Publication Abstract

A geostatistical analysis of contaminated sediment in a commercial dock in the United Kingdom

J. Reed,  A.Chappell, J.R French and M.A. Oliver

Dredge materials are now regarded as a resource and are being promoted for beneficial uses such as beach, saltmarsh and wetland restoration, although historically they have been treated as waste and disposed of at sea. Such a variety of end-uses requires more complex risk assessments, particularly with regard to contaminant loadings and their likely fate in sensitive receiving environments. A case study of polychlorinated biphenyls (PCBs) concentrations in the sediments of a large (1.5 km x 0.5 km) industrialised dock is used to explore sampling issues and their analysis using geostatistics. A nested sampling scheme with 101 sites is used to identify the magnitude and scale of spatial variation of sediment PCBs. Experimental variograms of individual congeners, total PCBs, particle size, total organic carbon and their principal components are computed and modelled. These provide a clear description of the spatial structure of PCBs and some insight into possible processes affecting their distribution. Block kriging is used to estimate PCB concentrations over the dock. Two areas in the dock exhibit elevated PCB concentrations, which might reflect particular point sources of contamination. The results confirm the effectiveness of the sampling for detecting the spatial scale of variation, and the suitability of geostatistical techniques for investigating the processes controlling the spatial distribution of contaminants. Accurate description of the spatial distribution of contaminants can reduce the risk of misclassification of material designated for remediation, disposal or beneficial use.

Reference:

J. Reed,* A.Chappell, J.R French, and M.A. Oliver (2000) A geostatistical analysis of contaminated sediment in a commercial dock in the United Kingdom. Proceedings of GeoEnv 2000