CP-2001-02
Occurrence of herbicides and their degradates in Hawaii’s groundwater
Li, Qing X., Eul-Chul Hwang, and Fengmao Guo
Hawaii, with its isolated insular location, unrelenting pest pressure, and complex volcanic geology, presents many unique challenges to protecting groundwater from pesticide contamination. The U.S. Environmental Protection Agency (EPA) estimated that about 10% of community water system wells and 4% of rural domestic wells in the U.S. contain at least one pesticide or pesticide degradation product (degradate) at the reporting limits of the survey (EPA 1990). Regular sampling of community water systems show pesticides and pesticide degradates in 68 of 457 drinking water sources in Hawaii (State of Hawaii Department of Health 1996). The previous monitoring primarily focused on fumigants such as ethylene dibromide and trichloropropane, triazine herbicides, and chlorinated insecticides such as dieldrin and lindane. The most frequently reported pesticides in Hawaii’s groundwater are fumigants used in pineapple fields, triazine herbicides used in sugarcane fields and termiticides. Agriculture in Hawaii is in a change from plantation to small family farms. Various pesticides have been used to control different pests. A recent study categorized a wide range of pesticides as “teachers” or “non-leachers” for a specific Hawaii hydrogeological setting.
This study was to monitor the occurrence of some herbicides found in groundwater in the continental U.S. in selected wells in Hawaii. These include alachlor, bromacil, dacthal, hexazinone, metolachlor, metribuzin, atrazine, ametryn and simazine and their degradates. Findings in this study have supported the log-transformed attenuation factor index ranking as a practical predication means to assist decision-making