A Granular Bed for Use in a Nanoparticle Respiratory Deposition Sampler

Area of Science:

• Environmental Science
• Materials Science
• Aerosol Science

Background:

• Nylon mesh screens are commonly used in nanoparticle respiratory deposition (NRD) samplers.
• Limitations exist in current NRD sampling methods for nanoparticles.

Purpose of the Study:

• To design and evaluate a granular bed as an alternative collection medium for NRD samplers.
• To compare the collection efficiency of the granular bed with theoretical models and the nanoparticulate matter (NPM) criterion.

Main Methods:

• A five-layer granular bed sampler was constructed with alternating mesh and bead layers.
• Collection efficiency was tested using varying small-bead layer depths and different particle shapes (cuboid and fractal).
• Experimental data were compared against theoretical predictions and the NPM criterion.

Main Results:

• The granular bed's collection efficiency curve shape closely matched the NPM criterion.
• Increasing the small-bead layer depth enhanced collection efficiency, shifting the 50% collection efficiency size (d50) for salt particles from 25 nm to 45 nm.
• Fractal particles larger than 50 nm showed higher collection efficiency than cuboid particles, likely due to increased interception.

Conclusions:

• The granular bed demonstrates effective nanoparticle collection, aligning with respiratory deposition principles.
• A 3.2 mm small-bead layer depth provided the best fit to the NPM criterion.
• The granular bed is a viable alternative to nylon mesh for NRD sampling, particularly for diverse nanoparticle shapes.