Expounding the origin of chromium in groundwater of the Sarigkiol basin, Western Macedonia, Greece: a cohesive statistical approach and hydrochemical study.

The aim of this paper is to provide a methodology including statistical tools and spatial techniques, in order to identify the various potential sources of chromium (Crtot) in the Sarigkiol basin, Western Macedonia, Greece, where elevated concentrations of Crtot in groundwater have been recorded since 1996. Integrated hydrochemical approach and statistical analyses including Pearson's correlation coefficient, multivariate statistical analyses (factor analysis and hierarchical cluster analysis), and spatial techniques (Moran's I spatial autocorrelation index and bivariate local indicator spatial association cluster map) were applied to evaluate the chemical analyses of 73 water samples, from irrigation wells, natural springs, and surface water. Both natural and anthropogenic sources of Crtot were recorded; the first (ultramafic-dominated environment) is strongly depicted on the natural spring water, in which Crtot concentrations as high as ~ 130 μg/L were recorded, whereas the second (agricultural activities) acts synergistically in the irrigation wells of the Sarigkiol basin, in which strong correlations of Crtot, P, and NO3- were defined. The paper highlights its findings by outlining the potential sources of elevated concentrations of Cr6+ in the Sarigkiol basin, stressing the need for a closer attention on the role of agricultural activities as an important, though commonly neglected, anthropogenic source of Crtot in groundwater.