Soil Arsenic Assessment Study Kea'au,Hawai'i Prepared for

240 Pages·2007·8.27 MB·English

Soil Arsenic Assessment Study
Kea‘au,Hawai‘i
Prepared for:
State of Hawai‘i Department of Health
Hazard Evaluation and Emergency Response (HEER) Office
919 Ala Moana Boulevard, Room 206
Honolulu, Hawai‘i 96814
Draft Report Prepared by:
AMEC Earth and Environmental, Inc.
3375 Koapaka Street, Suite F251
Honolulu, Hawai‘i 96819
Project #: 3-251-90015
March 2005
Report Finalized and Updated by HEER Office
December 2007
TABLE OFCONTENTS
FORWARD...................................................................................................................................vii
EXECUTIVESUMMARY..........................................................................................................viii
1 INTRODUCTION...............................................................................................1-1
1.1 SiteDescription....................................................................................................1-1
1.2 Previous Investigations........................................................................................1-1
1.3 Physical Characteristics.......................................................................................1-3
1.3.1 GeologyandSoils................................................................................................1-3
1.3.2 SurfaceWaterHydrology....................................................................................1-4
1.3.3 GroundwaterHydrology......................................................................................1-4
2 FIELD INVESTIGATION..................................................................................2-1
2.1 InvestigationObjectives.......................................................................................2-1
2.2 IdentificationofDecisionUnits...........................................................................2-2
2.3 SurfaceSoil SampleCollection...........................................................................2-2
2.4 SurveyofDecisionUnits.....................................................................................2-3
2.5 FieldQualityAssurance/QualityControl (QA/QC)Procedures.........................2-4
2.6 InvestigationDerivedWaste................................................................................2-4
2.7 ProduceSampleCollection..................................................................................2-4
3 ANALYTICALPROGRAM...............................................................................3-1
3.1 NorthcreekAnalytical Laboratory–Total InorganicArsenicAnalyses............3-1
3.2 Brookside Laboratories–Soil ChemistryandPhysical Properties .....................3-3
3.3 Exponent Laboratory–BioaccessibilityTesting.................................................3-3
3.4 FDAProduceTesting..........................................................................................3-3
4 RESULTS............................................................................................................4-1
4.1 Total Arsenic(<2mm Soil Fraction)....................................................................4-1
4.2 Total Arsenic(<250-µm Soil Fraction)...............................................................4-2
4.3 ArsenicEnrichment inFineSoil Fraction...........................................................4-2
4.4 BioaccessibleArsenicAnalyses Results..............................................................4-3
4.5 Soil ChemistryandPhysical Properties...............................................................4-4
4.6 QualityControl Data............................................................................................4-4
4.7 ArsenicinCommunityGardenProduce..............................................................4-4
5 SCREENING LEVELASSESSMENTOFARSENIC DATA...........................5-1
5.1 Comparison ofTotal ArsenicDatatoHDOHAction Levels..............................5-1
5.2 EvaluationofBioaccessibileArsenicData..........................................................5-2
5.3 BioaccessibilityVersus Soil ChemistryandPhysical Properties........................5-4
5.4 BioaccessibilityVersus Soil ParticleDistribution...............................................5-7
5.5 PossibleFactors ofHigh Arsenic BioaccessibilityinCommunityGardens........5-8
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5.6 EvaluationofTotal ArsenicinProduce...............................................................5-8
5.7 UncertaintyAnalysis............................................................................................5-8
5.7.1 SamplingApproach.............................................................................................5-8
5.7.2 ArsenicAnalysis..................................................................................................5-9
5.7.3 BioaccessibilityAnalysis.....................................................................................5-9
5.7.4 BioaccessibilityandSoil ChemistryCorrelationAnalyses...............................5-10
6 SUMMARYANDRECOMMENDATIONS......................................................6-1
6.1 Summary..............................................................................................................6-1
6.2 Recommendations................................................................................................6-2
7 REFERENCES....................................................................................................7-1
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LIST OFTABLES
NUMBERS TITLE
2.1 SummaryofSelectedDecisionUnits
2.2 SummaryofProduceTypes Collectedfrom Gardens
3.1 Soil ChemistryandPhysical PropertyAnalyses
4.1 Total ArsenicConcentrationResults- <2mm SizeSoil Fraction
4.2 Total ArsenicConcentrationResults <250µm SizeSoil Fraction.
4.3 Total Soil Arsenic Concentrations (<2mm and <250µm Fractions) and Percent Increase
withReducedSizeSoil Fraction
4.4. Total Soil Arsenic Concentrations at <2mm and <250µm Size Fractions Versus Arsenic
Bioaccessibility
4.5 Estimated Bioaccessible Arsenic Concentrations in Decision Units with Both <250µm
SizeFractionSoil DataandBioaccessibilityData
4.6 Estimated Range of Soil Bioaccessible Arsenic in Decision Units with <2mm Size
FractionTotal Arsenic DataOnly
4.7 MajorCationandSoil PropertyData
4.8 Soil ParticleSizePercentageforthe<250µm ParticleSizeGroup
4.9 Fieldand LaboratoryPrecisionData
4.10 Summary of Total Arsenic in Produce Samples Collected from Kea‘au Community
Gardens vs FDAMarket Basket Studies
4.11 SummaryofTotal ArsenicData BasedonProduceTypevs FDAMarket Basket Studies
5.1 CategorizationofSites withRespect toPotential Residential HealthRisks
6.1 Actions Recommendedfor Individual DecisionUnits
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LIST OFFIGURES
NUMBERS TITLE
1.1 SiteVicinityMap
1.2 Site LocationMap
1.3 Kea‘auSoil Map
2.1 DecisionUnits ofKea‘au Soil Assessment
5.1 RegressionAnalysis: Al Concentrationvs. As Bioaccessibility
5.2 RegressionAnalysis: Fe Concentrationvs. As Bioaccessibility
5.3 RegressionAnalysis: MgConcentrationvs. As Bioaccessibility
5.4 RegressionAnalysis: CaConcentrationvs. As Bioaccessibility
5.5 RegressionAnalysis: As Concentration(<250um SizeFraction)vs. As Bioaccessibility
5.6 RegressionAnalysis: As Concentration(<2mm SizeFraction)vs. As Bioaccessibility
5.7 RegressionAnalysis: P Concentrationvs. As Bioaccessibility
5.8 RegressionAnalysis: Mn Concentrationvs. As Bioaccessibility
5.9 RegressionAnalysis: CationExchangeCapacityvs. As Bioaccessibility
5.10 RegressionAnalysis: pHvs. As Bioaccessibility
5.11 RegressionAnalysis: Soil OrganicMattervs. As Bioaccessibility
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LIST OFAPPENDICES
LETTER TITLE
A FieldPhotographs
B FieldSoil Logs
C ProduceSamplingProtocols and LaboratoryReports
D Exponent Report: Bioaccessibilityof Arsenic from 14Hawaii Soils
E Soil LaboratoryReports
F Soil ActionLevels andCategories forBioaccessibleArsenic
G Arsenic Fact Sheet
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LIST OFACRONYMS
ASTM AmericanSocietyforTesting&Materials
CEC CationExchangeCapacity
COC ChainofCustody
DI DeionizedWater
ESA Environmental SiteAssessment
GPS Global PositioningSystem
HDOH Hawaii Department ofHealth
HDPE High-DensityPolyethylene
HSP HealthandSafetyPlan
ICP InductivelyCoupledPlasma
IDW InvestigationDerivedWaste
LCS LaboratoryControl Sample
mg/kg milligrams/kilogram
MS/MSD Matrix Spike/Matrix SpikeDuplicate
NCA NorthCreekAnalytical Laboratory
NIST National InstituteofStandards andTechnology
pH Potential ofHydrogen
PRDL Project RequiredDetection Limit
QA/QC QualityAssurance/QualityControl
SAP SamplingandAnalysis Plan
SAS Soil Assessment Study
SOM Soil OrganicMatter
SRM StandardReferenceMaterial
TCLP ToxicityCharacteristic LeachingProcedure
UCL UpperConfidence Level
UIC Underground InjectionControl Line
USCS UnifiedSoil ClassificationSystem
USDA UnitedStates Department ofAgriculture
USEPA/EPA UnitedStates Environmental ProtectionAgency
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FORWARD
Fieldworkdetailedinthis report was conductedin late2004and2005bytheHawai‘i
Department of Health(HDOH)HazardEvaluation &EmergencyResponse Office (HEER
Office)together withHDOHcontractors from AMEC EarthandEnvironmental, Inc.(AMEC)
underanon-emergencyresponsecontract (ASO LogNo.98-418). Adraft report was developed
byAMEC in2005,and a communitymeetingwas subsequentlyheldbythe HEER Office in
Kea‘autodescribethefindings ofthesoil arsenic testing.This report finalizes documentationof
theworkconductedin2004and2005,andupdates thereport withinformationonproduce
testing(April andAugust 2005),additional evidencesupportingtheuseofsoil arsenic
bioavailabilityintheKea‘auarea(2006 and2007),andonHEER Office guidancerelatingtouse
andinterpretationofsoil arsenicbioaccessibilitytestingresults (August 2006).
TheHEER Officewould liketoacknowledgethecooperationoftheStateDepartment of
Education,W.H.Shipman, Ltd.,andotherprivate landowners forprovidingaccess totheir
properties forsoiltestingintheKea‘auarea.
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EXECUTIVE SUMMARY
This report summarizes an investigation carried out in 2004 and 2005 to examine soil arsenic
levels in a number of areas around the town of Kea`au, Hawai`i (located near Hilo). The
investigation focused on areas formerly used to cultivate sugarcane that are now used by
residents on a regular basis. The investigation was undertaken by the Hawai`i Department of
Health (HDOH), Hazard Evaluation and Emergency Response Office (HEER Office) with the
assistance of an environmental consulting firm (AMEC Earth and Environmental, Inc.). The
goals oftheinvestigationincluded:
 Identify average total arsenic levels in surface soils of public areas where Kea`au
residents may come in contact with soils on a regular basis, including schools, parks, and
communitygardens.
 Identify average total arsenic levels in surface soils of undeveloped land adjacent to
residential subdivisions. This was used to estimate arsenic levels in surface soils that
werepresent beforeindividual residences weredeveloped.
 Estimate the amount ofbioaccessible arsenic in surface soils, and examine soil chemistry
andphysical properties that mayinfluence arsenicbioaccessibility.
Soils were tested for both total and bioaccessible arsenic in order to better evaluate potential
risks to human health. The investigation also included the use of multi-increment soil sample
collection techniques to better estimate representative total and bioaccessible arsenic levels
across thespecificareas sampled,or“decisionunits”.
A total of 18 decision units were evaluated, ranging is size from approximately4,000 square feet
to 1 acre in size. A multi-increment soil sample was collected from the 0-3 inch depth surface
soil interval in each decision unit. Replicate samples were collected in selected decision units in
order to evaluate the precision of the field sample collection, lab sub-sampling, and analytical
work. The soil samples were air-dried and sieved to the <2mm particle size in the lab before
sub-sampling and analysis for total arsenic. Soil chemistry and physical properties were also
evaluated for the <2mm soil particle size fraction. Soil samples were further sieved to <250 μm
particlesizeforbioaccessibilityanalyses.
Total arsenic concentrations in surface soils collected at the 0-3 inch depth in the 18 decision
units ranged from 0.7 mg/kg to 366 mg/kg (dry weight). The community garden decision units
contained the highest concentrations of total arsenic (mean 331 mg/kg, n=3), followed by
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undeveloped land adjacent to residential subdivisions (mean 278 mg/kg, n=6), parks (mean 121
mg/kg,n=3) andschools (mean37.0,n=6).
Concentrations of total arsenic in the surface soils of 13 of the 18 decision units sampled
exceeded the HDOH soil arsenic Environmental Action Level of 20 mg/kg (EAL, or initial soil
screening level established by the HEER Office). Exceeding the 20 mg/kg total arsenic
screening level does not necessarilyindicate that the arsenic poses adverse health risks at a given
site,onlythat furtherevaluationis warranted.
Most samples that exceeded the initial screening level of 20 mg/kg were subsequently tested for
bioaccessible arsenic. “Bioaccessibility” (in-vitro) laboratory tests are used to estimate the
proportion of arsenic that could be stripped from the soil in a person’s digestive system and be
available for uptake. The fine-grained portion of the soil samples is utilized in the
bioaccessibility tests (<250μm particle size). This is believed to be the fraction of soil that
humans may be most exposed to, and is most relevant for estimation of risks to human health.
Bioaccessibility is then used to estimate “bioavailability,” the actual fraction of arsenic in soil
that may enter a person’s bloodstream, if inadvertently ingested. The fraction of arsenic that is
bioavailable is considered to pose potential risks to human health. The remainder is considered
tobeessentiallynontoxic.
Bioaccessible arsenic tests were run on soil samples collected from 12 of the 18 decision units,
including 10 decision units that did not pass the initial screening level of 20 mg/kg total arsenic.
Enrichment of total arsenic in the fines fraction of the soil was evident in all but one of 12
samples. Arsenic bioaccessibility in the soils ranged from 1.5% to 20% (i.e., 80% to 98.5% of
the arsenic in the soil is essentially “nontoxic”). Bioaccessibility was highest in the two
community gardens, ranging between 18% and 20% bioaccessible. Arsenic bioaccessibility in
theremaining,non-gardendecisionunits rangedfrom 1.5%to9.6%.
Actual concentrations of bioaccessible arsenic in decision units were estimated by multiplying
the reported total arsenic in the fines soil particle fraction (<250 μm) times the reported
bioaccessibility for the same fraction. The concentration of bioaccessible arsenic in soil was
then compared to more detailed, risk-based HEER Office soil action levels for residential
exposure,andareas investigatedwereplacedinto oneofthreecategories.
“Category 1” (bioaccessible arsenic in soil <4.3 mg/kg) indicates minimal potential health risk.
All but one of the school sites fell into Category 1 (six sites total). No further action is
recommended fortheseareas.
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