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NTN vs CAPMoN UofI statistics students USGS Bucket sampling vs bag sampling USGS field audit

Bias and Uncertainty of NADP Total Inorganic Nitrogen Measurements Greg Wetherbee Mark Rhodes U.S. Geological Survey NADP Program Office - TDEP Committee Meeting Spring 2013. NTN vs CAPMoN UofI statistics students USGS Bucket sampling vs bag sampling USGS field audit

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NTN vs CAPMoN UofI statistics students USGS Bucket sampling vs bag sampling USGS field audit

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  1. Bias and Uncertaintyof NADP Total Inorganic Nitrogen MeasurementsGreg Wetherbee Mark RhodesU.S. Geological Survey NADP Program Office-TDEP Committee Meeting Spring 2013

  2. NTN vs CAPMoN UofI statistics students USGS Bucket sampling vs bag sampling USGS field audit Collocated equipment studies ACM vs ACM collector ACM vs N-CON collector Confidence Intervals

  3. PA15 CAPMoN MIC / MICB NADP ACMs

  4. AIRMoN and NTN Aerochem Metrics 301 CAPMoN MIC

  5. grid sensor AIRMoN and NTN grid sensor CAPMoN

  6. CAPMoN / NADP Co-located Sites • CAPMoN • Daily samples • No Filtration • “Sterile” bag liner in bucket with no transfer to bottles. • MIC opens earlier than ACM at ppt onset • NADP • Weekly samples • Filtered • “DI-cleaned” reuseable buckets (and bottles) are not sterilized • ACM 7-grid sensor

  7. CAPMoN / NADP Co-located Sites • CAPMoN • Analysis by Environment Canada • Science and Technology Branch, Dorsett, Ontario • NADP • Analysis by Illinois State Water Survey • Central Analytical Laboratory, Champaign, IL • Laboratories compare very well! • USGS interlaboratory-comparison program

  8. PA15 CAPMoN – NTN Correlation Values • SO42-: 0.9606 N=1,060 records • NO3-: 0.9296 N=1,060 records • NH4+: 0.843 4 N=1,049 records UofI statistics students 2013 analysis for PA15

  9. Bag Sampling

  10. NTN Bucket Blanks, NH4+

  11. Rank Sum Test p values

  12. How does weekly field exposure of samples affect [N]inorganic? USGS Field Audit Program Results

  13. LOSS CONTAMINATION FIELD AUDIT Nitrate LOSS & CONTAMINATION

  14. Will new N-CON Collectors affect N deposition estimates? Yes

  15. Nitrate CA50 & MA01 ACM ACM N-CON N-CON

  16. Ammonium CA50 & MA01 ACM ACM N-CON N-CON

  17. 2012 Co-located Results N-CON ACM

  18. 2012 Co-located Results N-CON ACM

  19. How much uncertainty isacceptable?

  20. USGS Co-Located Sampler Sites CAN5 OR02 MA01 WI98 CA76 CA50 CO98 CO02 CO00 NM07 AZ03 OK00 TX22 Sites not included in Wetherbee, et al., 2004

  21. The Math Step 1: Calculate 2-sample relative standard deviations for co-located total annual N deposition measurements. Step 2: Compute the average of the 2-sample relative standard deviations for many co-located sites.

  22. Step 3: “Wetherbee’s” Minimum Resolvable Difference Estimator (md) md = .

  23. Confidence Limits CLUpper = md ×Annual Dissolved Inorganic N (kg/ha) CLLower = Annual Dissolved Inorganic N (kg/ha) ÷md Confidence Interval = CLUpper - CLLower

  24. Take-Home Messages Consider data uncertainty for evaluation of critical loads. Inorganic N annual deposition md values 1.254 95% confidence, 1.209 90% confidence, and 1.159 80% confidence

  25. Summary • NADP inorganic N uncertainty = +25% with 95% confidence. • NADP inorganic N contamination happens, but loss is more common - possibly enhanced in regions with fog & drizzle precip types. • CAPMoNNinorg > NADP Ninorg by approximately 15% due to many factors.

  26. Summary • Bag sampling could help preserve Ninorg . • N-CON collector data will predominantly shift [Ninorg ] possitively, but perhaps not for all sites.

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