Long-term ground water quality impacts from the use of hexazinone for the commercial production of lowbush blueberries

Lowbush blueberries, native to eastern Canada and Maine, are an important e conomic crop in these areas. Herbicides containing the active ingredient he xazinone are commonly applied to blueberry fields, and there is a high freq uency of detection of relatively low concentrations of hexazinone in domest ic wells located close to areas of lowbush blueberry production. The object ive of this study was to determine the long-term impacts from hexazinone-ba sed herbicide use on ground water quality in the immediate growing areas. Physical and chemical hydrogeologic data were collected for an outwash sand and gravel aquifer in southwestern New Brunswick, Canada. The majority of the land overlying the aquifer is devoted to lowbush blueberry production. Twenty-one nested monitoring wells were sampled for hexazinone and hexazino ne metabolites over a four-year period. Hexazinone was consistently detecte d at values of 1 to 8 parts per billion (ppb) in all but two of these wells , one that is upgradient of herbicide applications, and one that is downgra dient with anoxic conditions. Hexazinone metabolites B and Al were also det ected in all but two of the 21 wells at values ranging from 0.5 to 2.5 ppb. The hexazinone and metabolite data suggest both aerobic and anaerobic degr adation of hexazinone. Complete degradation of hexazinone appears to occur only in the one downgradient well exhibiting anoxic ground water conditions . Concentrations of hexazinone and its metabolites in the ground water were essentially constant over the four-year period.