Use of chloride and fluorescent dye as tracers in measuring nitrate and Atrazine transport through soil profile under laboratory conditions1

Abstract

Laboratory experiments were conducted using undisturbed soil columns (one from no‐tillage and one from moldboard plow fields) to monitor the performance of adsorbed and nonadsorbed tracers in predicting nitrate and atrazine movement through the soil profile and to the shallow groundwater systems. Chloride (Cl) and Rhodamine WT dye were used as surrogate tracers for nitrate‐nitrogen (NO3‐N) and atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine), respectively. The chemical solution containing 0.005 M calcium nitrate, 0.005 M calcium chloride, 83 ppb atrazine, and 1 ppm Rhodamine was used for developing breakthrough curves to observe chemical leaching through saturated soil columns. Similarity between the NO3‐N and Cl breakthrough curves suggested that Cl ion can successfully be used as a tracer for observing NO3‐N transport through soil columns. Significant difference between the Rhodamine WT and atrazine breakthrough curves indicated that use of Rhodamine WT is not an ideal tracer for monitoring atrazine transport through soils. Breakthrough curves for nitrate and chloride were similar under both tillage systems but atrazine breakthrough curves showed a greater degree of preferential movement through no‐tillage soil column.