Degree of trace metal pyritization in sediments from the Pacific coast of baja california, mexico

C Nava-López,Ma Huerta-Díaz

doi:10.7773/cm.v27i2.456

Abstract

We analyzed sediments from a core collected on the Pacific coast of Baja California, ~45 km off the city of Tijuana and at 1257 m water depth (32º29.5′N, 117º28.3′W), for trace metal content in two operationally-defined fractions, HCl and pyrite. Our results indicate a transference of Cu > Ni > Zn >> Hg and Ag from the HCl to the pyrite fraction. Sediments have degrees of pyritization (DOP) that averaged 7.2 ± 4.9%, with a maximum value of 18.5%. Average degrees of trace metal pyritization (DTMP) ranged from 6.2 ± 2.1% to 83 ± 18% for Mn and Hg, respectively, although maximum values for some metals were close to 100%. This transference is apparently a function of the solubility products of metal sulfides and the relative abundances of metals in the HCl fraction, as suggested by the significant correlation (p < 0.001) observed between these two parameters and the DTMP of a number of trace metals. A similar correlation was obtained from published data of two cores collected in the Gulf of Mexico.

Highlights

INTRODUCCIÓNKnowledge of the distribution of trace elements among major geochemical fractions of marine sediments is important since this association will determine whether metals will be preserved in the sediments or recycled back into the water column
This concept was further extended to other metals by Huerta-Díaz and Morse (1990), who introduced the concept of degree of trace metal pyritization (DTMP), which can be calculated with the following equation: degrees of trace metal pyritization (DTMP)
Sediments from the Pacific coast of Baja California are not pyritized to a great extent

Summary

Introduction

Knowledge of the distribution of trace elements among major geochemical fractions of marine sediments is important since this association will determine whether metals will be preserved in the sediments or recycled back into the water column. Information on this subject has important implications for studies on biogeochemical cycles and residence time of trace metals in the marine environment. Depending on which mineral phase they are associated with, trace metals in

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