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VII Jornadas Técnicas de Medio Ambiente Problemática de los suelos contaminados SUSTAINABLE REMEDIATION OF SOILS AND GROUNDWATERSAFFECTED BY CHLORINATED SOLVENTS by Dra. Amparo Cortés Full Professor at Universitat de Barcelona firstname.lastname@example.org 16 – 17 de Noviembre 2011, Barcelona
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
CHLORINATED SOLVENTS WIDESPREAD USESIndustry Industrial processesElectronics manufacturing Metal cleaningSolvent production Metal machiningPesticide / herbicide manuf. Die operations cutting, bending, forming, drawing and squeezingDry cleaning Vapour and liquid degreasingInstrument manufacturing Paint strippingSolvent recycling Storage and transfer of solventsEngine manufacturingSteel product manufacturingChemical productionRocket engine / fuel manufacturingAircraft cleaning / engine degreasing
ATTRIBUTES, and INDUSTRIAL VALUES OF CHLORINATED SOLVENTS Source: DDES, 2008
CHLORINATED SOLVENTS HUMAN TOXICITY CHLORINATED ETHENESPCE 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 aVC number of other conditions, including Raynauds syndrome, angiosarcoma, and acroosteolysis.
CHLORINATED SOLVENTS HUMAN TOXICITY CHLORINATED METHANESCT 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.
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.
CHLORINATED SOLVENTS RELEASED AT THE ENVIRONMENT: PRODUCTION AREAS
CHLORINATED SOLVENTS RELEASED AT THE ENVIRONMENT: END POINTS
CHLORINATED SOLVENTS ENVIRONMENTAL DISTRIBUTION halos source
SOURCE ZONEA chlorinated solvent source zone is a subsurface reservoir that:a) initially contains DNAPL andb) sustains plumes (including vapor plumes).The source zone also includes high concentration dissolved- andsorbed-phase halos around the DNAPL region.Some chlorinated source zones are depleted of DNAPL; than thehigh-concentration halo can be a reservoir that sustains plumes.
DENSE NON-AQUEOUS PHASE LIQUIDS DNAPL include chlorinated solventsImmiscibility with water - they form separate ‘phases’.Low absolute solubilities - DNAPL can’t dissolve quickly in groundwater: it may persistfor decades before dissolving.Relatively high densities - DNAPLs are denser than water, and can therefore sinkbeneath the water table, polluting the full thickness of an aquifer.Low viscosities – that allows rapid subsurface migration.
DNAPL MASS REDUCTIONPump and treat in the source Initially Later
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.
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).
PhytoscreeningSoil and groundwater contaminants are uptaken and transported by sap in theoutermost wood rings. These can easily be micro-sampled (0.2 g) andanalyzed for the sap enriched contaminants.This method allows to qualitatively and quantitatively identify or exclude thepresence of underground contaminants such as PCE, TCE, DCE …The correlation coefficient between tree and underground contamination isrespectable (and up to 0.9).Whenever a site is properly vegetated, Phytoscreening can be used for arapid identification or exclusion of contamination, for clarifying contaminantdistribution by fast low cost measurements, for identification of release spotsand 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 forPAH, PCB and other organic compounds.
Dendrochemical Age-DatingDue 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 arebeing built in and fixed to wood cells.Accordingly and besides heavy metals pollutant specific tracer elements such asChlorine (for chlorinated organic compounds like PCE) or Chlorine and Sulfur (forFuel Hydrocarbons) are built in and fixed to the wood cells.This growth related element incorporation exclusively takes place within theyoungest annual ring with the resulting element concentration depending on therespective element availability in soil and groundwater. The change in concentrationover all annual rings of a tree core sample from the stem can be gained for 30elements with the help of energy-dispersive X-Ray-analysis (ED-XRF).
Dendrochemical Age-DatingThis process delivers the concentration profiles of 30 elements over the total lifetime 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 Chlorineanomalies (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 ascontaminant transport velocities can be revealed.
IN SITU SOURCE TREATMENT TECHNOLOGIES Source: DDES, 2008
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
BIODEGRADATION EVALUATIONIsotope analysis is a powerful tool to evaluate natural and/or enhancedbiodegradation 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
SUSTAINABLE REMEDIATIONAbility of a system to maintain important attenuation mechanisms through time.Sustainability is affected by the rate at which the contaminants are transferred from thesource area and whether the protecting mechanisms are renewable.In the case of reductive dechlorination, sustainability might be limited by the amount ofelectron 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.
REDUCTIVE DECHLORINATION SUSTAINABILITYChlorinated solvents and other organic pollutants may also act as electron donorsproviding an energy source for certain microorganisms. With the continualexchange of electrons, redox chemistry is an important factor in chlorinatedsolvents biodegradation.PCE, TCE, and CT generally require reducing conditions before they willtransform to aliphatic compounds. Such conditions require the presence ofenough 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) beforedechlorinating bacteria will successfully compete to reduce chlorinated aliphatichydrocarbons.
At site B nitrate levels are low, but still reach bad levels forreductive dechlorination. A previous water nitrate reductiontreatment is needed in the site.
The biodegradation of chlorinatedsolvents in soils, at lowconcentrations can be enhancedby using adapted mycorrhizedtrees producing phenolicexudates, but suchbiodegradation could be alsoaffected by the ionic strength ofnitrates or other salts whenpresent.Plants will also contribute to thesoil remediation via chlorinatedsolvent uptake and dechlorinationin plant systems.
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.
D R+ WORKING GROUP GEA Grup R+D de Geologia Econòmica i AmbientalDra. Amparo Cortés (UB-Farmàcia) i HidrologiaDr. 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 environmentalrisks;• Reducing costs of sustainable soils and ground watersremediation, while increasing efficiency and preventing health risks.