Low-permeability lenses represent potential sources of long-term release when filled from contaminant solute through direct contact with dissolved plumes. The redistribution of contaminant from low to high permeability aquifer zones (Back-Diffusion) was studied. Redistribution causes a long plume tail, commonly regarded as one of the main obstacles to effective groundwater remediation. Laboratory tests were performed to reproduce the redistribution process and to investigate the effect of pumping water on the remediation time of these contaminated low-permeability lenses. The test section used is representative of clay/silt lenses (k ≈ 1 ∗ 10− 10 m/s/k ≈ 1 ∗ 10− 7 m/s) in a sand aquifer (k ≈ 1 ∗ 10− 3 m/s). Hence, an image analysis procedure was used to estimate the diffusive flux of contaminant released by these low-permeability zones. The proposed technique was validated performing a mass balance of a lens saturated by a known quantity of tracer. For each test, performed using a different groundwater velocity, the diffusive fluxes of contaminant released by lenses were compared and the remediation times of the low-permeability zones calculated. For each lens, the obtained remediation timeframes were used to define an analytical relation vs groundwater velocity and the coefficients of these relations were matched to grain size of the low-permeability lenses. Results show that an increase of the velocity field is not useful to diminish the total depletion times as the process mainly diffusive. This is significant when the remediation approach relies on pumping technology.

Contaminant back-diffusion from low-permeability layers as affected by groundwater velocity: A laboratory investigation by box model and image analysis / Tatti, Fabio; Papini, Marco Petrangeli; Sappa, Giuseppe; Raboni, Massimo; Arjmand, Firoozeh; Viotti, Paolo. - In: SCIENCE OF THE TOTAL ENVIRONMENT. - ISSN 0048-9697. - ELETTRONICO. - 622-623:(2018), pp. 164-171. [10.1016/j.scitotenv.2017.11.347]

Contaminant back-diffusion from low-permeability layers as affected by groundwater velocity: A laboratory investigation by box model and image analysis

Tatti, Fabio
;
Papini, Marco Petrangeli;Sappa, Giuseppe;Arjmand, Firoozeh;Viotti, Paolo
2018

Abstract

Low-permeability lenses represent potential sources of long-term release when filled from contaminant solute through direct contact with dissolved plumes. The redistribution of contaminant from low to high permeability aquifer zones (Back-Diffusion) was studied. Redistribution causes a long plume tail, commonly regarded as one of the main obstacles to effective groundwater remediation. Laboratory tests were performed to reproduce the redistribution process and to investigate the effect of pumping water on the remediation time of these contaminated low-permeability lenses. The test section used is representative of clay/silt lenses (k ≈ 1 ∗ 10− 10 m/s/k ≈ 1 ∗ 10− 7 m/s) in a sand aquifer (k ≈ 1 ∗ 10− 3 m/s). Hence, an image analysis procedure was used to estimate the diffusive flux of contaminant released by these low-permeability zones. The proposed technique was validated performing a mass balance of a lens saturated by a known quantity of tracer. For each test, performed using a different groundwater velocity, the diffusive fluxes of contaminant released by lenses were compared and the remediation times of the low-permeability zones calculated. For each lens, the obtained remediation timeframes were used to define an analytical relation vs groundwater velocity and the coefficients of these relations were matched to grain size of the low-permeability lenses. Results show that an increase of the velocity field is not useful to diminish the total depletion times as the process mainly diffusive. This is significant when the remediation approach relies on pumping technology.
2018
Molecular diffusion; Persistence contamination; Pumping technology; Remediation time; Secondary source; Environmental Engineering; Environmental Chemistry; Waste Management and Disposal; Pollution
01 Pubblicazione su rivista::01a Articolo in rivista
Contaminant back-diffusion from low-permeability layers as affected by groundwater velocity: A laboratory investigation by box model and image analysis / Tatti, Fabio; Papini, Marco Petrangeli; Sappa, Giuseppe; Raboni, Massimo; Arjmand, Firoozeh; Viotti, Paolo. - In: SCIENCE OF THE TOTAL ENVIRONMENT. - ISSN 0048-9697. - ELETTRONICO. - 622-623:(2018), pp. 164-171. [10.1016/j.scitotenv.2017.11.347]
File allegati a questo prodotto
File Dimensione Formato  
Tatti_Contaminant-back-diffusion_2018.pdf

solo gestori archivio

Tipologia: Versione editoriale (versione pubblicata con il layout dell'editore)
Licenza: Tutti i diritti riservati (All rights reserved)
Dimensione 1.97 MB
Formato Adobe PDF
1.97 MB Adobe PDF   Contatta l'autore

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1073056
Citazioni
  • ???jsp.display-item.citation.pmc??? 1
  • Scopus 59
  • ???jsp.display-item.citation.isi??? 52
social impact