Analysis and Detection of Cyanazine-Specific Degradates in Minnesota Groundwater Using LC-MS/MS.

Drinking Water
Oral Presentation

Prepared by B. VanRyswyk, H. Johnson, B. Schaefer, B. Bruening, K. Reynolds, D. Tollefson, M. Ribikawskis
Minnesota Department of Agriculture, 625 Robert Street North, Saint Paul, MN, 55155, United States


Contact Information: [email protected]; 507-344-3203

ABSTRACT

Cyanazine, a triazine herbicide, was used extensively to control weeds in corn in Minnesota from the early 1970s through the 1990s. Use of cyanazine stopped in 2002 after registration was voluntarily cancelled nationally due to human health and environmental concerns. The cyanazine degradation pathway identifies seven different possible degradates, two of which are common to atrazine, another corn herbicide that is still in use. Following product cancellation, analysis for the cyanazine-specific degradates in water samples was limited to the U.S. Geological Survey Organic Geochemistry Research Laboratory, resulting in limited surface water and groundwater data collection nationally. In 2019, the Minnesota Department of Agriculture Laboratory and a contract laboratory successfully developed solid phase extraction (SPE) and direct aqueous injection (DAI) LC-MS/MS methods, respectively, for the analysis of the cyanazine-specific degradates. Over 1,600 samples were collected from surface water and groundwater locations across Minnesota in 2019, including over 1,100 samples from private drinking water wells. Results indicated limited detections of cyanazine-specific degradates in surface waters (rivers and streams) and shallow groundwater. However, detections were more frequent in private drinking water wells in areas of the State characterized as having vulnerable groundwater, with some detections exceeding the state drinking water human health risk limit for total cyanazine (1.0 µg/L). Of the cyanazine-specific degradates, deethylcyanazine acid was detected most frequently and at the highest concentrations in private drinking water well samples, indicating long-term persistence of this degradate in groundwater. Data will be presented from over 100 split samples that were collected and submitted for analysis using SPE and DAI LC-MS/MS methods. The effectiveness of home point-of-use, reverse osmosis (RO) water treatment systems was also evaluated in select wells with pesticide detections. Results indicated complete removal of the cyanazine-specific degradates in the 44 RO treatment systems evaluated.