Phyto-DSS

Brett Robinson1, Steve Green1, Chris Anderson2, and Brent Clothier1

1HortResearch, Palmerston North, New Zealand2Massey University, Palmerston North, New Zealand

A PHYTOEXTRACTION DECISION SUPPORT SYSTEM AND ITS USE IN THE COMMERCIAL

ENVIRONMENT

Phyto-DSS

� Stabilise polluted sites and prevent leaching

� Break-down some toxic chemicals in the soil

� Remove heavy-metals

CnH2nOn

M2+

H2O

Contaminantdegradation& stabilisation

Contaminant extraction

Phytoextraction: using the sun�s energy to extract water and contaminants

Phyto-DSS

Generic pros and cons of phytoextraction

� Low cost� High public appeal� Permanent� Leaves site fertile� Can involve local

communities� May generate a profit off

contaminated land

� Limited to areas that support plant-growth

� Long time-frame� Most effective on

surface contamination� Unsuitable for rapid

cleansing

Phyto-DSS

When should phytoextraction be used?

� Most cost-effective long term strategy

� Satisfies environmental legislation

Phyto-DSS

Major drawback of phytoextraction in the commercial environment

� Unlike other land-treatment technologies, the cost and performance of phytoextraction on a given site can be difficult to predict.

� Phytoextraction is very sensitive to

� climate� chemical, physical and biological properties of the

substrate.� local ecosystem

Phyto-DSS

AIM:To create a Phytoextraction Decision Support

System (Phyto-DSS) that predicts performance and cost of phytoextraction.

Phyto-DSS

groundwater

�Climate

�Plant water-use and growth parameters

�Plant contaminant-uptake parameters

�Substrate properties affecting water movement and contaminant solubility

�Cost over time of phytoextraction compared to other technologies or inaction

M2+

M2+

Phyto-DSS

Transpiration �T (L d-1 )�

Metal in soil solution �C (mg L -1)�

The process of phytoextraction

ΦRoot

Adsorption Factor

Root fraction�R�

( )( ) dzdtztCztCtTztRtM Rz t

∫ ∫=0 0

`)`(`)()`,()( φ

Phyto-DSSPhytoextraction in action: contaminated sawdust

� A 5ha, 15m deep pile of sawdust leaching unacceptable amounts of boron into local waterways

�The Regulatory Authority demanded a US$ 700,000 capping of this site

Phyto-DSS

200 300 400 500 600 700 800 900

0

500

1000

1500

2000

2500 measured ET Phyto-DSS ET measured drainage Phyto-DSS drainage (5)

Volu

me

(L /

tree)

Day of experiment

Phyto-DSS

Dec Feb Apr Jun Aug Oct Dec Feb Apr0.00.20.40.60.81.01.21.41.61.82.02.22.42.62.83.0 Measured

Phyto-DSSBo

ron

conc

entra

tion

in le

acha

te (m

g/L)

Phyto-DSS

28-Oct 12-Nov 26-Nov 11-Dec 25-Dec 9-Jan 23-Jan 7-Feb 22-Feb0

100

200

300

400

500

600

700

800 measured Phyto-DSS

Boro

n co

ncen

tratio

n (m

g kg

-1)

Date

Using the correct varieties and soil amendments is essential�.

Phyto-DSSPhyto-DSS plant properties

Phyto-DSS

1 99 2 19 93 1 99 4 19 95 1 99 6 19 97 1 99 8 1 9 99 2 00 00

50

1 0 0

1 5 0

2 0 0

2 5 0

3 0 0

3 5 0

4 0 0

Leac

hing

(mm

)

Y e a r

1 99 2 19 93 1 99 4 19 95 1 99 6 19 97 1 99 8 1 9 99 2 00 00

50

1 0 0

1 5 0

2 0 0

2 5 0

3 0 0

3 5 0

4 0 0

Leac

hing

(mm

)

Y e a r

Bare sawdust

Planted in poplar

Phyto-DSS

2000

2002

Phyto-DSSPhyto-DSS economic variables

Phyto-DSSPhyto-DSS economic variables

Phyto-DSS

0 200 400 600 800 1000 1200 1400 1600 18000

200

400

600

800

1000

1200

1400

1600

1800C

alcu

late

d bo

ron

in le

aves

(mg/

kg)

Measured boron in leaves (mg/kg)

Phyto-DSSAssessment of phytoextraction at Kopu

� Phytoextraction satisfies environmental legislation on this site

� The total cost of phytoextraction over a ten-year period will be US$ 170,000 compared to capping at US$ 950,000

� Selective coppicing will allow B to be removed from the site

� Harvested material could be used as an organic B-rich mulch on nearby avocado orchards that are deficient in B

Phyto-DSS

Field trial for gold phytomining

Phyto-DSS

0

20

40

60

80

100

0

20

40

60

80

100

Control A B C

Plan

t [Au

] mg

kg-1

dry

mat

ter

Induced gold uptake in Brassica juncea - greenhouse experiment

Substrate [Au]: 0.5 mg kg-1

amendment

Phyto-DSSGold extracted by Brassica juncea

Phyto-DSS

Phyto-DSSPhyto-DSS economic inputs

Phyto-DSSPhyto-DSS induced gold uptake

Phyto-DSS

Phyto-DSS

Phyto-DSSAssessment of gold phytomining

� Most effective on small �orphan sites� where conventional extraction is uneconomic

� Can be effectively combined with the rehabilitation of the site

� Timing of amendment addition is critical

� Highly sensitive to the price of gold

Phyto-DSS

Conclusions

� Modelling can be used to predict the appropriateness of phytoextraction

� Accurate site assessment is essential

� Science costs are part of phytoextraction� Correct species / variety� Substrate amendments� Irrigation regime