ADSORPTION AND TRANSPORT OF NITRATE AND BROMIDE IN A SPODOSOL

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 contaminan ts; hence, it could minimize the contamination of groundwater by agric hemicals applied to soils. In this study, adsorption and leaching of n itrate and bromide in soil samples taken from three horizons of a Spod osol (Oldsmar sand; sandy silicious, hyperthermic Alfic Arenic Haplaqu ods) were evaluated with batch equilibration and leaching column exper iments, Adsorption of nitrate and bromide was negligible by the A (sur face 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 n itrate, applied on the surface of the soil column, recovered in 4.5 po re 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 ho rizon samples. A 2-fold increase in rate of application of either nitr ate or bromide had a negligible effect on the cumulative leaching of t he ions in relation to the quantity applied.