Field validation of the new miniature Versatile Aerosol Concentration Enrichment System (mVACES)

Recently a new compact aerosol concentration enrichment system was developed at the University of Southern California, specifically intended to provide particle-laden air at flow rates and pressures suitable for interfacing with on-line continuous aerosol instrumentation for chemical analysis such as mass spectrometers. The re-design and engineering of the miniature Versatile Aerosol Concentration Enrichment System (mVACES) and primarily laboratory-based validation of the individual components and overall system has been previously reported (Geller et al. 2005). From September to December 2005, a field performance validation study of the mVACES was conducted in Los Angeles, California at a mixed urban site influenced by both freeway traffic and construction. A variety of continuous and semi-continuous physical and chemical composition measurements were performed to assess the performance of the mVACES compared to accepted methods for validation. Near-ideal performance for aerosol concentration enhancement by the mVACES was observed for mass and number distribution with minimal evidence for distortion of the size distribution. Similarly, near-ideal concentration enhancement factors were observed for both inorganic and organic species suggesting that the mVACES works equally well across the range of externally mixed urban aerosol. The data suggest that aerosol concentration enhancements up to an ideal factor of 20 in a delivered flow on the order of 1.5 liters min(-1) are readily achievable in an urban environment for the ambient conditions studied.