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Geochemical interactions study in surface river sediments at an artisanal mining area by means of Canonical (MANOVA)-Biplot

Abstract:

This paper analyzes trace elements concentrations from surface detrital sediments corresponding to 4 rivers located in the artisanal gold mining area of Ponce Enríquez (southern Ecuador) to assess the contamination levels. Moreover, their potential environmental threats were evaluated using both the enrichment factors (EFs) approach and sediment quality guidelines (SQGs). The study showed extremely high concentrations of Hg in certain locations of the Villa river (up to 50 mg/kg), which exceeded the probable effect levels (PELs) for Hg up to 50 times. Similarly, average EFs for As elements reached average values of 87, exceeding up to 80 times the SQGs. Moreover, Cr and Cu were also significant contributors to sediment pollution. In this study, the Canonical/MANOVA-Biplot, a technique to properly represent the multivariate differences among locations, is introduced as an alternative to the more descriptive approach provided by the most popular Principal Components Analysis. The technique can be viewed as a graphical representation of MANOVA, the adequate technique to stablish the statistical significance of the differences. The procedure established clear differences among the contamination patterns of the 4 river locations.