COMPARISON OF THE MOBILITY OF THE HERBICIDES 2,4-D AND 14C-PARAQUAT IN SELECTED MALAYSIAN AGRICULTURAL SOILS
|Ismail B.S1*, Sameni M2 and Halimah M3
|Corresponding Author: Ismail B.S, E-mail: [email protected]|
|Received: 02 July 2013 Accepted: 20 July 2013|
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The increased use of agricultural chemicals has raised questions about the adverse effects of pesticides, consequences of leaching of toxic residues into water bodies. In the current study, the leaching behavior of 2,4-D (2,4-Dichlorophenoxyacetic acid) and paraquat (1,1’-dimethyl-4,4’-bipyridylium dichloride) was investigated under laboratory conditions. The residue levels of 2,4-D and 14C-paraquat in the soil profile was determined using the High Performance Liquid Chromatography (HPLC) and the Liquid Scintillation Counter (LSC), respectively. The mobility of 2,4-D and 14C-paraquat in two soil types (clay and clay loam) of the Kerian ricefields was determined using laboratory column experiments. The study showed that the mobility of 2,4-D is greater than paraquat in both soil types. The greater mobility of 2,4-D and its deeper penetration into the soil column probably due to its lower adsorption relative to that of paraquat. The difference in the 2,4-D mobility in the two soil types appears to be related to the organic carbon distribution in the soil profile, whereas, results showed that the total amount of 14C-paraquat moving downward in both soil types was not affected significantly by the soil structure. The mobility of 2,4-D was found to be sensitive to the amount and duration of the percolated rainfall. The total amount of 14C-paraquat that leached into the soil was not significantly affected by increase in the amount and duration of rain. Comparison of the mobility of 2,4-D and 14C-paraquat in the intact-core and packed columns revealed that the extent of mobility was less in the intact soil core.