Diagrams, including sedimentation pattern and force-separation curves, from a study on the influence of hydrocarbon contamination on clay soil microstructure

Microstructural (fabric, forces and composition) changes due to hydrocarbon contamination in a clayey soil (glacial till) were studied using scanning electron microscopy (microfabric analysis), atomic force microscopy (force measurement) and a sedimentation bench test (particle size measurements). Non-polluted and polluted glacial till from NE Poland (in the area of a fuel terminal) were used for the study.

Figure 1 is the sedimentation pattern for the soil in deionized water and diesel oil.  Figure 2 are images of fabric changes in NP (unpolluted, SEM micrographs A1, B1, C1) and P (polluted, SEM micrographs A2, B2, C2) clay soil. Magnification: A, 200×; B, 1600×; C, 6500×.  Figure 3 shows examples of orientation diagrams and average values of anisotropy coefficient (Kaav) for NP soil (a) and P soil (b); α, angle of structural elements orientation. Figure 4 is force–separation curves on approach (A series) and withdrawal (B series) for the interaction between platelets in the NP clay sample in water (A1, B1), in 0.01 m KCl (A2, B2) and in 0.1 m KCl (A3, B3). The solid lines in the force measurement on approach represent forces measured between the silica probe and the bare mica surface at the relevant KCl electrolyte concentration.  Figure 5 is Force–separation curves on approach (A series) and withdrawal (B series) for the interaction between platelets in the P clay sample in water (A1, B1), in 0.01 m KCl (A2, B2), and in 0.1 m KCl (A3, B3). The solid lines in the force measurement on approach represent forces measured between the silica probe and the bare mica surface at the relevant KCl electrolyte concentration.