Calculating critical loads for acidity with the simple mass balance method

The critical load for acid deposition to forest soils, groundwater and surface water can be calculated using a simple mass balance model, taking into account all sources of acidity and alkalinity in the system. The model is very simple to apply, and the major difficulty lies primarily in the estimation of reasonable values for the required input data such as the weathering rate. Methods for its estimation are indicated here. Examples are given for the application of the simple mass balance method (SMB) to Dutch and Swedish forest soils, lakes and shallow groundwater. This work outlines and explains the actual application of the consept as it is being carried out regionally for all European nations.