ABSTRACT
Enhanced acid deposition on to the canopies of conifer forests in upland Wales has contributed to the release of AI into stream waters. Relatively little is known about how soil hydrological and chemical processes interact, in response to acid deposition, to transfer of Al-rich soil waters into streams. A hydrochemical field study monitored the hydrology and soil water chemistry of an afforested stagnopodzol at Llyn Brianne (Mid-Wales). Water moved vertically through the soil aided by root macropores. Simulated soil water fluxes indicated that 89% of effective precipitation drained vertically through the soil profile. Precipitation was acidified as water moved through the forest canopy and into the soil and AI was mobilized by cation exchange processes. Leaching of AI occurred during hydrological events and the estimated total flux was 3.39 kmolc ha-1 a-1. It is likely that Al-rich soil water draining from the base of stagnopodzols provides a significant input into streams during acid episodes.
