Coupled Transport of Nitrate and Chloride Through Layered Porous Media.

Nitrate is a conservative solute in soils and could move quickly through the soil profile leading to plant nutrient loss and groundwater pollution. The purpose of this research was to evaluate the coupled transport of nitrate and chloride in soil columns under different pore water velocities through layered porous media. The transport behavior of nitrate and chloride was studied in 10 cm long-columns packed with a layer of loam overlying a layer of sand. Calcium nitrate and calcium chloride solutions of 0.05 M and 0.1 M with a 1:1 equivalent ratio of nitrate and chloride were applied from bottom of the columns under nearly saturated conditions. The chloride and nitrate concentrations in the effluent solution were measured and the CXTFIT program was used to determine the two region model (TRM) parameters. The results showed that nitrate and chloride exhibit similar transport behavior in layered porous media. The dispersion coefficient and retardation factor increased with pore water velocity in soil columns permeated with 0.05 and 0.1 M solutions. The findings of this study indicate that the risk of groundwater pollution in shallow aquifers with nitrate could be reduced by examining the movement of chloride to predict the nitrate mobility through the soil profile.