Baseflow and stormflow metal concentrations in streams draining contaminated peat moorlands in the Peak District National Park (UK)

Abstract

Leaching of previously deposited metals from atmospherically contaminated peat moorlands to receiving surface waters is an area of concern. Headwater streams in the Peak District National Park were sampled during baseflow and stormflow conditions to investigate the spatial and temporal variability in dissolved metal concentrations, the source of dissolved metals and the role of dissolved organic carbon (DOC) in the mobilisation and transport of dissolved metals. Under baseflow and stormflow conditions, Cu, Ni, Pb, Ti, V and Zn concentrations are highly variable. The results of this study reveal that Cu, Ni, Pb, V and Zn are leached from the contaminated peat soils into headwater streams. Ni and Zn are mobile within the peatland fluvial system due to poor sorption of these metals to organic matter. Elevated Zn concentrations in the headwater streams can be explained by the severely acidic nature of surface waters in this region. Stepwise multiple linear regression analysis reveals that the most important variable in explaining stormflow Pb, Ti and V concentrations is DOC. Due to the strong complexation of these metals by DOC, the export of dissolved Pb, Ti and V in peatland systems is likely to be controlled by DOC availability. Elevated stormflow dissolved Pb concentrations are due to the large store of Pb within the peat soils and high stream water DOC concentrations in surface waters of this upland area. Contemporary dissolved metal export from peat moorlands in the Peak District National Park may provide an analogue for future dissolved metal export in other contaminated peatland systems.