The application of some mineral magnetic measurements and heavy metal analysis for characterising fine sediments in an urban catchment, Coventry, UK

Mineral magnetic measurements allow the quick and non-destructive characterisation of environmental materials in order to act as a proxy for heavy metal concentrations in solid deposits, correlate across a suite of lake cores and trace sediments. They have been very successful in a wide variety of environments and climatic conditions. Their success has mainly been in terms of discriminating between sediments with very different magnetic characteristics such as topsoil and subsoil in relatively undisturbed lake catchments. The urban environment, however, is characterised by constant disturbance, with many diverse point and diffuse sources and unique processes which change environmental conditions and the composition of the resulting sediment mixture. This paper applies mineral magnetic measurements to urban dusts and sediments from lakes, streams, streets and wetlands in Coventry, UK. Statistical correlation of the magnetic and heavy metal characteristics of a variety of urban dusts and deposits to investigate the relationship between these properties proved inconsistent at best. Using chi (lf) and SIRM measurements to trace sediments moving in an urban lake-catchment showed that biogeochemical processes occurring while the sediment moves from source to deposit precludes the use of the chosen parameters for tracing studies. Correlation of a suite of cores across a paired lake-catchment study proved ineffective due to catchment disturbance. Catchment disturbance and multiple sources may therefore make techniques developed in less complex environments unsuitable when applied to the urban "multicomponent, multiphase" one [D.R. Turner, 1992. The chemistry of metal pollutants in water. In: Harrison, R.M. (Ed.). Pollution: Causes, Effects and Controls. Royal Society of Chemistry, Cambridge. pp. 19-32]. (C) 2001 Elsevier Science B.V. All rights reserved.