A compact semi-continuous atmospheric aerosol sampler for elemental analysis: A preliminary result

A compact semi-continuous atmospheric aerosol sampler has been developed for subsequent elemental analysis by inductively coupled plasma mass spectrometry (ICP-MS). The sampler is basically a downsized and simplified version of the University of Maryland Semi-continuous Element in Aerosol Sampler-II (SEAS-II) and is hereafter referred to as the Korean version of SEAS (KSEAS). It has four major components: a steam generator, a particle growth chamber, a particle impactor, and a fractional XY collector. The air flow rate of this sampler is 16.7 L min^-1, roughly one fifth of the flow rate of SEAS- II. Due to the lower volume sampling rate, a virtual impactor is not needed, which makes it simple to fabricate and use. The absence of a virtual impactor also improves sample collection efficiency. Ambient air is withdrawn to a particle growth chamber where it mixes with a hot steam flow. As the resulting supersaturated air flows downward, its temperature decreases due to heat loss to the lower part of the water-chilled glass wall. Finally, air-flow is directed to a particle impactor where moisturized aerosol-laden droplets accumulate at the bottom as an aqueous solution, which is withdrawn periodically to a fraction collector. To evaluate the validity and field applicability of our sampler, we used it and SEAS-II to collect PM_2.5 and PM₁₀ in Seoul, Korea over the period of a month. Collected samples were analyzed for several key elements using ICP-MS. Elemental analysis results showed good to excellent correlation coefficients, ranging from 0.3~0.9 (n = 586), between the two samplers, confirming the validity of KSEAS. Due to the lower volume sampling rate, the detection limits of KSEAS is higher than those of SEAS-II (2~5 times higher). However, lower sampling volume needs lower power for operation and provides a better field applicability.