Unravelling long-term source removal effects and chlorinated methanes natural attenuation processes by C and Cl stable isotopic patterns at a complex field site
| Autor: | Cristina Domènech, Massimo Marchesi, Daniel Hunkeler, Jordi Palau, Mònica Rosell, Clara Torrentó, Albert Soler, Diana Rodríguez-Fernández |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Pollution
Environmental Engineering media_common.quotation_subject Case study 0208 environmental biotechnology Aquifer 02 engineering and technology 010501 environmental sciences 01 natural sciences Geologia isotòpica Òdena site Vadose zone 2D-CSIA Environmental Chemistry Carbon tetrachloride Cloroform Waste Management and Disposal 0105 earth and related environmental sciences media_common Pollutant geography geography.geographical_feature_category Chemistry Soil contamination 020801 environmental engineering Wastewater Chloroform Environmental chemistry Leaching (metallurgy) Isotope geology Groundwater |
| Zdroj: | Dipòsit Digital de la UB Universidad de Barcelona |
| ISSN: | 0048-9697 |
| Popis: | The effects of contaminant sources removal in 2005 (i.e. barrels, tank, pit and wastewater pipe sources) on carbon tetrachloride (CT) and chloroform (CF) concentration in groundwater were assessed at several areas of a fractured multi-contaminant aquifer (Odena, Spain) over a long-term period (2010–2014). Changes in redox conditions, in these chlorinated methanes (CMs) concentration and in their carbon isotopic compositions (δ13C) were monitored in multilevel wells. δ13C values from these wells were compared to those obtained from sources (barrels, tank and pit before their removal, 2002–2005) and to commercial solvents values in literature. Additionally, CMs natural attenuation processes were identified by C-Cl isotope slopes (Λ). Analyses revealed the downstream migration of the pollutant focus and an efficient removal of DNAPLs in the pit source's influence area. However, the removal of the contaminated soil from former tank and wastewater pipe was incomplete as leaching from unsaturated zone was proved, evidencing these areas are still active sources. Nevertheless, significant CMs degradation was detected close to all sources and Λ values pointed to different reactions. For CT in the tank area, Λ value fitted with hydrogenolysis pathway although other possible reduction processes were also uncovered. Near the wastewater pipe area, CT thiolytic reduction combined with hydrogenolysis was derived. The highest CT degradation extent accounted for these areas was 72 ± 11% and 84 ± 6%, respectively. For CF, the Λ value in the pit source's area was consistent with oxidation and/or with transport of CF affected by alkaline hydrolysis from upstream interception trenches. In contrast, isotope data evidenced CF reduction in the tank and wastewater pipe influence areas, although the observed Λ slightly deviates from the reference values, likely due to the continuous leaching of CF degraded in the non-saturated zone by a mechanism different from reduction. |
| Databáze: | OpenAIRE |
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