Environmental Engineering Reference
In-Depth Information
As distribution in surface tailings
100%
75%
Residual
Oxalate—colloidal
Phosphate—exchangable
Sulfate—soluble
50%
25%
0%
0
1.5
Exposure time (years)
5
FIGURE 20.5
Relative. abundance. of. arsenic. in. the. different. phase. of. the. four. step. sequential. extraction.
procedure.
through.the.oxidation.process..The.pH.of.deeper.unoxidized.tailings.were.
consistently. >pH.7. and.were. oxidation. had.occurred. it. was. pH. 6.5-7.. This.
indicates. that. there. is. signiicant. acid. neutralizing. capacity. in. the. tailings..
Proliferation. of. cracks. enhanced. washing. of. the. secondary. minerals,. e.g.,.
gypsum,.down.the.proile.away.from.the.root.zone.
The. average. density. of. different. size. classes. of. roots. at. different. depths.
underneath.
E. cladocalyx
. seedlings. is. illustrated. in. Figure. 20.6.. This. spe-
cies.is.deep-rooted.and.the.fastest.growing.of.the.eucalypts.in.the.trial.and.
would. show. greater. stress. responses. from. limiting. factors. after. 2.5. years..
Proliferation. of. roots. in. the. deeper. reaches. of. the. proile. appears. to. be.
strongly.related.to.the.presence.of.cracks.in.the.tailings.. Preferential.path-
ways.are.created.for.water.to.percolate.through..Formation.of.ine.and.very.
ine.roots.was.greatest.in.the.upper.layers..These.are.predominantly.roots.of.
pasture.species;.however,.eucalypt.roots.were.evident.in.the.deeper.cracks.
down.to.almost.1.m.depth.
Discussion
The. compounding. effects. of. drought,. salinity,. and. weed. competition. lim-
ited. the. establishment. of. eucalypts. on. sulide. mine. tailings. during. the.
experimentation.at.Stawell.Gold.Mine..Mortality.of.all.eucalypts.in.biosolids.
treatments.may.have.been.due.to.the.initial.salinity.as.well.as.competition.
from. vigorous. exotic. pasture. growth.. A. major. limitation. in. establishment.
of.eucalypts.in.reafforestation.programs.has.been.attributed.to.inadequate.
weed.control.(Venning.1988,.Dalton.1993,.Falkiner.et.al..2004)..Several.factors.
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