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STN Carbon Field Blank Analysis, Derived Organic Carbon Analysis and IMPROVE blank corrected artifact analysis Bret Schichtel.

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Presentation on theme: "STN Carbon Field Blank Analysis, Derived Organic Carbon Analysis and IMPROVE blank corrected artifact analysis Bret Schichtel."— Presentation transcript:

1 STN Carbon Field Blank Analysis, Derived Organic Carbon Analysis and IMPROVE blank corrected artifact analysis Bret Schichtel

2 Incomplete Observations from Analysis STN field blank carbon concentrations Met One, Anderson and R & P 2300 have similar field blank concentrations Urg and R & P 2025 samplers have carbon concentrations a factor of 2 to 4 smaller than the other samplers. There is little seasonality in the field blank carbon concentrations. Appears to be some spatial variability with the Eastern U.S. having higher blank values than most of the west. However, there are plenty of exceptions making any definitive statement on the spatial variability difficult to judge.

3 Incomplete Observations from Analysis Derived Carbon Artifacts from STN Data There is a strong seasonality in the derived artifact with summer values 50 – 100% higher than winter. Spring and Fall are between the winter and summer values. The winter artifacts are similar to the field blank carbon concentrations Like the field blanks, Met One, Anderson and R & P 2300 have similar carbon artifacts with smaller values for the Urg samplers There is a strong spatial variability with lower artifacts in the Eastern U.S. (opposite the field blanks) during the winter, spring and fall. During the summer the lowest artifacts are generally at the northern sites. The highest artifacts occur in southern California The site by site difference between the field blanks and derived carbon artifact are compared in Slide 23. As shown the field blanks are typically larger than the derived artifact in the eastern US and smaller in the west and midwest.

4 Incomplete Observations from Analysis Derived Carbon Artifacts from IMPROVE Data (OC vs PM) On average the derived carbon artifacts are small, but positive, 0.1 to 0.4 micro-grams/m3 –The IMPROVE artifact correction appears to work! Weak seasonality in the carbon artifacts Weak spatial variability during winter, spring and fall with somewhat higher values in the eastern U.S. than west Strong spatial variability during the summer with concentrations of 0.5 to 1 micro-g/m3 in the eastern U.S. and Southwest but ~0 micro-g/m3 in the northwest and north great plains.

5 STN Carbon Artifact Correction The analyses clearly shows a large positive organic carbon artifact on the STN filters. On average, the STN field blanks and derived carbon artifacts are consistent during the winter, spring and fall. However, the summer field blanks are 50%-100% smaller during the summer. This is consistent with the IMPROVE data in the eastern and southwestern U.S. It is not apparent if the carbon artifact is actually larger than the field blank during the summer or if this is an “artifact” of the analysis. The field blanks and derived artifacts have different seasonality. It is not clear what is driving these differences. Does the “true” carbon artifact have a different seasonal pattern than the field blanks or is the seasonal variation an “artifact” of the analysis? Base on this STN will be carbon artifact corrected similar to IMPROVE, i.e. estimate a seasonal artifact from the field blanks and apply to all sites.

6 Seasonal median of STN Carbon Field Blanks Met One Sampler, trip blnks used for missing field blnks WinterSpring SummerFall

7 Seasonal median of STN Carbon Field Blanks Anderson Sampler, trip blnks used for missing field blnks WinterSpring SummerFall

8 Seasonal median of STN Carbon Field Blanks Urg Sampler, trip blnks used for missing field blnks WinterSpring SummerFall

9 Seasonal median of STN Carbon Field Blanks R&P 2025 Sampler, trip blnks used for missing field blnks WinterSpring SummerFall

10 Seasonal median of STN Carbon Field Blanks R&P 2300 Sampler, trip blnks used for missing field blnks WinterSpring SummerFall

11 STN Carbon Blank Stats

12 Comparison of OC vs PM The OC artifact is approximated by regressing the measured OC against measured PM or PM minus aerosol components The Theil regression is used with the slope fitted thought the medians to find the intercept. To reduce the variability, the data were first sorted by the PM concentrations and placed into 33 to 100 bins. The data in each bin were averaged together and regressed against each other. The analysis is conducted for each season, for the different samplers and for PM, PM minus Amm. Sulfate, Fine Soil; and PM minus Amm. Sulfate, Fine Soil, Amm. Nitrate and EC. The analysis was conducted by first aggregating the data from all sites together, then conducting the regression on each individual site and aggregating the results together. The following slides presents the scatter plots and statistics for the aggregation of data across all sites. Note only the scatter plots for the OC vs PM minus Amm. Sulfate, Fine Soil

13 Seasonal OC vs PM2.5: Met One Sampler, All Sites Data sorted on PM, placed into 100 bins and averaged White line – Theil Regression Megenta – Linear Regression

14 Seasonal OC vs PM2.5: Anderson Sampler, All Sites Data sorted on PM, placed into 33 bins and averaged

15 Seasonal OC vs PM2.5: Urg Sampler, All Sites Data sorted on PM, placed into 33 bins and averaged

16 Seasonal OC vs PM2.5: R&P Seq. Quartz, All Sites Data sorted on PM, placed into 33 bins and averaged

17 Seasonal OC vs PM2.5: R&P Seq. Quartz VSCC, All Sites Data sorted on PM, placed into 33 bins and averaged

18 Seasonal OC vs PM2.5: R&P 2300 Seq Quartz, All Sites Data sorted on PM, placed into 33 bins and averaged

19 OC vs PM at individual sites - Spatial Variation in the Carbon Artifact Spatial analysis of derived organic artifact –Used Theil regression comparing measured OC to reconstructed OC where reconstructed OC, OCrec = (PM2.5 – Ammonium Sulfate – Fine Soil)/1.4 At each monitoring site. –Data were sorted on OCrec and placed into 33 bin. The OC and OCrec in each bin was averaged together. –All figures are for only the Met One sampler.

20 Theil Intercept from OC vs. (PM2.5 – Amm SO4 – Fine Soil) Met One Sampler for sites with r>0.7

21 Median of the Regression Line Intercept, Slope, correlation across all Sites with r > 0.7, for each season and each sampler Compared OC to PM2.5 – Amm. SO4 - Soil Compared OC to PM2.5

22 Median of the Regression Line Intercept, Slope, correlation across all Sites with r > 0.7, for each season and each sampler Compared OC to PM2.5 – Amm. SO4 - Soil

23 Difference Plots: Derived Artifact - Field Blank at each site then contoured This is for the Met One Sampler, derived used PM-AS-Soil Similar to the Slide 26 – IMPROVE derived artifact from blank corrected data Winter: Avg=0.11; median=0.04 ug/m3 Spring: Avg=0.2; median=0.24 ug/m3 Summer: Avg=0.57; median=0.61 ug/m3 Fall : Avg=0.24; median=0.2 ug/m3

24 IMPROVE data Data from all sites were used in the following analyses

25 Seasonal OC vs PM2.5: IMPROVE, All Sites ( ) Data sorted on PM, placed into 150 bins and averaged

26 Seasonal theil Intercept from OC vs. (PM2.5 – Amm SO4 – Fine Soil) with r>0.7, IMPROVE data WinterSpring SummerFall

27 Median of the Regression Line Intercept, Slope, correlation across all Sites with r > 0.7, for each season

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29 Others Spatial patterns of derived carbon artifact from STN data for each season, sampler and different PM minus aerosol components

30 Monitor (813=Met one), Season (0=win), OCrec (0 = (PM25- AS-Soil-AN-EC)/1.4)

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