Detection of Erionite and Other Zeolite Fibers in Soil by the Fluidized Bed Preparation Methodology

Erionite is a zeolite mineral that can occur as fibrous particles in soil. Inhalation exposure to erionite fibers may result in increased risk of diseases, such as mesothelioma. Low level detection of mineral fibers in soils has traditionally been accomplished using polarized light microscopy (PLM) methods to analyze bulk samples providing detection limits of around 0.25% by weight. This detection level may not be sufficiently low enough for protection of human health and is subject to large variability between laboratories. The fluidized bed asbestos segregator (FBAS) soil preparation method uses air elutriation to separate mineral fibers, such as erionite, from soil particles with higher aerodynamic diameter and deposits those mineral fibers onto filters that can be quantitatively analyzed by microscopic techniques, such as transmission electron microscopy (TEM). In this study, performance evaluation (PE) standards of erionite in soil with nominal concentrations ranging from 0.1% to 0.0001% by weight were prepared using the FBAS soil preparation method and the resulting filters were analyzed by TEM. The analytical results of this study illustrate a linear relationship between the nominal concentration of erionite (as % by weight) in the PE standard and the concentration estimated by TEM analysis expressed as erionite structures per gram of test material (s/g). A method detection limit of 0.003% by weight was achieved, which is approximately 100 times lower than typical detection limits for soils by PLM. The FBAS soil preparation method was also used to evaluate authentic field soil samples to better estimate the concentrations of erionite in soils on a weight percent basis. This study demonstrates the FBAS preparation method, which has already been shown to reliably detect low levels of asbestos in soil, can also be used to quantify low levels of erionite in soil.