Compound Specific Isotope Analysis ((13)C, (37)Cl,( 2)H) to trace induced attenuation of chlorinated organic contaminants in groundwater

by Carme Audí Miró

Institution: Universitat de Barcelona
Year: 2014
Keywords: Dissolvents; Disolventes; Solvents; Depuració de residus industrials; Tratamiento de residuos industriales; Purification of factory and trade waste; Hidròlisi; Hidrólisis; Hydrolysis; Compound Specific Isotope Analysis (CSIA); Anàlisi isotòpic de compost específic (AICE); Análisis isotópico de compuesto específico (AICE); Permeable reactive barrier; Barrera permeable reactiva; Ciències Experimentals i Matemàtiques
Record ID: 1124476
Full text PDF: http://hdl.handle.net/10803/145921


Chloroform (CF), tetrachloroethene (PCE) and trichloroethene (TCE) are dense chloro-aliphatic hydrocarbons (CAH) extensively used as industrial solvents. These compounds have been largely released to the environment due to poor waste management. In this thesis, the effect of a ZVI-PRB installed at a field site contaminated mainly with PCE, TCE and cis-DCE was evaluated. Moreover, a novel strategy to degrade the recalcitrant CF -alkaline hydrolysis induced by concrete-based recycled construction wastes- was proposed and developed in order to test its efficiency in degrading this pollutant. Compound specific isotope analysis (CSIA) is a valuable tool for monitoring an environmental treatment in the field, based on the isotope fractionation of an element during transformation reactions. Therefore, the general aim of this thesis is to use compound specific isotope analysis of 13C, 37Cl and 2H as a tool to assess both induced attenuation processes 1) chlorinated ethenes degradation by a ZVI-PRB installed at the field sited; and, 2) the proposed new remediation technique based on the use of concrete-based recycled construction wastes to degrade chloroform (CF) by alkaline hydrolysis applied at a site contaminated by this pollutant. First, laboratory experiments were conducted to study both ZVI and concrete effects on the chlorinated ethenes and the chloroform, respectively. ZVI experiments yielded carbon isotope fractionation values of the chlorinated ethenes degradation by the specific ZVI used in the field application, as well as, the first chlorine isotope fractionation values of TCE and cis-DCE associated to this reaction. Two promising approaches to discriminate the abiotic ZVI degradation versus biotic degradation present at the field site were brought forward 1) the dual isotope C-Cl approach, which distinguished slopes 4 times lower than for biodegradation of cis-DCE by the commercially available Dehalococcoides-containing culture mixed culture KB-1; and 2) the product-specific carbon isotope fractionation that showed a 10‰ difference between those products coming from β-dichloroelimination and hydrogenolysis reactions. Concrete experiments with CF achieved a 95% CF degradation after 28 d, accompanied by a significant carbon isotope fractionation. The carbon isotopic fractionation associated with alkaline hydrolysis of CF was -53±3‰. The obtained laboratory data permitted the assessment of the respective induced degradation treatments applied at the field site. At the site with the ZVI-PRB treatment, both, occurrence of biodegradation and degradation by ZVI-PRB were evidenced by means of detected metabolites and 13C data, with quantitative estimates of ZVI-PRB efficiency of less than 10% and 2% for PCE and cis-DCE, respectively. Dual element 13C-37Cl isotope plots confirmed that the effect of the ZVI-PRB was masked by biodegradation. Based on carbon isotopes data, 49% and almost 100% of PCE and TCE, respectively, were estimated to be removed by biodegradation. Finally the combination of 2H with 13C and 37Cl…