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Data Analysis Techniques Using Hydrocarbon and Carbonyl Compounds
Note: EPA no longer updates this information, but it may be useful as a reference or resource.
Definitions
1996
List of PAMS Target Volatile Organic Compounds
VOC Data Retrieval
Importance of VOC Data Validation
Information Critical to VOC
Data Analysis
VOC Data Validation Tasks
Tips and Tricks for VOC QC and Data
Analysis
Examples of Data QC
Example Data Validation
Tool: VOCDat
Spatial and Temporal Characteristics
Summary
References
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PAMS Target Species
55 C2-C12 hydrocarbons
3 carbonyl compounds
NMHC - Nonmethane Hydrocarbons
Sum of identified species and unidentified mass from C2 through
C12
NMOC - Nonmethane Organic Compounds
Sum of NMHC and carbonyl compounds
VOC - Volatile Organic Compounds
Used in this presentation interchangeably with NMOC
|
Note that many definitions of NMHC, NMOC, and VOC exist; for example, definitions vary widely depending on analytical techniques. |
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| AIRS No. | Abbreviation | Compound | Class |
| 43206 | acety | Acetylene | Olefin |
| 43203 | ethyl | Ethylene | Olefin |
| 43202 | ethan | Ethane | Paraffin |
| 43205 | prpyl | Propylene | Olefin |
| 43204 | propa | Propane | Paraffin |
| 43214 | isbta | Isobutane | Paraffin |
| 43280 | 1bute | 1-Butene | Olefin |
| 43212 | nbuta | n-Butane | Paraffin |
| 43216 | t2bte | trans-2-Butene | Olefin |
| 43217 | c2bte | cis-2-Butene | Olefin |
| 43221 | ispna | Isopentane | Paraffin |
| 43224 | 1pnte | 1-Pentene | Olefin |
| 43220 | npnta | n-Pentane | Paraffin |
| 43243 | ispre | Isoprene | Olefin |
| 43226 | t2pne | trans-2-Pentene | Olefin |
| 43227 | c2pne | cis-2-Pentene | Olefin |
| 43244 | 22dmb | 2,2-Dimethylbutane | Paraffin |
| 43242 | cypna | Cyclopentane | Paraffin |
| 43284 | 23dmb | 2,3-Dimethylbutane | Paraffin |
| 43285 | 2mpna | 2-Methylpentane | Paraffin |
| 43230 | 3mpna | 3-Methylpentane | Paraffin |
| 43246 | 2m1pe | 2-Methyl-1-Pentene | Olefin |
| 43231 | nhexa | n-Hexane | Paraffin |
| 43262 | mcpna | Methylcyclopentane | Paraffin |
| 43247 | 24dmp | 2,4-Dimethylpentane | Paraffin |
| 45201 | benz | Benzene | Aromatic |
| 43248 | cyhxa | Cyclohexane | Paraffin |
| 43263 | 2mhxa | 2-Methylhexane | Paraffin |
| 43291 | 23dmp | 2,3-Dimethylpentane | Paraffin |
| 43249 | 3mhxa | 3-Methylhexane | Paraffin |
| 43250 | 224tmp | 2,2,4-Trimethylpentane | Paraffin |
| 43232 | nhept | n-Heptane | Paraffin |
| 43261 | mcyhx | Methylcyclohexane | Paraffin |
| 43252 | 234tmp | 2,3,4-Trimethylpentane | Paraffin |
| 45202 | tolu | Toluene | Aromatic |
| 43960 | 2mhep | 2-Methylheptane | Paraffin |
| 43253 | 3mhep | 3-Methylheptane | Paraffin |
| 43233 | noct | n-Octane | Paraffin |
| 45203 | ebenz | Ethylbenzene | Aromatic |
| 45109 | m/pxy | m/p-Xylene | Aromatic |
| 45220 | styr | Styrene | Aromatic |
| 45204 | oxyl | o-Xylene | Aromatic |
| 43235 | nnon | n-Nonane | Paraffin |
| 45210 | ispbz | Isopropylbenzene | Aromatic |
| 45209 | npbz | n-Propylbenzene | Aromatic |
| 45208 | 124tmb | 1,2,4-Trimethylbenzene | Aromatic |
| 45207 | 135tmb | 1,3,5-Trimethylbenzene | Aromatic |
| 45211 | oetol | o-Ethyltoluene | Aromatic |
| 45212 | metol | m-Ethyltoluene | Aromatic |
| 45213 | petol | p-Ethyltoluene | Aromatic |
| 45218 | mdeben | m-Diethylbenzene | Aromatic |
| 45219 | pdeben | p-Diethylbenzene | Aromatic |
| 45225 | 123tmb | 1,2,3-Trimethylbenzene | Aromatic |
| 43238 | ndec | n-Decane | Paraffin |
| 43954 | nundc | n-Undecane | Paraffin |
| 43502 | form | Formaldehyde | Carbonyl |
| 43551 | acet | Acetone | Carbonyl |
| 43503 | aceta | Acetaldehyde | Carbonyl |
| 43000 | sum | Sum of target NMHC | |
| 43102 | NMOC | Total NMOC |
Abbreviations from the PAMS manual.
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AIRS Requirements (for importing data to VOCDat):
- Use Report #370 Raw Data Conversion
- Select Card Image File (not workfile)
- Select Action Code = I (for insert)
- Unmark "Generate Workfile" and "Exceptional Data Options"
Example entry for AIRS data retrieval of PAMS hydrocarbon and carbonyl compound data.
|
State |
County |
Site |
Parameter |
Method |
Interval |
Begin Date |
End Date |
| 25 |
013 |
0008 |
L | 940601 | 940930 |
- For sites approved as a PAMS, monitor type=P will download all data from the sites
Example entry for AIRS data retrieval of PAMS hydrocarbon and carbonyl compound data.
| State |
County |
Site |
Parameter |
Method |
Interval |
Begin Date |
End Date |
Monitor Type |
| 09 | 940601 | 940930 | P |
Turbochrome
- CT DEP has documented how to prepare specially formatted *.TX0 files from Perkin-Elmer Auto-GC data
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- Remove calibration data from ambient data.
- Identify operating problems (e.g., cold trap temperature problems).
- Correct misidentification problems.
- Identify potential contamination problems (e.g., shelter off-gassing, handling problems, nearby sources).
|
Result is a more robust database for analyses. |
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Figure 1
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- Sample collection specifications and special features.
- Sampling location description.
- Audit, blank collection, collocated sampler descriptions.
- Sample analysis and instrument calibration descriptions.
- Example calculations of concentrations and any data conversions.
- Laboratory quality control (QC) descriptions.
- Reported units, site, date, sample start and end times, specification of daylight or standard time.
- Treatment of missing data and data below detection.
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- Assess audit results (accuracy).
- Assess laboratory and field blank results.
- Assess collocated sample results (overall precision) and replicate analyses (analytical precision).
- Compare reported speciation to other databases (including special studies data).
- Prepare univariate statistics of concentration and weight fraction:
- Stratify data by date, time of day, and sampling location.
- Determine completeness of data. - Employ graphical procedures including scatter, box-whisker, time series, and fingerprint plots.
- Employ internal consistency checks using ratios of individual species or species group concentrations to other species, NMHC, and CO.
- Example guidelines for flagging samples:
- Carbon fraction of a species exceeds 20 percent of the NMHC or is 3s above the mean of that species.
- Total unidentified NMHC exceeds 15 percent (or user-defined) or is negative (i.e., reported total NMHC is less than the sum of identified species).
- Normally abundant species present in low concentrations when concentrations of other species are high.
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Overall
Total VOC --> Species groups --> Individual species
Inspect every species
Time Series
Inspect time series for the following:
- Large "jumps" or "dips" in the concentrations
- Periodicity of peaks, calibration carryover
- Expected diurnal behavior (i.e., isoprene)
- Expected relationships among species
- High single-hour concentrations of less abundant species
Scatter Plots
Prepare scatter plots of the following:
- Total NMOC vs. species group totals, vs. individual species
- Benzene vs. Toluene, Acetylene, Ethane
- Species that elute close together
- Isomers
- Other
Fingerprints
Prepare and inspect fingerprint plots for the following:
- Identify calibration data.
- Investigate hours surrounding suspect and invalid data.
- Obtain overall view of diurnal changes.
Additional Data
To further investigate outliers, use:
- Wind direction data
- Other air quality data (e.g., ozone, NOx)
- Subsets of data (e.g., high ozone days only)
- Industrial or agricultural operating schedules
- Traffic patterns
- Other
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EXAMPLES OF DATA QC
- Species group time series - example of misidentification
- Species time series - example of contamination
- Species time series - change in species reporting
- Species time series - example of misidentification
- Scatter plot - example of misidentification
- Fingerprint - example of "typical" data
- Fingerprint - example of calibration data
- Species time series - example of calibration "carryover"
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Figure 2
Time series plot of several species groups at Stafford, CT in 1994. Example of misidenitification of a parrafin for an unidentified peak. (Level 0, preliminary data, CT DEP)
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Figure 3
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Figure 4
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Figure 5
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Figure 6
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Figure 7
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Figure 8
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VOCDat is a Windows-based, menu-driven program providing a graphical platform to:
- Display VOC data.
- Perform QC tasks on the data.
- Begin data analyses.
VOCDat was initially designed for auto-GC (hourly data) but may also be used for data collected over other intervals and in canisters.
VOCDat provides the following features:
- Import AIRS format or Turbochrome files.
- Edit data QC codes on-screen (keep log of changes).
- Compare data among sites.
- Prepare and print graphical displays.
- Export to AIRS format.
Figure 9
VOCDat allows the analyst to rapidly gain knowledge of the database. |
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- Histogram
- Summary statistics
- Composition - box plots by time of day, date
- Inter-species relationships - scatter plot matrices
- Species
- Comparison between sites
- Change with time of day
- "Aged" vs. "Fresh" fingerprints
- Isoprene and acetylene diurnal profiles
- Surface vs. aloft VOC - Use of data subsets (stratifying data)
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Figure 10
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Figure 11
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Figure 12
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Figure 13
Box plot of total NMHC by hour (CST) during June 1996 at Chicago, IL (top) and Gary, IN (bottom). Note that nine data values greater than 500 ppbC were omitted from the Chicago box plot for clarity. (Level 1, AIRS data)
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Figure 14
Box plots of total NMHC by date during June 1996 at Chicago, IL (top) and Gary, IN (bottom). Note that nine data values greater than 500 ppbC were omitted from the Chicago box plot for clarity. (Level 1, AIRS data)
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Figure 15
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Figure 16
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Figure 17
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Figure 18
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Figure 19
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Figure 20
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Figure 21
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Figure 22
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Figure 23
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Most of the QC and data analysis techniques shown may be applied to all four PAMS site types.
| Analysis/Procedure | Objectives |
| Data Validation: Scatter plots Time series Fingerprints Box plots Summary statistics |
Prepare robust database: identify outliers, invalid data; investigate diurnal behavior, relationships, patterns |
| Frequency Distributions | Overall view of database |
| Spatial and Temporal: Bar, line, box plots Maps |
Identify and explore spatial, temporal variations in data |
| Inter-Site Comparisons: Scatter, relational plots |
Assess transport, emission sources, species relationships |
| Inter-Species Comparisons: Scatter plot matrices Linear regression |
Investigate species relationships, emission sources |
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