Phytostabilization for Sustainable End-Use of Arsenic-Rich Mine Tailings in the Victorian Goldfields, Australia - Environmental Contamination: Health Risks and Ecological Restoration - page 441

than.50%.survival..Biosolids.treatments.were.not.so.effective.in.enhancing.
survival. with. a.rate. of. only. 27%.in. the. oxide. with.low.biosolids. and.47%.
in. the. oxide. with. high. biosolids.. E. viridis . was. the. least. successful. of. the.
eucalypts..Survival.of.planted.seedlings.in.December.2001.was.greatest.in.
the.topsoil.and.oxide.cover.(70%).and.then.in.the.biosolids-amended.oxide.
(60%)..Other.treatments.had.<50%.survival..At.the.end.of.the.irst.season,.
survival. had. declined. in. the. best. treatments. such. that. topsoil. and. oxide.
cover. was. the. only. one. with. >50%. survival.. Mortalities. in. the. biosolids-
enriched.waste.rock.cover.continued.into.the.second.year,.whereas.all.seed-
lings.which.had.survived.in.the.other.treatments.continued.to.persist.to.the.
end.of.the.trial.
Leaf.samples.of.eucalypts.were.taken.for.analysis.from.seedlings.from.sev-
eral.of.the.experimental.covers..Equivalent.leaf.samples.were.collected.from.
eucalypt.seedlings.from.a.nearby.farming.property.for.comparison..Arsenic.
concentration.in.dried.leaf.tissues.of. E. cladocalyx .was.not.signiicantly.dif-
ferent.between.the.control.and.the.experimental.covers.with.concentration.
ranging.from.0.9.to.2.7.mg/kg..The.other.three.eucalypt.species.had.leaf.As.
concentrations. signiicantly. greater. in. the. plots. growing. on. the. amended.
tailings.than.in.the.farm-grown.control.plants..Leaves.of. E. melliodora .from.
farm. controls. had. As. concentrations. of. 0.08.mg/kg,. while. samples. from.
treatment. plots. ranged. from. 1.3. to. 2.5.mg/kg.. Leaves. from. the. oil. mallee,.
E. polybractea ,.had.As.concentrations.of.0.09.mg/kg.from.the.control.site.and.
0.7-1.8.mg/kg.in.the.treatment.plots..The.least.successful.of.the.eucalypts,. E.
viridis ,.was.only.sampled.in.three.plots:.topsoil.and.oxide;.low.biosolids.and.
high.biosolids-amended.oxide.and.in.the.farm.area..The.mean.concentration.
of. As. in. farm. samples. was. 0.09.mg/kg. and. 1.1-1.8.mg/kg. in. the. treatment.
plots..Translocation.of.As,.Cu.and.Zn.into.leaf.tissue.occurred.in.the.biosol-
ids.treatments,.but.no.phytotoxic.effects.could.be.observed,.with.low.As.take.
up.of.<5.mg/kg..Uptake.of.As.into.plants.in.the.ield.trials.was.an.order.of.
magnitude.less.than.recorded.in.previous.pot.trials,.indicating.the.natural.
attenuation.of.As.toxicity.(Doronila.et.al..2004)..Plant.growth.on.the.thin.cov-
ers.has.encouraged.oxidation.and.weathering.of.the.upper.proile.and.has.
also.created.conditions.that.reduce.mobility.of.As,.namely,.the.formation.of.
abundant.iron.oxyhydroxides.that.strongly.adsorb.the.metalloid.
Geochemical Development of Substrate
A. fundamental. requirement. for. the. success. of. the. thin,. permeable. covers.
is. that. they. allow. for. continuous. downward. oxidation. of. the. sulidic. tail-
ings. while. not. enhancing. the. mobility. and. bioavailability. of. toxic. metals.
and. arsenic..The. ield. trials. on.proto-TERF.and.TERF.showed.no. evidence.
of. AMD. after. 3. years.. In. parallel. leaching. column. tests. in. the. laboratory,.
employing. wetting/drying. cycles,. the. leachate. was. consistently. neutral. to.
alkaline.over.3.years..The.only.exception.was.in.covers.with.biosolids.that.
produced.leachate.with.pH.of.approximately.3.on.start-up,.although.this.too.