Collection characteristics of a batch-type wetted wall bioaerosol sampling cyclone

Abstract

The collection efficiency and sample retention of a batch-type wetted wall bioaerosol sampling cyclone (BWWC) were experimentally characterized. The BWWC is designed to sample air at 400 l/min and concentrate the particles into 12 ml of water. Aerosol is transported into a cylindrically-shaped axial flow cyclone through a tangential slot and the particles are impacted on the inner wall, which is wetted by air shear acting on a liquid pool at the base of the cyclone. The retention of collected particles and the aerosol collection efficiency of the BWWC were evaluated with polystyrene latex beads (PSL), sodium fluorescein/oleic acid droplets, and Bacillus atrophaeus (aka BG) spores. The retention of particles was determined by adding hydrosol directly into the device, running the BWWC for a pre-set period of time, and then determining the amount of particulate matter recovered relative to the initial amount. For 1-lm diameter PSL, 90% of the particles were recoverable from the cyclone body immediately after their introduction; however, only 10% were retained in the collection liquid after 8 h of operation. The aerosol sampling efficiency was determined by comparing the amount of particulate matter collected in the liquid with that collected by a reference filter. The collection efficiency was 50-60% for 1-and 3-lm polystyrene (PSL) particles, and 1.5% for 10-lm oleic acid particles. The efficiency for 3-lm oleic acid droplets was 35%. Explanations are provided for the difference between liquid and solid particle behavior, and for the low efficiency for the large liquid particles. The collection efficiency for single spore BG was slightly lower than that for 1-lm PSL.

Diversity of airborne bacteria in samples collected using different devices for aerosol collection

“…If the composition of microorganisms in the sample stays the same as in the ambient air, the sampling efficiency is not all that important for determining microbial diversity as long as enough material can be collected for further analysis. However, different samplers also perform differently as a function of particle size (Kesavan et al 2010;King et al 2009). This is considerably more serious, since if the size of collected particles changes with sampling approach, the results will inevitably be affected since the diameter of airborne microorganisms can vary from tens of nanometers to one hundred micrometer (Wittmaack et al 2005).…”

“…However, the extant studies use various sampling approaches, which complicates the comparison of microbial communities, diversity, and ecology. While many studies have compared the sampling efficiency of different aerosol collectors (Fields et al 1974;Jensen et al 1992;Kesavan et al 2010;King et al 2009;Whyte et al 2007), no study, to the best of our knowledge, has addressed how the sampling strategy can affect apparent microbial diversity of air samples. Since different devices have different particle cut-off diameter, the choice of sampling technique may certainly affect the composition of the sampled community; let alone the most common bacteria may range in diameter from 0.1 to 5 lm, while airborne fungal spores and algae are typically 5-15 lm and may be as large 100 lm (Tormo et al 2001;Wittmaack et al 2005).…”

Development of an automated wet-cyclone system for rapid, continuous and enriched bioaerosol sampling and its application to real-time detection

“…Such systems achieve high sampling performance and enable the concentration of samples due to the high flow rate ratio between the incoming air and drainage liquid. Considerable research has focused on the development of wet-cyclone bioaerosol samplers [26][27][28][29][30]; however, these have a large particle cut-off diameter, and a low particle collection efficiency and aerosol-to-liquid transfer rate; furthermore, the twophase flow operation is unstable and few fully integrated bioaerosol sampling systems are capable of continuous real-time sampling.…”

Development of an Automated Electrostatic Sampler (AES) for Bioaerosol Detection

“…Among the aerosol-to-hydrosol sampling technologies developed King et al 2009;McFarland et al 2010), use of electrostatic sampling for collecting bioaerosols is increasing (Mainelis et al 1999(Mainelis et al , 2002bYao and Mainelis 2006;Han and Mainelis 2008;Madsen and Sharma 2008;Yao et al 2009;Han et al 2010). Electrostatic sampling technique is a collection method that uses the electrostatic field to collect the charged bioaerosols.…”