Land Reclamation / Phytoremediation
There is a total of 10,771 hectares of Vacant and Derelict land across Scotland which is equivalent to nearly 2 Dundees!
60% of Glasgow's population lives within 500m of Vacant and Derelict land much of this could be contaminated.
Eadha Enterprises are working to establish new productive community woodlands and biomass plantations in urban areas, where commonly the sites will have been previously developed with various industries in the past. These brownfield sites are often recorded by local authorities as Vacant and Derelict land and are also potentially subject to soil and groundwater contamination although not officially classified as such. Eadha's model for new urban woodlands based primarily on the use of aspen can provide a cost effective solution to site remediation and deliver lasting community benefits.
Phytoremediation is the term used to describe the use of plants to remediate soil and groundwater contamination. Phytoremediation trials using willow have been undertaken in the UK in the past, however there has been no research into the use of native aspen. However, aspen has been used successfully for this purpose in North America and eastern Europe where it is considered to be the ideal species for remediation. Aspen represent optimal plants for absorption, accumulation, storage, and degradation of environmental pollutants such as heavy metals, mercury, PCBs, nitrates, pesticide and herbicide residues, aromatics, wood preservatives, explosives and other waste products.
Most forest tree species return between 50% and 80% of their annual nutrient uptake to the soil but aspen retains over half of its uptake and is particularly efficient at retaining calcium, sulphur and zinc, thereby limiting loss by leaching and improving soil fertility. The ability to absorb zinc and other trace elements allows aspen to survive on the spoil heaps of mining operations and assist in the reclamation of post-mining landscapes, for example lignite mines in Germany, opencast oil shale quarries in Estonia and many sites laid bare by coal spoil, heavy metal and smelter pollution in North America. In North America aspen has been found to naturally colonise large areas of polluted industrial sites and to tolerate soils with low pH, low fertility and heavy metal content. The ability to sucker is also an advantage for rapidly extending across new areas of bare ground. Some aspen forests have developed diverse habitats and thrived for over 70 years on mine tailings near smelter sites. Aspen has a mutualistic relationship with a small group of mycorrhizal fungi from the genera Laccaria, Inocybe, Paxillus and Scleroderma which help to increase phosphorus uptake and ameliorate soil conditions and may be essential for aspen to establish in contaminated soils. Beneficial mycorrihiza such as Laccaria laccata have been recorded with aspen and other Populus species on uranium tailings and the spoil heaps of old arsenic mines in England.
Extract from “Ecology, Conservation and Management of Aspen, A Literature Review, Neil Mackenzie, Scottish Native Woods, 2010
Aspen can reduce hotspots of certain contaminants to safe levels over long time frames. However, notwithstanding the hyperaccumulation properties of aspen, increasingly the process of phytostabilisation rather than phytoextraction is being regarded as the more viable option. Rather than focusing on the removal of contaminants from the soil, phytostabilisation is all about locking them safely up within the soil, through accumulation and adsorption within the root zone. This process lowers the leachability of contaminants which effectively can reduce risks to the environment and human health to within safe limits. Theoretically this process can be effective as soon as the roots have sufficiently spread. In the interim, plants such as Reed Canary Grass can be planted to provide some immediate stability to the surface soils and act as a nurse crop for subsequent tree establishment.
Eadha is taking a clonal forestry approach to tree production. Clones are tested and selected for superior growth qualities. Eadha holds the national collection of aspen clones. This represents a unique resource on which to base research and development of phytotechnologies and other forestry related applications. Each clone has evolved as a genetically unique specimen with unique growth characteristics and tolerances to different physical conditions. Eadha is developing a unique system based on native aspen to provide the following:
- Contaminated Land Remediation
- Temporary Greening
- Nitrate buffer zones
- Landfill Leachate Mitigation with Aspen
Eadha is seeking sites to develop urban woodland projects in partnership with local communities.
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