Presentation on theme: "Soil Geochemical Survey of Florida Ming Chen, PhD Quality Assurance Officer University of Florida, IFAS Belle Glade, FL 33430."— Presentation transcript:
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 Lena Q. Ma Willie G. Harris Willie G. Harris Tait Chirenje Tait Chirenje Florida Cooperative Soil Survey Florida Center for Solid & Hazardous Waste Management Florida Power and Light Florida DEP
What We Did in Florida? B ackground of 21 Elements in Soils. Determination (total vs. total-recoverable) Interpretation (baseline vs. taxonomy) G eochemical Survey of As in Urban Soils Sampling protocol Golf course study S oil Digestion - Method Development USEPA vs. Europe Hotplate vs. Microwave
What is Background ? Pristine Agricultural Urban N atural Background (NB) (USEPA, 1995) C oncentrations of chemicals in soils without human influence (USEPA, 1995) A nthropogenic Background (AB) AB = NB + Anthropogenic input from non-point sources
NB- variability & soil taxonomy: N = [(S x t 0.05 )/R] 2 AB - sample distribution & land use: To obtain 95 th quantile at =0.05 Sample Size Consideration
G eometric Mean vs. Arithmetic Mean Pattern of Distribution U pper Percentile Level (UPL) UBL-97.5% Upper Percentile of data (USGS, 1993) UBL = GM GSD 2 Large database U pper Confidence Level of Mean (UCL) Site specific cases Small database Ways to Interpret
UCL vs. UBL GM GM X GSD GM X GSD 2 GM / GSD 2 No. of Occurrences Baseline (95%) Baseline (95%) Upper confidence limit (UCL) Upper baseline limit (UBL) When sample size is big enough, …AM
Sample Selection N ear 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 R epresentative of Samples 7 orders - 19 suborders - 33 Great Groups 51 counties - 80% acreage V erification Samples
Statistical Consideration T T est 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) R R educe Number of Non-detects Updated procedure or instrument to low MDL. Use 0.5 MDL for non-detects (< 20 %) O O utliers: Q-Q Plot
As vs. Soil Suborders Wet soils (73) GM=1.28 Upland soils (293) GM=0.18 Borderline(82)GM=0.29
Factors Contribute to As 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
Toxicity N o. 1 priority hazardous substance (275) (ATSDR, 1999) C lass A human carcinogen ( USEPA, 1998) – Taiwan – Bangladesh – Florida Drinking Water Standard U SEPA 10 ppb (2006) Why Arsenic?
Survey: As - Herbicide Usage on Golf Courses - ( Chen & Ma, 2000 )
Lysimeter Study: As Held by Surface Soil (Chen & Snyder, 2002)
D aytona Beach/ Volusia Gainesville /Alachua Ft. L auderdale/ Broward Miami/Dade Commercial40 Parks40 Residential38 Public Building79 As in Urban Soils
Why Methods Development ? u Worldwide Geo-chemical Survey needs Unified Methodology and Standards Standard Operation Procedure (SOPs): data comparison Standard Operation Procedure (SOPs): data comparison Certified Reference Materials (SRM): Data validation. Certified Reference Materials (SRM): Data validation. u Digestion Methods are lab-dependent Europe: Aqua regia (HNO 3 /HCl =1:3) + HF Europe: Aqua regia (HNO 3 /HCl =1:3) + HF USEPA Methods (3050, 3051, 3051a and 3052) (HNO 3 /HCl =3:1) USEPA Methods (3050, 3051, 3051a and 3052) (HNO 3 /HCl =3:1) u 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.
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 CONCLUSION