Investigation of biodegradation and effects of sunlight, temperature and microorganisms on some pesticides

XVI ABSTRACT PhD Thesis INVESTIGATION OF BIODEGRADATION AND EFFECTS OF SUNLIGHT, TEMPERATURE AND MICROORGANISMS ON SOME PESTICIDES Yakup CUCİ Fırat University Graduate School of Natural and Applied Sciences Department of Environmental Engineering 2005, Page : 143 In the first stage of this study, loss and vaporization amounts of concentrations of chlorpyrifos and tebuconazole pesticides those commonly used in Elazığ were investigated at laboratory conditions. These loss and vaporization result from sun light, temperature and UV light effect. Pesticide solutions those prepared at various starting concentrations were let in open and closed vessels and watched for changes in concentrations of pesticides. The effect of UV light on both pesticides was less than effects of temperature and sun light, although the effects change with starting concentrations. Concentration of insecticide of Chlorpyrifos reduced max. in operations done at 40 °C. Chlorpyrifos decreased with a percent of 29.34 according to the starting concentration, in experiments done in closed vessel at 40 °C. Also, concentration of fungicide of tebuconazole changed max. in operations done at 40 °C and concentration of tebuconazole e decreased with a percent of 46.87 according to the starting concentration. UV effects on pesticide concentration decrease with increase in starting concentrations of pesticide. Full loss was not seen till the end of day 90, although amounts of loss of both pesticides increase with increase in temperature. Loss amount as a result of sun light was more than the loss amount as a result of U V. In the studies done at effects of sun light, temperature and UV light amount of loss of tebuconazoleXVII was lower than amount of loss of chlorpyrifos. In the second stage of the study, biodegradation of the pesticides was investigated in the batch stirred reactor. Glucose was used as carbon source in addition of pesticide. The effects of initial pH, temperature and initial pesticide concentration on the substrate removal and specific growth rates and yields were investigated and results were compared. Optimum initial pH values were obtained as 8 for chlorpyrifos and 6.5 for tebuconazole e which optimum temperature as 30 °C and 50 mg/L respectively. In this optimum conditions, the maximum microorganism's specific growth and pesticide removal rates were determined as 0.0395 h"1 and 1.51 mg/g. d m.o. h for P. putida and 0.043 h"1 and 1.69 mg/g. d m.o. h for P. fluoresceins and respectively. In the biodegradation of tebuconazole e by P. putida, the maximum microorganism's specific growth rate was determined as 0.0298 h"1 and pesticide removal rate was obtained as 1.598 mg/g. d m.o. h while specific growth and pesticide removal rates were determined as 0.0305 h"1 and pesticide removal rate was obtained as 1.604 mg/g. d m.o.h for P. fluorescens respectively. At higher pesticide concentration (>50 mg/L), substrate inhibition was observed, it was reported that, competitive (Eq.3.7), noncompetitive (Eq.3.12 ) and uncompetitive (Eq. 3.10) toxic inhibition models for specific growth rate of microorganism presented the system well. These inhibition models were solved by using non-linear regression method and for biodegradation of chlorpyrifos by P. putida, the microorganisms saturation constant (Ks) and inhibition constant (Ki) values were determined as 0.054 h"1, 3.62 mg/L and 171.71 mg/L respectively. For tebuconazole the maximum specific growth rate, saturation and inhibition constants were obtained as 0.074 h"', 149.53 mg/L and 158.39 mg/L respectively. For biodegradation chlorpyrifos by P. fluorescens, maximum specific growth rate, Ks and KI values were determined as 0.062 h'1, 0.016 mg/L and 6.15 mg/L while same values reported as 0.064 h"1, 408.01 mg/L and 429.99 mg/L for tebuconazole respectively. The results show that, the growth of both microorganisms was highly inhibited by tebuconazole and P. fluoresce s was for effective for biodegradation of the pesticides than P. putida. Keywords: Chlorpyrifos, Tebuconazole, UV light, Temperature, Sun Light, Biodegradation, P. putida, P. fluorescens.