Hydrochemical distribution patterns in stream waters, Trøndelag, central Norway.

A regional geochemical sampling program of stream waters has been carried out in the Nord-Trøndelag region of central Norway. This area has hitherto been little affected by regional anthropogenic sources of pollution. Hydrochemical trends appear to be dominated by interplay of two main factors: (i) input of sea salts via marine aerosols in precipitation: and (ii) geological sources (mineral weathering). Factor (i) results in a predominance of Na-Cl waters near the coast, and may also be partially responsible (via proton displacement from soil ion-exchange sites by marine cations) for lower pH values in near-coastal waters. Further inland, the importance of marine salts decreases and waters become dominantly Ca-(Na)-HCO3. Sub-regional anomalies in geochemical maps for, e.g. nitrate and copper may indicate anthropogenic sources for these parameters from agriculture or mining activities.