TOOLBOX / BSLA
speculation arose that these plants could
be grown and then harvested to remove
metals from contaminated sites (White and
Newman, 2011). Field sites were planted,
and the performance for metals remediation
was mixed; failures outnumbered successes
mostly because implementation occurred
before the science was substantiated in the
laboratory (White and Newman, 2011). For
example, uptake and remediation of lead
by sunflowers was hailed as an exemplary
remediation tool without the biology and
mechanisms being fully understood. When
actually applied on contaminated sites, it
was found that many metals remediation
plantings were unsuccessful when applied
at field scale. In the late 90s and 2000s,
the credibility of the field was seriously
questioned, and confusion about what is
possible still exists today.
However, while many metals remediation
projects were failing to perform in the
research projects of the 1990s, many
phytotechnology projects to mitigate organic
contaminants such as fuel and solvent spills
were having significant success. Poplars
were being successfully used to stop plumes
of dry cleaning solvents, and trees were
planted in buffers to mitigate gas and oil
spills at stations and refineries. Plants were
also playing a role in filtering pollutants from
stormwater in bioswales and constructed wetlands.
So where does the science stand now?
The Basics—Organics vs Inorganics and
in Soil, Water or Air?
The first two steps in deciding if phytotechnology
systems may be applicable for contaminants in a
given site is to 1) identify if the targeted pollutant
is either organic or inorganic and then further
identify the exact contaminant; and 2) identify
where the pollutant exists, in soil, air or water and at
what depth? Phytotechnology treatment techniques
are incredibly contaminant and media specific and
ALW
AYS require the assistance of a phytotechnology
specialist. A broad overview is provided below
to develop an understanding of opportunities to
consider when phytotechnology could be considered
for a particular project.
Organic pollutants are mostly man-made compounds
that contaminate sites from fuel and solvent spills,
explosives, and agricultural pesticides and herbicides
(Pilon Smits, 2005). Since these pollutants are various
compounds of oxygen, carbon and nitrogen, if
phytotechnology is an applicable solution, many can
be degraded, breaking them down into smaller, less
toxic components that plants and microorganisms can
process (ITRC, 2009). Phytotechnology systems for
the treatment of organics can be an ideal remediation
option where the pollutant is degraded and
disappears, and there is no need to harvest the plants.
List of Common Organic Pollutants Successfully Degraded or
Volatilized at Field Scale with Phytotechnologies
Pollutant
Typical Sources
Petroleum Hydrocarbons: Oil, Gasoline,
Benzene, Toluene, PAHs and Gas additive: MTBE: Methyl
Teritiary Butyl Ether
Fuel Spills, Leaky Underground or Above Ground Storage
Tanks
Chlorinated Solvents: such as TCE: trichloroethylene (Most
common pollutant of groundwater), PERC (PCE)
Industry and Transportation, Drycleaners
Pesticides: Atrazine, Diazinon, Metolachlor, and Temik (To
name a few)
Herbicides, Insecticides and Fungicides from agricultural
and landscape applications
Explosives: RDX
Military Activities
List of Common Organic Pollutants NOT easily Degraded or
Volatilized at Field Scale with Phytotechnologies
Pollutant
Typical Sources
Persistent Organic Pollutants: Including DDT, Chlordane,
PCBs
Historic use as pesticides or in products such as insulation
and caulking
Explosives: TNT
Military Activities
Boston Society of Landscape Architects Fieldbook
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