Highly Time Resolved Fine Particle Nitrate Measurements at the Baltimore Supersite

Details

• Personal Author:
  Buckley T ; Harrison D ; Jayanty RKM ; Kim SR ; Ondov J ; Park SS
• Description:
  Nitrate in particles smaller than 2.5 µm was measured at 10-min intervals at the Baltimore Supersite in east Baltimore from 14 February through 30 November 2002, using the R&P 8400N semicontinuous monitor to determine its contributions to fine-particle aerosol mass concentrations. Comparison with 24-h filter-based measurements, revealed a discrepancy of 33% between the 24-h averages derived from the two methods, for most of the 9.5 month study period, despite corrections for conversion efficiency and Reaction Cell Pressure deviations, suggesting a true conversion efficiency of 68%. Estimates of precision in individual 10-min measurements averaged 8.7% and ranged from 6.3% to 23%, excluding uncertainty encompassing dissociation losses. Uncertainties in 24-h averages of the 10-min measurements were generally larger (median of 9.1%) owing to missing or invalid values. The detection limits for 24-h averaged and 10-min concentrations were typically 0.17 and 0.24 µg m-3, respectively, during the study (both after slope correction to achieve agreement with 24-h speciation measurements). Regression slopes were statistically equivalent for all months except February and October (an outlier not understood). Intercepts were generally small and insignificant. Good agreement between the 24-h data sets was achieved after the monthly mean regression slopes were applied to the 10-min data. In February, when flat flash strips were used and instrument compartment/outdoor ambient temperature differences were often severe, the regression slope was statistically larger than the average for the remaining months and the intercept was positive and significant. Results of a nonlinear least squares model used to estimate dissociation losses suggest that the largest errors occurred when concentrations are near the detection limit, instrument-outdoor temperature differences were large, and ambient RH low (<40%), i.e., conditions which most frequently and severely occurred in February and March. In February, dissociation losses as large as 1.65 µg m-3 (100% of the slope-corrected measured value) may have occurred and such losses were predicted to be >30% in 63.5% of the 10-min measurements for that month. However, model predictions for the other months, when new ridged-flash strips were used, suggest that dissociation losses were much less significant, i.e., <15% in >95% of the measurements. Our experience suggests that the semicontinuous monitor can produce reliable 24-average concentrations when instrument-outdoor differences are kept small, an independent measurement is used to correct the data, and are improved when grooved flash strips are used. [Description provided by NIOSH]
• Subjects:
  Aerosols Air Pollutants, Occupational Air Pollution Air Pollution, Indoor Dust Environmental Monitoring Occupational Health Particulate Matter Safety
• Keywords:
  Aerosol-particles Air-contamination Air-quality Air-quality-control Air-quality-measurement Air-quality-monitoring Air-samples Air-sampling Air-sampling-equipment Airborne-dusts Airborne-fibers Airborne-particles Author Keywords: Nitrate Measurement-equipment Monitoring-systems Monitors Nanotechnology Particulates R&P8400N Semicontinuous Nitrate Monitor

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• ISSN:
  1352-2310
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  Maryland ; North Carolina ; OSHA Region 3 ; OSHA Region 4
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  38
• Issue:
  31
• NIOSHTIC Number:
  nn:20037335
• Citation:
  Atmos Environ 2004 Oct; 38(31):5321-5332
• Contact Point Address:
  John Ondov, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA
• Email:
  jondov@wam.umd.umd
• Federal Fiscal Year:
  2005
• Performing Organization:
  Johns Hopkins University
• Peer Reviewed:
  True
• Start Date:
  20050701
• Source Full Name:
  Atmospheric Environment
• End Date:
  20280630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:be77913e938e68bb779e509dd344118f8902887807d3ca3bcd284aad119bd3ea06a1f32c295984f18ede5b83b22d07f373c58a815d64dbaafffbf4d490d01925
• Download URL:
  https://stacks.cdc.gov/view/cdc/188440/cdc_188440_DS1.pdf
• File Type:
  [PDF - 632.89 KB ]