Particle Deagglomeration and Reentrainment in a PM-10 Sampler

Abstract

Field tests have revealed large differences in the sampling efficiencies among PM-10 samplers that previously satisfied EPA performance requirements in wind tunnel testing. To investigate causes due to processes internal to the samplers, a laboratory method was used, based on the introduction of aerosol to the sampler in a manner that approximates ambient sampling. Reentrainment of deposited particles in a dry sampler from air flow alone is found to be negligible, but it is found that particle bombardment can produce significant reentrainment. The main cause of oversampling in the Sierra-Andersen sampler is identified to be the deagglomeration of large soil particles on the impaction surface. Optical counter measurements with soil aerosol show that the mass concentration of particles smaller than 10 μm is 1.6 times greater below the impaction plate than above. Oiling the impaction plate reduces the ratio to 1.1.