The stream at the Svartberget Forest Research Station (64° 14′ N, 10° 46′ E, altitude 235–310 m) drains a 50 ha† catchment with an 8 ha open mire. The chemistry of atmospheric deposition and streamwater were measured between June 1985 and June 1989.

Wet deposition of sulphate was 40 meq m-2 a-1. Total deposition roughly balanced stream output. The catchment was a sink for nitrate, ammonium and hydrogen ions. Marine excess sulphate in precipitation was 95%. Weekly stream pH varied between 6.8 and 4.2 with a weighted mean of 4.7. Sulphate concentrations in streamwater were negatively correlated with hydrogen ion concentration, with the exception of one, three month winter period.

A balance between major cations and anions was found in the precipitation, but there was an anion deficit of about 50% in streamwater. The stream carried 5–30 mg Cl-1, and unmeasured organic anions may account for the anion deficit. Concentrations of total aluminium were often 0.25 mg l-1 but less than 20% was in the labile monomeric form.

The high concentrations of organic carbon and low fraction of labile monomeric aluminium offer a ‘signature’ of organic acidity that can be used to distinguish streams acidified by mineral acids. The possibility that anthropogenic acid deposition has altered the complex organic chemistry and pH of the Svartberget stream cannot be dismissed.