Weathering and pedogenesis at the watershed scale: some recent lessons from studies of acid-deposition effects.

Geochemical mass balance is commonly used to calculate mineral weathering rates. Such studies invariably find higher present-day rates and generally conclude that the higher rates are a consequence of recent environmental acidification. However, because the residual solids which are the basis of the long-term estimate are time-integrated accumulations of weathering products, it may be inappropriate to compare short-term rates from solute input-output budgets with0long-term rates from bulk profile chemistry. There are disparities in both the time-scales over which the two methods measure rates, and the volume fraction of the regolith being sampled. Soils better integrate time; solute budgets better integrate space.