Geographical Information Systems And Geostatistics For Modelling Radioactively Contaminated Land Areas

Natural Hazards (2005) 35: 229–242 DOI 10.1007/s11069-004-5206-7


Springer 2005

Geographical Information Systems and Geostatistics for Modelling Radioactively Contaminated Land Areas NAZZARENO DIODATO1,w and MICHELE CECCARELLI2 1

Monte Pino Research Observatory on Climate and Landscape–ROC&L, Contrada Monte Pino, 82100 Benevento, Italy; 2Research Center on Software Technologies-RCOST, University of Sannio – via Port’Arsa 11, 82100 Benevento, Italy (Received 15 July 2003; accepted: 14 October 2004)

Abstract. The Chernobyl plume contaminated vast lands of Europe with radiocaesium (137Cs) in 1986 because of the deposition of radionuclides on the ground by wet and dry deposition processes. Nevertheless, in a nuclear emergency, contamination data may be very sparse and there is need to make rapid and scientifically supported decisions. Here we analyze the rainfall field, an important precursor of the wet deposition, during the passage of the plume. Thus, estimating rainfall spatial variability can help to identify possible contaminated areas and associated risks when rainfall exceeded a given threshold. In this paper, we show that the conditional probabilities of exceeding threshold rainfall values could be spatially assessed using the mutual benefits of linking geostatistical and geographical information system (GIS) to quantify the evaluation of the risk involved in decision making. In particular, the nonparametric geostatistic technique, termed Indicator Kriging (IK), enables one to efficiently estimate the probability that the true value exceeds the threshold values by means of the indicator coding transform. Afterward, GIS has been used to find the areas probably affected by wash-out (probability >0.5 that rainfall is above a certain threshold). The experimental study has been focused on a test site in Beneventan agroecosystem (Southern Italy) to model the spatial uncertainty over a continuous area from sparse rainfall data. This enabled to generate probability maps delineating area potentially affected by to contamination to be monitored after wet deposition of Chernobyl releases. Key words: Chernobyl plume, deposition, threshold rain, geostatistics, GIS, probability maps, monitoring areas, Benevento (southern Italy)

1. Introduction Radioactive land contamination caused by the Chernobyl accident features extremely complex spatial pattern. This is due to various causes, among other are meteorological conditions, landscape and land use, soil type, source term and others (Clark and Smith, 1988; Savelieva et al., 1999). Contamination of soils by washout during the passage of the radioactive plume could be a w

Author for correspondence: E-mail: [email protected]