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Trends and Transformation of Nutrients and Pesticides in a Coastal Plain Aquifer System, United States
Author(s) -
Denver Judith M.,
Tesoriero Anthony J.,
Barbaro Jeffrey R.
Publication year - 2010
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2009.0107
Subject(s) - groundwater , aquifer , nitrate , environmental chemistry , coastal plain , hydrology (agriculture) , soil water , environmental science , organic matter , water table , atrazine , fertilizer , chemistry , geology , pesticide , soil science , agronomy , paleontology , geotechnical engineering , organic chemistry , biology
Four local‐scale sites in areas with similar corn ( Zea mays L.) and soybean [ Glycine max (L.) Merr.] agriculture were studied to determine the effects of different hydrogeologic settings of the Northern Atlantic Coastal Plain (NACP) on the transport of nutrients and pesticides in groundwater. Settings ranged from predominantly well‐drained soils overlying thick, sandy surficial aquifers to predominantly poorly drained soils with complex aquifer stratigraphy and high organic matter content. Apparent age of groundwater, dissolved gases, N isotopes, major ions, selected pesticides and degradates, and geochemical environments in groundwater were studied. Agricultural chemicals were the source of most dissolved ions in groundwater. Specific conductance was strongly correlated with reconstructed nitrate (the sum of N in nitrate and N gas) ( R 2 = 0.81, p < 0.0001), and is indicative of the relative degree of agricultural effects on groundwater. Trends in nitrate were primarily related to changes in manure and fertilizer use at the well‐drained sites where aquifer conditions were consistently oxic. Nitrate was present in young groundwater but completely removed over time through denitrification at the poorly drained sites where there were variations in chemical input and in geochemical environment. Median concentrations of atrazine (6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine), metolachlor (2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl)acetamide), and some of their common degradates were higher at well‐drained sites than at poorly drained sites, with concentrations of degradates generally higher than those of the parent compounds at all sites. An increase in the percentage of deethylatrazine to total atrazine over time at one well‐drained site may be related to changes in manure application.