Some spatial modelling examples Marian Scott SAGES March 2009

ECCOMAGS Project Funded by EC FPV – Nuclear Safety, Partners –BfS (Germany), CEA (France), DEMA/DTU (Denmark), GBA (Austria), HSK (Switzerland), IGM (Portugal), SSI (Sweden), SGU (Sweden), STUK (Finland), SURRC (UK) Airborne Gamma-ray Spectrometry (AGS) T o assess comparability of the European AGS systems To assess comparability of AGS with ground- based systems.

Exercise Survey Areas

Ground sampling locations

Pre-Characterisation-sampling plan for in-situ measurement Expanding hexagonal sampling pattern showing the radial numbers and shell designations.

137 Cs Map 6 th June

Area X – 137 Cs

137Cs regridded maps – Area Y

137Cs regridded maps – Area Z

Shape Analysis – Wigtown Merse TeamP (km)A (km 2 )P/A (km -1 ) BFSA BFSB CEA DEMA SGU SSI SURRC Mean Map

Lochs in area Y

Example: Mapping SO 2 over Europe and through time How has SO 2 levels changed over time as a result of international agreements? How is SO 2 distributed over Europe?

At each time point a plane across space was fitted and Gaussian Variograms of the residuals were computed. The average of the variogram parameters estimates were used to obtain the spatial covariance matrix. Spatial Analysis Across Time

Example: River quality over a river basin How have nitrate levels changed over time as a result of changes in management and diffuse pollution control? How are nitrate levels distributed over river basin?

network design-ECN

try the Mururoa and Rosyth examples again and look at the map that is produced and compare it with the truth

Example: 60 Co activity in sediment of an estuary Suppose wanted to estimate the inventory of 60 Co in the sediments of an estuary whose boundaries have been clearly defined. We know that 60 Co is particle reactive and we have a map of sediment type in the estuary. How would we make use of this information?

Stratified sampling chosen

Example: tritium in a South Pacific atoll Suppose wanted to map the distribution of tritium inside and atoll (tritium in sea water). This will require us to collect water samples. How should we do this?

Transect sampling chosen

Summary Spatial modelling is an important skill, since much environmental data are spatially registered the complexities include describing the spatial correlation structure and considering if there is a temporal component how this can be modelled.