Phytoremediation of heavy metals

Gyeongsang National University

Environmental Engineering Laboratory

Le Ngoc Thuan

** 김 투 안 **

Overview

1. What are heavy metals?

2. Sources of heavy metal in the environment

3. Pollutants removal by Phytoremediation

4. Phytoremediation for heavy metal removal

5. Advantages and disadvantages of Phytoremediation

1. What are heavy metals?

A metal with a specific gravity greater than about 5.0, especially

one that is poisonous, such as lead (Pb), mercury (Hg), chromium (Cr),

cadmium (Cd),…

They can damage living things at low concentrations and tend to

accumulate in the food chain

2. Sources of heavy metal in the environment

Municipal and Industrial waste Sediment from wastewater treatment plant

There are some main sources of heavy metal in the environment

Sources of heavy metal in the environment (cont.)

Mining wasteLeachate from solid waste treatment plant

3. Pollutants removal by Phytoremediation

The use of plants to remove pollutants from contaminated soils or water, base on ability of the uptake of contaminants by special plants (hyperaccumulators). In this process there is also combination of bacterial bioremediation.

Overview of Phytoremediation-Related Plant Activities

Types of Phytoremediation

Phytotransformation – uptake of contaminants from soil & groundwater by plants and their subsequent transformation in roots, stems, and leaves

Rhizosphere Bioremediation – occurs in the root-zone; also known as phytostimulation or plant-assisted bioremediation; results in increase of soil organic carbon, and bacterial and fungal populations.

Phytostabilization – refers to holding of contaminated soils in place by vegetation, and immobilization (physically orchemically) of contaminants

Phytoextraction – use of metal-accumulating plants that translocate metals from the soil to their roots and concentrate the metals to aboveground stems and leaves.

Rhizofiltration – use of plants to sorb, concentrate, and/or precipitate metal contaminants from surface waters(treatment wetlands) or groundwater

4. Phytoremediation for heavy metal removal

Plants, so called hyperaccumulators are usually used, they take up 100 times the concentration of metals over other plants.

Heavy metals are removed from soil by moving up into plant roots, stems, and leaves.

The plant is then harvested and disposed of and the site replanted until heavy metals in the soil is lowered to acceptable levels.

How can heavy metals move into the cell?

Heavy metal accumulation by Indian Mustard Brassica juncea Brassica juncea: After

havested, average concentration of

lead from all the crops exceeded

1,000ppm

Thlaspi caerulescens was

shown to accumulate up to

26,000ppm while a regular plant

accumulates about 100 ppm

Several metal hyperaccumulator species and their bioaccumulation potential.

Plant species Metal Leaf content (ppm) Reference

Thlaspi caerulescens Zn:Cd 39,600:1,800Reeves & Brooks (1983):

Baker & Walker (1990

Ipomea alpina Cu 12,300 Baker & Walker (1990)

Haumaniastrum robertii

Co 10,200 Brooks (1977)

Astragalus racemosus Se 14,900 Beath et al. (1937)

Sebertia acuminata Ni 25% by wt dried sap Jaffre et al. (1976)

Approximately 400 plant species from at least 45 plant families have been reported to hyperaccumulate metals.

Phytoremediation using Cash Crops Phytoremediation using Poplars

Wild mustard plant for metals phytoextraction

Wild mustard plant willhyperaccumulate nickel,reaching shootconcentrations as highas 1.2%.

Considering Phytoremediation for Your Site

Yes

Yes

Yes

Yes

Yes

No

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No

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No

Additional Considerations

Infrastructure Requirements: need to be accessible to farm implements (tractors with tilling/plowing, fertilizing, seeding, and harvesting equipment) and sufficiently dry to allow for cultivation and avoiding waterlogged conditions to support growth of plants.

Long-Term Remedy: the area will look like a restored wetland/upland area. During active remediation, the area will look like a cultivated field.

Process Residuals Management: The harvested biomass will be analyzed and disposed of according to its composition such as: processing for volume reduction, composting, either land filling or incinerating in approved facilities.

Need for Long-Term Monitoring: Monitoring the technology’s performance (removal rates) will be continuous until cleanup is complete and the site has been restored.

5. Advantages and disadvantages of Phytoremediation

Advantages Disadvantages

-In situ

-Low cost

-Well suited for use at very large field sites

-Transfer is faster than natural attenuation

-High public acceptance

-Fewer air and water emissions

-Soils remain in place and are usable following treatment

- Compatible with engineered technologies

- Long duration of time for remediation

- Not all compounds are susceptible to rapid and complete degradation

- High concentrations of hazardous materials can be toxic to plants

- Effective only for moderately hydrophobic contaminants

- Toxicity and bioavailability of degradation products is not known

- Potential for contaminants to enter food chain through animal consumption

- Hyperaccumulators are often slow growers

- Need to dispose plant biomass

Review from:

1. Brian R. Shmaefsky: Heavy metal tolerant transgenic plant

2. Ray R. Hinchman et. al., Phytoremediation: Using green plants to clean

up contaminated soil, groundwater, and wastewater

3. Dang Thi An et. al., Evaluation of the water quality of the Nhue-To Lich

river system; utilization of biological indices and bioaccumulation.

4. Mitch M. Lasat: The Use of Plants for the Removal of Toxic Metals from

Contaminated Soil

Thank you for your attention!