Several years have passed since the global phase-out of leaded petrol use. Nonetheless, emissions from anthropogenic activities remain the principal source of Pb to the oceans. The distribution of elemental Pb and its stable isotopes throughout the surface ocean provide information on the source and transport of these anthropogenic inputs. This study presents dissolved Pb concentrations and isotopic distributions from 110 surface water samples collected during the Malaspina 2010 Circumnavigation Expedition. Dissolved Pb concentrations ranged from 10 pM to 49 pM across the sampling stations covering all major ocean basins. The highest concentrations were found in the northeast Atlantic Ocean and the lowest in both the south Pacific and south Atlantic Oceans. Lead concentrations measured in the north Pacific Ocean, near Hawaii, were compared to previously published data from the same region. That comparison showed that Pb concentration has decreased ∼40% since 1975, although the rate of decrease has slowed in the past two decades. The overall decline in concentration probably has been induced by the cessation of leaded gasoline use in North America. The temporal evolution of stable Pb isotopes in this region shows a shift from dominant North American-like composition in 1979 towards a more Asian-like composition in later years. More widely, the distribution of Pb and Pb isotopes measured in the Malaspina sample set of global surface waters were compared with previously published ratios of aerosols and other atmosphere-derived Pb sources from the countries surrounding the different ocean basins. This comparison identified the potential Pb sources to each ocean basin, providing new insights into the transport and fate of Pb in the oceans.
|Original language||English (US)|
|Number of pages||14|
|Journal||Geochimica et Cosmochimica Acta|
|State||Published - Jun 5 2018|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This research was partially supported by NSF OCE (award #1335269), a USC Graduate School Dissertation Completion Fellowship, and the Spanish Ministry of Economy and Competitiveness through the Malaspina 2010 expedition project (Consolider-Ingenio 2010, CSD2008-00077). We thank L. Pinho, E. Mesa, H. Marota and A. Dorsett for help with metal sampling, and the captain and crew of R/V Hespérides for help during the circumnavigation. Three reviewers and the Associate Editor are thanked for constructive comments that helped improve the manuscript. This work was presented in the 2015 AGU trace metal session entitled as an “unofficial” tribute to Russ Flegal. This work is dedicated to Russ.