Analisi geostatistica spazio-temporale di parametri di qualità delle acque sotterranee

The space-time behavior of hydrochemical parameters of contamination of groundwater could be studied by means of the tools provided by geostatistics. The cross-variogram, if built crossing the changes of two set of data related to two different times, can express the spatial continuity and the relative temporal persistence ofthe parameter. The cross-variogram allows us to improve the estimate of the parameter which a limited number of samplings has been sampled. This characteristic hm been used to set a procedure in order to assess the optimal sampling arrangement for estùnating concentrations in particular criticai sites. Reduced and optimal configuration of a network suffers from the uncertainties caused by the variographer's choices on type and parameters of the variogram. Using a fuzzy approach to represent the uncertainties, the variogram parameters can be deseribed as fuzzy numbers and the parameter uncertainties by means ofmembership functions. Using such fuzzy variograms, the cokriging method produces membership functions of both the estimation and the CEVo An application of the sequential research algorithm, based on the fuzzy CEVs, has been carried out in order to verify the methodolngy.