Preparation of Soil Thin Sections for Contaminant Distribution Studies

Abstract

Dynamic models of the transport and fate of radionuclides in ecosystems include many parameters that can not be easily estimated and often their estimates vary by many orders of magnitude. Estimation of these parameters requires knowledge of such factors as physical and chemical properties of soil, radionuclide depth distribution, concentration, bioavailability, migration mechanisms, root uptake, leaching into the deep soil and other factors. The physical location of radioactive contaminants in soils is an important factor in understanding contaminant migration mechanisms and estimation of models parameters. The common approach in parameters estimation is the assumption that the radionuclides are homogeneously distributed either uniformly or with some exponential depth profile under the ground surface. Soil, however consists of various size clay, sand, rock etc. particles bonded together by organic and inorganic materials [4]. The soil pores provide networks for vertical and horizontal transport of water, gases, dissolved nutrients etc. “A crushed or pulverized soil is related to the soil formed by nature like a pile of debris to a demolished building” [2]. The architecture of building can no more be determined from a pile of rubble than the structure or site-specific composition of a soil from a crushed bulk sample. Examination of soil thin sections having the original soil structure intact has developed over last three decades. The production of thin sections from hard rocks for examination under a microscope is one of techniques used in petrological laboratories. The production of thin soil sections from unconsolidated and/or radioactively contaminated soil is not a widely known or established technique and requires some different materials, safety measures and protocols.