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| Kentucky Water Science Center |
U.S. Geological Survey, Scientific Investigations Report 2006-5142
By Angela S. Crain
In cooperation with the Kentucky Department of Agriculture
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Water resources in the Little River Basin are potentially vulnerable to applications of pesticides associated with both agricultural and nonagricultural activities, because much of the basin is characterized by karst topography. Concerns about water quality resulting from pesticide use in karst areas and lack of data on concentrations of pesticides in surface water led to further investigation of water quality in the Little River Basin, which includes about 600 square miles in Christian and Trigg Counties and a portion of Caldwell County in western Kentucky. Water samples were collected in streams in the Little River Basin, Kentucky during 2003-04 as part of a study conducted in cooperation with the Kentucky Department of Agriculture. The objectives of the study were to assess the occurrence and distribution of pesticides, to evaluate the spatial and seasonal variability of pesticides, and to evaluate loads and yields of selected pesticides in the basin. A total of 91 water samples was collected at 4 fixed-network sites from March through November 2003 and from February through November 2004. An additional 20 samples were collected at 5 synoptic-network sites within the same period.
Twenty-four pesticides were detected of the 127 pesticides analyzed in the stream samples. Of the 24 detected pesticides, 15 were herbicides, 7 were insecticides, and 2 were fungicides. The most commonly detected pesticides—atrazine, simazine, metolachlor, and acetochlor—were those most heavily used on crops during the study. Atrazine and simazine were detected in 100 percent of all surface-water samples, and metolachlor and acetochlor were detected in more than 45 percent. The pesticide degradate, deethylatrazine, was detected in 100 percent of the samples. Only one nonagricultural herbicide, prometon, was detected in more than 50 percent of the samples. Diazinon, the most commonly detected insecticide, was found in 25 percent of all samples and was found at all sites except Casey Creek. Metalaxyl was the most commonly detected fungicide (14 percent); most detections were in samples from the Sinking Fork subbasin.
Concentrations of herbicides were highest following application in the spring (March–May). In contrast, insecticides typically were present during the summer (June-August). The most commonly detected pesticides in the Little River Basin were found at low concentrations in streams year-round. Atrazine and simazine (row-crop herbicides) had the highest measured concentrations (22 and 6.1 micrograms per liter (µg/L), respectively) and were the most heavily applied herbicides in the basin. Metolachlor also was heavily applied in the basin, but measured concentrations did not exceed 0.32 µg/L. The insecticide, Malathion, was only detected in 4 percent of the samples, although it was heavily applied in the basin during 2003-04. Most detections of pesticides were at low concentrations in relation to drinking-water standards and guidelines established for the protection of aquatic life. Only two pesticide compounds—atrazine and simazine—exceeded the U.S. Environmental Protection Agency (USEPA) standards for drinking water. Atrazine exceeded the USEPA’s maximum contaminant level (MCL) 19 times in 111 detections; simazine exceeded the established MCL 2 times in 111 detections. These exceedences occurred in the spring. Concentrations of atrazine also exceeded the established aquatic-life criterion (1.8 µg/L) in 32 samples collected from all sites.
Concentrations of deethylatrazine, an herbicide-transformation compound, tended to follow the same monthly concentration pattern as its parent compound (atrazine), but concentrations of deethylatrazine were lower than those of atrazine. Atrazine may have been present in the soil much longer at these sites, which might have allowed microbial populations to transform atrazine into deethylatrazine.
A statistical comparison of concentrations of selected pesticides among four fixed-network sites showed higher differences in median concentrations of atrazine, simazine, and diazinon at the North Fork Little River site than at the other sites. Median concentrations of deethylatrazine were appreciably lower at the North Fork Little River site than at the other sites. Concentrations of metolachlor were higher at Sinking Fork near Cadiz than at the other three sites.
The largest mean annual loads of selected pesticides among the fixed-network sites were at the Little River near Cadiz. Loads were not estimated for the fixed-network site at Sinking Fork near Cadiz. The Little River near Cadiz site had the largest mean annual loads of atrazine (2,337 pounds per year (lb/yr)), metolachlor (19.51 lb/yr), and simazine (330.8 lb/yr) during 2003-04. The North Fork Little River site had the largest mean annual load of diazinon (5.57 lb/yr). The mean annual load of acetochlor (190 lb/yr) was largest at the South Fork Little River site.
The estimated annual loads of acetochlor, atrazine, diazinon, metolachlor, and simazine for the study period were about 0.01 to 2.2 percent of the amount applied in the basin. Atrazine had the largest estimated use and the largest estimated loads in the basin. The load for diazinon, an insecticide that is primarily used for nonagricultural purposes, was less than agricultural herbicides. The largest load of diazinon, estimated at the North Fork Little River site, was less than 1 percent of the atrazine load.
Total yields of atrazine ranged from 9.07 to 10.88 pounds per year per square mile ((lb/yr)/mi2). The South Fork Little River site had the largest yields of commonly used row-crop herbicides (acetochlor, atrazine, and metolachlor). The yield of atrazine was 10.88 ((lb/yr)/mi2); acetochlor and metolachlor yields were 3.27 and 0.18 ((lb/yr)/mi2), respectively. Simazine, another commonly used row-crop herbicide, had the largest yield at the Little River near Cadiz site (1.36 (lb/yr)/mi2). The North Fork Little River site, a more urban site, had the largest yield of diazinon (0.08 (lb/yr)/mi2).
Abstract
Introduction
Purpose and Scope
Description of the Little River Basin, Kentucky
Geology
Streamflow
Land Use
Pesticide Use, Properties, and Sales
Study Design and Methods
Sample-Site Selection and Sampling Frequency
Sampling Methods
Analytical Methods
Quality Control
Statistical Analysis of Selected Pesticides
Load-Estimation Methods
Pesticides in Streams in the Little River Basin, Kentucky
Occurrence and Distribution
Seasonal Variability in Concentrations of Pesticides
Spatial Variability in Concentrations of Pesticides
Concentrations of Stream Pesticides Compared to Drinking-Water Standards and Aquatic-Life Guidelines
Estimated Loads and Yields of Selected Pesticides
Summary
Acknowledgments
References Cited
1-5. Maps showing:
1. Location of the surface-water-sampling sites in the Little River Basin, Kentucky, study area.
2. Surficial geology in the Little River Basin, Kentucky, study area.
3. Generalized distribution of sinkholes in the Little River Basin and throughout Kentucky.
4. Location of fixed-network sampling sites and graphs showing precipitation and daily mean streamflow at selected surface-water sites in the Little River Basin, Kentucky, study area, 2003-04.
5. Land cover in the Little River Basin, Kentucky, study area, 2001.
6-10. Graphs showing:
6. Occurrence of pesticide compounds from all samples at all sites in the Little River Basin, Kentucky, study area, 2003-04.
7. Monthly concentrations of selected pesticides at all sampling sites in the Little River Basin, Kentucky, study area, 2003-04.
8. Seasonal variability of atrazine and its transformation product, deethylatrazine, at three selected sampling sites in the Little River Basin, Kentucky, study area, 2003-04.
9. Monthly detection rates of selected insecticides (diazinon and disulfonton sulfone) in the Little River Basin, Kentucky, study area, 2003-04 .
10. Concentrations of selected pesticides (metolachlor, diazinon, simazine, and atrazine) at all sampling sites in the Little River Basin, Kentucky, study area, 2003-04.
1. Pesticide active-ingredient sales and detections in surface-water samples, Christian and Trigg Counties, Kentucky, 2003-04.
2. Description of surface-water sampling sites in the Little River Basin, Kentucky.
3. Summary of percent recovery data for commonly detected pesticides spiked in the field for the Little River Basin, Kentucky, 2003-04.
4. Summary of replicate sample data for commonly detected pesticides and pesticide-transformation compounds.
5. A comparison of loads for selected pesticides at three sites using LOADEST predefined and user-defined models.
6. Pesticides and pesticide-transformation products analyzed in surface-water samples from the Little River Basin, Kentucky, 2003-04.
7. Summary statistics of the detected herbicides, insecticides, and fungicides in samples collected in the Little River Basin, Kentucky; laboratory reporting limits; drinking-water standards; and aquatic-life criteria.
8. Mean annual load and yield of selected pesticides at selected fixed-network sites in the Little River Basin, Kentucky, 2003-04.
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Suggested Citation:
Crain, Angela S., 2006, Occurrence, Distribution, Loads, and Yields of Selected Pesticides in the Little River Basin, Kentucky, 2003-04:
U.S. Geological Survey Scientific Investigations Report 2006-5142, 25 p.
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Persistent URL: https://pubs.water.usgs.gov/sir20065142 Page Contact Information: Publications Team Last modified: Thursday, 01-Dec-2016 19:09:35 EST |
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