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About the Data
Criteria Pollutant Data
- Source: Air Quality System (AQS)
- Selection Methods: All data matching the parameter codes for the pollutants listed below are retrieved from AQS, regardless of monitoring method. In most cases the data are from Federal Reference (or equivalent) Methods. Daily averages from continuous monitors are included for PM10 (in addition to data from the mass instruments). Data from continuous monitors are not included for PM2.5.
- Parameter Descriptions:
| Parameter | Code | Averaging Time | Measurement Units |
| CO | 42101 | Maximum daily 8-hour non-overlapping average | parts per million (ppm) |
| Pb | 12128 | Daily average | micrograms per cubic meter (ug/m3) |
| NO2 | 42602 | Daily average | parts per million (ppm) |
| O3 | 44201 | Maximum daily 8-hour average | parts per million (ppm) |
| PM10 | 81102 | Daily average | micrograms per cubic meter (ug/m3) |
| PM2.5 | 88101 | Daily average | micrograms per cubic meter (ug/m3) |
| SO2 | 42401 | Daily average | parts per million (ppm) |
- AQI Calculations: In some applications, pollutant concentrations are converted to AQI values to display relative magnitude on a normalized scale and to show relevant health implications. The conversions follow the Guideline for Reporting of Daily Air Quality - Air Quality Index (AQI).
PM2.5 Speciation Data
- Source: Air Quality System (AQS)
-
Selection Methods: PM2.5 data from all monitor types are included. The data reflect the actual, "reported sample values" from AQS, except in the cases described below. The table below shows the how data were processed to determine the major PM2.5 chemical speciation components. For further details on these post-processing steps, please see: V. Rao, N. Frank, A. Rush, F. Dimmick, "Chemical Speciation of PM2.5 in Urban and Rural Areas", In the Proceedings of the Air & Waste Management Association Symposium on Air Quality Measurement Methods and Technology, San Francisco, November 13-15, 2002.
- Parameter Descriptions:
| Parameter | Used as Extracted from AQS? | Comments |
| Sulfate (SO4) | Yes | Measured Sulfate |
| Nitrate (NO3) | Yes | Measured Nitrate |
| Ammonium (NH4) | Yes | Measured Ammonium |
| Total Carbonaceous Mass (TCM) | No | TCM calculated as sum of Organic Carbon Mass and Elemental Carbon. Organic Carbon Mass (OCM) is estimated as measured and blank-corrected Organic Carbon multiplied by 1.40. TCM~OCM+EC, where OCM~ OC*1.4. OC is blank corrected based on network wide correction factor. |
| Crustal Material | No | Crustal (or "Fine Soil") component calculated using appropriately weighted trace elements according to IMPROVE-based equation: 2.2[Al] + 2.49 [Si] + 1.63 [Ca] + 2.42 [Fe] + 1.94[Ti] |
- Additional Information: For more information on the PM2.5 speciation network, see http://www.epa.gov/ttn/amtic/siteindx.html