AEROBIC BIODEGRADATION OF STRYCHNINE ALKALOID RODENTICIDE IN SOIL

An aerobic soil biodegradation study was conducted with strychnine alk aloid to evaluate loss of the parent compound (non-radiolabeled) from sandy loam and sandy clay loam soils during 2 months of incubation, an d to detect non-volatile products which occurred during this period. T he biologically active soil samples were treated with the strychnine a lkaloid to yield an overall concentration of 10 ppm. The treated sampl es and controls were held in an environmental chamber under dark condi tions at a temperature of 25 degrees C and a soil moisture content of 75% of field capacity. Eight sampling periods were chosen; at each tim e interval, three treated samples and a control were selected for stry chnine extraction and analysis using high performance liquid chromatog raphy (HPLC/u.v.) at a wavelength of 254 nm. Degradation of strychnine in both the sandy loam and sandy clay loam soils occurred in three di stinct phases, which included a lag phase, a rapid loss phase and a le veling off or soil binding phase. It is believed that the lag phase ma y have been due to a microbial adaptation period combined with soil so rption. Approximately 50% of the strychnine was lost from the sandy lo am and sandy clay loam soils in 24 and 27 days, respectively. Within a period of 33-40 days, about 90% of the strychnine had dissipated from both soils. The appearance of a degradation product occurred early in the study (day 7) and reached a maximum concentration at either day 1 4 (sandy loam) or day 21 (sandy clay loam). The initial degradates of strychnine are believed to be polar compounds with strong sorption cha racteristics. A discussion is presented in this paper of these possibl e products, together with a mechanism by which strychnine is theorized to have degraded in the soils.