SPRING SAMPLING FINDS HERBICIDES THROUGHOUT MISSISSIPPI RIVER
RESTON, Va., Nov. 19 /PRNewswire/ -- Herbicides were detected in the Mississippi River and several major tributaries throughout April, May and June of this year, according to a report released today by the U.S. Geological Survey, Department of the Interior.
USGS scientists reported that the herbicide atrazine was detected in each of 146 water samples collected at eight locations on the Mississippi, Ohio and Missouri rivers and on three smaller tributaries, the Illinois, Platte and White rivers. More than three-fourths of these samples also contained the herbicides alachlor, cyanazine and metolachlor.
The results of the study are being shared with a number of state and federal agencies, including the U.S. Department of Agriculture and the U.S. Environmental Protection Agency, under President Bush's water-quality initiative to reduce the impacts of agriculture chemicals on the nation's water resources.
"One of the significant findings of the study is that atrazine concentrations were found to exceed EPA's maximum contaminant level (mcl) continuously for several weeks in rivers as large as the Missouri and Mississippi. These rivers drain areas of more than half a million square miles," said Don Goolsby, USGS hydrologist, Denver, and senior author of the report.
These results are consistent with other recent studies by USGS on smaller rivers in the Midwest that indicate a sharp increase in concentrations of the herbicides following their application to croplands in April and May. The increases are caused by late spring and summer rainfalls that flush some of the herbicides into the streams. Studies conducted by the USGS on 150 streams in 1989 and 1990 found herbicide levels decreased to levels below the mcl during the fall.
Samples and results in this study are for untreated river water whereas mcl's apply to water supplied to the user after treatment.
According to EPA, the mcl is the maximum permissible level of contaminant in water that is delivered to any user of a public water system. MCL's are based on a lifetime of exposure to the contaminant and include a margin of safety. Compliance with the mcl for atrazine is based on an annual average of quarterly samples. Because treatment by activated carbon can remove these herbicides, levels in finished drinking water can be lowered by such treatment or by blending with water from other sources.
According to the USGS report, atrazine exceeded the mcl of three parts per billion (ppb) in 27 percent of the 146 samples. The mcl was exceeded in samples collected at six of the eight sampling sites. Alachlor exceeded the mcl of two ppb in 4 percent of the samples, all of which were collected from the three smaller tributaries.
Herbicide concentrations increased in early May as a result of rainfall that flushed herbicides into streams after spring application to cropland. Atrazine concentrations were higher than the mcl for about a month in the Illinois River, Platte River in Nebraska, White River in Indiana and the lower Missouri River near St. Louis. Atrazine concentrations also exceeded the mcl at two sites on the Mississippi River in some samples collected during May and June. Concentrations began to decrease in early to mid-June.
An earlier study showed that concentrations of herbicides were widespread in strpercent of the streams sampled in 1990. Herbicide concentrations up to 100 ppb were measured. Atrazine was found to be the most persistent of the herbicides measured, and was detected year-round in the majority of the streams sampled.
The 1989 and 1990 study also indicated that significant quantities of herbicides are transported to streams each year during late spring and summer, and ultimately are discharged into the Mississippi river and its major tributaries.
The U.S. Department of Agriculture reports that it has established a series of field projects in this area to increase the rate of farmer-adoption of best management practices; to evaluate current farming systems and to develop new farming methods; and to accelerate the transfer of new technology to farmers, thus reducing the impacts of agricultural chemicals on water quality.
An estimated 200-300 million pounds of herbicides are applied annually to control weeds in the production of crops in the Midwestern United States. Herbicides used in this region account for about 60 percent of the total herbicide use for agriculture in the nation. These herbicides are used in the production of about 75 percent of the nation's corn and 60 percent of its soybeans.
The present USGS study began in April 1991 and will continue until April 1992. The major objectives are to determine the time distribution and annual mass transport of herbicides in the Mississippi River and its major tributaries. Data for the study are being collected at the following locations:
-- Illinois River at Valley City, Ill.
-- Platte River at Louisville, Neb.
-- White River at Hazelton, Ind.
-- Missouri River at Hermann, Mo.
-- Ohio River at Grand Chain, Ill.
-- Mississippi River at Clinton, Iowa
-- Mississippi River at Thebes, Ill.
-- Mississippi River at Baton Rouge, La.
Results from the first three months of the study have been published in U.S. Geological Survey Water Resources Investigation Report 91-4163, titled "Distribution of Selected Herbicides and Nitrate in the Mississippi River and Its Major Tributaries, April through June, 1991," by D.A. Goolsby, R.C. Coupe, and D.J. Markovchick. Copies of the report are available from the U.S. Geological Survey, Books and Open-File Services Section, Federal Center, Bldg. 810, Box 25425, Denver, Colo., 80225-0425, telephone 303-236-7476.
As the nation's largest water-resources information agency, the USGS collects data on surface-water and ground-water quantity and quality at more than 50,000 locations nationwide in cooperation with more than 1,000 state, local and federal agencies.
/NOTE: Specific information on the atrazine levels from each state are available from the appropriate USGS Water Resources Division district chief listed below. Questions about the overall herbicide sampling program can be directed to Donald Goolsby, USGS, Denver, 303-236-5925. Related questions can be directed to Sean McElheny, water issues, or Al Heier, pesticides, EPA, 202-260-4355; or Larry Adams, USDA, 202-720-4751.
Arkansas E.E. Gann 501-324-6391 Little Rock, Ark.
Illinois S.F. Blanchard 217-398-5353 Urbana, Ill.
Indiana J.A. Macy 317-290-3333 Indianapolis
Iowa N.B. Melcher 319-337-4191 Iowa City, Iowa
Kansas R.A. Herbert 913-842-9909 Lawrence, Kans.
Louisiana D.D. Knochenmus 504-389-0281 Baton Rouge, La.
Minnesota W.J. Herb 612-229-2600 St. Paul, Minn.
Mississippi M.W. Gaydos 601-965-4600 Jackson, Miss.
Missouri D. Bauer 314-341-0824 Rolla, Mo.
Nebraska M.V. Shulters 402-437-5082 Lincoln, Neb.
Ohio S.M. Hindall 614-469-5553 Columbus, Ohio
Wisconsin W.A. Gebert 608-276-3535 Madison, Wisc.
Kentucky A.L. Knight 502-582-5241 Louisville, Ky.
Tennessee F. Quinones 615-736-5424 Nashville, Tenn./
/CONTACT: Rebecca Phipps of the U.S. Geological Survey, 703-648-4460/ CO: U.S. Geological Survey ST: IN: SU: TW -- DC021 -- 5076 11/19/91 15:42 EST