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Research Project
NanoDC - Electrokinetic remediation of soil contaminated with persistent organic pollutants using iron nanoparticles
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Authors
Publications
Heavy metal and PCB spatial distribution pattern in sediments within an urban catchment: contribution of historical pollution sources
Publication . Ferreira, Célia; Pato, Rosinda L.; Varejão, Jorge B.; Tavares, Alexandre O.; Ferreira, Antonio J. D.
Purpose This work analyzes polychlorinated biphenyl (PCB)
and heavy metal contamination in fluvial sediments and soils
in an urban catchment, according to the geo-accumulation
index and to soil and sediment quality guidelines. The catchment is located in Coimbra, Portugal, being affected by frequent flooding, and its main stream is a tributary to one of the
major rivers in Portugal (Mondego). Given the presence of
industrial activities over time, some inputs of pollutants are
expected, but so far, the legacy of historic pollution in this
catchment has not yet been investigated.
Materials and methods Twenty-five samples were collected
from nine sampling sites at the depths of 0–20, 20–40 and 40–
60 cm (to provide a historic perspective) along longitudinal
profiles (streamlines) and in soils downstream of pollution
sources. These samples were analyzed for six heavy
metals (Cu, Cr, Pb, Cd, Zn, Ni), organic carbon, pH
and ten PCBs (IUPAC numbers 28, 30, 52, 101, 138,
153, 166, 180, 204, 209).
Results and discussion Total PCB concentrations ranged
0.47–5.3 ng g−1 dry weight (dw), and levels increase from
the bottom to the top layers, suggesting an increased input
over the last 100 years. PCB congener distribution shows
the dominance of hexachlorobiphenyls, especially PCB138,
suggesting the existence of local sources. PCB levels did not
exceed sediment quality levels, placing sediments/soil under
class 1 (not contaminated) or class 2 (trace contamination)
with respect to PCB. All six metals exceeded the lowest effect
level for sediment quality criteria, and three (Cd, Pb and Zn)
largely exceeded the clean levels for dredged materials, placing sediments in class 5 (heavily contaminated). Sampling site
S1 presented the highest concentrations of Zn, Pb and Cd, and
historic vehicle traffic was identified as the most likely source,
given the vertical and horizontal profiles.
Conclusions High levels of Pb, Cd and Zn were found in
fluvial sediments at some locations of the Loreto catchment,
likely from historic traffic sources. This urban area is frequently affected by flooding events and is currently being subject to
urban redevelopment. During these events/actions, historic
pollutants in the sediments might surface and be redistributed,
impacting the downstream ecosystem of the major Mondego
River or increasing the risk of exposure of the urban
population.
Overview of in situ and ex situ remediation technologies for PCB-contaminated soils and sediments and obstacles for full-scale application
Publication . Gomes, Helena I.; Ferreira, Célia; Ribeiro, Alexandra B.
Polychlorinated biphenyls (PCB) are persistent organic pollutants used worldwide between the 1930s and
1980s. Although their use has been heavily restricted, PCB can be found in contaminated soils and sediments.
The most frequent remediation solutions adopted are “dig and dump” and “dig and incinerate”, but there are
currently new methods that could be more sustainable alternatives. This paper takes a look into the remediation options available for PCB-contaminated soils and sediments, differentiating between biological, chemical, physical and thermal methods. The use of combined technologies was also reviewed. Most of them are
still in an initial development stage and further research in different implementation issues is needed.
There is no single technology that is the solution for PCB contamination problem. The successful remediation
of a site will depend on proper selection, design and adjustment of the technology or combined technologies
to the site characteristics.
Numerical prediction of diffusion and electric field-induced iron nanoparticle transport
Publication . Gomes, Helena I.; Rodríguez-Maroto, José Miguel; Ribeiro, Alexandra B.; Pamukcu, Sibel; Ferreira, Célia
Zero valent iron nanoparticles (nZVI) are considered very promising for the remediation of contaminated
soils and groundwaters. However, an important issue related to their limited mobility remains unsolved.
Direct current can be used to enhance the nanoparticles transport, based on the same principles of
electrokinetic remediation. In this work, a generalized physicochemical model was developed and solved
numerically to describe the nZVI transport through porous media under electric field, and with different
electrolytes (with different ionic strengths). The model consists of the Nernst–Planck coupled system of
equations, which accounts for the mass balance of ionic species in a fluid medium, when both the
diffusion and electromigration of the ions are considered. The diffusion and electrophoretic transport of
the negatively charged nZVI particles were also considered in the system. The contribution of
electroosmotic flow to the overall mass transport was included in the model for all cases. The nZVI
effective mobility values in the porous medium are very low (10 7
–10 4 cm2V 1 s 1
), due to the
counterbalance between the positive electroosmotic flow and the electrophoretic transport of the
negatively charged nanoparticles. The higher the nZVI concentration is in the matrix, the higher the
aggregation; therefore, low concentration of nZVI suspensions must be used for successful field
application.
Nanoremediation coupled to electrokinetics for PCB removal from soil
Publication . Gomes, Helena I.; Fan, Guangping; Ottosen, Lisbeth M.; Ferreira, Célia; Ribeiro, Alexandra B.
Organizational Units
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Keywords
Contributors
Funders
Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
5876-PPCDTI
Funding Award Number
PTDC/AGR-AAM/101643/2008