Environmental Engineering Reference
In-Depth Information
into. shallow. stainless. steel. sample. holders. for. x-ray. diffraction. analysis..
XRD. patterns. were. recorded. with. a. PANalytical. X'Pert. Pro. Multi-purpose.
Diffractometer.using.Co.Kα.radiation,.variable.divergence.slit,.postdiffrac-
tion.graphite.monochromator,.and.fast.X'Celerator.Si.strip.detector..The.dif-
fraction.patterns.were.recorded.in.steps.of.0.05°.2θ.with.a.0.5.s.counting.time.
per.step.and.logged.to.data.iles.for.analysis.
Total. elemental. concentrations. (strong. acid-solubilized. metals/metalloids).
in.the.bulk.tailings.and.house.dust.were.measured.by.ICP-MS.(7500CS,.Agilent.
Technologies,.Santa.Clara,.CA).from.multiple.diluted.acid.extracts.following.
a. reverse. Aqua. Regia. digestion. process. in. accordance. with. the. Australian.
Standard.AS4479.2.(Standards.Australia.1997)..This.method.is.consistent.with.
NEPM. requirements. as. well. (NEPC. 1999).. Briely,. about. 1.g. of. bauxite. and.
house. dust. was. accurately. weighed. into. a. Pyrex. beaker,. covered. in. reverse.
Aqua.Regia.acid.(10.mL).and.allowed.to.stand.at.room.temperate.with.a.watch.
glass.before.a.gentle.relux.for.2.h.at.120°C.on.a.temperature-controlled.heating.
block..The.digest.was.allowed.to.cool.before.dilution.to.100.mL..Further.mul-
tiple.dilutions.were.made.to.this.digest.(to.make.digested.solution.to.inal.dilu-
tions.of.500.times.and.500,000.times).before.analysis,.in.order.to.accommodate.
high. and. low. concentrations. of. various. analytes. in. the. bauxite. sample.. The.
inal.ICP-MS.analyzing.solution.contained.2%.nitric.acid.and.various.internal.
standards..All.solutions.were.analyzed.for.Al,.Ti,.V,.Cr,.Mn,.Fe,.Co,.Ni,.Cu,.Zn,.
As,.Se,.Sr,.Ag,.Cd,.Pb,.and.U..The.risk.assessment.focuses.exclusively.on.ele-
ments.that.have.high.concentrations.and.can.adversely.affect.human.health.
Certiied. reference. materials,. including. TM28.3. (water,. National. Water.
Research.Institute,.Environment.Canada,.Canada),.BCSS-1,.and.PCSS-1.(sedi-
ment,.NRC-CNRC,.Canada),.were.analyzed.in.the.same.manner.with.an.opti-
mum.sample.weight.of.0.25.to.0.5.g..These.QC.standards.allow.for.the.evaluation.
of.instrument.performance.and.assay.precision..They.also.allow.for.the.selec-
tion.of.best.dilution.factor.for.each.speciic.certiied.elemental. concentration..
This.provides.a.guide.for.selection.of.dilution.applicable.to.individual.elements.
in.the.sample..The.certiied.reference.material.results.are.shown.in.Table.6.2.
Bulk. tailings. and. house. dust. as. collected. and. their. respective. PM
10
. frac-
tions.were.measured.for.bioaccessibility.(BAC),.using.a.physiologically.based.
extract. test. (PBET). method. (Ruby. et. al.. 1996).. Physiologically. based. extract.
test.methods.have.been.widely.adopted.for.the.estimation.of.bioavailability.
internationally. and. in. Australia,. for. risk. assessment. of. metal-contaminated.
sites.(Bruce.et.al..2007,.Diacomanolis.et.al..2007,.Juhasz.et.al..2007,.2009a,b)..BAC.
has.been.validated.against.
in vivo
.models.and.accepted.by.USEPA.(2007)..It.has.
also.been.recently.recommended.for.use.by.an.NEPM.review.(Ng.et.al..2010).
Briely,.each.sample.was.extracted.using.a.synthetic.gastrointestinal.luid.
in.a.solid:liquid.ratio.of.1:100.at.pH.values.of.1.5,.2.5,.4.0,.and.7.0.over.a.num-
ber. of. hours,. simulating. the. GI. tract. pH. conditions. representing. fasting,.
semi-fed,. and. fully. fed. stomach. (Phase. I. or. stomach. phase). and. the. small.
intestine,.respectively,.over.a.period.of.4.h..Each.sample.was.assessed.across.
all. pH. values. and. 3. different. time. intervals. to. derive. a. set. for. 12. extracts..
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