Bulk and bioavailable heavy metals (Cd, Cu, Pb, and Zn) in surface sediments from Mazatlan Harbor (SE Gulf of California)

This work evaluates current metal concentrations (Cd, Cu, Pb and Zn) and the operational bio-available chemical extraction fraction in surface sediments in Mazatlan Harbor in Northwest Mexico. Sediment samples were also analyzed for organic carbon, carbonates and particle size. Ranges of bulk metal were as follows: Cd from 3.1 to 3.3 mu g/g, Cu from 31.9 to 44.9 mu g/g, Pb from 49.6 to 54.0 mu g/g, and Zn from 217.8 to 323.5 mu g/g. In terms of biological effects, metals concentrations in the sediments lie between the low and median ranges of the mean quality guideline criteria. Comparatively, the metals concentrations increased from 1983 to 1994 and then for 2006, except Pb and Cd that decreased in the last period of time. The bio-available fraction of metals increased from 1983 to 1994, but only bio-available Cu increased from 1994 to 2006, due to mobilization of this metal from the organic matter-sulfide phase.