Surface water acidification and critical loads for the French Ardennes Massif

A survey on the sensitivity of freshwater to acidification was pei formed i n the French Ardennes Massif. For that purpose, the relationships between a cidifying factors (such as atmospheric deposition). buffering factors (such as bedrock and soil type) and surface water acidity were investigated. Cri tical loads of acidity were calculated for 36 characteristic streams. Resul ts show that spruces, aluminium-enriched schists and plateaus with silts se em to be the most important factors controlling surface water chemistry. Su ch a combination occurs in the central part of the French Ardennes, where 7 0% of the investigated streams were found to be acidic. Moreover, the corre sponding critical loads for these catchments are the lowest in this area (< 1.2 keq.ha(-1).yr(-1)). (C) Academie des sciences / Elsevier, Paris.