Field performance of the radon-deficit technique to detect and delineate a complex DNAPL accumulation in a multi-layer soil profile

Barrio Parra, Fernando and Izquierdo Díaz, Miguel and Díaz Curiel, Jesús María and Miguel García, Eduardo de (2021). Field performance of the radon-deficit technique to detect and delineate a complex DNAPL accumulation in a multi-layer soil profile. "Environmental Pollution", v. 269 ; p. 116200. ISSN 0269-7491. https://doi.org/10.1016/j.envpol.2020.116200.

Description

Title: Field performance of the radon-deficit technique to detect and delineate a complex DNAPL accumulation in a multi-layer soil profile
Author/s:
  • Barrio Parra, Fernando
  • Izquierdo Díaz, Miguel
  • Díaz Curiel, Jesús María
  • Miguel García, Eduardo de
Item Type: Article
Título de Revista/Publicación: Environmental Pollution
Date: 2021
ISSN: 0269-7491
Volume: 269
Subjects:
Freetext Keywords: Site characterization; Radon-deficit; DNAPL; Depth; Vertical resolution
Faculty: E.T.S.I. de Minas y Energía (UPM)
Department: Energía y Combustibles
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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Abstract

The performance of the radon (222Rn)-deficit technique has been evaluated at a site in which a complex DNAPL mixture (mostly hexachlorocyclohexanes and chlorobenzenes) has contaminated all four layers (from top to bottom: anthropic backfill, silt, gravel and marl) of the soil profile. Soil gas samples were collected at two depths (0.8 m and 1.7 m) in seven field campaigns and a total of 186 222Rn measurements were performed with a pulse ionization detector. A statistical assessment of the influence of field parameters on the results revealed that sampling depth and atmospheric pressure did not significantly affect the measurements, while the location of the sampling point and ground-level atmospheric temperature did. In order to remove the bias introduced by varying field temperatures and hence to be able to jointly interpret 222Rn measurements from different campaigns, 222Rn concentrations were rescaled by dividing each individual datum by the mean 222Rn concentration of its corresponding field campaign. Rescaled 222Rn maps showed a high spatial correlation between 222Rn minima and maximum contaminant concentrations in the top two layers of the soil profile, successfully delineating the surface trace of DNAPL accumulation in the anthropic backfill and silt layers. However, no correlation could be established between 222Rn concentrations in superficial soil gas and contaminant concentration in the deeper two layers of the soil profile. These results indicate that the 222Rn-deficit technique is unable to describe the vertical variation of contamination processes with depth but can be an effective tool for the preliminary characterization of sites in which the distance between the inlet point of the sampling probe and the contaminant accumulation falls within the effective diffusion length of 222Rn in the affected soil profile.

Funding Projects

TypeCodeAcronymLeaderTitle
Madrid Regional GovernmentP2018/EMT-4317CARESOIL-CMUnspecifiedCaracterización, Remediación, Modelización y Evaluación del Riesgo de la Contaminación de Suelos y Aguas Subterraneas
Government of SpainCTM2016-77151-C2-2-RCAREDENSEUnspecifiedCombinación de técnicas geoquímicas y geofísicas para la caracterización espacial de contaminantes densos en suelos y acuíferos superficiales

More information

Item ID: 66057
DC Identifier: http://oa.upm.es/66057/
OAI Identifier: oai:oa.upm.es:66057
DOI: 10.1016/j.envpol.2020.116200
Official URL: https://www.sciencedirect.com/science/article/pii/S0269749120368895?via%3Dihub
Deposited by: Memoria Investigacion
Deposited on: 17 Feb 2021 09:19
Last Modified: 17 Feb 2021 09:29
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