Estimation of leachability and persistence of pesticides at golf courses from point-source monitoring and model to predict pesticide leaching to groundwater

The monitoring of 19 pesticides in drainage and groundwater at a golf course was performed when there was no runoff water. The loading rates of most pesticides via leaching water were lower than 4% of application amount, except for more than 23% for terbutol. The times of pesticides loading into the drainage reducing to 50% of initial [t(1/2)(loading)] were 40.3 months for terbutol, 9.4 months for isoprothiolane, 6.6 months for flutolanil, and within 1 month for the other pesticides. On the basis of several published models for predicting pesticides leaching to groundwater at agricultural land, the pesticides having the GUS score greater than 0.4 or exhibiting K-oc less than 7000 cm(3) g(-1), and t(1/2)(soil) greater than 3 days were classified as the pesticides leaching to groundwater at golf courses. The golf course is a high pollution potential area compared with agricultural land. For the persistence of terbutol at golf courses, the concentrations of terbutol in subsoils at the depth greater than 50 cm were higher than the other pesticides after 4 years when terbutol was applied. The half-life [t(1/2)(soil)] of terbutol, isoprothiolane, and fltutoranil in the turf grass soils under an aerobic condition was 200, 180, and 360 days, respectively. Organic carbon partition coefficient (K-oc) and relative mobility in the soil column of terbutol were the same as isoprothiolane and flutoranil. These results suggested that persistence of terbutol was mainly caused by slow degradation rate in the subsoils.