Paper Title: Remediation of Heavy Metal Impacts in Roadside Corridors, Wet Tropics World Heritage...
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Transcript of Paper Title: Remediation of Heavy Metal Impacts in Roadside Corridors, Wet Tropics World Heritage...
Paper Title:Paper Title: Remediation of Heavy Metal Remediation of Heavy Metal
Impacts in Roadside Impacts in Roadside Corridors, Wet Tropics World Corridors, Wet Tropics World
Heritage Area, AustraliaHeritage Area, Australia
• Heavy metals derived from motor vehicles Heavy metals derived from motor vehicles accumulate in road sedimentsaccumulate in road sediments
• These metals are mobilised by rainwater runoff These metals are mobilised by rainwater runoff into streams and soils in roadside corridorsinto streams and soils in roadside corridors
• Exposure of organisms to elevated heavy metal Exposure of organisms to elevated heavy metal loadsloads
Heavy metals in roadside corridorsHeavy metals in roadside corridors
Sources of heavy metals in Sources of heavy metals in roadside corridorsroadside corridors
Brake pads, engine wear = Cd, Cu, Ni
Tyres = Zn
Exhaust = Pb
Research Research AreaArea
Cairns
Location
Reasons for investigationReasons for investigation
►Upgrading Kuranda Range RoadUpgrading Kuranda Range Road
► Previous Honours investigations Previous Honours investigations identified identified elevated heavy metal elevated heavy metal concentrations in roadside soils in the concentrations in roadside soils in the Cairns areaCairns area
Kuranda Range Kuranda Range RoadRoad
World heritage World heritage rainforestrainforest
World heritage World heritage rainforestrainforest
Research aimsResearch aims
Determine:Determine:
► Heavy metal levels in road sediments along Heavy metal levels in road sediments along Kuranda Range RoadKuranda Range Road
► Heavy metal levels in runoff waters along Kuranda Heavy metal levels in runoff waters along Kuranda Range RoadRange Road
► Potential of zeolites to adsorb metals from runoff Potential of zeolites to adsorb metals from runoff waters; limit their dispersal into roadside rainforest waters; limit their dispersal into roadside rainforest streams, soilsstreams, soils
ResultsResults
ResultsResults
Cd(mg/kg)
Cu(mg/kg)
Pb(mg/kg)
Ni(mg/kg)
Zn(mg/kg)
Kuranda Range Road (median, N=18) 0.190 43 54 43 933
ANZECC Guidelines
for sediments 1.500 65 50 21 200
Background levels for local stream sediments (median, N=8)
0.028 23 21 14 27
Heavy metal concentrations in Kuranda Range Road sedimentsHeavy metal concentrations in Kuranda Range Road sediments(Results in mg/kg)(Results in mg/kg)
ResultsResults Grain size distribution in road sedimentsGrain size distribution in road sediments
0
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Weight %
of
sediments
<38 μm >4mm
Sediment size
ResultsResults Heavy metal concentrations (mg/kg) in Heavy metal concentrations (mg/kg) in
different grain size fractionsdifferent grain size fractions
0.00
0.05
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Cd Cu Pb
Ni Zn
Coarse Fine Coarse Fine Coarse Fine
Coarse Fine Coarse Fine
ResultsResults
Cd Cu Pb Ni ZnFirst Flush (January 03) ≤0.05 14.3 0.618 5.24 562
Subsequent flushes (February 03)
≤0.05 14.2 0.405 1.49 141
ANZECC Draft Guidelines – for sensitive environments
0.06 1 1 8 2.4
Background stream levels (February 04)
≤0.05 0.891 0.646 0.161 ≤5
Heavy metal concentrations in Kuranda Range Road runoff water Heavy metal concentrations in Kuranda Range Road runoff water samples (Results in samples (Results in μμg/kg)g/kg)
Adsorption experimentsAdsorption experiments
0
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Cd Cu
Pb
Ni
Zn
ppb
ppb
ppbppb
ppb
5 minutes 5 minutes 5 minutes
5 minutes 5 minutes
1 hour 1 hour 1 hour
1 hour 1 hour
24 hours 24 hours 24 hours
24 hours 24 hours
Zeolite-treated leachate
untreated leachate, contaminated with road sediments
ResultsResults
Conclusions and Conclusions and recommendationsrecommendations
Road sediments on Kuranda Range Road Road sediments on Kuranda Range Road contaminated with elevated levels of contaminated with elevated levels of heavy metals, particularly in fine-medium heavy metals, particularly in fine-medium sized particlessized particles
Conclusions and Conclusions and recommendationsrecommendations
Runoff waters also contain high dissolved Runoff waters also contain high dissolved heavy metals loads, particularly during heavy metals loads, particularly during early rainfall eventsearly rainfall events
Conclusions and Conclusions and recommendationsrecommendations
Active remediation – too expensive, not warranted
Large-scale wetland, inappropriate for rugged terrain
Conclusions and Conclusions and recommendationsrecommendations
PVC drum/container
Outlet
Runoff waters
Zeolites, adsorber
Plastic grate to keep zeolites at base
Treated water
Small-scale adsorption traps
Conclusions and Conclusions and recommendationsrecommendations
Zeolites show strong potential to adsorb Zeolites show strong potential to adsorb elevated dissolved Zn loads in runoff, elevated dissolved Zn loads in runoff, but ineffective for other metalsbut ineffective for other metals
Conclusions and Conclusions and recommendationsrecommendations
Still, Zn is most abundant, dissolved Still, Zn is most abundant, dissolved levels of other metals is quite lowlevels of other metals is quite low
Further testing of zeolite’s potential to Further testing of zeolite’s potential to adsorb these other metals may involve adsorb these other metals may involve agitation of solution to increase agitation of solution to increase exposure of reactive surfaces of exposure of reactive surfaces of zeoliteszeolites
Conclusions and Conclusions and recommendationsrecommendations
Zeolites seen as useful substances to incorporate Zeolites seen as useful substances to incorporate into filter traps in drains along Kuranda Range into filter traps in drains along Kuranda Range Road and other roads of similar natureRoad and other roads of similar nature
Weaknesses in the research: Weaknesses in the research: remediation of runoff watersremediation of runoff waters
Main problem - zeolites only effective for Zn, Main problem - zeolites only effective for Zn, need options for reducing other metal need options for reducing other metal concentrations especially Cuconcentrations especially Cu
Need to ensure that adsorptive material has Need to ensure that adsorptive material has long enough time to react with runoff waters long enough time to react with runoff waters without blocking drains – need to ensure without blocking drains – need to ensure constant flow of runoffconstant flow of runoff
How to treat runoff waters that flow directly over How to treat runoff waters that flow directly over soils that do not collect in drainssoils that do not collect in drains
Weaknesses in the research: Weaknesses in the research: remediation of runoff watersremediation of runoff waters
Limitation of remediation to sediment bound Limitation of remediation to sediment bound metals – does not address airborne metal metals – does not address airborne metal phases that settle in soils or on roadside phases that settle in soils or on roadside vegetationvegetation