Dissipation of Herbicide Oxyfluorfen in Subtropical Soils and Its Potential to Contaminate Groundwater

 

Jui-Hung Yen, Wey-Shin Sheu and Yei-Shung Wang1

Department of Agricultural Chemistry, National Taiwan University, Taipei 10617, Taiwan

 

 The dissipation and mobility of herbicide oxyfluorfen (2-chloro-a,a,a-trifluoro- p-tolyl 3-ethoxy-4-nitrophenyl ether) in the field soil of Taiwan was investigated in the laboratory with six tea garden soils.  The dissipation coefficients of the oxyfluorfen in soils at different moisture contents (30, 60 and 90% of soil field capacity) and soil temperatures (10, 25 and 40) were studied.  Results indicated that half-life of oxyfluorfen was from 72 to 160 days for six tea garden soils.  It was found that if the temperature is high, the dissipation rate is rapid, and that there is almost no dissipation at 10.  The possible contamination of groundwater by the herbicide oxyfluorfen was assessed using the behavior assessment model (BAM) and the groundwater pollution-potential model (GWP).  The results obtained after evaluating the residue and travel time using the GWP model, illustrated that the mobility of oxyfluorfen in soil is not very fast and may not lead to contamination of groundwater under normal conditions.  But in the case of soil which contents with extreme low organic carbon and coarse in texture, oxyfluorfen has the potential to contaminate the groundwater if groundwater depth is less than 3 m.

Key words: Dissipation, oxyfluorfen, subtropical soil, groundwater