RESUMEN

Colloidal activated carbon (CAC) is an emerging remedial enhancement fluid that is injected into the subsurface to adsorb hazardous industrial compounds for subsequent removal. CAC-enhanced remediation relies on accurate subsurface characterization and monitoring to ensure CAC reaches intended treatment locations. The objective of this study was to assess the effectiveness of the spectral induced polarization (SIP) technique to track CAC migration within porous media and its adsorption of the chlorinated solvent, tetrachloroethylene (PCE). Dynamic column experiments were performed with cyclic injection and flow of groundwater, CAC, and PCE within porous media, and simultaneous measurements of SIP and effluent quality. Results showed an increase in both the real and imaginary conductivities of the SIP response during injection/flow of CAC within porous media. Real conductivity returned to pre-CAC levels during subsequent flushing of CAC with groundwater, which had left behind only carbon-coated soil grains; however, imaginary conductivity identified the change in polarizability due to the alterations on the grain surface. The subsequent adsorption of aqueous phase PCE did not generate a distinctive change in SIP response, mainly due to the low 50 mg/L concentrations used. Overall, this study suggests that SIP can be a valuable tool to effectively and non-invasively track the migration of injected CAC within porous media for contaminant adsorption, suggesting it can be used to enhance the implementation and management of environmental remediation programs.

Asunto(s)

Carbono , Restauración y Remediación Ambiental , Agua Subterránea , Contaminantes Químicos del Agua , Agua Subterránea/química , Restauración y Remediación Ambiental/métodos , Contaminantes Químicos del Agua/química , Carbono/química , Adsorción , Tetracloroetileno/química , Carbón Orgánico/química

RESUMEN

Lindane (γ-hexachlorocyclohexane) manufacture in Spain generated nearly 200,000tonnes of HCH wastes; near 160,000tonnes were originated by the Inquinosa factory located in Sabiñánigo (northern Spain) and were deposited in unlined landfill sites. This study reports for the first time the content of polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/Fs) in non-recycled HCH wastes that had been disposed in the Bailín landfill site in Sabiñánigo. Samples from solid HCH powder residues (white HCH and δ-paste wastes) and the dense non-aqueous phase liquids (DNAPLs), as well as landfill leachates, soil and sediments have been characterized. White HCH wastes exhibited a toxicity of 1488ngWHO-TEQ2005·kg-1 (Σ17 PCDD/Fs), while δ-paste wastes presented a noticeable higher toxicity (12,094ngWHO-TEQ2005·kg-1). Nevertheless, the maximum toxicity value was found for DNAPLs (37,353ngWHO-TEQ2005·L-1). Dioxins were predominant in the DNAPL waste whereas furans predominated in the landfill leachates, soil and sediments. However, in solid HCH wastes, PCDD and PCDFs contributed in a similar proportion. The PCDD/Fs congener profiles in landfill leachates, soil and sediments do not resemble the PCDD/Fs profiles found for the HCH wastes. These preliminary results will be of paramount importance in order to estimate the total quantities of PCDD/Fs disposed to the landfill site and to assess the potential mobility of PCDD/Fs, especially to groundwater and landfill leachates. Besides, this information is of great value to design periodical monitoring plans to evaluate the presence of PCDD/Fs in the impacted groundwater and leachates and finally, to evaluate the risk of PCDD/Fs for the environment and human health.

RESUMEN

Perchloroethene, trichloroethene, and other chlorinated solvents are widespread groundwater pollutants. They form dense non-aqueous phase liquids that sink through permeable groundwater aquifers until non-permeable zone is reached. In Italy, there are many situations of serious contamination of groundwater that might compromise their use in industry, agriculture, private, as the critical case of a Central Italy valley located in the province of Teramo ("Val Vibrata"), characterized by a significant chlorinated solvents contamination. Data from the various monitoring campaigns that have taken place over time were collected, and new samplings were carried out, resulting in a complete database. The data matrix was processed with a multivariate statistic analysis (in particular principal component analysis, PCA) and was then imported into geographic information system (GIS), to obtain a model of the contamination. A microcosm anaerobic study was utilized to assess the potential for in situ natural or enhanced bioremediation. Most of the microcosms were positive for dechlorination, particularly those inoculated with a mineral medium. This indicate the presence of an active native dechlorinating population in the subsurface, probably inhibited by co-contaminants in the groundwater, or more likely by the absence or lack of nutritional factors. Among the tested electron donors (i.e., yeast extract, lactate, and butyrate) lactate and butyrate enhanced dechlorination of chlorinated compounds. PCA and GIS studies allowed delimiting the contamination; the microcosm study helped to identify the conditions to promote the bioremediation of the area.