Marine sediments: A sink for geogenic and anthropogenic metals, a case study of Ridge flank and near vent sediments in Carlsberg Ridge, Indian Ocean

Abstract

Marine sediments found in the Mid-Ocean Ridges serve as repositories for both naturally occurring (geogenic)and human-generated (anthropogenic) metals. Understanding the geochemistry and processes of these sediments is crucialfor assessing their source, compositional end-members, and environmental impact. This study applied geochemical ratiosand proxies to representative samples from the Carlsberg Ridge, Indian Ocean, to determine the influence of hydrothermalcirculations on the near-vent hydrothermal sediments (NVS) and ridge flank sediments (RFS) and the potential effect oftoxic trace metals on the benthic ecosystems. The bulk chemical compositions of seven representative hydrothermalindicator metals (Ca, Al, Ti, Fe, Mn, Cu, and Zn) and seven representative toxic trace metals (Pb, Ni, Co, Cr, As, Cd, andCo) were analyzed at the A laboratory services in Guangzhou, China, by Agilent 7700 Inductively Couple Plasma MassSpectrometer (ICPMS). The geochemical signatures Fe/(Al + Fe + Mn) > 0.5; Al/(Al + Fe + Mn) < 0.3; (Fe + Mn)/Al >2.5; and (Fe + Mn)/Ti > 25 affirm the proximity of the NVS and the distal position of RFS to the Wocan vent site in theCarlsberg Ridge, Indian Ocean. The pollution indices, ecological risk index, and sediment quality guidelines showed lowto moderate contamination, low to moderate severity, and low to moderate ecological risk of As, Cd, Sb, Pb, Ni, Co, andCr to the benthic ecosystems at RFS. This is an indication of low to moderate anthropogenic influence from hydrothermalventing to the ridge flank sediment (RFS). This study has shown that an understanding of background and thresholdconcentrations can guide the development of strategies to reduce the impact of human activities on marine ecosystems.