Importance of Background Samples - CLRA Conference 2012


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Presentation given at Alberta CLRA conference in 2012 on the importance of background samples. Brief covers case study for naturally elevated metals in undisclosed location in Alberta.

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Importance of Background Samples - CLRA Conference 2012

  1. 1. Importance of Knowing What is Normal (the need for control or background samples)? Court D. Sandau, PhD, PChem CLRA Alberta Chapter 2012 Conference
  2. 2. Good Science, Needs Control • All investigations require control samples • Controls are needed to eliminate alternate explanations of experimental results – Environmental investigations general hypothesis – “Is the site contaminated?”
  3. 3. Other Terms
  4. 4. Case Studies for Controls
  5. 5. Arson Investigations • Controls are called comparison samples – Not known until after analyzed, whether or not accelerants are present
  6. 6. Litigation Cases • Sample unusual locations – Furnace filters – Furnace ducting – Attic dust • Controls deliberately left out as concentrations of contaminants are usually found to be “normal” • Without controls, +ve hit indicates pollution, which could = $$$
  7. 7. Litigation • Sampling homes or yards from surrounding municipalities • Sampled carpet dust (exposure) and soils (guidelines) • Provides comparison data to otherwise unknown levels of contaminants in unfamiliar matrices
  8. 8. Metals Case Study • Development of historical pasture/farm land adjacent to municipality in Alberta • Approximately ½ quarter section • No known or identifiable sources of anthropogenic contamination • Potential for incidental farm related spills • No visible signs of impacts
  9. 9. Definitions for Soil Background • Environmental Geochemistry Definition – relative measure to distinguish between natural element or compound concentrations and anthropogenically influenced concentrations in‐ real sample collectives (Matschullat et al. 2000) • ISO soil background content guidance – Content of a substance in a soil resulting from both natural geological and pedological processes and including diffuse source inputs (BS EN ISO 19258)
  10. 10. Soil Sampling • Consultant identified arsenic exceedances of Tier 1 AB Guidelines (17 mg/kg) • Consultant undertook vigorous sampling program n = 473 samples (surface to 2 mbg) n = 18 background samples • Comprehensive, but limited to arsenic and a few other metals (barium, selenium and thallium)
  11. 11. Choosing Location for Background • Concentration will vary with soil parent material, soil depth, and hydrologic regime • Sufficient (?) representative samples outside area affected (more than 3) • Statistical analysis likely required Systematic grid Define average
  12. 12. Regulations or Guidance PROTOCOL FOR THE CONTAMINATED SITES REGULATION UNDER THE ENVIRONMENT ACT PROTOCOL NO. 9: Determining Background Soil Quality Prepared pursuant to Part 6 – Administration, Section 21, Contaminated Sites Regulation, OIC 2002/171 The Contaminated Sites Regulation provides a "release" as a contaminated site when the concentrations of substances at a site do not exceed local background levels. EPA 540-R-01-003 OSWER 9285.7-41 September 2002 Guidance for Comparing Background and Chemical Concentrations in Soil for CERCLA Sites Office of Emergency and Remedial Response U.S. Environmental Protection Agency Washington, DC 20460 If background levels exceed remediation criteria, it is futile to reduce the contamination levels to meet the remediation criteria. It is only possible to remediate to background levels. Environment Canada (http:// tab08- e.html)
  13. 13. Site Data x = 11.5 GM = 8.1 Max = 45.0 95% = 26.0 95UCL = 12.3 Med = 9.3 23% Above
  14. 14. Control Data x = 14.9 GM = 11.0 Max = 29.0 95% = 29.0 95UCL = 19.4 Med = 19.4 44% Above
  15. 15. Results • Site is similar to background site • Site likely has baseline levels of arsenic that sporadically exceed Tier 1 (17 mg/kg) and Soil contact (21 mg/kg) guidelines • Presented to regulators and stakeholders
  16. 16. Alberta Guidelines ALBERTA TIER 2 SOIL AND GROUNDWATER REMEDIATION GUIDELINES 2.4.2 Background Soil Quality …In cases ‘where’ the natural background is demonstrated to be greater than Tier 1 guidelines, the remediation level shall be to natural background or to guidelines developed using Tier 2 procedures.
  17. 17. Results of Study • Definitively proved background concentrations exceeded Tier 1 • Regulator requires proof that no risk exists on site – Through bioavailability study • Under negotiations but due to time constraints, may not be possible
  18. 18. Lessons • It’s hopeless! • Need to get regulators involved early in the process when there may be background issues • Provide a solid study design and statistical summary – Need to show that the data is understood • For contentious contaminants, may still require additional study (sometimes it is just optics)
  19. 19. Questions? Contact Info: Chemistry Matters Court Sandau Twitter – EnviroCertainty