Factors affecting the susceptibility of Irish soft‐water streams to forest‐mediated acidification

Hydrochemical sampling was carried out at forty seven sites on upland soft-water streams in the eastern region of Ireland. The majority of sites were circum-neutral during dry weather but became episodically acidic during heavy or prolonged rainfall. Sensitive sites were characterized by low alkalinity (< 200 μeq L–1) and low non-marine hardness (< 120 μeq L–1) values and high levels of natural acidity (DTOC). These sensitive, naturally acidic waters were shown to be susceptible to acid inputs from forestry. The high acidity levels associated with some afforested catchments were attributed to inputs of sulphates, nitrates and hydrological factors.