposal of Unused Pesticides, Pesticide Wastes, and Pesticide Containers

Abstract

Abstract With a view toward the disposal of large quantities of pesticides in the soil, the biodegradation and the effects on the soil microflora of 20 single analytical grade and formulated pesticides and 7 mixtures of formulations were investigated in a calcareous West Point loam. The soil was amended with 11,227 kg/ha (5 tons/acre) of the respective active ingredient(s) and subsequently incubated for 56 days. The extent of biodegradation was estimated from the CO 2 evolved during the incubation and the effects on the microbial populations were determined from plate counts of the incubated samples. Four of the standards and eight of the formulations apparently were partly degraded. Single pesticides severely inhibited bacterial growth but affected streptomyces and fungi much less drastically. Mixtures of formulations seemed to be more biodegradable than the single pesticides provided that at least one or two pesticides in a mixture were relatively rapidly biodegraded. The mixtures severely reduced the numbers of bacteria but in general favored growth of streptomyces and fungi. Incineration of liquid formulations at 900C produced little ash. The incineration of solids, however, yielded substantial amounts of incombustible residues. Analysis of the ash from the solids indicated in several cases the presence of toxic elements such as Br, As, Zn, etc.