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

10

20

30

40

50

60

70

80

90

100

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

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0

10

20

30

40

50

60

70

80

90

0

20

40

60

80

100

120

0

10

20

30

40

50

60

70

80

90

0

500

1000

1500

2000

2500

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

0.2

0.4

0.6

0.8

1

1.2

0

20

40

60

80

100

120

140

0

5

10

15

20

25

30

0

5

10

15

20

25

30

35

0

500

1000

1500

2000

2500

3000

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