The use of Nuclear Magnetic Resonance Imaging (MRI) to assess impact of oil-related waste on estuarine sediments and sediment dynamics

Abstract

Abstract The Marine Pollution Control Unit of the Department of Transport are at present testing the suitability of burial and landfarming of oily residues in sandy coastal environments as an alternative to landfill sites. The tendency for oil related compounds to sorb to sediments (and hence to affect their cohesiveness) has been extensively investigated, but this has not involved or permitted the ‘observation’ or measurement of advection/diffusion processes or the breakdown of these residues within sediments. MRI, which is a multidimensional technique allowing the position of nuclei (most commonly protons) to be located within a known volume of substrate, for example sediment, provides a means of monitoring the change in position and the eventual breakdown of oil within sediments, thus offering a method of assessing the harming potential of oils in near-shore environments. Two dimensional (2D) and three dimensional (3D) MRI analysis of the movement of oil in estuarine sediments show that, using appropriate parameters, movement of the oil can be both observed and quantified. To aid quantification a sample holder fabricated from polyvinylsiloxane, an inert material visible in magnetic resonance images has been used as an internal intensity standard. The results show the great potential of MRI in studying protonated contaminants in these materials, notwithstanding the presence of paramagnetic species in estuarine sediments, which might distort the image. Sediments studied thus far have been collected from the Tay Estuary, NE Scotland.