A method for dry extracting large volumes of fine particulate matter from bulk soil samples

A significant part of ambient dust consists of fine particles derived from natural soils. Because many toxic constituents are concentrated in the smallest particle fractions, and because these small particulates are the most easily inhaled, the fine-particle fraction of soil (PM10 and smaller) is what presents the greatest health concern. Assessing the potential risk of a soil requires examining its chemical content, its biological and mineralogical composition, its sedimentological characteristics, detailed data on grain size distribution, and other information. This analysis requires a relatively large mass of appropriate size fraction(s), obtained by dry extraction. Most methods for extracting fine particulates from soil collect only small amounts of sediment, or use wet extraction. This paper describes the Soil Fine Particle Extractor, a setup for dry extracting large volumes (dozens of grams and more) of fine particulate matter (PM10 and smaller) from bulk soil samples. Separation takes place in two steps. Primary separation in a cylindrical separator 70?cm high and 40?cm in diameter removes all coarse particles from the sample. The remaining sediment then flows through a 200?cm long and 7?cm diameter inclined elutriator connected to a three-engine vacuum cleaner. The setup allows extraction of different size fractions depending on the adjustment of the control parameters (suction rate, length, diameter and inclination of the elutriator, thickness of the sediment layer drawn in by the system). The article presents examples of extractions from soil collected in loess and desert environments, ranging from PM2.5 to PM10. It also evaluates the efficiency of the technique by investigating the extraction efficiency for a large number of particle sizes, varying from 0.1 to 70???m. Extraction occurs most efficiently for particles between 1 and 10???m, with an optimum around 5???m.