Developing a critical load approach for national risk assessments of atmospheric metal deposition.

The critical load approach has been proposed for evaluation of the need to reduce atmospheric emissions of metals that lead to transboundary transport and deposition across Europe. The present study demonstrates and evaluates the application of a critical load approach for national-scale risk assessment of metal deposition in the United Kingdom. Critical load maps, calculated using critical limits based on pH-dependent free metal ion activities, are presented.