Coupled Transport of Nitrate and Chloride in Unsaturated Soil Columns.

Nitrate, an important nitrogenous compound in a fertilizer, is of environmental concern regarding groundwater contamination. Nitrate is weakly adsorbed by 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. The transport behavior of nitrate and chloride was studied in 10 cm long-columns packed with sand and loam. A 0.1 M calcium nitrate and calcium chloride solution (1:1) was applied from top though the columns at -0.30 kPa suction. The chloride and nitrate concentrations in the effluent solution were measured and the CXTFIT program was used to determine the two region non-equilibrium transport model parameters. Initial results showed that nitrate and chloride exhibit similar behavior pattern in sand and loam. Further experiments are underway under different pore water velocities to confirm these results and evaluate the effect of pore water velocity and water content on the transport parameters.