Leaching of Pesticides Applied to an Experimental Putting Green and Their Fate in a Reservoir

An investigation into the leaching of 6 organophosphorus pesticides applied to an experimental putting green and their fate in a reservoir was conducted. Analyses were carried out by GC (FPD). Leaching was observed in highly water soluble trichlorfon, but the leaching ratio was only 0.014% with 40 mm/hr of sprinkle water. The other 5 pesticides were rarely found. The residual concentration of pesticides in pond water decreased with time and half-lives were longest at 17 hr for fenitrothion and diazinon, followed by chlorpyrifos > butamifos = prothiofos > trichlorfon. Although prothiofos and chlorpyrifos disappeared from the water, they persisted in the sediment. The fates of pesticides in a water-sediment system were also investigated in laboratory tests. When pesticides were applied to the water, significant differences in their half-lives were observed between field and laboratory tests, but their degradation patterns were similar. The low water soluble pesticides, prothiofos and chlorpyrifos, were rapidly and easily adsorbed by sediment with more than 40% of the applied amount take up at 3 days after application. Generally, a correlation with the solubility in water was found and a correlation (r=0.8624) between the value of octanol-water partition coefficients and adsorption in the sediment was recognized.