Role of assisted natural remediation in environmental cleanup
D.C. Adrianoa, W.W. Wenzelb, J. Vangronsveldc,
N.S. Boland
aUniversity of Georgia. Savannah River Ecology Laboratory,
Drawer E, Aiken, SC 29082. USA
bUniversitat flir Bodenkultul; lnstihlt flir Bodenforschung.
nelIna, Austria
cLimburgs Universitair Centrum, Environmental Biology Program.
Diepenbeek, Belgium
dMassey University, Institute of Natural Resources, Palmerston
North. New Zealand
Available online 17 March 2004
Abstract
Metals are common contaminants worldwide. Long-teml deposition of metals
in soils can lead to accumulation, transport and biotoxicity/zootoxicity
caused by mobility and bioavailability of significant fraction of the
metals. Contaminant bioavailability is increasingly being used as a key
indicator of potential risk that contaminants pose to both environmental
and human health. However; the definition of bioavailability and the concepts
on which it is based are still unclear, the methods adopted for its
their ecotoxicological impacts on soil biota. Moreover, bioavailability
is often assumed to be static in nature where most decisions on risk and
remediation are based on laboratory estimations of the bioavailable fraction,
which may vary with time, nature of species as well as with temporal variation
in environmental factors. Because of their immutable nature, strict natural
attenuation processes alone may not be sufficient in mitigating the risks
from metals. However, accelerating these processes with human interference
(i.e., assisted natural remediation) that effectively immobilizes metals
might be a viable option. Application to soils of certain amendments that
enhance key biogeochemical processes in soils that effectively immobilize
metals have already been demonstrated in Europe and North America on a
field scale. Case studies using lime, phosphate and biosolid amendments
have demonstrated, under field conditions, enhanced natural remediation
resulting in substantially improved vegetation growth, invigorated microbial
J?Opulation and diversity, and reduced offsite metal transport. Depending
on soil/hydrogeochemical properties, source term and metal form/species,
and land use, the immobilization efficacy induced by such assisted natural
remediation may be enduring. The use of green plants as a remediation
tool in environmental cleanup has also offered some potential. Plants
can uptake and bioaccumulate (phytoextraction) as well as immobi]ize (phytoirnmobilization)
certain trace elements, in conjunction with their rhizospheric processes.
While long-teml stability of certain metal complexes, such as metal pyromorphites
has been shown in model systems, the influence of plant roots and its
microbial and mycorrhizal association on such stability is unknown. A
suite of chemical and biological tests are available to monitor the efficacy
of assisted natural remediation.
Keywords: Trace metals; Bioavailability; Natural remediation;
Risk assessment; Cleanup; Health
SREL Reprint #2790
Adriano, D. C., W. W. Wenzel, J. Vangronsveld and N. S. Bolan. 2004. Role of assisted natural remediation in environmental cleanup. Geoderma 122:121-142.
