Scott's major interest is in trace element, heavy metal and radionuclide dynamics in soils.
Current research areas include:
- Measuring and modelling the solubility and adsorption in soils of heavy metals such as Pb, Ni, Cr(VI), Cd, Zn, Cu;
- Chemistry of selenium, zinc and iodine as vital trace elements, in relation to their bioavailability;
- Trace element biofortification of crops to meet human nutritional requirements;
- Fixation of the radionuclides uranium and thorium in soils.
These research areas have involved the development of analytical approaches to quantifying time-dependent metal fixation using stable isotopic dilution to assay the chemically-reactive pool of metals and metalloids in soils using inductively coupled plasma mass spectrometry (ICPMS) coupled to chromatography instrumentation.
Most of my professional experience in teaching and research lies in understanding, and modelling, soil and water chemical processes. In recently years, this has focussed on potentially toxic trace metals, especially cadmium and arsenic, through projects looking at long-term changes in metal reactivity in soils, metal solubility and plant uptake.
Studying metal 'reactivity' has involved the development of isotopic dilution techniques employing radiotracers such as 109Cd, 65Zn, 73As and 209Hg. This has enabled the development of kinetic and diffusion-based models of metal ion fixation within mineral substrates. This area is now leading into the development of parallel techniques employing stable isotopes, assayed by ICPMS.
With colleagues, I have developed solubility algorithms for trace metals in soils which relate pore water activities of free metal ions to their radio-labile pool in soil and other soil characteristics. This is a pragmatic approach which has the benefit of being widely applicable and follows from earlier work on radiocaesium dynamics undertaken in the early 1990s.
I have developed models of trace metal uptake by plants, based on the popular 'free ion activity' and 'biotic ligand' models which have seen widespread use in aquatic research. These are relations driven by our models of metal solubility developed for Cd, Zn, Cu, Pb, Ni and As. They have been employed in the contexts of 'phytoremediation' studies with the hyperaccumulators Thlaspi caerulescens (Cd, Zn) and Pteris vittata (As) and also uptake by food crops. The latter has lead to my involvement with risk assessment models arising from predictive uptake of metals by agronomic grain crops and by 'home grown' vegetables. This has enabled the reinterpretation of urban geochemistry surveys as 'risk assessment' maps and, most recently, a substantial interest in 'peri-urban agriculture in developing countries such as China, India and Uganda and in the UK. Recent phytoremediation projects have led to the development of a user-advice system comparing 3 contrasting approaches to phytoextraction of soils subject to long-term amendment with sewage sludge.
I have an interest in nitrogen dynamics in soils and broader ecosystems - especially in marginal ecosystems such as the Arctic. Again the use of isotopic dilution (with 15N) has been a cornerstone of my research involvement in projects based in Spitzbergen and in the Komi Republic.
Scott's main teaching responsibilities lie in areas related to soil geochemistry, environmental pollution and agronomy.
Taught modules include:
Environmental Geoscience (Level 1);
Hydrogeochemistry (Level 2);
Hydrogeochemistry Field Course (Level 2);
Soil Science (Level 2);
Soil and Water Science (Level 3);
Soil and Water Pollution and Reclamation (Level 3).
Risk assessment in peri-urban agriculture
Urban and peri-urban agriculture is increasingly important - both in the developed world in response to the perception that locally-sourced food has positive environmental impacts and in developing countries as an inevitable consequence of urban expansion. This research area follows from earlier work modelling metal solubility and uptake by (food) plants which lead to the development of risk assessment models and thereby the translation of urban geochemical surveys into spatially co-ordinated risk assessment maps of conurbations. Currently I have two students working on projects based in the UK and in Uganda.
Modelling uptake of trace metals by cereals.
This project utilizes the wealth of data available from the National Sludge Trials undertaken across the UK which provide invaluable information on metal uptake by cereal crops coupled to key soil (and soil solution) measurements. My project started in October 2003 as a studentship funded by the Lawes Trust, in co-operation with Rothamsted Research, Severn Trent Water Ltd. and with funding for one student from the Mexican Government.
Phytoremediation of arable sludged soils; the 'PASS' project.
Phytoremediation is the use of plants to 'clean up' soil by extracting metallic contaminants (Hg, Cd, Pb, Cu, Ni etc) or enhancing the rate of decomposition of organic pollutants to harmless residues. This project will assess the viability of phytoremediation of arable land subject to applications of metal-bearing sewage sludge and other wastes. Three alternative strategies are being investigated: (i) crops which produce a large biomass (eg maize) combined with soil treatment to enhance metal solubility, (ii) hyperaccumulator plants which have a natural ability to accumulate some metals and (iii) coppiced biofuel crops (willow) grown long term to offset costs. The outputs of the project now include a user-support guide which includes elements of modelling metal offtake, financial considerations and risk assessment. PASS is jointly funded under the Bioremediation Link Initiative by the BBSRC and Severn Trent Water Ltd.
Phytoremediation of contaminated land.
A number of PhD students are currently involved in projects which are aimed at developing phytoremediation strategies. Hyperaccumulator plants such as Thlaspi caerulescens and Pteris vittata are being investigated as potentially useful for the extraction of cadmium and arsenic respectively. These are funded from a variety of sources, including the Lawes Trust and involve co-operation with other Divisions within BioSciences and outside organisations such as Rothamsted Research.
Nitrogen dynamics in Arctic Ecosystems
The 'Carbo-North' project is based in Northern Russia and aims to assess the degree of nitrogen limitation to expansion of the sub-arctic treeline in response to global warming. This project will build on previous experience looking at N dynamics in the high arctic (NERC-GANE) which employed similar approaches including the use of stable N-15 as a tracer.
CROUT, N.M.J., TYE, A.M., ZHANG, H., MCGRATH, S.P. and YOUNG, S.D., 2006. Kinetics of metal fixation in soils: measurement and modeling by isotopic dilution Environmental Toxicology and Chemistry. 25(3), 659-663
Measuring and modelling trace metal solubility and 'lability' in soils.
Several projects have been involved in developing methods to 'speciate' potentially toxic metals and metalloids in soils and develop pragmatic models of metal solubility and time-dependent 'fixation' in soil matrices. These employ various forms of analysis, including isotopic dilution using radioisotopes of the target metal/metalloid - eg 109Cd, 65Zn, 73As and 209Hg. Funding has been from a range of sources including NERC, BBSRC and two joint studentships with the British Geological Survey. Characterising metals in soils is simply the first step towards improving risk assessments which is the ongoing direction of this research theme.
Nitrogen dynamics in arctioc ecosystems
A project funded by the NERC-GANE initiative used stable N-15 approaches to following the dynamics of nitrogen assimilation by soil-plant systems in the high arctic (Svalbard).
In addition to the ongoing development of the topics listed in 'current' and 'past' sections (phytoremediation, peri-urban agricultural risk assessment, dynamics of metal fixation in soils, nitrogen dynamics in arctic ecosystems) I hope to develop several new areas of research. In the immediate future, this will include phytoremediation of hydrocarbon contaminated soils in Nigeria and the isotopic dilution approaches to metal fixation using stable isotopes assayed by our Division's new ICPMS facility.