Optical microscopy is a useful tool in dust characterisation and environmental forensics. An in-house methodology has been developed at DustScanAQ that is based on established techniques employed in a variety of fields such as mineralogy, petrography, palynology and pedology. DustScanAQ uses a standard petrological microscope with additional lighting capabilities to analyse mounted dust samples. With this setup, it is possible to view dust samples under different lighting conditions including reflected light, plane polarised (transmitted) light and cross polarised (transmitted) light. Typically, microscopy is used to examine the physical properties of dust including the colour, morphology, approximate size, relative proportion, lustre, as well as opacity and other refractive properties.
Dust samples collected using DustScan directional or depositional dust monitoring equipment may be analysed using optical microscopy by removing a sub-sample of the material and mounting on a glass slide. Loose deposited dust sweepings can also be prepared for analysis in a similar manner.
It is useful to obtain reference samples of materials handled onsite to use as a comparison. Any samples collected by clients using methods other than DustScan monitoring equipment should be supplied in a clear polythene bag or suitable sealable container.
The results of optical microscopy analysis are presented in a short detailed report with example images of the materials observed and a brief written interpretation. Common materials that can be identified include; mineral grains, metallic fragments, organic and synthetic fibres, pollen, coal dust and tyre rubber.