LATERAL AND VERTICAL BROMIDE ION-TRANSPORT IN A PIEDMONT LANDSCAPE

Variation in soil physical properties and soil water transport can aff ect solute transport at different positions within a landscape. Our ob jective was to evaluate the magnitude of lateral and vertical transpor t of Br- under natural rainfall conditions as a function of landscape position. Potassium bromide was surface applied (300 kg Br-/ha) on thr ee transects of Georgeville soil (clayey, kaolinitic, thermic Typic Ha pludults) in the Piedmont of North Carolina. Each transect included a footslope, linear slope, and interfluve landscape position. The KBr wa s applied on alternate plots (5 by 2.7 m) on two transects and on cont iguous plots on the third transect. Soil cores as deep as 3 m were col lected after 140, 560, and 1460 mm of rainfall. Extent of lateral Br- transport was determined using cores from plots that did not receive s urface application of KBr. After 140 mm of rainfall, the maximum Br- c oncentration remained in the upper 30 cm and some measurable lateral B r- transport occurred at all landscape positions. After 560 mm of rain fall, the maximum Br- concentration was above 60 cm, but some was dete cted at 150 cm on the footslope and interfluve positions. Lateral tran sport of Br- at the footslope and linear slope positions was 150 cm, b ut maximum concentrations occurred 10 to 45 cm downslope. After 1460 m m of rainfall, most Br- disappeared from the footslope. Downslope late ral transport of Br- was 225 cm at all landscape positions. Both verti cal and lateral Br- transport were greatest at the footslope. The vari ability in Br- transport is related to soil profile characteristics an d hydrology at different landscape positions.