EFFECT OF pH, HUMIC ACID AND MOISTURE CONTENT ON PHOTO CATALYTIC DEGRADATION OF HERBICIDES IN LOAMY SAND SOIL

The dissipation kinetics activity of FeTiO2 nanoparticles on four herbicides (dicamba, imazethapyr, metsulfuron-methyl and clodinafop-propargyl) in loamy sand soil was investigated with effect of soil pH, moisture and humic acid content on the decontamination of herbicide in photocatalysis were investigated. The effective concentration of humic acid required for the rapid decontamination of herbicide residues on soil was established by varying the amount of humic acid in the range of 10 to 40 mg/Kg and the effective concentration of humic acid was 10 mg/Kg for dicamba, 30 mg/Kg for metsulfuron-methyl and clodinafop-propargyl and there was no effect on imazethapyr. The effect of pH of soil on the decontamination of herbicide residues in soil was investigated by varying the pH of soil from 4.0 to 9.7 and the rapid degradation was observed in soil of pH 9.7 for dicamba, imazethapyr, metsulfuron-methyl and clodinafop-propargyl in soil of pH 4 when compare to other pH of soil. The degradation order was pH 4 < pH 6.5 < pH 8.0 < pH 9.7 for dicamba and imazethapyr and for metsulfuron methyl and clodinafop-propargyl was pH 6.5 < pH 8 < pH 9.7 < pH 4. The effect of moisture content on decontamination of herbicide residues in soil was investigated by varying moisture content in soil from 20 to 50 mL/Kg. The effective moisture content for rapid degradation of dicamba was 50 mL/kg, while imazethapyr, metsulfuron-methyl and clodinafop-propargyl was 40 mL/kg.