Date of Award

8-2002

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Food Science and Human Nutrition

Advisor

Rodney J. Bushway

Second Committee Member

Alfred A. Bushway

Third Committee Member

Mary Ellen Camire

Abstract

Hexazinone, a systemic herbicide registered for use on wild blueberries in 1983 is credited with increasing Maine's wild blueberry crop by three-fold over a 10 year period, while also increasing overall fruit quality. Unfortunately, the high water solubility of hexazinone gives it a high leaching potential. This solubility factor is exacerbated by the sandy soils where wild blueberries are commonly propagated. In 1991 a routine screen for pesticides used in blueberry agriculture revealed traces of hexazinone in water samples from property formerly used for blueberry production. This discovery has led to the development of solid phase extraction (SPE) and direct-injection high performance liquid chromatographic (HPLC) methods capable of detecting hexazinone in ground water at limits of quantitation (LOQ) of 0.1 and 0.33 pg/L, respectively. These techniques were proven rapid, accurate and inexpensive. The HPLC method was used to monitor seven test wells in and near actively managed blueberry agricultural areas. Over a ten-year period, five of these sites showed decreasing hexazinone levels, while two of the wells exhibited large fluctuations in herbicide concentration. The decreased leaching of hexazinone at some sites was attributed to lower application rates, better management techniques and the development of slow-release formulations, such as impregnated diammonium (DAP) and granulated Pronone. In 1994, 1998 and 1999 private wells in seven Maine counties, determined to have high potential of hexazinone contamination from blueberry cultivation practices were randomly sampled for hexazinone analysis. Most wells were sampled in the spring, fall and in two separate years. Approximately 61 % of the total samples tested positive for the herbicide at levels ranging for 0.1 to 6 pg/L. Levels of hexazinone generally fluctuated little between spring and fall. Concentrations were the same (27%) or lower (66%) in 1998 and 1999 as compared to initial values determined in 1994. HPLC and Enzyme immuno assay EIA methods were developed to measure the hexazinone content of soil. LOQ's for these techniques were 25 and 50 nglg for HPLC and EIA, respectively. These methods were used to ascertain the effect of hexazinone formulation type on leaching potential through the soil profile. Granulated Pronone was the most highly retained by soil.

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