Water Table Depth and Rainfall Timing Effect on BR⁻ and NO3- Transport

Abstract

Effect of water table depth and rainfall timing on bromide and nitrate transport was investigated using large undisturbed columns (30 cm in diameter and 90 cm long) obtained from Rossburg silt loam and Clermont silt loam soils. Three water table treatments and two time delays (the time interval between chemical and water applications) were used to simulate a range of saturated conditions in the soil profile and rainfall timing. Water was applied for 60 d at a rate of 970 mL/d, equivalent to a daily rainfall of 13.3 mm, using an automated irrigation system. Discharge from the water table control pipe at each column was sampled for bromide and nitrate concentration. Findings from this study include: (1) water table depth significantly affected bromide and nitrate breakthrough patterns and nitrate recovery; (2) water table depth and time delay interactively affected nitrate transport; (3) soil type was not a significant factor in this case; and (4) bromide and nitrate had similar breakthrough characteristics, yet the relative concentration of nitrate was consistently lower than that of bromide.