The distribution of lead concentrations and isotope compositions in the eastern Tropical Atlantic Ocean

File Description SizeFormat 
1-s2.0-S001670371830036X-main.pdfPublished version2.01 MBAdobe PDFView/Open
Title: The distribution of lead concentrations and isotope compositions in the eastern Tropical Atlantic Ocean
Authors: Bridgestock, L
Rehkamper, M
Van de Flierdt, T
Paul, M
Milne, A
Lohan, MC
Achterberg, EP
Item Type: Journal Article
Abstract: Anthropogenic emissions have dominated marine Pb sources during the past century. Here we present Pb concentrations and isotope compositions for ocean depth profiles collected in the eastern Tropical Atlantic Ocean (GEOTRACES section GA06), to trace the transfer of anthropogenic Pb into the ocean interior. Variations in Pb concentration and isotope composition were associated with changes in hydrography. Water masses ventilated in the southern hemisphere generally featured lower 206Pb/207Pb and 208Pb/207Pb ratios than those ventilated in the northern hemisphere, in accordance with Pb isotope data of historic anthropogenic Pb emissions. The distributions of Pb concentrations and isotope compositions in northern sourced waters were consistent with differences in their ventilation timescales. For example, a Pb concentration maximum at intermediate depth (600–900 m, 35 pmol kg−1) in waters sourced from the Irminger/Labrador Seas, is associated with Pb isotope compositions (206Pb/207Pb = 1.1818–1.1824, 208Pb/207Pb = 2.4472–2.4483) indicative of northern hemispheric emissions during the 1950s and 1960s close to peak leaded petrol usage, and a transit time of ∼50–60 years. In contrast, North Atlantic Deep Water (2000–4000 m water depth) featured lower Pb concentrations and isotope compositions (206Pb/207Pb = 1.1762–1.184, 208Pb/207Pb = 2.4482–2.4545) indicative of northern hemispheric emissions during the 1910s and 1930s and a transit time of ∼80–100 years. This supports the notion that transient anthropogenic Pb inputs are predominantly transferred into the ocean interior by water mass transport. However, the interpretation of Pb concentration and isotope composition distributions in terms of ventilation timescales and pathways is complicated by (1) the chemical reactivity of Pb in the ocean, and (2) mixing of waters ventilated during different time periods. The complex effects of water mass mixing on Pb distributions is particularly apparent in seawater in the Tropical Atlantic Ocean which is ventilated from the southern hemisphere. In particular, South Atlantic Central Water and Antarctic Intermediate Water were dominated by anthropogenic Pb emitted during the last 50–100 years, despite estimates of much older average ventilation ages in this region.
Issue Date: 2-Feb-2018
Date of Acceptance: 15-Jan-2018
URI: http://hdl.handle.net/10044/1/56094
DOI: https://dx.doi.org/10.1016/j.gca.2018.01.018
ISSN: 0016-7037
Publisher: Elsevier
Start Page: 36
End Page: 51
Journal / Book Title: Geochimica et Cosmochimica Acta
Volume: 225
Copyright Statement: 2018 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/ licenses/by/4.0/).
Sponsor/Funder: Natural Environment Research Council (NERC)
Natural Environment Research Council (NERC)
Funder's Grant Number: NE/H005390/1
NE/J021636/1
Keywords: 0402 Geochemistry
0403 Geology
Geochemistry & Geophysics
Publication Status: Published
Appears in Collections:Faculty of Engineering
Earth Science and Engineering



Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Creative Commons