English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Any effort to reconstruct Earth history using variations in authigenic enrichments of redox-sensitive and biogeochemically important trace metals must rest on a fundamental understanding of their modern oceanic and sedimentary geochemistry. Further, unravelling the multiple controls on sedimentary enrichments requires a multi-element approach. Of the range of metals studied, most is known about the behavior of Fe, Mn, and Mo. In this study, we compare the authigenic enrichment patterns of these elements with a group whose behavior is not as well defined (Cd, Cu, Zn, and Ni) in three oxygen-poor settings: the Black Sea, the Cariaco Basin (Venezuela), and the Peru Margin. These three settings span a range of biogeochemical environments, allowing us to isolate the different controls on sedimentary enrichment. Our approach, relying on the covariation of elemental enrichment factors [EF, defined for element X as: EFX = (X/Al)sample/(X/Al)lithogenic], has previously been applied to Mo and U to elucidate paleoenvironmental information on, for example, benthic redox conditions, the particulate shuttle, and the evolution of water mass chemistry. We find two key controls on trace metal enrichment. First, the concentration of an element in the lithogenic background sediment (used in calculating EFX) controls the magnitude of potential enrichment. Maximum enrichment factors of 376 and 800 are calculated for Mo (∼1 ppm in detrital sediments) and Cd (∼0.3 ppm), respectively, compared to values not greater than 17 in any setting for the other five metals (∼45 ppm to ∼4.5 wt.% in detrital sediments). Second, there is a relationship between the aqueous concentration of the element in overlying seawater and its degree of enrichment in the sediment. We further identify four important processes for delivery of trace metals to the sediment. These are: (1) cellular uptake (especially important for Zn and Cd), (2) interaction/co-precipitation with sulfide (Mo, Cu, and Cd), (3) passive scavenging via the traditional particulate shuttle (Mo, Ni, and Cu), and (4) an association with the benthic Fe redox shuttle (Mn, Ni). Finally, we summarize the oceanic mass balance of Cd and Mo and place the first constraints on the contribution of reducing sediments to the oceanic mass balance of Cu, Zn, and Ni. We show that reducing sediments are the ultimate repository for up to half the total output flux of these elements from the oceanic dissolved pool.

Controls on trace metal authigenic enrichment in reducing sediments: Insights from modern oxygen-deficient settings