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United Nations Environment Programme
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Freshwater Management Series No. 7

Phytotechnologies

A Technical Approach in Environmental Management

IV. Important Considerations For The Application of Phytotechnologies >

A. Site Characterization

A complete site characterization is essential for the application of phytotechnologies. Characterization should include an evaluation of surface features, structures and buried services to determine whether the site is amenable to a phytotechnology application. Site characterization should provide data on the following:

Site description
Geological data
Hydrogeologic data
Aquifer characteristics
Soil conditions
Air quality
Climatic conditions
Geochemical data
Microbiology
Presence and distribution of contaminants (if any)
Risk assessment.

Assessment of available data should include an analysis of the sufficiency and validity of the data in relation to the proposed phytotechnology application.

As part of the site characterization, agronomic studies should be conducted to determine if site conditions will support plant growth. Soil samples should be collected and analyzed for soil parameters influencin g plant growth, including soil pH, soil fertility and nutrient content, soil structure, soil texture, soil temperature, and soil depth. Saline groundwater conditions may adversely affect plant growth of some species of plants. The site soils should be amended as necessary to optimize plant growing conditions. The need for an irrigation system should also be determined.

B. Plant Selection

Close-up of a sunflower

Native, non-agricultural plants are generally preferred for phytotechnology applications. In most applications, plants that are adapted to local conditions will have better chances of success than non-adapted plants. The use of mixed species of vegetation can also lead to greater chances of success than the use of monocultures. Care should be taken not to introduce specie s of plants that are invasive or a nuisance. In cases where the spread of a plant is undesirable, the plants should be selected to prevent reproduction.

The long term establishment of vegetation at a site is dependent on the project goals and the future intended use of the site. For phytotechnology applications involving little or no maintenance at a given site, it is likely that there will be a succession of plants. If so, this succession could be planned when considering types and timing of vegetation. Plant rotation could be important when short-lived vegetation is used that does not meet overall objectives or for vegetation that should not be replanted in the same place.

C. Modelling

Models are essentially a simplified picture of reality that can be used to help solve problems. The use of modelling in the environmental field has developed rapidly during the last two decades due to:

The development of computer technology, which can handle very complex mathematical systems,
A better understanding of pollution problems, including the recognition that complete elimination of pollution (or “zero discharge”) is not feasible, but that proper pollution control within the limitations of available financial resources requires serious consideration of the potential impacts of pollution on ecosystems,
Increasing knowledge regarding the quantitative relationships in ecosystems, and between the various ecological properties and environmental factors.

Ecosystem models can be considered a synthesis of what we know about the ecosystem, or a component of the ecosystem, with reference to a given problem. It is therefore not surprising that ecological models have been used increasingly as a tool to understand the properties of the ecosystem. The principal advantages of models are that they can be used to survey complex systems, reveal system properties and gaps in our knowledge, and help establish research priorities. Models are useful in tests of scientific hypotheses because they can simulate real conditions, which can then be compared with actual observations.

Modelling may be necessary to optimize the phytotechnology application or to predict behavior. For example, plant uptake models may be used to predict the rate at which a contaminant will be degraded within a plant. Similarly, ecosystem models can be used to understand the relationships between the physical and biological components of phytotechnologies as part of the overall ecosystem.

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