Resuspension of Threat Agents from Paved Surfaces and Recommended Resuspension Factors — Field Experiments with Pedestrian or Personnel Activity and Vehicles

Resuspension of hazardous particles from paved surfaces poses significant risks during radiological contamination scenarios. Accurate modeling of particle resuspension dynamics is essential for developing effective mitigation strategies and ensuring public and responder safety. However, default resuspension factors in models may underestimate risks, particularly during emergency operations involving pedestrian and vehicle activity on freshly contaminated surfaces. To address these gaps, we conducted pilot-scale field experiments using Arizona Test Dust (ATD) as a surrogate for threat agents. Human activities included casual walking, vigorous walking (marching), and vacuuming on concrete surfaces, while vehicle tests involved driving a sport utility vehicle (SUV) over asphalt in both drive-through (tires passing over dust) and drive-over (undercarriage passing over dust) configurations. Resuspension factors (Sf) were calculated for particle size ranges from 0.5-10 µm. Casual walking produced low resuspension factors, from <10-5 m-1 for 0.5-1.0 μm particles to <3 × 10-3 m-1 for 5-10 μm particles. In contrast, marching, which served as a surrogate for vigorous pedestrian or personnel movement, substantially increased resuspension, with Sf values ranging from 2 × 10-5 m-1 at 0.1-1 μm to 2 × 10-3 m-1 for 5-10 μm particles. Vacuuming caused measurable resuspension for smaller particles (Sf = 1.4 × 10-3 m-1), while larger particles remained undetectable. Vehicle tests showed higher resuspension factors for larger particles, with Sf values ranging from 3 × 10-4 m-1 to 2 × 10-2 m-1 during the first pass. Subsequent passes eventually reduced resuspension factors by an order of magnitude. These findings reveal significantly higher resuspension during emergency operations than many models assume. Our results apply to scenarios involving radioactive fallout, chemical, and biological agents, offering critical data to improve contamination control, emergency response planning, and risk assessment models.