agriculture is becoming more important in today's cities. It has great
potential to improve the quality of life in urban areas by increasing
food security, providing opportunities for community development,
and improving the aesthetics of the urban landscape. Community organizations
practicing urban agriculture face many obstacles, such as land availability,
restricted budgets and soil contamination. Soil contamination is a
major barrier to urban agriculture initiatives, because contaminants
are present in most urban soils at levels higher than are accepted
for agricultural use. These contaminants can be taken up by plants
grown in these soils, and can be harmful to human health if the produce
is consumed. The barrier of land availability could be partially overcome
if brownfields could be used as sites for urban agriculture. Brownfields
are unused plots of urban land that are contaminated from previous
land uses. If these brownfields could be remediated by community groups,
they would further the development of urban agriculture projects.
Remediation involves the removal of contaminants, in this case such
that the soil meets conditions for urban agriculture.
Excavation refers to physically removing contaminated soil, normally for disposal at a landfill. Excavation is generally accomplished with heavy machinery. New soil is needed after the excavation.
Geotextiles are a synthetic blanket-like material. They can be used after the excavation process to provide a protective barrier, impermeable to contaminants which may otherwise migrate into the new soil after excavation. One concern with geotextiles is that the fabric can tear, allowing contaminants to pass through into the new soil.
Soil washing is a technique which involves the physical removal of the contaminated soil, followed by treatment at a plant on or off-site. After the contamination is removed through the treatment process, the soil is put back into the ground.
vapour extraction involves the installation of wells and
pipes in the soil, through which soil contaminants are extracted in
Microbial remediation refers to the use of microbes in degrading contaminants into a less toxic form. This technique can be very effective in the treatment of hydrocarbons, PAH's, pesticides, and PCB's.
Phytoremediation is the process of using plants to degrade organic contaminants or to extract toxic metals from the soil and transport them into the above-ground shoots. In the case of extraction, the contaminated plants must later be disposed of.
Fungal remediation refers to the use of certain species of fungus to degrade contaminants, particularly hydrocarbons.
Compost remediation involves the addition of compost to the soil. It is not a true remediation technique, as the contaminants generally remain intact in the soil. The addition of compost can, however, be used to create a raised bed, in which the plant roots may not reach the contaminated soil.