The need and means to characterize sediment structure and behaviour prior to the selection and implementation of remediation plans

Remediation of contaminated sediments requires detailed characterizations of the speciation of the toxic substances and their transformations with regard to time and spatial distribution. While many approaches exist to address dissolved species of toxicants, there is a need to characterize sediments per se in terms of materials or particles which bind toxicants and modulate their bioavailability and rate of burial. Such specific information can be achieved through the correlative use of analytical microscopies, applied directly to native aquatic materials and used in conjunction with novel particle isolation methods and standard techniques of analytical chemistry. Such sedimentary `materials' are dominated by clays and other colloidal minerals, microorganisms, humic substances, organic debris, iron and manganese oxide coatings and extracellular polymeric substances. By using new technology to (1) identify particles and their relative abundances, (2) examine specific toxicant/particle associations at the scale of individual abundant particles, and (3) follow transformations over time, we produce information more insightful than was obtainable previously. Such knowledge will assist in determining which remediation technologies would be best for a given contaminated sediment (i.e. `intrinsic remediation' or dredging/disposal).