Environmental Engineering Reference
In-Depth Information
(US.EPA.1986)..The.sites.contaminated.with.mixtures.are.therefore.complex,.
multicomponent. systems. with. a. range. of. different. organic. and. inorganic.
chemicals.coexisting.under.various.physiochemical.conditions.(Thavamani.
et. al.. 2011).. Although. some. potential. environmental. hazards. involve. sig-
niicant. exposure. to. only. a. single. chemical. compound,. most. instances. of.
environmental. pollution. involve. concurrent. or. sequential. exposures. to. a.
mixture. of. compounds. that. may. induce. similar. or. dissimilar. effects. over.
exposure.periods.ranging.from.short.term.to.lifetime.
Mixed.contamination.could.be.due.to.the.occurrence.of.organic-organic.
(e.g.,.pesticides.plus.their.metabolites),.organic-inorganic.(e.g.,.DDT-As),.and.
inorganic-inorganic. (e.g.,. sewage. sludge. containing. several. heavy. metals).
chemicals..Mixtures.of.compounds.that.are.placed.in.the.same.area.for.dis-
posal. or. storage. have. the. potential. in. causing. toxicity. to. biota. because. of.
the.combined.effect.of.pollutants.(US.EPA.2000)..Multichemical.exposures.
are. ubiquitous. including. air. and. soil. pollution. from. municipal. incinera-
tors,.leakage.from.hazardous.waste.facilities.and.uncontrolled.waste.sites,.
and.drinking.water.containing.chemical.substances.formed.during.disin-
fection.. Manufactured. gas. plant. (MGP). sites. contain. mixed. contaminants.
of. organic. and. inorganic. chemicals. such. as. polyaromatic. hydrocarbons.
(PAHs).and.metals,.and.the.remediation.of.these.sites.is.more.complex.and.
challenging.. This. chapter. focuses. on. mixed. contamination. of. MGP. sites,.
with.special.emphasis.on.issues.such.as.bioavailability.and.toxicity.associ-
ated.with.bioremediation.of.those.sites.
SiteswithMixedContaminants
Almost.all.the.contaminated.sites.have.more.than.one.type.of.pollutants..
In.fact,.40%.of.the.hazardous.waste.sites.in.the.National.Priority.List.(NPL).
of.the.U.S..Environmental.Protection.Agency.are.contaminated.with.mix-
tures. of. metals. and. organic. pollutants. (Sandrin. et. al.. 2000).. Metals. most.
frequently. found. at. Superfund. sites. include. arsenic,. barium,. cadmium,.
chromium,.lead,.mercury,.nickel,.and.zinc..Common.organic.contaminante.
include. petroleum,. chlorinated. solvents,. and. pesticides.. Following. are.
some.of.the.identiied.sites.contaminated.with.such.mixtures.worldwide:
Manufacture.gas.plant.sites
—
PAHs.and.metals
Petrochemicals.units
—
TPHs.and.metals
Sheep.and.cattle.dip.sites
—
DDT.and.As
Wood.preservation.sites
—
Creosote.(PAHs),.Cu,.Cr,.and.As
Electronic.waste.processing.sites
—
PAHs,.PCBs,.and.metals
Military.sites
—
Nitro.compounds.and.As
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