Transcript Document

Role of Plant Architecture and Cuticular Features in Removing Iron From Wetlands Constructed to Treat Abandoned Mine Drainage
Rachel Giroux, Beth Karwaski, Kenneth Klemow, Donald Mencer, Therese Wignot, and Brian E. Whitman
College of Science and Engineering, Wilkes University, Wilkes-Barre, PA 18766
Results
Background
Plant Species
Typha latifolia: Cattail
•Inset graphs contain rescaled versions for cattail, great bulrush and soft rush
respectively to allow for a more detailed view of the data.
Abandoned mine drainage (AMD) is a primary contributor to aquatic
pollution nationwide. Heavy metals dissolved in AMD become oxidized,
forming insoluble metal hydroxides deposited in stream beds. AMD kills
aquatic vegetation and impairs macroinvertebrate communities needed for
healthy aquatic food chains.
The common cattail has long,
broad, slightly waxy leaves.
A thick cylindrical column of
tightly bound leaves is
exposed to the water in the
wetland.
Ca t t a i l : I r on We i ght v s. S ur f a c e Ar e a
Figure II: Cattail: Iron Weight vs. Surface Area*
Reed: Iron Weight vs. Surface Area
Figure I: BurBurrreed:
Iron Weight vs. Surface Area
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Statement of Problem
•Identify the species of wetland plant best suited to remove the
most iron per unit area in order to achieve maximum iron
removal potential.
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Iron (Fe2O3) Weight (grams)
Some plant species remove iron more effectively than others. Plants with
diffuse submerged stem and root structures appear to bind more iron than
those with unbranched stems. However, the proportion of the plant
covered by non-polar vs. polar non-cuticled plant surfaces may also affect
the adsorption of polar hydroxides.
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Iron (Fe2O3) Weight (grams)
AMD is often treated by diverting contaminated mine water into
constructed wetlands. In the mid-1990s, an interdisciplinary team of
Wilkes biologists and environmental engineers designed two wetland
systems that successfully removed iron from mine water. These wetlands
improve water quality by adsorbing particulate iron onto the surface of
individual plants, including introduced and naturally colonizing species.
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Sparangium americanum: Bur
reed
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Figure 2 shows cattail’s iron accumulation per square
centimeter of plant matter. There is a much smaller iron
mass for each square centimeter compared to the burreed. The cattail data also included a degree of scatter,
which is a topic of future study.
Figure 1 shows the relationship between iron accumulation and
surface area for bur-reed. For the most part, there is an upward
trend, indicating an increase in accumulation with an increase
in surface area as expected. There is significant scatter
indicating that other factors are involved when determining a
plants ability to trap iron.
The stem of bur reed
produces short, broad,
ridged leaves. The column
exposed to the water in the
wetland can be branched
or tightly bound as in the
cattail.
Juncus effusus: Softrush
Softrush has long, thin,
smooth tubular leaves.
They are frequently found
in large clumps where the
columns exposed include a
collection of tubular leaves.
S of t r ush: I r on We i ght v s S ur f a c e A r e a
Hypothesis
•Plants with a thick waxy cuticle will most likely prevent heavy
iron accumulation as opposed to plants with a thinner cuticle
layer.
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•The plant structures were rinsed with tap water to remove the
iron material. The water containing iron material was oven
dried.
•The iron material was ignited at 800°C for 2 hours to burn off
any organic matter, evaporate any remaining water, and convert
the material into Fe2O3. This material was then weighed.
•The surface areas of the plant structure were determined by first
spray painting the plants black and then using a CI-202 Area
Meter.
•Iron weight was graphically correlated to plant surface area for
each species.
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Scirpus validus: Great
bulrush
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Surface Area
•Several dozen plants of four species were collected removed
from an AMD-treatment wetland near Nanticoke in Luzerne
County, PA. The potions of the plants exposed to the water
column were isolated.
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Materials and Methods
Figure IV: Softrush: Iron Weight vs. Surface Area
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Iron (Fe2O3) Weight (grams)
•Plants with smoother, less branched leaves, such as the great
bulrush and soft rush, will accumulate less iron.
Figure 3: Great bulrush: Iron Weight vs. Surface Area
Iron (Fe2O3) Weight (grams)
•The plant species able to trap the most iron will most likely
have broad ridged leaves with a branched structure, such as the
bur-reed.
R e e d: I r on We i ght v s S ur f a c e A r e a
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Figure 3 depicts the great bulrush’s iron accumulation:
surface area relationship. The great bulrush was notably
smaller in size and collected a much smaller amount of
iron than bur reed. Cattail adsorbed a slightly larger
amount of iron where the surface areas were similar.
Scatter was also an issue when dealing with the detailed
great bulrush graph.
Figure 4 illustrates the relationship between iron
accumulation and surface area of softrush. Softrush and
great bulrush adsorbed similar amounts of iron. Softrush,
however, included a larger variety of plant surface area
where accumulation increased. Scatter was again observed
with the softrush.
Conclusions
•Bur reed accumulates a greater amount of iron per unit area compared to the cattail, great bulrush and softrush.
•Preliminary cuticle analysis proved to be inconclusive. Further experiments may be done to optimize cuticle wax
extraction.
Literature Cited
Matthew A. Jenks, Hillary A. Tuttle, Sandford D. Eigenbrode, and Kenneth A. Feldmann. Leaf Epicuticular Waxes of the Eceriferum Mutants in Arabidopsis.
Plant Physiology. (1995) 108: 369-377.
Abdelali Hannoufa, John McNevin, and Betrand Lemieux. Epicuticular Waxes of Echeriferum Mutants of Arabidopsis thaliana. Phytochemistry. (1993). 33: 851855.
Funding for this project was provided by a grant from Merck / AAAS to Wilkes University
Great bulrush also has long
tubular leaves. Many of the
plants also included an outer
smooth layer of dead matter.
The columns exposed to the
water often contained a
collection of plant leaves.
Future Work
•Examination of biofilms (bacteria or other micro-organisms)
may reveal additional insight concerning the adherence of
iron to plant cuticles.
•Chemical analysis of the iron material found in mine
drainage would also be useful when deciding how to remove
the material from the environment.
•A study comparing the live plant material to the dead plant
matter could determine whether the dead matter in the
wetland accumulates a greater amount of iron.
•Analysis of plant densities throughout the wetland may also
be performed to determine if groups of a particular species
optimize iron removal.