Natural and anthropogenic sources of copper to organic soils: a global, geochemical perspective

Copper (Cu) is essential for all organisms but is commonly deficient in organic soils or found locally in excess. Natural and anthropogenic inputs of Cu were examined using 32 peat cores from bogs in Europe, North America, New Zealand, Greenland, and Antarctica. The natural abundance of Cu in ombrotrophic (rainwater-fed) peat was studied using (1) samples from pre-industrial periods (representing background values), (2) bromine (Br) concentrations and the background Cu/Br ratio, and (3) cores from remote locations. Etang de la Gruere in Switzerland provides a record of 15 000 yr of peat accumulation. The lowest Cu concentrations (1.0 +/- 0.20 mgkg(-1)) are found in 18 peat layers dating from ca. 6000 to 9000 cal yr BP, when atmospheric deposition of soil-derived dust was at a minimum. Similar background values occur in peat bogs from other regions. Recent peat layers from bogs in developed areas reveal much greater concentrations. Using the Cu/Br ratio, "excess" Cu in peat profiles can be calculated and attributed either to anthropogenic inputs in recent peats or natural inputs from mineral-water interactions in deeper layers. Peat cores from remote regions of northern Alberta show little or no evidence of anthropogenic Cu.