GEOSTATISTICAL INTERPOLATION OF CHEMICAL CONCENTRATION

Measurements of contaminant concentration at a hazardous waste site ty pically vary over many orders of magnitude and have highly skewed dist ributions. This work presents a practical methodology for the estimati on of solute concentration contour maps and volume averages (needed fo r mass calculations) from data obtained from the analysis of water and soil samples. The methodology, which is an extension of linear geosta tistics, produces a point estimate, i.e., a representative value, as w ell as a confidence interval, which contains the true value with a giv en probability. The approach uses a parsimonious model that accounts f or the skewness by adding only one parameter to those used in linear g eostatistics (variograms or generalized covariances). The resulting no nlinear kriging method is not substantially more difficult to use than linear geostatistics. The methodology is most appropriate when concen tration measurements are available on a reasonably dense grid and no a dditional information (based on modeling dow and transport) can be use d. We present and illustrate through an application, a practical appro ach to estimate all the parameters needed and to select and test the m odel. Copyright (C) 1996 Elsevier Science Ltd