DISSOLVED AND PARTICULATE TRACE-METALS IN A SCOTTISH SEA LOCH - AN EXAMPLE OF A PRISTINE ENVIRONMENT

In the near pristine environment of a silled fjord on the west coast o f Scotland samples were taken for the determination of dissolved and p articulate trace metals (Fe, Mn, Cu, Ni, Cd, Zn and Pb), together with nutrient and hydrographic data, during 19 surveys carried out over a year. An indication of the pristine nature of the environment are the low concentrations of dissolved silicon, phosphate and nitrate which a re considerably lower than those of coastal waters which are subject t o larger anthropogenic burdens. Distributions of dissolved Cu, Ni and Cd were found to broadly reflect conservative mixing of freshwater and seawater with both end members having similar concentrations. The con centration of dissolved Cu and Ni in seawater entering upper Loch Linn he (Cu 0.28 mu g 1(-1); Ni 0.26 mu g 1(-1)) was consistent with the 1: 1 conservative mix of Irish Sea water and North Atlantic surface water predicted from radiocaesium tracer experiments (Mackay & Baxter, 1985 ). Atmospheric input of trace metals to upper Loch Linnhe appeared to be a relatively minor term in the mass balance relative to fluvial inp uts. Values of distribution coefficients K-d were similar to those pre viously reported for the coastal environment. Iron showed the stronges t affinity for the suspended sediments; with particulate percentages o f the total load usually greater than 80%. Lead and Mn showed a simila r strong affinity to the particle phase. For Cu, Ni and Zn the mass of the element in the dissolved phase was generally greater than that in the particulate fraction. Cadmium, was least associated with the part icles, with typically greater than 90% existing in the dissolved phase . Copyright (C) 1996 Elsevier Science Ltd