Carbofuran removal from soil by supplementation with agricultural residues

This research investigated the effects of organic amendments i.e., rice straw (RS), cassava pulp (CS), cattle manure (CM), compost (CP), corn cob (CC), glucose (GL), and molasses (ML) and inorganic amendment on removal of carbofuran from soil and aged soil. Initial carbofuran concentration at 50 mg/kg soil was spiked into soil microcosm. Results showed that 1.5% RS effectively stimulated indigenous microorganisms indicating by the shortest t1/2 of carbofuran of 7 days and high microbial activity. CP and CM were found to inhibit microbial activity suggesting by a decrease in dehydrogenase activity and a low carbofuran degradation. GL and ML at high load of 1.0% to 5.0% were more favorable to be used as C-source for indigenous microorganisms, therefore there was low carbofuran degraded in soil amended with GL and ML but there was high microbial activity. Inorganic amendment was found to inhibit carbofuran degradation as well as microbial activities in soil with t1/2 of 20-21 days. Addition of 1.5% RS or 1 mL of inorganic amendment into aged soil improved carbofuran degradation ability and microbial activities of indigenous microorganisms. Growth kinetic analysis of carbofuran degraders obtained from 1.5% RS stimulated soil indicated that carbofuran concentration in the contaminated site should be lower than 17.88 mg/L which corresponds to 13.23 L/kg soil, base upon Kd value of 0.74 in our soil sample, in order to obtain an effective biostimulation process by indigenous carbofuran degraders in soil sample used in this study.