Nitrate and Pesticide Penetration into a Northern Mississippi Valley Loess Hills Aquifer

Background/Need: The leakage of NO₃ and pesticide residues from agricultural landscapes to groundwater degrades drinking water resources and exports contaminants to surface waters, threatening both freshwater and marine ecosystems. This leakage has increased greatly over the last several decades, driven by increasing fertilizer and pesticide use particularly over the period of about 1960 to 1990. Given that the increase in pollutant leakage is recent compared with the residence time of ground water in many aquifers, aquifer pollutant loads may not generally be at a steady-state with pollutant leakage in many agricultural regions. In the absence of a steady-state, pollutants will continue to penetrate more deeply into aquifers, increasing pollutant load and pollutant export to surface water.

Objectives: Determine (1) the pollutant leakage chronology of a Northern Mississippi Valley Loess Hills aquifer, (2) whether a modern pollutant load penetrates the entire aquifer thickness, (3) if degradation mechanisms limit pollutant penetration, and (4) what pollutant conditions might develop in the future.