Vs And Mine Rehabilitation

VETIVER GRASS TECHNOLOGY FOR MINE REHABILITATION IN QUEENSLAND, AUSTRALIA Paul Truong, DNR, Brisbane, Australia Vetiver Vetiver grass grass (Vetiveria (Vetiveria zizanioides zizanioides L.) L.) has has been been shown shown to to have have high high level level of of tolerance tolerance to to adverse adverse climatic climatic and and edaphic edaphic conditions, conditions, and and heavy heavy metal metal toxicities. toxicities. Vetiver Vetiver Grass Grass Technology Technology has has been been used used very very successfully successfully for for the the rehabilitation rehabilitation of of overburden overburden and and tailings tailings of of coal, coal, gold, gold, bentonite bentonite and and arsenic arsenic mines mines in in Queensland, Queensland, Australia. Australia. Heavy Metal Contents of a Representative Gold Mine Tailings in Australia. Heavy Metals

Arsenic Chromium Copper Manganese Lead Strontium Zinc

Total Contents (mgKg-1)

1 120 55 156 2 000 353 335 283

Tolerance Range of Vetiver Grass

Environmental Threshold levels (mgKg-1)*

20 50 60 500 300 NA 200

* Maximum levels tolerated by environmental and health authorities in Australia and New Zealand. NA Not available

Deep and extensive root system binds the soil and enhances drought tolerance Vetiver is the only species among the 6 tested that can be established easily and produced very good growth on this coal tailings dam which is highly saline and alkaline

Adverse Soil Conditions Acidity Aluminium level (Al Sat. %) Manganese level Alkalinity (highly sodic) Salinity (50% yield reduction) Salinity (survived) Sodicity Magnesicity

pH 3.3 Between 80% - 87% > 578 mgkg -1 pH 11.5 17.5 mScm -1 47.5 mScm -1 33% (exchange Na) 2 400 mgkg -1 (Mg)

Heavy Metals Arsenic Cadmium Copper Chromium Nickel Mercury Lead Selenium Zinc.

100 - 250 mgkg -1 20 mgkg -1 35 - 50 mgkg -1 200 - 600 mgkg -1 50 - 100 mgkg -1 > 6 mgkg -1 > 1 500 mgkg -1 > 74 mgkg -1 >750 mgkg -1

Location

Equator to 41 0N

Climate Annual Rainfall (mm) Frost (ground temp.) Heat wave Drought (without effective rain) Fertiliser Vetiver can be established on very infertile soil due to its strong association with mycorrhiza

250 - 5 000 -140C 550C 15 months N and P (300 kg/ ha DAP)

Threshold Levels of Heavy Metals of Vetiver Growth as Compared with Other Species. Heavy Metals

Arsenic Cadmium Copper Chromium Lead Mercury Nickel Selenium Zinc

Thresholds to Plant Growth (mgKg-1) Hydroponic levels (a) 0.02-7.5 0.2-9.0 0.5-8.0 0.5-10.0 NA NA 0.5-2.0 NA NA

Soil levels (b) 2.0 1.5 NA NA NA NA 7-10 2-14 NA

Thresholds to Vetiver Growth (mgKg-1) Soil levels Shoot levels 100-250 20-60 50-100 200-600 >1 500 >6 100 >74 >750

21-72 45-48 13-15 5-18 >78 >0.12 347 >11 880

Average Distribution of Heavy Metals in Vetiver Shoots and Roots. Metals

Dense growth retards water flow and traps sediments

Arsenic Cadmium Copper Chromium Lead Mercury Nickel ( Ni) Selenium Zinc

Soil (mgKg -1) 688.4 1.025 50 283 469 1.98 300 19.86 390

Shoot (mgKg -1) 8.44 0.30 13 9 35.32 0.05 448 4.44 461

Root (mgKg -1 ) 180.2 10.97 68 1108 45.88 2.27 1040 8.37 643

Shoot / Root % 4.8 3.1 19 <1 57 6 43 53 69

Shoot / Total % 4.6 2.9 16 <1 33 5 30 33 40

Vetiver were planted on this highly alkaline and sodic coal mine overburden in central Queensland.

This 40 year old coal mine overburden stock pile remains bare of vegetation. Several rehabilitation attempts have failed

These 8 year old gold tailings are highly acidic (pH 2.7) and high in As, SO4, Zn and Cu

Gold mine tailings dump near Georgetown remained bare of vegetation for more than 15 years and is highly susceptible to both water and wind erosion

This bentonite mine waste and overburden is highly sodic and erodible. Both wind and water erosion is a major concern

Despite very dry weather over the next 4 years, at least 40% of the Vetiver survived, and stabilised the side for the establishment of other species

Vetiver established successfully in the gully to stop further erosion and across the toe slope to trap eroded material

Excellent growth of vetiver 12 months after planting with 20t/ha of lime and 800kg/ha of DAP

Vetiver planted for both erosion and sediment control. Vigorous growth was recorded 6 months after planting

Vetiver was established successfully on the site and excellent growth is recorded after 7 months