OCCURRENCE OF FUNGICIDES ASSOCIATED WITH POTATO CULTIVATION IN SURFACE WATER AND GROUNDWATER IN IDAHO, MAINE, AND WISCONSIN

Data that document the fate and effects of fungicides in the aquatic environment are limited despite decades of agricultural and urban use. Fungicides include organic compounds that span many chemical classes and vary with respect to their hydrophobicity, persistence, and toxicity. Typically, fungicides are applied repeatedly throughout the growing season, whereas most herbicides and insecticides are applied only once. Although fungicides and their degradates have been detected in various environmental compartments at concentrations that may adversely affect aquatic organisms, they are often underrepresented in monitoring programs because analysis for fungicides can be problematic. Therefore, a series of studies is being conducted by the US Geological Survey as part of its Toxic Substances Hydrology Program to investigate the occurrence of the highest-use fungicides in a variety of agricultural, climatic, and hydrologic settings.

In the United States, potatoes receive 3,270 metric tons of fungicides per year. Because potatoes are typically grown in well-drained soils, fungicides used in these agricultural settings may be easily transported to groundwater systems. Study sites are located in areas of intense potato cultivation with sandy soils that represent a range of climatic and hydrologic settings within first-order stream drainage systems in Idaho, Maine, and Wisconsin. The fungicides used most on potatoes include chlorothalonil and organometallic compounds, but use of newer compounds such as conazoles and strobilurins is increasing as a result of their greater effectiveness and lower application rates. Filtered water samples were extracted onto a hydrophilic lipophilic balanced solid phase extraction cartridge, dried, eluted with ethyl acetate and analyzed for a suite of 33 fungicides using gas chromatography ion trap mass spectrometry. Initial results indicate that chlorothalonil, fludioxinil, boscalid, pyraclostrobin, and azoxystrobin are present in the surface waters draining study sites. A better understating of the partitioning and transport of these fungicides will be developed by combining these findings with the analyses of sediments from cores in the unsaturated and saturated zones beneath the agricultural sites and bed and suspended sediment from streams draining the sites.