Environmental Fate and Transport - Nanotechnology and the Environment - page 124

. intRoduCtion
The. environmental. fate. and. transport. of. a. given. chemical. can. usually. be. charac-
terized. or. predicted. based. on. a. relatively. small. set. of. characteristics. These. typi-
cally.include.phase.properties.(boiling.point,.melting.point,.vapor.pressure);.afinity.
properties.(air/water,.water/soil,.etc.);.media.reactivity.(hydrolysis,.oxidoreduction,.
photoreactivity);. and. biological. degradation. rates. Most. models. of. environmental.
fate. and. transport. use. a. combination. of. some. or. all. of. these. properties. to. predict.
concentrations.within.various.environmental.media. The.potential.for.environmen-
tal. risk. can. then. be. determined. from. these. predicted. concentrations. based. on. the.
toxicity.of.the.materials.
This.chapter.examines.the.fate.and.transport.of.free.nanomaterials.in.the.envi-
ronment. In. some. cases,. nanomaterials. may. be. considered. in. a. manner. identical.
to.smaller.molecular.materials. Other.cases.require.special.methods.to.account.for.
differences.in.the.physical.and.chemical.properties.of.nanomaterials.as.well.as.their.
peculiar.phase.properties. (See.Chapter.2.for.a.discussion.of.the.critical.properties.
of.nanomaterials.)
Figure.6.1.illustrates.the.primary.forces.that.determine.the.fate.and.transport.of.
nanoparticles.in.suspension. Upon.an.initial.release.of.disperse.nanoparticles,.buoy-
ancy.suspends.the.nanoparticles.in.the.luid. Van.der.Waals.forces,.relatively.weak.
forces.resulting.from.transient.shifts.in.electron.density,.cause.the.nanoparticles.to.
FiguRe . Conceptual. model. of. primary. forces. determining. fate. and. transport. of.
nanoparticles.in.solution.