The primary goal of the MDA's pesticide groundwater monitoring is to provide detailed information on the occurrence and concentrations of pesticides in Minnesota's groundwater resources. Protection of Minnesota's citizens and water resources from agricultural chemicals is the fundamental purpose of this goal. The program focus is monitoring vulnerable groundwater in the agricultural and urban areas of the state.

In 2017, the MDA’s ambient monitoring program sampled over 160 monitoring wells, naturally occurring springs and private drinking water wells throughout the state for pesticides.

2017 Groundwater sampling sites

History

In 1987, the Minnesota Legislature amended the Minnesota Pesticide Control Law. It directed the MDA to determine the impact of pesticides on the environment, including the impacts on surface water and groundwater.

In response to this charge, the MDA initiated a pesticide groundwater monitoring program in 1987 and in 1991, began surface water monitoring. The MDA has one of the most comprehensive pesticide monitoring programs in the country.

Groundwater Monitoring Results for 2017

  • 690 pesticide samples were collected from 168 routine groundwater monitoring sites (monitoring wells, springs and private drinking water wells).
    • 37 different pesticides or pesticide degradates were detected out of 150 pesticide analytes that were analyzed by the MDA Laboratory.
    • Metolachlor ESA was the most frequently detected analyte (82%).
    • Glyphosate, and its degradate AMPA, were not detected in the 194 samples that were analyzed.
    • Glyphosate/AMPA samples were collected at least once from every groundwater site.
    • Six neonicotinoid insecticides, and two neonicotinoid insecticide degradates, were analyzed in the groundwater samples.
      • There were no detections of neonicotinoids in urban monitoring wells.
      • Clothianidin, imidacloprid, and thiamethoxam were detected in 8 to 16% of the samples collected.
    • Chlorantraniliprole was detected for the first time.
    • No pesticide detections exceeded an applicable human health-based drinking water reference value.

Common Detection Pesticides

Common detection is an official state designation made by the MDA Commissioner of Agriculture and is defined as “detection of a pollutant that is not due to misuse or unusual or unique circumstances but is likely to be the result of normal use of a product or a practice” (Minn. Stat. § 103H.005, Subd. 5). Pesticides, and select degradates, that have been designated as “common detection” receive heightened scrutiny from the MDA during reporting of monitoring results. Acetochlor, alachlor, atrazine, metolachlor, and metribuzin are the current common detection pesticides. Atrazine, metolachlor and metribuzin were designated in 2002. Acetochlor and alachlor were designated in 2003.

The graphics below indicate statewide groundwater pesticide detection frequency from 2010 through 2017. Also presented are the annual statewide 90th percentile concentrations for pesticides detected in greater than 10% of samples.

Pesticide detection frequency for statewide gw monitoring 2010 - 2017
 
Statewide groundwater monitoring 2010 - 2017 time series

Data Availability and Future Work

All of the pesticide data collected as part of MDAs ambient monitoring program is publically available through the Water Quality Portal or by contacting MDA. The MDA will continue to improve its program to expand monitoring to new locations and to include additional pesticide analytes, as resources and needs permit. The MDA is committed to maintaining its long-term data record to allow for continued assessment of the impacts of pesticides on surface water from routine use.