Cardiff University | Prifysgol Caerdydd ORCA
Online Research @ Cardiff 
WelshClear Cookie - decide language by browser settings

Evaluation of uptake mechanisms of phosphate by Fe(III)(oxyhydr)oxides in Early Proterozoic oceanic conditions

Hemmingsson, Christoffer, Pitcairn, Iain and Chi Fru, Ernest 2018. Evaluation of uptake mechanisms of phosphate by Fe(III)(oxyhydr)oxides in Early Proterozoic oceanic conditions. Environmental Chemistry 15 (2) , pp. 18-28. 10.1071/EN17124

[img]
Preview
PDF - Accepted Post-Print Version
Download (3MB) | Preview

Abstract

Banded iron formations (BIF) are proxies of global dissolved inorganic phosphate (DIP) content in Precambrian marine waters. Estimates of Precambrian DIP rely on constraining the mechanisms by which Fe(III)(oxyhydr)oxides scavenge DIP in NaCl solutions mimicking elevated Precambrian marine Si and Fe(II) concentrations. The two DIP binding modes suggested for Early Proterozoic marine waters are 1) surface attachment on pre-formed Fe(III)(oxyhydr)oxides (adsorption), and 2) incorporation of P into actively growing Fe(III)(oxyhydr)oxides (coprecipitation) during the oxidation of Fe(II) to Fe(III)(oxyhydr)oxides in the presence of DIP. It has been suggested that elevated Si concentrations such as those suggested for Precambrian seawater, strongly inhibit adsorption of DIP in Fe(III)(oxyhydr)oxides, however recent coprecipitation experiments show that DIP is scavenged by Fe(III)(oxyhydr)oxides in the presence of Si, seawater cations and hydrothermal As. In this study we show that the DIP uptake onto Fe(III)(oxyhydr)oxides by adsorption is less than 5% of that by coprecipitation. Differences in surface attachment and the possibility of structural capture within the Fe(III)(oxyhydr)oxides are inferred from the robust influence Si has on DIP binding during adsorption, but inhibited for coprecipitation when As(III) and As(V) are present. The data imply that in the Early Proterozoic open oceans, Fe(III)(oxyhydr)oxides precipitated when deep anoxic Fe(II)-rich waters rose and mixed with the first permanently oxygenated ocean surface waters, caused DIP removal from surface waters through coprecipitation rather than adsorption. Local variations in DIP and perhaps even stratification of DIP in the oceans were likely created from the continuous removal of DIP from surface waters by Fe(III)(oxyhydr)oxides, and its partial release into the anoxic bottom waters and in buried sediments. In addition to a DIP famine, the selectivity for DIP over As(V) may have led to As enrichment in surface waters both of which would have most likely decreased the productivity of cyanobacteria and O2 production.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Publisher: CSIRO Publishing
ISSN: 1448-2517
Funders: European Research Council
Date of First Compliant Deposit: 12 January 2018
Date of Acceptance: 13 October 2017
Last Modified: 18 Oct 2019 21:14
URI: http://orca.cf.ac.uk/id/eprint/108124

Citation Data

Cited 3 times in Scopus. View in Scopus. Powered By Scopus® Data

Actions (repository staff only)

Edit Item Edit Item

Downloads

Downloads per month over past year

View more statistics