Applicability of a Portable Particle Monitor for Measuring TSP and PM10 in the Ambient Environment

Abstract

The National Ambient Air Quality Standard (NAAQS) was established and revised to regulate PM10 (particles less than or equal to 10 μm in aerodynamic diameter), as these small particles were found to penetrate and deposit in human respiratory tract, causing adverse health effects. The FRM and FEM sampler designated by the USEPA to monitor PM10 and Total Suspended Particles (TSP) mass concentration require either expensive equipment or tedious tests. In many cases, a faster and easier measurement is desired. The goal of this study was to test the applicability of a handheld particle monitor (Aerocet 831, Met One Instruments, Grants Pass, OR) for monitoring PM10 and TSP in the ambient air. This monitor is capable of measuring PM10 and TSP mass concentration in just one minute. To achieve this goal, monodisperse solid ammonium fluorescein aerosols of aerodynamic diameter 3, 5, 7, 9, 10, 11, 13, 15, and 17 μm were generated and introduced into wind tunnel at speed of 2, 8 and 24 km/h. The Aerocet 831 and an isokinetic (reference) air sampler were co-located in the wind tunnel to monitor and collect aerosols simultaneously. Separate tests were performed to find out a mathematical correlation equation between fluorescence intensity unit (FIU) and a wide range of fluorescein particle mass (0-240 μg). The FIU of the particles deposited on filter of isokinetic sampler in each wind tunnel test was measured and converted to particle mass using the correlation equation. Then the sampling effectiveness values were obtained, corrected and fitted to lognormal distribution curves. The Aerocet 831 is suggested having good performance for monitoring PM10 at wind speed of 2 km/h, however its applicability for measuring PM10 at 8 and 24 km/h is limited due to the oversampling at small particle sizes. It is expected for the Aerocet 831 to be able to monitor TSP in a size range of 0 to 50 μm, but the maximum particle size detection of Aerocet 831 shown from the TSP sampling effectiveness curves is only about 23 μm.