Newsletter and Technical Publications
Freshwater Management Series No. 5
Guidelines for the Integrated Management of
- Phytotechnology and Ecohydrology -
for reducing soil erosion and nutrient losses to aquatic systems
As noted above, phytotechnologies can be
utilised to minimise erosion by wind and water from the land surface. Plants
can be used to bind contaminants, limiting their availability for transport
into surface and ground waters. The degree to which plants can reduce soil and
nutrient losses is a function of the type and density of plant cover; site
hydrology and hydraulics; and the distribution of plants within or along a
Vegetative cover refers to
the long-term, self-sustaining community of plants growing in and/or over the
land surface. When this concept is applied to phytotechnologies, it refers
specifically to plant communities associated with materials that pose an
environmental risk. Use of vegetative cover may reduce that risk to an
acceptable level. Vegetative alternatives generally require minimal
maintenance. There are two types of vegetative cover:
- Evapotranspiration cover that is composed of the
soil and plant system engineered to maximise the available storage
capacity of the soils, evaporation rates, and the transpiration process of
the plants to minimise water infiltration. An evapo- transpiration cap,
commonly used at sealed landfill sites, is a form of hydraulic control by
plants that reduces environmental risk by limiting the human or wildlife
exposure to contaminants and reducing leachate formation and movement.
- Phytoremediation cover consists of a soil and
plant system designed to minimise infiltration of water into a
contaminated site, thereby aiding in the degradation of the underlying
waste. Risk reduction relies on the degradation of contaminants, the
isolation of contaminants to prevent human or wildlife exposure, and the
reduction of leachate formation and movement.
Hydraulic controls use plants to remove
groundwater through uptake and consumption in order to contain or control the
migration of contaminants. Hydraulic control is also known as phytohydraulics
or hydraulic plume control. Trees such as the willow are often utilised for
hydraulic control purposes since these trees have an high water demand.
Buffer zones are generally applied along
streams and river banks to control and treat contaminated surface runoff and
groundwater moving into the river. These systems can also be installed to
prevent downgradient migration of contamination plumes in groundwater systems.
Often these systems are utilised in projects that encourage phytodegradation of
contaminants in a plume.
P. Selection criteria for phytoremediation
The main consideration in the evaluation of
phytoremediation alternatives in the remediation of contaminated sites is
related to the type of soil media and water source, the concentration of the
contaminant(s) of interest, and the potential for effective vegetation growth
at the site.
The decision-making process for evaluating
whether or not phytoremediation are viable options is summarised in the
- Define the problem
- conduct a site characterisation,
- identify the problem: media and/or contaminant,
- identify regulatory requirements,
- identify remedial objectives,
criteria for defining the success of the phytoremediation system.
- Evaluate the site for potential application of phytoremediation
a phytoremediation -oriented site characterisation and risk assessment
appropriate phytoremediation that address the media/ contaminant/goals,
the most appropriate plant species to be used, based upon consideration of the
site conditions, pollutant(s) involved, and the ability of the plant(s) to
absorb or translocate significant levels of the contaminant(s),
known information about the identified phytoremediation,
potential plants and sources of plants (local plants are best).
- Conduct preliminary studies and make a decision
- conduct screening studies,
optimisation studies to determine optimal planting densities and types,
- conduct field plot trials prior to full-scale implementation,
the selection of plants for use with the phytoremediation, if necessary.
- Evaluate a full-scale phytoremediation system
the system, including measures to limit flooding, control erosion, and dispose
of harvested plant materials,
- construct the system,
and operate system for at least one full growth cycle,
- evaluate and modify the system,
- evaluate system performance.
- Continue to achieve the objectives
quantitative measurements to monitor system operation and performance,
the degree to which the technology has met the criteria for success.
of the fundamental tenets of the concept of sustainable development is the
maintenance of a homeostatic equilibrium within the ecosystem.
Over-exploitation of the ecosystem, or degradation of its biotic structure,
alters ecosystem processes to the point whereby the ability of the ecosystem to
meet desired conditions is seriously diminished. Water is the medium for all
ecological processes, from the molecular to the global scales. The physical
quantification of ecological processes, in terms of water and energy, is
fundamental to the scientific investigations that should underpin a programme
of sound ecosystem management.
The most appropriate scale for measuring and quantifying energy and nutrient
dynamics in aquatic ecosystems is the mesocycle within a basin, which forms the
basic geographic unit within which to determine and quantify the interconnected
processes that comprise the ecosystem and provide a framework for the
interactions between its biotic, physical and chemical elements.
The degradation of freshwater ecosystems can be characterised in terms of two
dimensions; namely, pollution, which can be reduced to a significant extent
using known technologies, and the degradation of established water and nutrient
cycles within the ecosystem as a whole. This second dimension is much more
complex. A new tool for resolving ecosystem-scale problems is the application
of ecohydrological principles and phytotechnologies. Our progressive
understanding of the range of anthropogenically-induced degradation of
hydrological, biogeochemical, and biological processes within water basins
indicates an urgent need to control and regulate nutrient and water dynamics by
increasing plant biomass and diversity. Phytotechnologies can be viewed as a
tool for increasing ecosystem carrying capacity and enhancing the resilience and
functionality of ecosystems at the basin scale. Phytotechnologies form the
medium by which to implement ecohydrological principles.
An interdisciplinary, holistic approach, based on an understanding of the role of
plant biomass in the control of water and biogeochemical cycles (i.e., "green
feedback", should lead to improved water quality, enhanced biodiversity and
agricultural production, and sustainable bioenergy generation, as well as
increased employment opportunities.
Preparation of this
chapter has been supported by Polish State Committee for Scientific Research
grant no KBN 6P04 611220.
|Advanced Applied Technology Demonstration Facility
|Air Force Center for Environmental
|Alternative Treatment Technology
|Brownfieldstech Internet web site
|CLU-IN: Hazardous Waste Clean-Up
|Environmental Security Technology
Certification Program (ESTCP)
|Federal Remediation Technologies
|GNET: The Global Network of Environment
|Great Plains/Rocky Mountain Hazardous
Substance Research Center
|Ground Water Remediation Technologies
|Innovative Treatment Remediation
|Interstate Technology and Regulatory
Co-operation Working Group
|PHYTONET - Phytoremediation Electronic
|Remediation Technologies Development Forum
|Phytoremediation of Organics Action Team
|Strategic Environmental Research and
||U.S. Army Corps of Engineers Phytoremediation Research
|U.S. Army Environmental Center (USAEC)
|U.S. Department of Agriculture (USDA)
LIST OF ACRONYMS
||Benzene, toluene, ethylbenzene, and xylene
||Polycyclic aromatic hydrocarbons
||Total petroleum hydrocarbons