Yang, Handong; (2000) Trace metal storage in lake systems and its relationship with atmospheric deposition with particular reference to Lochnagar, Scotland. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Anthropogenic trace metals (Hg, Pb, Zn, Cd and Cu) at Lochnagar are derived solely from atmospheric deposition. Sixteen lake sediment cores along five transects radiating from a central point of the lake and ten soil cores representing different areas of the catchment were taken during July 1997 and July 1998. Trace metals were analysed in all these cores along with catchment plants, aquatic macrophytes, zooplankton, epilithic diatoms, monthly bulk deposition and lake water samples. Through the use of multiple cores a full lake catchment (lake sediments and catchment soils) trace metal distribution was measured, and revealed that trace metal concentrations and deposition fluxes to the sediments changed with water depth. Hg, Pb, Zn and Cu were shown to have similar distribution patterns whilst Cd showed different patterns in the lake sediments. Trace metals were found to be mobile in the catchment soils, and the soils filter trace metals from rain water resulting in accumulation of metals in the soils. The proportion of trace metals derived from anthropogenic emissions in total storage in lake sediments and catchment soils were calculated. The number of cores representative of the whole lake sediment basin is discussed. The relationship of trace metal levels in the lake ecosystem was studied with respect to atmospheric deposition fluxes (historic trends). With sediment core correlation, trace metal inventories in different chronological sediment layers for the whole lake basin were established. By matching the present deposition fluxes to the chronological sediment inventory records, the trace metal atmospheric deposition history was established. Trace metal storage in the lake system including the catchment was determined so that a metal budget could be established, and hence an assessment of possible targets for emission sources related directly to the ecosystem metal levels achieved. Finally, Lochnagar was compared with three other European lakes to determine the influence of anthropogenic emissions on these remote ecosystems.

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