A Microorifice Uniform Deposit Impactor (MOUDI): Description, Calibration, and Use

Abstract

An eight-stage cascade impactor, with cut-sizes ranging from 0.056 to 18 pm at a flow rate of 30 L/min, has been developed, calibrated, and tested in field programs. This impactor, called a microorifice uniform deposit impactor, has several features not normally found in cascade impactors. Ultrafine particles as small as 0.056 pm are collected while keeping the pressure drop moderate by utilizing multiple nozzles (up to 2000) as small as 52 pm in diameter. At each stage the collected particles are deposited uniformly over the entire impaction plate by rotating the impaction plate relative to the nozzles and by the correct radial placement of the nozzles. The particle cutoff characteristics (collection efficiency curves) of each stage and interstage losses were determined by means of monodisperse aerosols. The cutoff characteristics were found to he sharp and similar for all stages.

Particulate matter characteristics, dynamics, and sources in an underground mine

“…Therefore, inversion of the raw data using calibrated collection efficiency curves was utilized to improve the size distributions. In this work, the collection efficiency curves for the MOUDI were adopted from Marple et al (1991). The three lowest stages of the MOUDI (cut-off diameters of 10, 18, and 32 nm) were not used in the data inversion because they had usually mass loadings close to or below detection limits of the analytical methods.…”

“…Particulate matter was collected offline by using the Nano-Micro-Orifice, Uniform-Deposit Impactor (Nano-MOUDI II, Model 125R, MSP Corp., Shoreview, USA, Marple et al 1991Marple et al , 2014) that has 13 stages between 10 nm and 10 mm (D a ). Two filter materials were used as substrates in the MOUDI; 3 mm pore size Fluoropore and 0.2 mm pore size polycarbonate membrane filters (Isopore, Merck Millipore Ltd., Billerica, USA).…”

Organic Constituents on the Surfaces of Aerosol Particles from Southern Finland, Amazonia, and California Studied by Vibrational Sum Frequency Generation

“…An example of such a PM1 particle sampler is shown in Figure 2A. More sophisticated approaches employ the use of microorifice uniform-deposit impactors (MOUDI, Figure 2B), 71 which can yield highly size-resolved particle samples down to ten nanometers, depending on the model. Such an approach was used in this work for the collection of particles in the central Amazon Basin.…”

A new methodological approach: The combined use of two-stage streaker samplers and optical particle counters for the characterization of airborne particulate matter

“…Nevertheless, while several devices have been manufactured and are commercially available to count particles and to measure their size distribution with high-time resolution (Knutson and Whitby, 1975;Bu¨ttner, 1990;Fissan et al, 1984;Winklmayr et al, 1991 and others), the assessment of elements and/or compounds size distribution is still quite tricky. Sizesegregated elemental concentration is commonly measured by cascade impactors (Hillamo and Kauppinen, 1991;Marple et al, 1991;Maenhaut et al, 1996) but very hardly they can be used to obtain long temporal trends since any set of filters should be kept under sampling for a few hours and then manually substituted. As a matter of fact, sampling campaigns using impactors often last a few days with a quite limited number of samples collected (Salma et al, 2005 and references therein).…”