Mixed Contamination of Polyaromatic Hydrocarbons and Metals at Manufactured Gas Plant Sites: Toxicity and Implications to Bioremediation - Environmental Contamination: Health Risks and Ecological Restoration - page 355

Diffusion in pores

Zn,Pb,Cd

Surface sorption

Water soluble fractions

As,Cu,Hg

Zn,Pb,Cd

Organic matter

Mineral fraction

Organic matter
Zn,Pb,Cd

Heavy metals

PAHs

Diffusion into glassy surface

Diffusion into rubbery surface

FIGURE 16.2
Conceptual.model.of.the.occurrence.of.PAHs.and.metals.in.mixed.contaminated.soils.

can. cause. bioaccumulation. and. even. biomagniication. through. the. food.
chain.. Thirty. PAHs. included. in. the. WHO. report. (UNEP-ILO-WHO. 1998).
were. identiied. with. genotoxicity. to. animals,. and. 17. were. suspected. to. be.
carcinogenic..Though.PAH.toxic.effects.toward.animals.are.widely.studied,.
their.direct.effects.on.plants.are.yet.to.be.completely.understood.(Efroymson.
et.al..1997)..The.sites.contaminated.with.PAHs.and.metals.are.considered.dif-
icult.to.clean.up.using.present.bioremediation.technologies.because.of.the.
toxicity.of.heavy.metals.to.microorganisms.

ToxicityofPAHsandMetalMixturestoBiota
Contaminants.in.mixtures.are.known.to.interact.with.biological.systems.in.
ways.that.can.greatly.alter.the.toxicity.of.the.individual.compounds..Some.
mixtures.of.contaminants.have.higher.toxicity.than.predicted.(Tsiridis.et.al..
2006).. Thus,. even. if. the. characteristics. of. individual. chemicals. are. known,.
their. behavior. in. mixtures. cannot. be. easily. predicted.. This. situation. sub-
jects.organisms.in.contaminated.environments.at.maximum.risk.from.their.
integrated. effects.. The. majority. of. studies. investigating. metal-PAH. joint.
toxicity. toward. various. organisms. suggest. that. contaminant. interactions.