Bioavailability of Metals and Arsenic on Brownfield Land: Remediation or Natural Attenuation for Risk Minimization? - Environmental Contamination: Health Risks and Ecological Restoration - page 475

for. either. plant. species.. The. best. explanation. of. Cd. uptake. was. obtained.
using.EDTA.(63%).or.rhizon.samplers.(70%),.but.when.data.were.combined.
for.both.plant.species,.only.49%.of.the.variability.was.explained.by.the.best.
method. (DGT).. No. single. method. could. predict. uptake. of. Cu. with. these.
eficiencies..Of.course,.the.scientiic.explanation.is.that.pH,.organic.matter,.
and.other.physicochemical.variables.also.partially.determine.the.uptake.of.
metals..Furthermore,.biotic.variables.play.a.role,.as.illustrated.by.the.differ-
ence.in.how.well.these.techniques.relect.uptake.in.the.two.species.of.grasses.
(Figure.22.1)..Other.less.closely.related.species.would.be.likely.to.respond.to.
the.four.metals.in.yet.different.ways.
In. terms. of. restoration. of. contaminated. urban. soils,. phytotoxic. concen-
trations. of. Cu,. Zn,. and. Ni. are. of. less. concern. where. human. health. is. the.
main. priority.. However,. enhanced. uptake. of. the. more. zootoxic. metal. Cd.
through.food.chains.could.compromise.animal.or.human.health.(Alloway.
1990,. Rodrigue. et. al.. 2007);. Cd. is. highly. mobile. in. environmental. media.
and.biological.tissues.(Dickinson.and.Pulford.2005)..Other.less.mobile.ele-
ments,.particularly.Pb.and.As,.frequently.present.concern.in.soils.polluted.
by.industrial.and.urban.fallout;.both.of.these.elements.are.potentially.haz-
ardous.to.human.health.(Hamilton.2000,.Datta.and.Sarkar.2005,.Hooker.and.
Nathanail. 2006).. An. urban. town. and. woodland. subjected. to. aerial. fallout.
from.100.years.of.Cu,.Cd,.Zn,.and.Pb.processing.at.Prescot,.United.Kingdom,.
was.found.to.present.very.limited.risk.to.biota.or.human.health.(Dickinson.
et.al..1996)..The.limited.risk.was.largely.due.to.very.restricted.pathways.that.

100

10

1

0.1

0.01

r 2 = 0.61, p < 0.001 (wheat)
r 2 = 0.42, p < 0.001 (ryegrass)

0.001

10 -5

10 -4 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3

Ca(NO 3 ) 2 Cd (mg/kg)

FIGURE 22.1
Relationship. between. uptake. of. Cd. by. wheat. seedlings. (⚪). and. pasture. ryegrass. (▵). and.
Ca(NO 3 ) 2 .extractability.of.Cd.from.soil..(From.Black,. A.,.Bioavailability.of.cadmium,.copper,.
nickel,.and.zinc.in.soils.treated.with.biosolids.and.metal.salts,.PhD.thesis,.Lincoln.University,.
Lincoln,.New.Zealand,.2010.)