Temporal trends of selected agricultural chemicals in Iowa's groundwater, 1982-1995: Are things getting better?

Journal of Environmental Quality
By: , and 



Since 1982, the Iowa Groundwater Monitoring (IGWM) Program has been used to sample untreated groundwater from Iowa municipal wells for selected agricultural chemicals. This long-term database was used to determine if concentrations of select agricultural chemicals in groundwater have changed with time. Nitrate, alachlor [2-chloro-2′-6′-diethyl-N-(methoxymethyl)-acetanilide], atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), cyanazine [2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino]-2-methylpropionitrile)], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] were selected for this temporal analysis of the data. Conclusive temporal changes in frequency of detection and median chemical concentrations were found only for atrazine (decrease) and metolachlor (increase). The greatest temporal chemical changes occurred in the shallowest wells and in alluvial aquifers—both relating to groups of wells generally having the youngest groundwater age. The temporal patterns found for atrazine and metolachlor are consistent with their patterns of chemical use and/or application rates and are suggestive of a causal relation. Only continued data collection, however, will indicate if the trends in chemical concentrations described here represent long-term temporal patterns or only short-term changes in groundwater. No definitive answers could be made in regards to the question of overall improvements in groundwater quality with respect to agricultural chemical contamination and time, due to the inherent problems with the simplistic measurement of overall severity (summation of alachlor + atrazine + cyanazine + metolachlor concentrations) examined for this study. To adequately determine if there is an actual decreasing trend in the overall severity of contamination (improving groundwater quality), the collection of additional water-chemistry data and the investigation of other measures of severity are needed.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Temporal trends of selected agricultural chemicals in Iowa's groundwater, 1982-1995: Are things getting better?
Series title Journal of Environmental Quality
DOI 10.2134/jeq1997.00472425002600040012x
Volume 26
Issue 4
Year Published 1997
Language English
Publisher ACSESS
Contributing office(s) Iowa Water Science Center, Toxic Substances Hydrology Program
Description 11 p.
First page 1007
Last page 1017
Country United States
State Iowa
Online Only (Y/N) N
Additional Online Files (Y/N) N
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