Environmental Engineering Reference
In-Depth Information
nondegradable. characteristics,. life. cycle. in. ecosystems,. and. high. toxicity,.
even.at.low.levels.
Arsenic. has. gained. great. notoriety. because. of. the. toxic. properties. of. a.
number. of. its. compounds. (Alloway. 1995).. Arsenic. contamination. in. soil.
is. generated. by. geothermal. systems,. including. hot. springs. and. geysers..
Mining. and. metallurgical. operations. can. also. concentrate. the. arsenic. into.
tailings.and.soil..Remediation.of.arsenic-contaminated.soil.can.be.achieved.
by. many. technologies,. including. biological. treatment,. phytoremediation,.
solidiication/stabilization,. ixation,. soil. lushing,. and. electrokinetic. reme-
diation.(Mulligan.et.al..2001,.US.EPA.2002)..Stabilization.is.a.process.where.
additives.are.mixed.with.waste.to.convert.the.hazardous.constituents.into.a.
form.that.minimizes.their.rate.of.migration.and.level.of.toxicity..Stabilization.
is.regarded.as.one.of.the.most.effective.and.eficient.methods.for.the.immo-
bilization.of.contaminants.in.waste..This.chapter.introduces.the.character-
istics.of.arsenic.in.soil.techniques.for.its.stabilization.and.some.of.their.ield.
applications.
ArsenicinMiningAreaSoils
Arsenic in Environment
Arsenic. is. a. naturally. occurring. element. that. ranks. 20th. in. abundance. in.
the. earth's. crust.. The. average. concentration. of. arsenic. in. the. earth. crust. is.
reported.to.be.1.5-2.mg/kg..As.the.level.of.arsenic.differs.with.respect.to.the.
origin.of.soils,.the.background.level.in.agricultural.soils.has.been.reported.
to.be.6.3.mg/kg.(Adriano.2001)..Sources.of.arsenic.are.divided.into.two.cat-
egories. (Adriano. 1986):. irst,. from. natural. phenomena,. such. as. weathering.
and.volcanic.activity,.which.are.the.main.source,.and,.second,.from.anthro-
pogenic.sources,.such.as.mine.tailings,.landill.sites,.waste.water.discharges,.
and.agricultural.activities,.which.account.for.60%.of.arsenic.contamination.
(Cullen.and.Reimer.1989,.Bhumbla.and.Keefer.1994).
Arsenic.is.often.found.in.contaminated.soils.as.a.result.of.natural.phenom-
ena..The.normal.concentration.range.of.arsenic.in.soils.is.1-40.mg/kg,.with.a.
mean.of.5.mg/kg,.but.in.most.soils.it.is.in.the.lower.half.of.this.range.(Bowen.
1979,.Kabata-Pendias.and.Pendias.1984,.Bañuelos.and.Ajwa.1999)..There.are.
ive. levels. of. arsenic. from. different. types. of. parent. rock,. especially. high.
levels. in. sedimentary. rocks. (shales,. mudstones,. and. slates).. The. National.
Research.Council.of.Canada.reported.that.soils.originating.from.sulide.ore.
deposits.contain.arsenic.at.high.concentrations,.even.up.to.several.hundreds.
of. mg/kg. (NRCC. 1978).. The. main. source. of. arsenic. in. the. environment. is.
the.parent.material.from.which.the.soil.is.derived..The.most.common.arse-
nic.mineral.in.the.environment.is.arsenopyrite.(FeAsS),.which.is.frequently.
associated. with. Au,. Cu,. Sn,. Ag,. Zn,. and. Pb. ore. deposits. (Smedley. and.
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