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Soil Geochemical Survey of Florida

Soil Geochemical Survey of Florida. Ming Chen, PhD. Quality Assurance Officer University of Florida, IFAS Belle Glade, FL 33430. ACKNOWLEDGEMENT. Univ. Florida - Soil & Water Dept. Lena Q. Ma Willie G. Harris Tait Chirenje Florida Cooperative Soil Survey

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Soil Geochemical Survey of Florida

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  1. Soil Geochemical Survey of Florida Ming Chen, PhD Quality Assurance Officer University of Florida, IFAS Belle Glade, FL 33430

  2. ACKNOWLEDGEMENT • Univ. Florida - Soil & Water Dept. • Lena Q. Ma • Willie G. Harris • Tait Chirenje • Florida Cooperative Soil Survey • Florida Center for Solid & Hazardous Waste Management • Florida Power and Light • Florida DEP

  3. What We Did in Florida? • Background of 21 Elements in Soils. • Determination (total vs. total-recoverable) • Interpretation (baseline vs. taxonomy) • Geochemical Survey of As in Urban Soils • Sampling protocol • Golf course study • Soil Digestion - Method Development • USEPA vs. Europe • Hotplate vs. Microwave

  4. SOIL BACKGROUND STUDY

  5. Pristine Agricultural Urban What is Background ? • Natural Background (NB) • Concentrations of chemicals in soils without human influence(USEPA, 1995) • AnthropogenicBackground (AB) • AB= NB + Anthropogenic input from non-point sources

  6. Sample Size Consideration • NB-variability & soil taxonomy: N = [(S x t0.05)/R]2 • AB - sample distribution & land use: To obtain 95th quantile at =0.05

  7. Ways to Interpret • Geometric Mean vs. Arithmetic Mean • Pattern of Distribution • Upper Percentile Level (UPL) • UBL-97.5% Upper Percentile of data (USGS, 1993) • UBL = GM  GSD2 • Large database • Upper Confidence Level of Mean(UCL) • Site specific cases • Small database

  8. No. of Occurrences Upper confidence limit (UCL) When sample size is big enough, … Upper baseline limit (UBL) AM GM / GSD2 GM X GSD2 Baseline (95%) UCL vs. UBL GM

  9. Sample Selection • Near Pristine Soils - N = 448 out of 7000 Soil Survey Archives • Undisturbed Soil (n =266) - with native vegetation • Disturbed Soil (n=182) - by plowing or clearing • Representative of Samples • 7 orders - 19 suborders - 33 Great Groups • 51 counties - 80% acreage • Verification Samples

  10. Geographical vs. Taxonomic

  11. Quality Assurance System • QA Plan: Florida DEP approval • NELAP Certification • Digestion Method: • EPA 3051a – HNO3/HCl • EPA 3052 – HNO3/HCl/HF • QA/QC sample: every 20 samples • regent blank ------- MDLs • certified standard soil --- method validation • spiked soil ---- precision • duplicate soil ----- accuracy

  12. Statistical Consideration • Test Sample Distribution for Normality: • Normally distributed datasets: t- UCL • Log-normally distributed datasets: H - UCL • Neither normally nor log-normally distributed datasets: Non-parametric tests (Pro- UCL) • Reduce Number of Non-detects • Updated procedure or instrument to low MDL. • Use 0.5 MDL for non-detects (< 20 %) • Outliers: Q-Q Plot

  13. As Distribution Pattern

  14. Is It a Real Soil Background- Q/Q Plot ? Undisturbed Soils (n=266) Disturbed Soils (n=182) Urban Soils (n=197)

  15. As Values in Florida & World Soils

  16. Wet soils (73) GM=1.28 Upland soils (293) GM=0.18 Borderline(82) GM=0.29 As vs. Soil Suborders

  17. Total Fe & Al PCA : explained 29% of variation (Chen et al., 1999) Partial regression <0.05 (Chen et al., 2002) Phosphate Deposit Total P: partial regression <0.05 (Chen et al., 2002) Distribution paralleled P rock: 7-121 vs. non- P rock: 2- 6.6 mg As /kg Wetland/vegetation – no direct evidence Factors Contribute to As

  18. Limestone 3-13 mg/kg: Everglades (Chen et al., 2000) 40 mg/kg: Avon Park limestone (Levy County) Sea snail and other marine animals Database: 61.2- snail, 38.1-mollusk shells. 144-484 mg/kg – marine snail shells (vs. 0.2 for land snail) 3.6-63 mg/kg - meat, wet weight Factors Contribute to As

  19. GEOCHEMICAL SURVEY OF AS IN URBAN SOIL

  20. Why Arsenic? • Toxicity • No. 1 priority hazardous substance (275) (ATSDR, 1999) • Class A human carcinogen (USEPA, 1998) • Taiwan • Bangladesh • Florida • Drinking Water Standard • USEPA 10 ppb (2006)

  21. Survey: As - Herbicide Usage on Golf Courses - (Chen & Ma, 2000)

  22. Lysimeter Study: As Held by Surface Soil (Chen & Snyder, 2002)

  23. Daytona Beach/ Volusia Gainesville/Alachua Ft.Lauderdale/ Broward Miami/Dade As in Urban Soils

  24. Sample Selection

  25. As in Urban Soils with Different Land Uses Gainesville, FL (N=201)

  26. METHOD DEVELOPMENT Soil Digestion Procedures

  27. Why Methods Development ? • Worldwide Geo-chemical Survey needs Unified Methodology and Standards • Standard Operation Procedure (SOPs): data comparison • Certified Reference Materials (SRM): Data validation. • Digestion Methods are lab-dependent • Europe: Aqua regia (HNO3/HCl =1:3) + HF • USEPA Methods (3050, 3051, 3051a and 3052) (HNO3/HCl =3:1) • Microwave vs. Hotplate

  28. USEPA Digestion Procedures • EPA 3051a is an overall better procedure in replacing the regulatory method 3050. • 3051a and 3050 only get partial recoveries for Ba, Cr, Mo, Ni, K, and Al in NIST SRMs.

  29. USEPA vs. Aqua Regia Methods • Aqua regia procedures are more aggressive than the relevant EPA procedures.

  30. CONCLUSION • Florida soils generally have low elemental backgrounds, which are based on: • soil type • soil property • land uses • Certain soil has naturally high As background: • marl soil (wet) • muck soil (wet) • P deposit soil • Fe coated soil • marine shelly soil • contaminated soils

  31. CONCLUSION • UBL value of soil Suborder is a better approach for soil As screening in a state level. However, • there is not a single magic number for regulatory uses. • Pilot study and method development can address issues like: • soil sampling protocol • soil digestion procedure • certified standard soils

  32. MING CHEN 561-993-1527 mchen@mail.ifas.ufl.edu THANK YOU

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