Surfactant-aided bioremediation of chlorpyrifos in the soil

Date

2002

Abstract

Bioremediation is the biologically catalyzed reduction in complexity of chemicals such as pesticides and petroleum oils by microorganisms utilizing them as carbon source for growth and metabolism. Bioremediation of pesticide contaminated soils is often hindered by absorption thus limiting the bioavailability of the chemical. Surfactants, compounds that reduce interfacial tensions, can enhance bioavailability of these chemicals. A laboratory study on the effect of a surfactant, coconut fatty alcohol sulfate (CFAS) on biodegradation rate of chlorpyrifos, an organophosphate insecticide, in the soil was conducted to evaluate the possible use of CFAS to facilitate bioremediation.Soil sampling and analysis were done at the National Crop Protection Center, UPLB, College, Laguna from January to March 2002. Four soil treatments with three replicates each, placed in covered square plastic containers were set-up to compare total bacterial colonies. Treatment 1 (T1) served as the control soil, Treatment 2 (T2) - with 0.5 g/L CFAS, Treatment 3 (T3) - with 3,125 ug/g chlorpyrifos 20EC and Treatment 4 (T4) - with 3,125 ug/g chlorpyrifos 20EC and 0.5 g/L CFAS. Total bacterial colonies served as an indication of the rate of biodegradation. The physico-chemical properties such as pH, organic matter, water holding capacity and textural grade of the soil used were determined to account for initial conditions that may affect total bacterial colonies. Total bacterial colonies were counted at 0,7,14,21,28,35 and 43 days. Soil samples from T3 and T4 taken at 0, 21 and 43 days were analyzed for remaining chlorpyrifos using gas chromatography. Values of the physico-chemical properties were pH, 6.0, organic matter, 3.55 percent waterholding capacity, 88.28 percent and a textural grade of clay. Mean total bacterial colonies expressed as 10 / 10g which do not differ significantly from each other. Total bacterial colonies for T4 (with chlorpyrifos and CFAS) ranged from 3 to 2870. From 14 days to 21

21 days, the mean total bacterial colonies for T4 increased by 1,893 percent. The increasing trend continued until 43 days. From 21 days to 43 days, total bacterial colonies increased by 2,199%.Mean concentration values for chlorpyrifos was significant at 0 and 43 days. Values (ug/g) for T3 were : 0 day, 1676 and 43 days, 837 and for T4 : 0 day, 1082 and 43 days, 338. T4 (with chlorpyrifos and CFAS) has a higher percentage decrease (75.94%) which complimented the high mean total bacterial colonies for this treatment compared with T3 (with chlorpyrifos) with a percent decrease of 61.33percent. The results showed that CFAS enhanced the rate of biodegradation of chlorpyrifos in the soil by increasing the bioavailability of chlorpyrifos for the growth and metabolism of bacteria.Half-life of chlorpyrifos in the soil from T3 using first-order kinetics was 43.31 days. T4 exhibited a shorter half-life of 25.67 days.

Document Type

Master Thesis

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 995 2002 E8 B63

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