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

Abstract

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 Ambient air is withdrawn to a particle growth chamber where it mixes with a hot steam flow.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a particle impactor where moisturized aerosol–laden droplets accumulate at the bottom as an aqueous solution, which is withdrawn periodically to a fraction collector.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 PM2.5 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.