Phytoremediation of

Lead contaminated soil

Green Technology

RASBIN BASNET(0917844)

UNIVERSITY OF WOLVERHAMPTON

Phytoremediation: an emerging technology that uses plants to clean up organic or inorganic contaminants in-situ from soil, groundwater, surface water and even the atmosphere.

Why Phytoremediation ?Land burial or incineration

$200 - $1500 per ton

Phytoremediation $10 - $50 per ton

EconomicalImproves quality and texture of soilMitigates erosion from wind and waterPossibility of bio-recoveryNo geographical restrictionEnvironmentally friendlyHigh public acceptance

BENEFITS

Gerhardt et al, 2009

Pesticides and fertilizersDumping of municipal wasteVehicle exhaustUsed in paint, batteries,

television glass, ammunition, etcIndustrial processes like mining

and smelting.

Soil quality degradationCrop yield reductionPoor quality of agricultural productsSignificant hazards to human, animal and ecosystem health

Sources of Lead

Effects of Lead

Health effects

Lead: A serious heavy metal pollutant

Lead poisoning (fatal).Impaired development in children with lower IQ.Mental deterioration.

Phytoremediation Techniques

Phytoextraction: Absorption and concentration of metals from the soil

into the roots and shoots of the plants.

Rhizofiltration: Absorb and adsorb pollutants in plant roots.

Phytostabilization: Root exudates cause metals to precipitate

and biomass becomes less bioavailable.

Phytovolatilization: Plants evaporate certain metal ions and volatile

organics

Phytodegradation: Microbial degradation in the rhizosphere region.

Phytotransformation: Plant uptake of organic contaminants and

degradation.

Removal of aerial contaminants: Uptake of various organics by

leaves. Yang et al, 2005

Major processes involved in heavy metals accumulation in plants

SOLAR DRIVEN BIOPUMPS

Yang et al, 2005

Selection of Plant

Fast growingHigh biomassExtensive root systemEasy to harvestTolerate and accumulate a range of heavy metals in their

harvestable parts

Selection of plant is an ongoing process which is based on following features:

Hyperaccumulation

Brassica juncea (Indian Mustard)Alternanthera philoxeroides (Cho-Ruk et al, 2006)

Bidens maximowicziana (Hong-qi et al, 2007)

Allium fistulosum (Onion) (Cho et al, 2009)

Lathyrus sativus (Grass pea) (Brunet et al, 2008)

Plants used for hyperaccumulating lead

(Lim et al, 2004)

Hyperaccumulators: plants capable of sequestering heavy metals in their shoot tissues at high concentrations.

Methodology

Plant preparation Soil preparation

ModificationPlant Harvest & Analysis

Use of soil amendments to increase the availability of heavy metals for plant uptake, like: EDTA, Citric acid, NaH2PO3.Use of specific microorganisms to facilitate Pb uptake

Lead content in different plant parts measured by inductively coupled plasma optical emission spectrometry (ICP-OES).

Solution of lead nitrate (PbNO3) in different concentration mixed to soil.

Seed germinated in seedbed.Precultured in seedbed.Plantlets transplanted and cultured in Pb contaminated soil.

Slow growth rate of plants.Restricted to sites with shallow contamination within rooting zone.Plant growth is hard to achieve in heavily impacted soil.Bioavailability of target metal(s).Disposal of plant biomass could be a RCRA regulated hazard substance.Introduction of non-native species may affect biodiversity.Unfavourable climate may limit plant growthPresence of stressors

Variation in temperatureAvailability of nutrientsHerbivoryPlant pathogensCompetition by weeds that are better adapted to the site

Limitations / Challenges

Overcoming challenges Future perspectives

Search for fast growing, metal tolerant hyperaccumulating plantswith extensive root system.

Engineering of common plantswith hyperaccumulating genes from microorganisms or from other plants .

Use of native plant species.

Use of plant growth promoting rhizobacteria to facilitate the growth of plants used for phytoremediation.

Use of chelating agents to increase the solubility of lead in soil.

DISCUSSION

Hyperaccumulators has potential for phytoremediation of metal contaminated soils.

This technology is still in its infancy and it has yet to be used commercially.

It is predicted to account for approximately 10-15% of the growing environment remediation market in 2010 (Glick, 2003).

Phytoremediation= Soil healing technique

References Brunet, J, Repellin, A., Varrault, G. Terryn, N. Zuily F. (2008) Lead accumulation

in the roots of grass pea (Lathyrus Sativus): a novel plant for phytoremediation : Competes Rendus Biologies, Vol.331(11), pp. 859-864

Cho-Ruk, K., Kurukote, J., Supprung, P. and Vetayasuporn, S. (2006) Perennial plants in the phytoremediation of lead contaminated soilsAvailable at: www.thaiscience.info

Cho, Y., Bolick, J.A. and Butcher, D.J. (2009), Phytoremediation of lead with green onions (Allium fistulosum) and uptake of arsenic compounds by moonlight ferns (Pteris cretica cv Mayii): Microchemical journal, Vol. 91, pp. 6-8

Glick, B.R. (2003) Phytoremediation: synergistic use of plant and bacteria to clean up the environment: Biotechnology advances, Vol.21, pp. 383-393

Gerhardt, K.E., Huang, X., Glick, B.R., and Greenberg, B.M. (2009) Phytoremediation and rhizoremediation of organic soil contaminants: Potential and challenges: Plant science, Vol.176, pp. 20-30

Hong-qi, W., Si-jin, LU, Hua. L. and Zhi-hua, Y.(2007) EDTA- enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana: Journal of Environmental sciences, Vol.19, pp. 1496-1499

Lim, J., Salido, A.L. and Butcher, D.J. (2004) Phytoremediation of lead using Indian mustard (Brassica juncea) with EDTA and electrodics: Microchemical journal, Vol. 76, pp. 3-9

Yang, X., Feng, Y., He, Z. and Stoffella, P.J. (2005) Molecular mechanisms of heavy metal hyperaccumulation and phytoremediation: Journal of trace elements in medicinea nd biology, Vol.18, pp.339-353