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Herbicides and nitrates in the Iowa River alluvial aquifer prior to changing land use, Iowa County, Iowa, 1996

Fact Sheet 085-97

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Abstract

The Iowa River alluvial aquifer in Iowa County, Iowa (fig. 1), underlies an area of intensive agricultural activity where pesticides and nitrogen-based fertilizers are extensively used. The effects of changing land use on shallow ground-water quality in part of the Iowa River alluvial aquifer are currently being investigated as part of the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Program. Approximately one-third of the cropland in the study area will be taken out of production over the next few years as part of wetland restoration. Over a three-week period in 1996, the USGS collected water samples from 23 observation wells completed in the Iowa River alluvial aquifer and analyzed the samples for selected agricultural chemicals.

Four herbicides (alachlor, atrazine, cyanazine, and metolachlor) and one nutrient (nitrate) were selected for study on the basis of frequent usage in Iowa and high detection rates in ground water (Detroy and Kuzniar, 1988). Alachlor was not detected at concentrations greater than the method detection limit (MDL). Atrazine was detected at concentrations greater than the MDL in samples from 48 percent of the 23 wells, cyanazine from 13 percent, metolachlor from 26 percent, and nitrate from 91 percent. None of the four herbicides were detected at concentrations greater than the respective U.S. Environmental Protection Agency's (USEPA) Maximum Contaminant Level (MCL) for drinking water. Thirteen percent of the samples had nitrate concentrations above the USEPA's MCL of 10 mg/L (milligrams per liter). Relations between constituent concentration and well depth were observed for specific constituents at individual well nests.

Study Area

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Herbicides and nitrates in the Iowa River alluvial aquifer prior to changing land use, Iowa County, Iowa, 1996
Series title:
Fact Sheet
Series number:
085-97
Year Published:
1997
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Iowa Water Science Center
Description:
4 p.
Country:
United States
State:
Iowa
County:
Iowa County
Other Geospatial:
Iowa River alluvial aquifer
Online Only (Y/N):
N
Additional Online Files (Y/N):
N