Juliana G. de
Freitas, University of Waterloo, Waterloo, Ontario, Canada
abstract
Olugbenga
J. Owojori, Stellenbosch University, Maitland, South
Africa
abstract
Zarath
M. Summers, University of Massachusetts, Amherst, MA
abstract
Juliana
G. de Freitas:
Challenges
for Ethanol Fuels Contaminated Sites Assessment
Juliana
G. de Freitas, Dept. of Earth and Environmental Sciences,
University of Waterloo, 200 University Avenue West,
Waterloo, ON, N2L 3G1, Canada, Tel: 519-888-4567
ext.35284, Fax: 519-746-7484, Email:
jgardena@scimail.uwaterloo.ca
James
F. Barker, Dept. of Earth and Environmental Sciences,
University of Waterloo, 200 University Avenue West,
Waterloo, ON, N2L 3G1, Canada, Tel: 519-888-4567 ext.
32103, Fax: 519-746-7484, Email:
jfbarker@sciborg.uwaterloo.ca
Ioannis Chatzis, Chemical Engineering, University of
Waterloo, 200 University Avenue West, Waterloo, ON, N2L
3G1, Canada, 519-888-4567 ext.33306, Fax: 519-746-7484,
Email: ichatzis@uwaterloo.ca
The
use of ethanol as an additive in gasoline is increasing
significantly in
North America
, raising concerns about the consequences of ethanol usage
when monitoring the subsurface for groundwater
contamination. One piece of the problem is the effect of
ethanol on contaminant distribution in the source zone.
Ethanol can change important properties of the system
which can result in an unexpected distribution of the
gasoline contaminants. Ethanol can also enhance the
solubility of aromatic hydrocarbons such as benzene.
In
2D visualization experiments gasoline was injected in the
top of the unsaturated zone and then ethanol was injected
in the same position. It was shown that ethanol can
mobilize the gasoline and alter its distribution
significantly. The visualization experiments also indicate
that ethanol stays mainly in the capillary fringe, being
transported above the water table along with cosolubilized
hydrocarbons. However, typical monitoring techniques
applied at fuel contaminated sites are not intended to
sample the capillary fringe. Although under some
conditions a typical monitoring well may draw some ethanol
contaminated water, providing an indication of
contamination, the sample will be diluted and therefore
the measured concentration may be significantly smaller
than the actual concentration in the capillary fringe.
Therefore, the horizontal transport of high concentrations
of hydrocarbons and ethanol in the capillary fringe at
field scale presents significant challenges for
monitoring. For example, since sampling in the vadose zone
requires suction, volatile losses are more likely to
happen when sampling water from the vadose zone.
Laboratory experiments showed that the use of ceramic
suction samplers may result in loss of volatile organics
of up to 30%, depending on the pressure applied and
compound properties. The concentration of ethanol in the
aqueous phase was also shown to interfere with the sample
bias.
Olugbenga
J. Owojori:
Influence
of Salinity on Uptake and Toxicity of Zinc in the
Earthworm Eisenia
fetida
Olugbenga
J. Owojori, MSc., Department of Botany and Zoology,
Stellenbosch University, Private Bag X1, Matieland,
7602, South Africa, Tel: +27 21 808 3471, Fax: +27 21
808 2405, Email: ojart@sun.ac.za
Adriaan J.Reinecke, PhD, Department of Botany and
Zoology, Stellenbosch University, Private Bag X1,
Matieland, 7602, South Africa, Tel: +27 21 808 3471,
Fax: +27 21 808 2405, Email: ajr@sun.ac.za
Andrei B. Rozanov, PhD, Department of Soil Science,
Stellenbosch University, Private Bag X1, Matieland,
7602, South Africa, Tel: +27 21 808 2397, Fax: +27 21
808 4791, Email: dar@sun.ac.za
Salinization of soil is a global problem especially in
semi-arid and arid regions. Few studies have
considered the influence of salinity on beneficial
soil organisms, and their uptake of metals. Recent
studies on the development of Biotic Ligand Model (BLM)
suggest that cations (at low concentrations), may
protect organisms against metal toxicity but effects
of these cations at high concentrations remain
speculative. In order to assess the influence of
salinity on uptake and toxicity of zinc to earthworms,
specimens of Eisenia
fetida were exposed to zinc for 28 days using OECD
artificial soil adjusted with 0 , 2000
and 4000 mg/kg NaCl. Zn was added as ZnCl2
in a range of concentrations (0, 250, 500, 750
and 1000 mg/kg Zn). The endpoints; mortality, weight
change, and internal zinc concentration were assessed
at Day 1, 7, 14 and 28 while cocoon production was
assessed only at day 28. In the substrates, nitric
acid, DTPA and CaCl2 extractable zinc
concentrations were also determined. The results
indicated that NaCl increased the availability of zinc
in the substrates. Weight, mortality and internal zinc
concentrations in the worms were not significantly
affected by NaCl and zinc as individual substances,
but in combination both had significant effects on all
of these parameters. In contrast, cocoon production
was significantly affected by increased NaCl and ZnCl2
as individual substances, and the effects were more
severe when both substances were present. The 28- d EC50
for cocoon production was 2020 mg/kg NaCl. The
observed increase in toxicity with increased salinity
could not be explained fully by zinc accumulation in
the tissues of the worm. It is concluded that salinity
as a result of increased Na+ has a synergistic effect
with zinc in toxicity to these earthworms. The
implications in the development of BLM for earthworms
are discussed.
Zarath
M. Summers:
Adaptive
Evolution: a Strategy for Better Understanding and
Optimizing Environmental Biotechnologies
Zarath M.
Summers, University of Massachusetts, 422A Morrill IV
North, 639 North Pleasant St, Amherst, MA, 01003, USA,
Tel: 413-577-3069, Email: zsummers@microbio.umass.edu
Derek R. Lovley, University of Massachusetts, 400 Morrill
IV North, 639 North Pleasant St, Amherst, MA, 01003, USA,
Tel: 413-545-9648, Email: dlovley@microbio.umass.edu
Adaptive
evolution studies can provide new insights into the
physiology and ecology of environmentally relevant
organisms by identifying which mutations in genes and
regulatory pathways are associated with adaptations
producing a more beneficial phenotype. Genome-scale in
silico modeling of the metabolism of Geobacter
species has indicated that these organisms have a
metabolic potential far beyond that previously
demonstrated in culture.
Some of these potential metabolic features may have
practical benefit. For example, lactate is a convenient
electron donor to add to the subsurface in order to
promote in situ
uranium bioremediation, but lactate is not a common
electron donor in natural anaerobic sedimentary
environments. Geobacter sulfurreducens does not naturally grow well on lactate,
but with the appropriate selective pressure a strain that
could rapidly grow on lactate was developed. In a similar
manner, strains of G. sulfurreducens have been evolved that can metabolize sugars and
glycerol, substrates that the wild-type strain does not
utilize. This
has important implications not only for bioremediation
applications, but also for the conversion of various
wastes to electricity in Geobacter-based
microbial fuel cells.
Effective subsurface bioremediation and electricity
production with Geobacter also requires higher rates of extracellular electron
transfer than is typical for Geobacter
in pristine subsurface environments. In order create a
strain of G.
sulfurreducens capable of more rapid extracellular
electron transfer; cells were repeatedly transferred as
rapidly as possible with Fe(III) oxide as the electron
acceptor. A
strain was developed which can transfer electrons to
Fe(III) oxide 10 times faster than wild type. Strains are
currently being adapted for other applications, such as
serving as syntrophs in the conversion of wastes and
hydrocarbons to methane. Whole-genome resequencing
facilitates the identification of the mutations associated
with these adaptations, which should aid in the further
optimization of application-specific strains for carrying
out complex cellular processes.
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