Effects of petroleum pollution on clay soil microstructure

In the paper, microstructural changes of clay soil – glacial till – caused by in-situ pollution with diesel oil are presented. STIMAN software was used for a quantitative analysis of scanning electron microscope-based photographs. As a result of pollution, the microstructure underwent substantial qualitative changes: the packing of particles and clayey microaggregates decreased and part of the microaggregates disintegrated, edges and corners of some clay particles were warped and the amount of intermicroaggregate pores and edge-to-face (EF) contacts among clay microaggregates increased. Diesel oil pollution entailed significant quantitative changes in the till pore space. The amount of mesopores, the maximum and average pore area, the maximum, minimum and average pore perimeter and the maximum and average pore diameter grew markedly while the value of the total pore perimeter decreased. As indicated by the drop of the microstructural anisotropy index and the amount of fissure pores as well as the growing average form index, the polluted clay became more isotropic. These changes might be due to the reduction of interparticle forces upon pollution with a fluid characterized by a dielectric constant lower than water.