Transport and Fate of Nitrate and Pesticides

Abstract

There is continuing concern over potential impacts of widespread application of nutrients and pesticides on ground- and surface-water quality. Transport and fate of nitrate and pesticides were investigated in a shallow aquifer and adjacent stream, Cow Castle Creek, in Orangeburg County, South Carolina. Pesticide and pesticide degradate concentrations were detected in ground water with greatest frequency and largest concentrations directly beneath and downgradient from the corn (Zea mays L.) field where they were applied. In almost all samples in which they were detected, concentrations of pesticide degradates greatly exceeded those of parent compounds, and were still present in ground waters that were recharged during the previous 18 yr. The absence of both parent and degradate compounds in samples collected from deeper in the aquifer suggests that this persistence is limited or that the ground water had recharged before use of the pesticide. Concentrations of NO(-)(3) in ground water decreased with increasing depth and age, but denitrification was not a dominant controlling factor. Hydrologic and chemical data indicated that ground water discharges to the creek and chemical exchange takes place within the upper 0.7 m of the streambed. Ground water had its greatest influence on surface-water chemistry during low-flow periods, causing a decrease in concentrations of Cl(-), NO(-)(3), pesticides, and pesticide degradates. Conversely, shallow subsurface drainage dominates stream chemistry during high-flow periods, increasing stream concentrations of Cl(-), NO(-)(3), pesticides, and pesticide degradates. These results point out the importance of understanding the hydrogeologic setting when investigating transport and fate of contaminants in ground water and surface water.

Influence of stream‐groundwater interactions in the streambed sediments on NO3− flux to a low‐relief coastal stream

“…In addition, flow paths are affected strongly by topography, and in some cases, discharging groundwater can bypass zones of high organic carbon content that are the sites of biogeochemical reactions. For example, Puckett and Hughes [2005] found limited NO 3 À removal within a riparian aquifer adjacent to a coastal stream. They proposed that the coarser-grained sediments in the surficial aquifer provided a preferential flow path that allowed NO 3 À in groundwater to pass beneath the shallow reducing layer in the riparian zone and to discharge directly into the streambed.…”

Upper Washita River Experimental Watersheds: Physiography Data

“…The hydrogeologic setting of a study area affects the transport and fate of contaminants in groundwater and surface waters (Puckett and Hughes, 2005). This is critical because the geologic formation affects properties such as K s , specific yields, and specific storage.…”

Eleven‐Year Trend in Acetanilide Pesticide Degradates in the Iowa River, Iowa

“…Acetanilide herbicides degrade rapidly in the root zone and are transported to shallow groundwater (Bayless et al, 2008) where they commonly occur in alluvial aquifers in Iowa Boyd, 2000). Because of the slow rate of fl ow through the shallow aquifers (Puckett and Hughes, 2005), degradates may move into rivers and streams years aft er the parent compounds were applied. Herbicide transport from the watershed may also be temporarily delayed by storage in infi ltration from the IR into adjacent alluvial aquifers during high streamfl ow in the spring and, through seepage, may move back into the river later when fl ow decreases (Squillace et al, 1993;Boyd, 2000).…”