The use of reservoir sediments as environmental archives of catchment inputs and atmospheric pollution

Lakes and reservoirs act as sinks for both catchment and atmospherically derived particulates and so their sediments can provide valuable information on temporal changes in these inputs. While the use of lake sediments as environmental archives is well established, reservoir sediments have less frequently been used as temporal records. Yet, for investigating pollution histories, reservoirs are ostensibly of greater interest: they are generally located close to urban and industrial sources of pollution and accumulate sediment rapidly and over similar time periods to major emissions of pollutants. The lack of interest in reservoir sediments stems from the perception that fluctuating water levels are likely to result in significant sediment disturbance. This perception is sustained, perhaps mistakenly, by a lack of research into reservoir sedimentary systems. There is, therefore, a need to review the available published research on reservoir sedimentation processes and patterns, the relatively few studies that have used reservoir sediments and relevant studies from the lake-sediment literature, and thus critically evaluate the potential and problems of using reservoir sediments as temporal records of pollution. Current understanding of the processes of sedimentation and resulting distributions are reviewed. Some significant differences between sedimentation in lakes and reservoirs are highlighted and the implications for sampling and interpretation of sedimentary records discussed. It is suggested that, at present, a valuable resource is being underutilized and it is demonstrated that, where sediment deposition patterns are taken into account, reservoir sedimentary records can provide important data for reconstructing past atmospheric and catchment pollutant inputs.