Abstract
The field-deployable Sunset Semi-Continuous Organic Carbon/Elemental Carbon (Sunset OCEC) aerosol analyzer utilizes the modified National Institute for Occupational Safety and Health thermal-optical method to determine total carbon (TC), organic carbon (OC), and elemental carbon (EC) at near real-time. Two sets of OC and EC are available: thermal OC and EC, and optical OC and EC. The former is obtained by the thermal-optical approach, and the latter is obtained by directly determining EC optically and deriving optical OC from TC. However, the performance of the Sunset OCEC is not yet fully characterized. Two collocated Sunset OCEC analyzers, Unit A and Unit B, were used to determine the pooled relative standard deviation (RSD) and limit of detection (LOD) between September 18 and November 6, 2007 in Richland, WA. The LOD of Unit A was approximately 0.2 μgC/m3 (0.1 μgC/cm2) for TC, optical OC, and thermal OC, and 0.01 μgC/m3 (0.01 μgC/cm 2) for optical EC. Similarly, Unit B had an LOD of approximately 0.3 μgC/m3 (0.2 μgC/cm2) for TC, optical OC, and thermal OC, and 0.02 μgC/m3 (0.01 μgC/cm2) for optical EC. The LOD for thermal EC is estimated to be 0.2 μgC/m3 (0.1 μgC/cm2) for both units. The pooled RSDs were 4.9% for TC (carbon mass loadings 0.6-6.0 μgC/cm2), 5.6% for optical OC (carbon mass loadings 0.6-5.4 μgC/cm2), 5.3% for thermal OC (carbon mass loadings 0.6-5.3 μgC/cm2), and 9.6% for optical EC (carbon mass loadings 0-1.4 μgC/cm2), which indicates good precision between the instruments. The RSD for thermal EC is higher at 24.3% (carbon mass loadings 0-1.2 μgC/cm2). Low EC mass loadings in Richland contributed to the poor RSD of EC. The authors found that excessive noise from the non-dispersive infrared (NDIR) laser in the Sunset OCEC analyzer could result in a worsened determination of OC and EC. It is recommended that a "quieter" NDIR laser and detector be used in the Sunset OCEC analyzer to improve quantification. Future work should re-evaluate the precision of the EC parameters in an environment favorable for EC collection. Investigation among quantification differences using various thermal-optical protocols to determine OC and EC is also in need.
| Original language | English |
|---|---|
| Pages (from-to) | 826-833 |
| Number of pages | 8 |
| Journal | Journal of the Air and Waste Management Association |
| Volume | 59 |
| Issue number | 7 |
| DOIs | |
| State | Published - Jul 2009 |
| Externally published | Yes |
Funding
This research was funded by the Science Undergraduate Laboratory Internship (SULI) program through the U.S. Department of Energy Office of Science, and by the Atmospheric Science Program at PNNL. All work was performed at PNNL, which is operated by Battelle for the U.S. Department of Energy. Jace J. Bauer thanks his mentor, Xiao-Ying Yu, who has always been more than willing to provide the guidance and knowledge necessary to understand and complete this project, and Susan Duhon, for help and support in editing this paper. The authors thank Phil Gram and David Smith of Sunset Laboratories, Inc., for their technical support.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | |
| Pacific Northwest National Laboratory |
