Hydrologic and land-use factors associated with herbicides and nitrate in near-surface aquifers

Journal of Environmental Quality
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Abstract

Selected herbicides, atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) metabolites, and NO3 were examined in near-surface unconsolidated and bedrock aquifers in the midcontinental USA to study the hydrogeologic, spatial, and seasonal distribution of these contaminants. Groundwater samples were collected from 303 wells during the spring and late summer of 1991. At least one herbicide or atrazine metabolite was detected in 24% of the samples collected for herbicide analysis (reporting limit 0.05 µg/L). No herbicide concentration exceeded the USEPA's maximum contaminant level (MCL) or health advisory level. The most frequently detected compound was the at razine metabolite deethylatrazine [2-amino-4-chloro-6-(isopropylamino)-s-triazine] followed by atrazine, deisopropylatrazine [2-amino-4-chloro-6-(ethylamino)-s-triazine], prometon (2,4-bis(isopropylamino)-6-methyoxy-s-triazine), metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1methylethyl)acetamide], alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide], metribuzin [4-amino-6-(tert-butyl)-3-methylthio-as-triazine-5(4H)-one], simazine [2-chloro-4,6-bis(ethylamino)-s-triazine], and cyanazine [2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino]-2-methylpropionitrile]. Nitrite plus nitrate, as nitrogen (N), exceeding 3.0 mg/L (excess NO3), was found in 29% of the samples, and 6% had 3exceeding the MCL of 10 mg/L. Ammonium as N was detected in excess of 0.01 mg/L in 78% of the samples. A nonlinear increase in the frequency of atrazine detection occurred with decreases in reporting limit. The frequency of atrazine residue detection (atrazine + deethylatrazine + deisopropylatrazine) was 25% greater than for atrazine alone. Herbicide detections and excess NO3 were notably lacking in the eastern part of the study region where it was estimated that herbicide and fertilizer use were among the largest in the region. Prometon, the second most frequently detected herbicide, was associated with non-agricultural land use. Herbicide and excess NO3 were more frequent in unconsolidated aquifers than in bedrock aquifers. Aquifer depth, as direct measurement of proximity to recharge sources, was inversely related to frequency of herbicide detection and excess NO3.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Hydrologic and land-use factors associated with herbicides and nitrate in near-surface aquifers
Series title Journal of Environmental Quality
DOI 10.2134/jeq1993.00472425002200040002x
Volume 22
Issue 4
Year Published 1993
Language English
Publisher American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
Publisher location Madison, WI
Contributing office(s) Iowa Water Science Center
Description 11 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Environmental Quality
First page 646
Last page 656
Country United States
Online Only (Y/N) N
Additional Online Files (Y/N) N
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