What type of sampling can be conducted on bulk materials for asbestos analysis?

The correct choice involves Polarized Light Microscopy (PLM) and Transmission Electron Microscopy (TEM) as the primary methods for analyzing bulk materials for asbestos.

PLM is widely used for its ability to identify asbestos fibers based on their distinct optical properties. This technique utilizes polarized light to examine the crystalline structure of samples, allowing for the identification of asbestos types and concentrations effectively. TEM, on the other hand, provides a more detailed analysis, particularly for identifying smaller fibers and distinguishing asbestos from other similar materials. This high-resolution technique examines the morphology and structural characteristics of fibers, which is crucial when dealing with the fine particles commonly found in bulk samples.

While the other methods mentioned in the options, such as gas chromatography, high-performance liquid chromatography, and visible light spectroscopy, can find applications in various fields, they are not standard or effective methods for asbestos analysis in bulk materials. These techniques are better suited for organic compounds or different types of chemical analyses, making them less relevant in the context of asbestos detection. Thus, PLM and TEM remain the accepted methodologies for accurate asbestos assessment in bulk samples.