URGENT: contaminated land investigation and remidiation

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.

Model behaviour

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.

Non-intrusive techniques

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.

Groundwater quality

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

abstractions.