Biogeochemistry and Biogeochemical Modelling

Biogeochemistry is concerned primarily with unravelling and understanding chemical cycling in the environment. Our focus is mainly on potentially hazardous trace elements (eg. Pb, Cd, As) and radionuclides (¹⁴C, ¹³⁷Cs, ¹²⁹I, ²³⁸U, ²³²Th) but also includes broader consideration of carbon and nitrogen dynamics and availability of micronutrients (Se, I, Zn) in soils and aquatic systems. We also have a considerable interest in trace gas behaviour in soils, in the near-surface atmosphere and at the soil-vegetation-atmosphere interface. Much of our work involves measurement and modelling of elemental and isotopic cycling and we combine data and modelling expertise in risk assessment applications.

Key aims and expertise

We have in-house expertise in multi element and ultra-low level trace element analysis using ICPMS, which is coupled with HPLC to identify inorganic or organic species of elements or isotopes. This capability is augmented by collaboration with specialist laboratories at the British Geological Survey. We use various methods to sample and analyse soil gases and to quantify soil-atmosphere exchange of CH₄, CO₂ and N₂O. Currently we are developing methods to measure fluxes of ²²²Rn, an inert radioactive gas, which can be used to quantify in situ diffusion coefficients in soils. We also have experience in measuring ¹⁴C and ¹³C labelled gases.

Current projects

TRansfer - Exposure - Effects (TREE): integrating the science needed to underpin radioactivity assessments for humans and wildlife (Crout, Young, Bailey, Shaw, funded by NERC)

The contribution of trees to tropical wetland methane emissions (Sjogersten, funded by NERC)

Experimental and modelling studies of C-14 behaviour in the biosphere (Shaw, funded by Nuclear Decommissioning Authority)

Significant results

• Integration of work on predicting the transfer of radionuclides in the food chain into the ARGOS nuclear and chemical emergency management system.
• Contributors to NDA’s Integrated Project Team on C-14 for radioactive waste disposal in the UK.
• Expert review of SKB’s licence application to build and operate a geological repository for spent nuclear fuel in Sweden.