ADSORPTION AND TRANSPORT OF NITRATE AND BROMIDE IN A SPODOSOL

Abstract

Spodosols are important soil types throughout much of the citrus belt in the south and east coast regions of Florida. The spodic horizon in these soils may play a role in restricting the transport of contaminants; hence, it could minimize the contamination of groundwater by agrichemicals applied to soils. In this study, adsorption and leaching of nitrate and bromide in soil samples taken from three horizons of a Spodosol (Oldsmar sand ; sandy, silicious, hyperthermic Alfic Arenic Haplaquods) were evaluated with batch equilibration and leaching column experiments. Adsorption of nitrate and bromide was negligible by the A (surface soil, 0-20 cm) and E (sand layer, 25-50 cm) horizon samples. The spodic horizon (B h , 55-70 cm), by comparison, retained a small amount of nitrate and bromide. In a leaching column study, the quantity of nitrate, applied on the surface of the soil column, recovered in 4.5 pore volumes of leachate was lower by 15% when the soil sample from the spodic horizon was used compared with using the surface or the sand horizon samples. A 2-fold increase in rate of application of either nitrate or bromide had a negligible effect on the cumulative leaching of the ions in relation to the quantity applied.