Application of GIS for population dose assessment in the Chernobyl accident area

The development of updated approaches to evaluating the long-term consequences of the Chernobyl accident is based on the experience of authors in assessing population doses and in creating Decision Support Systems (DSS) in radioecology with the use of GIS technologies. 'Dose block' is a key component of the PRANA GIS-DSS on rehabilitation of contaminated territories after Chernobyl accident. When estimating internal and external doses to the local population the following components of PRANA are used: electronic maps for territories under investigation (5 contaminated districts of Bryansk reg.); databases (including database associated with polygons of vector electronic maps, and database for model and other input parameters); updated and modified mathematical models for assessing external and internal doses to the local population (from 137Cs and 90Sr); corresponding computer modules and user interface. Library of electronic maps includes different layers of vector maps of landuse for territories under consideration. Map of landuse for each district comprises all elements of land use: agricultural fields (arable lands, pastures and hayfields), forests, gardens, settlements, swamps and water bodies. Databases associated with polygons of vector maps include the following main monitoring data for each polygon: for fields - soil contamination density with 137Cs and 90Sr, soil type, mechanical and chemical composition, crop rotation; for settlements - contamination density, monitoring data of internal and external doses, local diet, behaviour and location and other factors, demographic data, etc. Other databases include all the parameters necessary for assessing contamination of agricultural products and internal/external doses: various transfer factors, parameters of countermeasures, productivity and/or production of agricultural crops, milk and meat (both for private and farm production), etc. Special attention was paid to developing and adjusting to elements of GIS the original multilevel probabilistic and adaptive dose models for assessing external/internal doses with a possibility of consideration of a wide class of protective measures and uncertainly analysis. One of the key features of dose models indicated is an active use of landuse map in combination with soil contamination map and the map of human occupation in a vicinity of the settlement under consideration. It is especially important in the Chernobyl case of inhomogeneous contamination of territory and allows estimating different scenarios of the local population behaviour and consumption of locally produced or gathered food. The possibility of connecting landuse polygons with the settlement is especially important when assessing contribution of milk and forest products into individual effective dose to local inhabitants. Such an approach comprises also analysing results of implementation of different countermeasures, including management on the use of contaminated territories. External and internal dose estimates based on GIS technique are compared with the data of individual dose monitoring obtained in the Bryansk region after the Chernobyl accident. Several variants of dose block have been developed: for practical use, for research, as well as for training and education. (author)