DEGRADATION OF 14C-DDT IN A SANDY LOAM AS FFECTED BY TEMPERATURE IN THE LABORATORY
Keywords:
14C-DDT, Evolved 14CO2, organic volatiles, mesophilic temperature, microbial degradationAbstract
One hundred gram (100g) portions of a moist sandy loam (Oxic Haplustalf), obtained from the plough layer of a plot with no known history of pesticide application at the University of Ilorin. Ilorin, Nigeria were amended with 8Ci of 14C-DDT (Dichloro-diphenyltrichloroethane) and 10mg cold DDT in 10ml n-hexane. Triplicate samples in static microcosm were incubated for 42 days at ambient (250 20), 350 and 450C respectively. The experimental design was completely randomised block. The experiment was extended to 91 days at ambient temperature. Evolved 14CO2 and organic volatiles were absorbed in 1N NaOH and n-hexane respectively. The 14C activity was determined weekly using a Beckman liquid scintillaton beta counter. Temperature quotients (QIO) were calculated for the loss of carbon as CO2 and organic volatiles.
The results show that the microbial degradation of 14C-DDT in soil takes place within mesophilic temperatures with optimum at about 35oC. Total loss of 14C-DDT as organic volatiles was not significantly increased at temperatures greater than 35oC. Over time, microbial degradation would be more important than volatilization in the process of loss of 14C-DDT from the soil system.
