This is an old revision of the document!
Table of Contents
Surface Area and Contamination
Much contamination within sediment is due to the adsorption of waterborne contamination onto the particles within the sediment. Smaller particles have a higher area per unit weight of material, as for example a 1cm^3 particle will have a surface area of 1cm^2, if you cut that particle in half then the surface area increases to 8cm^2, slice those particles in half along the same axis as before and the surface area is not 12cm^2. For sediments the particle size ranges from gravels of many millimetres to silts of only a few microns in size, meaning that the surface of a gravel containing sediment will be orders of magnitude smaller than a silt containing sediment.
Contaminants which are adsorbed require surface to be adsorbed to, so the higher the surface area, the more contaminant will be contained in the sediment.
The level of contamination is controlled by many factors, local contamination release, flow of the river etc.. So the role of surface area can be difficult to determine in the chemical analyses of different sediments.
The overspill from dredging barges and the resuspension which happens during dredging is mainly composed of the finest particles within the sediment. The finest particles are likely to contain the highest levels of contaminants.
19th October 2023 - MLA/2015/00088 - Mid-licence sampling
The set of samples taken as part of the mid-licence sampling of the River Tees dredge disposal licence show a strong correlation between relative total surface area and the level of polycyclic aromatic hydrocarbon contamination. MLA/2015/00088 19th October 2023.
Particle Size
By weight
By area
By type
Weight
Total Surface Area
Area
Cumulative Particle Size Distributions
This
