Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 5/29/2005
Publication Date: 8/11/2005
Citation: Rice, C., Bialek Kalinski, K.M., Angier, J., Mccarty, G.W. 2005. Pesticide and nitrate-n behavior in groundwater within a riparian wetland. American Geophysical Union.
Technical Abstract: Information regarding the behavior and fate of agrochemicals in groundwater within riparian ecosystems is essential in order to assess the overall function of riparian systems at contaminant removal. This study included analysis of pesticides and nutrients in groundwater from a first-order riparian wetland that borders a conventionally farmed cornfield. Vertical depth profiles of groundwater were analyzed for agricultural chemicals. Samples were obtained from piezometers nested at various depths in different locations throughout the riparian wetland. Some of the nests were in areas with little or no visible groundwater seepage to the surface, others were placed in zones of active groundwater emergence (upwelling) onto the land surface (within zones of continuous surface saturation). In those profiles where upwelling was low, there was a clear demarcation in nitrate-N and oxygen contents at depths (between 135 and 175 cm) within the piezometer nests. This same horizon also coincided with the region where atrazine and atrazine degradates (desethyl- and desisopropyl-atrazine) concentrations substantially diminished. Another herbicide, metolachlor, and degradates (metolachlor ethane sulfonic acid and metolachlor oxanilic acid), showed only a slight reduction in concentrations over this zone and maintained a fairly uniform concentration over the vertical profile. Vertical depth profiles in areas where upwelling was high did not show significant variations in herbicide residues; e.g., the concentrations throughout the profile were similar to the levels measured at the deepest zone within the underlying aquifer. Processes leading to these differences were preferential degradation and sorption. This spatial disparity was reflected in the surface water and may affect the overall contaminant-mitigating properties of the riparian system.