These notes are from the Pesticides in Groundwater Seminar at the
Wallace building this morning.
The first presentation was by Dr. Mary Scopec (not sure how to
spell that) of the University of Iowa, who has been studying
pesticides for the past 9 years in cooperation with the Department of
Agriculture.
The program she has been working on is called IAPEST. It
utilized information from USGS, EPA, INDR EPC, and IDNR Geological Survey
Bureau as well as the University Hygenic Lab.
Among the sites used for these studies were public water supplies,
domestic water supplies, monitoring wells, springs and surface
waters.
She mentioned that surface water has greater concentrations of pesticides
than groundwater.
They found no correlation between rainfall and the pesticide content of
the groundwater.
They found a negative correlation between sales of pesticides and
detection of pesticides in groundwater, indicating that better management
practices are paying off.
They found a decrease in the incidence of Atrazine and Alachlor in
groundwater and an increase in Metolachlor.
Overall they found a decrease in the incidence of four major pesticides
in groundwater, however, there are new pesticides on the market for which
they are not equipped to test.
Different pesticides are used in different areas of Iowa. Atrazine,
for example, is most heavily used in Northeastern Iowa, but not in
western or southern Iowa.
The second presentation was made by Dana Copeland of
USGS
This program tested for 12 pesticides and their degradates (the
compounds they break down into, the toxicity, short and long term, often
unknown).
This study was done on 131 municipal wells over a period of five
years.
Atrizine was the most frequently detected parent compound.
On average they found a mix of 6 compounds in the samples. This
makes for added toxicity.
Many tests of pesticides do not include tests for degradents, many of
which are stable and consistent and are what actually gets into the
water.
The highest concentrations were found in alluvial areas - 87.7% and
bedrock aquifers in carst regions - 77.4%.
Lower concentrations were found in glacial drift areas - 51.6% and
bedrock non-carst regions - 12.5%.
Groundwater age will tell how likely you are to detect pesticides.
In general, the deeper the well the less pesticides you will find, unless
these wells are in carst regions.
Younger water has more pesticide incidence and greater concentrations of
pesticides;
Older water has less pesticide incidence and less concentration of
pesticides.
The incidence patterns follow changes in use.
The third speaker was Steve Kalkhoff, who has been involved with
the Eastern Iowa Basins study 1996-98.
This includes the Wapsicicon River, the Cedar River,The Iowa River, and
the Skunk River.
The study included carst areas, the Des Moines Lobe, and the Des Moines
Lobe with CAFOs.
They chose 12 sites representative of the area. In 1997 they
concentrated on 3 sites with weekly or bi-weekly testing.
They tested for 47 compounds some of which are not used in Iowa, to
conform to a national protocol.
Atrizine and Metolachlor were found in every sample. He noted here
that their methods could detect very small amounts.
The next most universally present pesticide was in 80% of the
samples.
Prometron, an urban compound was detected in 80%. It has a half
life of 3 years.
MetolachlorESA and Alachlor ESA, degradates of Metolachlor and
Alachlor, respectively, were .2 or greater and were present in every
sample.
Over 80% of their samples had 5-9 compounds.
Concentrations of both Atrizine and Metolachlor increase and decrease
with waterflow. There is no dilution in a flood.
Peggy Murdock