Use of Tracers and Dyes to Assess Ground Water Contamination Potential for Glacial Till Aquifers

Abstract

Studies were conducted to evaluate the effectiveness of chloride, bromide, lithium, and a fluorescent dye for tracing the movement of agricultural chemicals to ground water. In one study, bromide, nitrate, lithium, and rhodamine WT were applied with irrigation water to the field plot through a sprinkler system. In the second study, bromide, chloride, and rhodamine WT were mixed with two herbicides (cyanazine and alachlor) and were sprayed on the surface of the plot, which received rainfall with a rainfall simulator. In the third study, chloride as a tracer was used to trace the movement of NO₃-N in the vadose zone. During and after the experiments, groundwater samples were collected. These samples were analyzed for tracer and chemical concentrations. Based on adsorption coefficients in the literature and field experiments, rhodamine WT dye is roughly 20 to 40 times more strongly adsorbed than the commonly used pesticides. Experimental results also indicate that a combination of adsorbed tracers (fluorescent dyes) and non-adsorbed tracers (anions) have the potential for tracing the movement of water as well as adsorbed and non-adsorbed chemicals (nitrates and pesticides) to ground water. This study shows that macropores provide potential paths for rapid transport of chemicals to ground water and tracers offer a potential to investigate ground water contamination problems.