Fig. 1. Bromide breakthrough from eight saturated columns. GA, Georgia soil; OM, organic matter; WWS, water-washed sand. The terms WWS + 1HA, WWS + 5HA, and WWS + 50HA refer to virus transports through WWS in phosphate-buffered saline (PBS) solution containing 1, 5, and 50 mg L^-1 humic acid, respectively.