Intercomparison and Evaluation of Semi-Continuous PM-2.5 Nitrate and Sulfate Instruments During PMTACS-NY Summer 2001 Campaign in New York City

During the PM2.5 Technology Assessment and Characterization Study (PMTACS-NY) intensive measurement campaign in New York City (Queens) during Summer 2001, several semi-continuous PM-2.5 nitrate and sulfate instruments were deployed and operated side-by-side. The instruments were Rupprecht and Patashnick Ambient Particulate Nitrate Monitor (8400N) and Ambient Particulate Sulfate Monitor (8400S), an Aerodyne Research, Inc. Aerosol Mass Spectrometer (AMS), a Particle into Liquid Sampler with IC (PILS-IC) developed by Georgia Institute of Technology, and a Continuous Sulfate Monitor developed by George Allen at Harvard School of Public Health (HSPH). The performance of each of the instruments in the field is described briefly. The intercomparison of the sulfate mass concentration measurements from the four semi-continuous instruments yields almost one-to-one correlation between four instruments with correlation coefficients (R²) values above 0.9. The intercomparison of the nitrate measurements from the three semi-continuous instruments yields (R²) values of approximately 0.9. The 8400N results are lower than the PILS-IC and AMS values. The AMS and PILS-IC mass concentrations agree within 10%. Semi-continuous nitrate measurements are compared against one set of 24-hour filter samples analyzed by ion chromatography. Semi-continuous sulfate measurements are compared against three sets of 24-hour filter samples and one set of 6-hour filter samples. Semi-continuous particulate nitrate and sulfate measurements are highly correlated to the filter samples with (R²)greater than 0.9. It appears that PILS and AMS nitrate measurements agree with the filter results to within 10%, while the 8400N nitrate mass concentration measurements are biased low by ~ 33%. Comparison of semi-continuous particulate sulfate measurements with the filter measurements shows that the former are biased low by about 15%. Possible explanations for these biases will be discussed.