Environmental Engineering Reference
In-Depth Information
continuous.release.results.in.equilibrium.of.spatial.size.distribution.that.is.the.result.
of.the.disequilibrium.of.the.materials.themselves.
In.this.example,.a.suspension.of.dispersed.C60 . fullerene.in.a.concentration.of.
0.1.milligram.per.liter.(mg/L).is.discharged.at.a.rate.of.1.liter.per.minute.(L/min).
to. a. lowing. creek. system. (0.1. m/sec).. The. Hamaker. constant. for. fullerene. ( A FWF ).
is.approximately.6.7.×.10 -21 .J.[14]..Assuming.a.water.hardness.of.approximately.80.
mg/L.CaCO 3 ,.yields.a. P ( F F ).of.approximately.0.63.
If.a.hypothetical.regulatory.limit.of.1.µg/L.of.particles.with.an.apparent.diam-
eter. less. than. 250. nm. is. imposed,. it. is. possible. to. predict. the. extent. to. which. the.
creek.is.potentially.out.of.compliance..Assuming.instant.chemical.equilibrium,.the.
material. would. be. expected. to. be. entirely. agglomerated. and. therefore. no. amount.
of. release. would. result. in. noncompliance.. Under. a. conservative. assumption. of. no.
agglomeration,. the. reach. of. the. river. that. would. be. considered. out. of. compliance.
would.extend.from.the.point.of.release.until.the.point.where.diffusion.and.mixing.
diluted. the. fullerenes. suficiently.. Compliance. would. require. dilution. by. a. factor.
of. 100:1.. Alternatively,. one. can. predict. the. extent. of. agglomeration. as. a. basis. for.
assessing.compliance..The.competitive.stochastic.modeling.allows.for.an.incremen-
tal. analysis. of. the. size. distribution. of. the. fullerenes. within. the. river. (Figure.6.7)..
The.agglomeration.model.indicates.that.compliance.would.be.achieved.within.9.m.
downstream.of.the.discharge.
.  ReseaRCh Results
Experimental.studies.regarding.the.fate.and.transport.of.nanomaterials.in.the.envi-
ronment.currently.fall.into.two.broad.categories:.behavior.in.aqueous.systems.and.
movement.through.porous.media..As.discussed.further.in.Chapter.7,.the.behavior.of.
nanomaterials.in.water.and.wastewater.has.been.investigated.as.a.basis.for.evaluating.
the.effectiveness.of.various.treatment.technologies.such.as.coagulation/locculation.
and. iltration.. Migration. of. nZVI. through. the. subsurface. has. been. studied. with.
regard. to. its. application. as. a. groundwater. treatment. technology,. as. described. in.
Chapter. 10.. The. indings. of. this. and. other. research. relevant. to. characterizing. the.
fate. and. transport. of. nanomaterials. in. surface. water,. sediments,. and. groundwater.
are.discussed.below.
Much.research.is.underway.to.characterize.the.behavior.of.nanoparticles.under.
“environmentally.relevant.conditions.”.This.research.shows.that.a.range.of.variables.
complicate.the.behavior.of.nanomaterials.in.the.environment..These.variables.include.
the.pH.and.ionic.strength.of.the.aqueous.solution,.the.presence.of.dissolved.organic.
matter,.and.the.organic.carbon.content.and.grain.size.of.the.soil..Modiications.in.
the.physicochemical.properties.of.the.nanoparticles,.either.engineered.or.occurring.
upon.release.to.the.environment,.may.lead.to.unpredictable.transport.behavior.in.sur-
face.water.and.groundwater..After.assessing.the.mobility.of.eight.different.nanoma-
terials.in.a.porous.medium.in.laboratory.experiments,.researchers.at.Rice.University.
concluded.that.“The.differences.in.the.environmental.transport.properties.for.these.
nanomaterials.underscores.the.need.to.address.environmental.impacts.of.nanomate-
rials.on.a.case-by-case.basis”.[17]..The.characteristics.of.both.the.nanomaterial.and.
the.environmental.system.will.affect.the.fate.and.transport.of.nanomaterials
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