Response of the West Bear Brook Watershed, Maine, USA, to the Addition of (NH sub(4)) sub(2)SO sub(4): 3-Year Results

Beginning in November 1989, dry ammonium sulfate was added in six bi-monthly applications to West Bear Brook Watershed, Maine, to assess its impact at collection basins throughout the watershed. The compound was added at 1800 eq/ha/yr, which is approximately twice the ambient wet plus dry loading. Data on water chemistry were compared to a control watershed. Over the subsequent 3 yr, cation concentrations in West Bear Brook increased steadily relative to those in East Bear Brook, which was used as the control. Higher concentrations of base cations became strongly seasonal, controlled by higher discharge in the fall winter spring period. Peak differences in SO sub(4) concentration between the streams occurred when discharge was high, indicating that shallow flow paths caused a greater transmission of the added SO sub(4). Nitrate concentrations also increased dramatically, with highest values occurring at high flow. Overall, West Bear Brook, which was originally less acidic than East Bear Brook, became chronically more acidic.