Single-stage NBI sampler for PM1 mass and five-stage NBI-NMCI sampler for PM1 mass distribution measurements

In recent years, concerns about the health and environmental risks associated with PM 1 particles have increased. However, existing PM 1 sampling instruments remain to be improved mainly because their PM 1 inlets have particle loading and bounce issues. To address these challenges, PM 1 inlets based on the Non-Bouncing Impactor (NBI) technique were developed. These inlets employ vacuum oil-wetted glass fiber filter (GFF) substrates to eliminate particle bounce and incorporate a daily vacuum oil injection to prevent particle loading. The 16.7 L/min PM 1 NBI, modified from the PM 2.5 M-WINS design with a reduced diameter of the single nozzle, was designed to adapt readily with current standard sampling and monitoring systems. The cut-size (D pa50 ) of 0.99 ± 0.02 μm was determined by considering the effects of Reynold number and the ratio of jet-to-plate distance and nozzle diameter. Field tests comparing the 16.7 L/min PM 1 NBI sampler to the 9-stage NCTU Micro-orifice Cascade Impactor (NMCI 9 ) revealed small sampling biases, with a mean difference of +0.26 ± 2.28 μg/m 3 for PM 1 measurements when silicone oil-coated aluminum foil (AF) and GFF-AF were used in the NMCI 9 . The NBI with the oil-wetted GFF substrate effectively removed particles larger than 1.0 μm, resulting in more accurate PM 1 mass concentration measurements. Additionally, the development of a 5-stage NMCI with the 30 L/min PM 1 NBI as the first stage enabled detailed measurement of PM 1 mass distribution in two modes, which was challenging when measuring the entire mass distribution of ambient aerosols. The distribution of size-dependent water-soluble inorganic ions in PM 1 showed dominance of SO 4 2− and NH 4 + in PM 1 compared to PM 2.5 . In summary, the PM 1 NBI enhances accuracy for long-term atmospheric sampling by addressing particle loading and bounce, making it a more reliable standard sampling instrument. • A 16.7 L/min Non-Bouncing Impactor (NBI) was developed with excellent cutoff characteristics (D pa50 = 0.99 μm). • The 16.7 L/min NBI can easily replace the existing PM 2.5 inlets and adapt readily to the current FRM samplers and FEM monitors. • The 30 L/min NBI was developed and used as the first stage of a 5-stage cascade impactor to remove particles larger than 1.0 μm. • The 5-stage NMCI-NBI enables detailed measurement of PM 1 mass distribution in two modes and its chemical composition.