| Summary: | 碩士 === 國立中興大學 === 土壤環境科學系 === 93 === Paraquat is widely used as a herbicide which have good effect, high-toxicity, stable structure and hard decomposition. We must detect paraquat of environment due to long-term accumulation in soils after long-term application of paraquat and that is leached into natural water. Furthermore, that is a importment topic for studying movement of paraquat in soils that is affected by various soil character, circumstanced condition and agricultural farming.
Three different soil groups (sandstone-shale alluvial soil, slate alluvial soil and red soil) were used for experiments with blank and organic matter treatment. We used respectively cations (NH4+, Na+, Ca2+, Mn2+, Cu2+, Pb2+ and Cd2+) and anions (SO42-, HPO42- and CO32-) to saturate soils and added paraquat, then respectively leached soil columns with deionized water, sulfuric acid and sodium hydroxide solution. We used electroanalytic technique in couple with chemically modified electrodes to determine paraquat of leached solution and compared the amounts of paraquat in leached solution of different treatments.
The experimental results indicated Nafion-modified electrode in couple electroanalytic technique (i.e. square-wave voltammetry) could precisely and sensitively determine paraquat of leached soilution. The movement of paraquat in soil had large difference among different soil groups and treatments. The movement of paraquat in red soil apparently fast than sandstone-shale alluvial soil and slate alluvial soil. Red soil had more kaolinite with varible charge that could adsorb less paraquat than smectite and vermiculite with permanent charge. Higher concentration of Cu2+ and Pb2+ would decrease the adsorbed capacity of paraquat by soil colloid due to specific adsorption of Cu2+ and Pb2+ could reduce the adsorptive amounts of paraquat on soil colloids. Moreover, added organic matter could increase adsorption of paraquat, and that could decrease movement of paraquat in soils. The experimental model of movement for paraquat in soils could provide an important reference for further management and application of paraquat on farmland.
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