Capture of arsenic by pyrite in near-shore marine sediments

Abstract

Evidence of pyrite formation during diagenesis of suboxic sediments in the Laurentian Trough, Canada, is presented. The process is slower than in salt marsh sediments probably due to the low sulfate reduction rate of 2–3 nmol cm −3 day −1 measured in the St. Lawrence sediments. A strong correlation is observed between arsenic and pyrite, suggesting the capture of this element in the lattice sites of pyrite with a Fe/As ratio of 10 3. It is important to consider this association of As with pyrite in the study of the marine geochemistry of Fe and As.