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Amparo Cortes - Sustainable remediation of soils and groundwaters affected by chlorinated solvents
1. VII Jornadas Técnicas de Medio Ambiente
Problemática de los suelos contaminados
SUSTAINABLE REMEDIATION OF
SOILS AND GROUNDWATERS
AFFECTED BY CHLORINATED SOLVENTS
by
Dra. Amparo Cortés
Full Professor at Universitat de Barcelona
acortes@ub.edu
16 – 17 de Noviembre 2011, Barcelona
2. SUSTAINABLE REMEDIATION OF SOILS AND GROUNDWATERS AFFECTED BY CHLORINATED SOLVENTS
INDEX
1. Chlorinated solvents: positive and negative properties
2. Release to the environment: environmental problems
3. Containment technologies
4. Treatment technologies
5. New trends in characterization
6. Some reflections
6. CHLORINATED SOLVENTS HUMAN TOXICITY
CHLORINATED ETHENES
PCE Tetrachloroethylene causes irritation of the upper respiratory tract and eyes, kidney
dysfunction, and at lower concentrations, neurological effects, such as reversible
mood and behavioral changes, impairment of coordination, dizziness, headache,
sleepiness, and unconsciousness.
TCE/ Trichloroethylene: Short-term exposure causes irritation of the nose and throat and
central nervous system (CNS) depression, with symptoms such as drowsiness,
TRI dizziness, giddiness, headache, loss of coordination. High concentrations have
caused numbness and facial pain, reduced eyesight, unconsciousness, irregular
heartbeat and death.
Vinyl Chloride: Aside from being a known carcinogen, it has been found to cause a
VC number of other conditions, including Raynaud's syndrome, angiosarcoma, and
acroosteolysis.
7. CHLORINATED SOLVENTS HUMAN TOXICITY
CHLORINATED METHANES
CT Carbon tetrachloride is listed as a suspect carcinogen, an animal carcinogen at
relatively high doses, not a likely human carcinogen; however, liver cancer has been
reported. It can be absorbed through intact skin. It causes CNS depression, can
damage the kidneys, liver, or lungs, and can cause anemia, rapid and irregular
heartbeats. Health effects appear to be greatly increased by alcohol consumption.
CF Chloroform is a suspect carcinogen. It causes CNS depression, rapid and irregular
heartbeat, and liver and kidney damage.
DCM Methylene chloride is listed as a potential carcinogen. It causes CNS depression,
liver and kidney damage, and can cause elevated blood carboxyhemoglobin.
8. ENVIRONMENTAL CHALLENGES OF CHLORINATED SOLVENTS
Source: DDES, 2008
1 L of TCE can theoretically contaminate 190,000 cubic meters of water with
TCE at a concentration above the drinking water standard.
13. SOURCE ZONE
A chlorinated solvent source zone is a subsurface reservoir that:
a) initially contains DNAPL and
b) sustains plumes (including vapor plumes).
The source zone also includes high concentration dissolved- and
sorbed-phase halos around the DNAPL region.
Some chlorinated source zones are depleted of DNAPL; than the
high-concentration halo can be a reservoir that sustains plumes.
14. DENSE NON-AQUEOUS PHASE LIQUIDS
DNAPL
include chlorinated solvents
Immiscibility with water - they form separate ‘phases’.
Low absolute solubilities - DNAPL can’t dissolve quickly in groundwater: it may persist
for decades before dissolving.
Relatively high densities - DNAPLs are denser than water, and can therefore sink
beneath the water table, polluting the full thickness of an aquifer.
Low viscosities – that allows rapid subsurface migration.
16. POTENTIAL NEGATIVE IMPACTS OF DNAPL MASS REDUCTION
Pump and treat
• Expansion of the source zone due to mobilization of residual DNAPL
• Undesirable changes in the DNAPL distribution
• Undesirable changes in physical, geochemical, and microbial conditions
• Adverse impact on subsequent remediation technologies
• Increased life-cycle costs of site cleanup.
18. SCREENING OF CONTAMINANTS
and AGING OF CONTAMINATION
• Phytoscreening focuses on the youngest tree rings (sap uptake of
contaminants) and reflects the current state of contamination in the root
zone. It can be used for mapping certain contaminants.
• Dendrochemistry focuses on the annual rings of the tree (xylem) which
reflect the changes (contamination) in the root zone. It can be used for age
dating of contamination (forensic, source identification).
19. Phytoscreening
Soil and groundwater contaminants are uptaken and transported by sap in the
outermost wood rings. These can easily be micro-sampled (0.2 g) and
analyzed for the sap enriched contaminants.
This method allows to qualitatively and quantitatively identify or exclude the
presence of underground contaminants such as PCE, TCE, DCE …
The correlation coefficient between tree and underground contamination is
respectable (and up to 0.9).
Whenever a site is properly vegetated, Phytoscreening can be used for a
rapid identification or exclusion of contamination, for clarifying contaminant
distribution by fast low cost measurements, for identification of release spots
and delineation or monitoring of plumes.
Being a standard method for CVOCs, BTEX and heavy metals (Cd, Cr, Cu,
Hg, Ni, Pb, Zn) we will see in the next future, if this method is also suitable for
PAH, PCB and other organic compounds.
21. Dendrochemical Age-Dating
Due to their seasonal growth, annual tree-rings represent a bio-archive of the past.
During this growth process elements taken up with the sap from the rhizosphere are
being built in and fixed to wood cells.
Accordingly and besides heavy metals pollutant specific tracer elements such as
Chlorine (for chlorinated organic compounds like PCE) or Chlorine and Sulfur (for
Fuel Hydrocarbons) are built in and fixed to the wood cells.
This growth related element incorporation exclusively takes place within the
youngest annual ring with the resulting element concentration depending on the
respective element availability in soil and groundwater. The change in concentration
over all annual rings of a tree core sample from the stem can be gained for 30
elements with the help of energy-dispersive X-Ray-analysis (ED-XRF).
22. Dendrochemical Age-Dating
This process delivers the concentration profiles of 30 elements over the total life
time of a tree can be obtained at a very high temporal resolution. Accordingly,
concentration anomalies of pollutant specific elements (tracers such as Chlorine)
can be dated exactly to reveal the beginning and duration of an underground impact
(such as by PCE).
In order to rule out or confirm the possibility of alternative sources for the Chlorine
anomalies (e.g. road salt), allied element concentration profiles (e.g. K, Ca, Mg, S)
are compared for Cl-synchronous anomalies (multi-element-analyses).
If more trees are available the spatiotemporal expansion of a plume as well as
contaminant transport velocities can be revealed.
23. IN SITU SOURCE TREATMENT TECHNOLOGIES
Source: DDES, 2008
25. ANAEROBIC REDUCTIVE DEHALOGENATION
PCE
Cl Cl
C C
Cl Cl
TCE
Cl Cl
C C
Cl H
1,1-DCE cis - 1, 2-DCE trans-1, 2-DCE
Cl H Cl Cl H Cl
C C C C C C
Cl H H H Cl H
Vinyl Chloride
H Cl
C C
H H
Ethene Complete Mineralization
H H O O O
Cl
C C C H H
H H
Ethane
H H
C C H
H H
26. BIODEGRADATION EVALUATION
Isotope analysis is a powerful tool to evaluate natural and/or enhanced
biodegradation of different contaminants.
Isotopes can also be used to conceptualize your site models (e.g. flow paths,
degradation pathways) and to identify additional sources of contamination.
Carmona et al., 2011
27. SUSTAINABLE REMEDIATION
Ability of a system to maintain important attenuation mechanisms through time.
Sustainability is affected by the rate at which the contaminants are transferred from the
source area and whether the protecting mechanisms are renewable.
In the case of reductive dechlorination, sustainability might be limited by the amount of
electron donor, which might be used up before remedial goals are achieved.
A competition for electrons is
established during degradation
between chlorinated solvents, other
organic pollutants, organic matter, and
other electron acceptors that can be
present at the media such as nitrates
and sulphates.
28. REDUCTIVE DECHLORINATION SUSTAINABILITY
Chlorinated solvents and other organic pollutants may also act as electron donors
providing an energy source for certain microorganisms. With the continual
exchange of electrons, redox chemistry is an important factor in chlorinated
solvents biodegradation.
PCE, TCE, and CT generally require reducing conditions before they will
transform to aliphatic compounds. Such conditions require the presence of
enough organic substrate to reduce all of the oxygen (below 0,5 mg/L), nitrate
(below 1 mg/L ideally), iron, and sulfate ideally (below 20 mg/L) before
dechlorinating bacteria will successfully compete to reduce chlorinated aliphatic
hydrocarbons.
29. At site B nitrate levels are low, but still reach bad levels for
reductive dechlorination. A previous water nitrate reduction
treatment is needed in the site.
30. The biodegradation of chlorinated
solvents in soils, at low
concentrations can be enhanced
by using adapted mycorrhized
trees producing phenolic
exudates, but such
biodegradation could be also
affected by the ionic strength of
nitrates or other salts when
present.
Plants will also contribute to the
soil remediation via chlorinated
solvent uptake and dechlorination
in plant systems.
31. ASSESSMENT of MASS DISCHARGE
FROM DNAPL ZONES
• Plane versus point measurements.
• Multi level sampling methods needed in a control plane.
• Main parameter influencing mass discharge calculations: Hydraulic conductivity .
• Effective number of sampling wells related to the value of the mass discharge (good
point for optimization to save money and time).
• Uncertainty analysis of mass discharge.
35. D
R+
WORKING GROUP GEA
Grup R+D de Geologia
Econòmica i Ambiental
Dra. Amparo Cortés (UB-Farmàcia) i Hidrologia
Dr. José Mª Carmona (UB-Geologia)
Dra. Diana Puigserver (UB-Geologia)
Dra. Magdalena Grifoll (UB-Biologia)
Dr. Manel Viladevall (UB-Geologia)
GROUP OBJECTIVES
• Improving knowledge on medias, and on health and environmental
risks;
• Reducing costs of sustainable soils and ground waters
remediation, while increasing efficiency and preventing health risks.
