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Influence of landscape position and irrigation on alachlor, atrazine, and selected degradates in selected upper regolith and associated shallow aquifers in Northeastern Nebraska
Abstract
Concentrations of alachlor, its ethanesulfonic acid degradate, atrazine, deethylatrazine, and deisopropylatrazine in upper regolith and associated shallow aquifers were determined in relation to landscape position and irrigation. Soils at the sampling sites generally were fine-silty mixed mesic Udic Haplustolls or Typic Hapludolls. Most detections of herbicides and degradates occurred in samples at shallow depths. Highest alachlor (Kd = 2.2-7.7) concentrations were detected at depths of 15 to 31 cm on floodplains and terraces (maximum 17.5 $\mu$g/kg). Detections of alachlor ethanesulfonic acid (Kd = 1.0 to 2.6) were numerous from a depth of 15 to 115 cm. This degradate was detected at a depth exceeding 270 cm. Highest concentrations occurred at depth 1 on floodplains and terraces (maximum 10.0 $\mu$g/kg). Atrazine occurred more readily on the floodplains at all depths. Atrazine tends to adsorb in A and B horizons, enriched in organic matter and clay with low pH. Deethylation as well as deisopropylation reactions of atrazine were common. Deisopropylatrazine was transported to depths exceeding 100 cm and deethylatrazine to depths exceeding 250 cm. Atrazine and alachlor ethanesulfonic acid concentrations were associated with landscape position, but not with irrigation. Larger concentrations of atrazine and the alachlor degradate tended to occur on the floodplains and terraces than on the upland. Concentrations of alachlor, deethylatrazine, and deisopropylatrazine were not significantly affected by either landscape position or irrigation. Differences in presence of these herbicides and degradates generally were associated with those soil chemical and physical properties which differ across landscape positions. Herbicides tended to be present in soils with high percent organic matter, low pH, and low sand content. Ground-water analytical results did not support the hypotheses that concentrations of these herbicides and degradates in ground water differed among landscape position or with irrigation.
Subject Area
Environmental science|Hydrology|Agronomy
Recommended Citation
Verstraeten, Ingrid Maria, "Influence of landscape position and irrigation on alachlor, atrazine, and selected degradates in selected upper regolith and associated shallow aquifers in Northeastern Nebraska" (1994). ETD collection for University of Nebraska-Lincoln. AAI9425310.
https://digitalcommons.unl.edu/dissertations/AAI9425310