Soil geochemical survey of florida
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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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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

  • Florida Center for Solid & Hazardous Waste Management

  • Florida Power and Light

  • Florida DEP


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


SOIL BACKGROUND

STUDY


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


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


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


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


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


Geographical vs. Taxonomic


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


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


As Distribution Pattern


Is It a Real Soil Background- Q/Q Plot ?

Undisturbed Soils (n=266)

Disturbed Soils (n=182)

Urban Soils (n=197)


As Values in Florida & World Soils


Wet soils (73)

GM=1.28

Upland soils (293)

GM=0.18

Borderline(82)

GM=0.29

As vs. Soil Suborders


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


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


GEOCHEMICAL

SURVEY OF

AS IN URBAN SOIL


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)


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


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


Daytona Beach/ Volusia

Gainesville/Alachua

Ft.Lauderdale/ Broward

Miami/Dade

As in Urban Soils


Sample Selection


As in Urban Soils with Different Land Uses

Gainesville, FL (N=201)


METHOD DEVELOPMENT

Soil Digestion Procedures


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


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.


USEPA vs. Aqua Regia Methods

  • Aqua regia procedures are more aggressive than the relevant EPA procedures.


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


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


MING CHEN

561-993-1527 mchen@mail.ifas.ufl.edu

THANK YOU


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