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Geochemical footprint of dredged material discharges and sediment health status in Todos Santos Bay, Mexico

Abstract:

Total Al, Fe, Mn, Cu, Zn, Pb and organic carbon concentrations in Todos Santos Bay (TSB) surficial sediments were analyzed over three different years. A geochemical “fingerprint” associated with material dredged in the Port of Ensenada, was clearly identified on the surficial sediments via spatial analysis of standard scores (Zscores), within TSB prior to 2006 (1992/1994) when discharges were first conducted outside the bay. Values of Zscores > +3, considered substantial, encompassed 41%–50% of the TSB area (240 km2) and were located around the dredge disposal site. Anthropogenic toxic elements, evaluated from 10 different geochemical indices, showed no clear evidence of health deterioration, potential ecological risk and/or adverse effects on TSB marine biota. However, total Pb concentration doubled from 1994 to 2018, averaging (3.02 ± 0.75) x 10−2 and (5.73 ± 0.67) x 10−2 μmol g−1, respectively. If this trend continues, Pb could in future become a contaminant capable of deteriorating the health of TSB and its biota.