Concentrations of Nutrients, Pesticides, and Suspended Sediment in the Karst Terrane of the Sinking Creek Basin, Kentucky, 2004

Water samples were collected in streams and springs in the karst terrane of the
Sinking Creek Basin in 2004 as part of study in cooperation with the Kentucky
Department of Agriculture. A total of 48 water samples were collected at 7
sites (4 springs, 2 streams, and 1 karst window) from April through November
2004. The karst terrane of the Sinking Creek Basin (also known as Boiling
Spring Basin) encompasses about 125 square miles in Breckinridge County and
portions of Meade and Hardin Counties in Kentucky.

Fourteen pesticides were detected of the 52 pesticides analyzed in the stream
and spring samples. Of the 14 detected pesticides, 12 were herbicides and 2
were insecticides. The most commonly detected pesticides; atrazine, simazine,
metolachlor, and acetochlor-were those most heavily used on crops during the
study. Atrazine was detected in 100 percent of all samples; simazine,
metolachlor, and acetochlor were detected in more than 35 percent of all
samples. The pesticide-transformation compound, deethylatrazine, was detected
in 98 percent of the samples. Only one nonagricultural herbicide, prometon, was
detected in more than 30 percent of the samples. Malathion, the most commonly
detected insecticide, was found in 4 percent of the samples, which was followed
by carbofuran (2 percent).

Most of the pesticides were present in low concentrations; however, atrazine
was found in springs exceeding the U.S. Environmental Protection Agency's
(USEPA) standards for drinking water. Atrazine exceeded the USEPA's maximum
contaminant level 2 times in 48 detections.

Concentrations of nitrate greater than 10 milligrams per liter (mg/L) were not
found in water samples from any of the sites. Concentrations of nitrite plus
nitrate ranged from 0.21 to 3.9 mg/L at the seven sites. The median
concentration of nitrite plus nitrate for all sites sampled was 1.5 mg/L.
Concentrations of nitrite plus nitrate generally were higher in the springs
than in the main stem of Sinking Creek.

Forty-two percent of the concentrations of total phosphorus at all seven sites
exceeded the USEPA's recommended maximum concentration of 0.1 mg/L. The median
concentration of total phosphorus for all sites sampled was 0.09 mg/L. The
highest median concentrations of total phosphorus were found in the springs.
Median concentrations of orthophosphate followed the same pattern as
concentrations of total phosphorus in the springs. Concentrations of
orthophosphate ranged from 0.006 to 0.192 mg/L.

Concentrations of suspended sediment generally were low throughout the basin;
the median concentration of suspended sediment for all sites sampled was 23
mg/L. The highest concentration of suspended sediment (1,486 mg/L) was measured
following a storm event at Sinking Creek near Lodiburg, Ky.