URGENT: contaminated land investigation and remidiation
The aim of the Natural Environment Research Council's URGENT programme is one of managing the interactions between natural processes and the effects of past, present and future human activities. Mike Welch, national facilitator for the programme and a consultant to the Chemical Industries Association, highlights URGENT activities in the field of contaminated land.
Funding of £9.7m has been allocated over seven years to 41 projects under
the NERC URGENT Programme, with additional support from local authorities, the
Environment Agency and industry.
As an example, the potential for rising groundwater under Wolverhampton to
mobilise contaminants, including toxic heavy metals that could pollute surface
waters and the local aquifer is being investigated by the University of Sheffield,
the British Geological Survey and the Macaulay Land Use Research Institute.
Researchers are using groundwater and geochemical modelling to predict the effect
of groundwater composition on mobilisation and as a means of assessing the impact
on groundwater quality of land remediation strategies and different abstraction
regimes. Work between Imperial College and the University of Nottingham, involving
brownfield sites in Nottingham as well as Wolverhampton, aims to provide assistance
to local authorities in the interpretation of urban geochemical maps and to
provide a decision support system for the risk assessment of metal contaminated
soils. A key issue is the extent to which contaminants are bioavailable and
therefore a risk to human health or the local ecosystem. A new model has been
developed to predict metal up-take by vegetable plants and a hazard quotient
used to give a measure of risk to potentially exposed populations consuming
locally grown vegetables. A battery of new chemical and biochemical analytical
tools has been developed in the course of these studies.
A joint project between the University of Edinburgh and the Macaulay Land Use
Research Institute has developed a model to predict the behaviour of chromium
at sites where chromite ore processing residues were deposited some 30 years
ago, and to simulate potential remediation treatments. Using sophisticated analytical
tools, the mechanism for the continual release of Cr(VI) from these sites has
been identified, and it has been shown that common remediation techniques, such
as the addition of ferrous sulphate to reduce Cr(VI) to the less harmful Cr(III)
can greatly increase the release of Cr(VI) via ion exchange with sulphate. The
work demonstrates that direct transfer of remediation techniques from one situation
to another needs to be very carefully considered, and the final version of the
model will enable users to understand better the issues at particular sites
and to simulate potential remediation treatments.
A project at the British Geological Survey with potentially very wide application
involves the development of non-intrusive techniques capable of providing 3D
views of underground structures, including waste deposits. Using electrical
resistivity measurements, high-resolution 3D images can be created that enable
complex underground features to be visualised more precisely than is possible
with conventional methods. Large volumes of ground can be scanned down to tens
of metres, and it can be used where there are buildings or roads. The technique
has already been used to view old waste depositories and landfills where it
shows the distribution of leachate and any points of leakage. Amongst other
applications it can be used to identify pockets of non-aqueous liquids, leakages
from underground transport systems, and potential physical hazards, such as
incipient landslips, subsidence, etc. Currently the technique is being developed
to provide a continuous record over time of changing conditions within landfills,
with data fed by telemetry to a remote monitoring point.
Remediation of degraded land by natural processes can take many years unless
contaminated soil is moved off-site or chemicals are used to encourage growth,
which may not be sustainable over time. Attempts to establish vegetation, such
as trees, which promote soil formation at a rapid rate and, in conjunction with
micro-organisms, help to reduce contaminants, tend to have limited success.
A team led by the University of York, however, has completed a project that
has identified fungi that are adapted to growing in contaminated soils with
high levels of organic contaminants and which can form a symbiotic relationship
that helps the tree to acquire important nutrients and protects it against disease.
Several projects in the programme are investigating ways of assessing the quality
of groundwater and the potential for using groundwater that is rising under
cities, such as Birmingham and Nottingham, to reduce the demands on other aquifers.
Direct Toxicity Assessment has been shown by the Royal Holloway University to
be a viable method of rating the quality of groundwater, and Research at Birmingham,
Sheffield and Surrey Universities is leading to the development of models that
can be used to show the likely impact of abstracting urban groundwater based
on activities in the area including actual or potential inputs and other local
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