Which recovery from acid rains in the Vosges Mountains after 30 years

Some 30 years ago, surveys of the surface water quality in the Vosges Moutains revealed a strong headstream water acidification, with high concentrations in dissolved aluminium, and the observed consequences on the aquatic biodiversity (Probst et al., 1990). In the early 2000s some of these headstreams (Grand Clos, Ventron, Rouge Rupt, Cellet) were included in a set of 16 headstreams which constitute the Vosges Acidification Observatory of the Zone Atelier du Bassin de la Moselle. Their surface water has been sampled monthly and analyzed in terms of major anions and cations, as well as dissolved aluminium and, since 2012, in terms of dissolved organic matter. In spring 2021, a new survey of the headstreams investigated in the 1990s was organized. Nineteen streams could be sampled. All the streams running on granite bedrock had a higher pH than in 1990. Most of them showed lower aluminium concentrations. The improvement for headstreams running on sandstone seems more limited and new data need to be collected. The presentation will include data collected in summer 2021 as well as long term data for the headstreams included in the Vosges Acidification Observatory to check seasonal and yearly effects.