Transfer of anthropogenic lead (Pb) to Antarctic waters and the Pb-inventory of the Southern Ocean water column

• Applicants: Dr. Marcus Gutjahr; Dr. Jörg Lippold
• Subject Area: Oceanography
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 522417065

In November 2023, a ten-week geochemical expedition (EASI-2 / PS140) on board the research vessel Polarstern will set off from Cape Town to East Antarctica. This is one of three coordinated Antarctic cruises that will work on independent but linked research topics (EASI-1-2-3). During this trip, water samples will be taken at regular intervals along two sections in the Indian sector of the Southern Ocean, as well as at a large number of stations in coastal waters on the East Antarctic shelf, using a trace metal-clean water sampler. The port of destination is Hobart (Tasmania), chief scientist will be co-applicant Dr. Marcus Gutjahr, and both applicants will take part on this scientific cruise. The scientific goal of this research proposal, which is to be realized as part of a two-year postdoctoral position, is the quantification of the input behavior of anthropogenic lead in the working area. In addition, we aim to explore how lead of anthropogenic origin enters Antarctic waters, where it mixes with naturally introduced dissolved lead. Anthropogenic lead in seawater can be easily distinguished from naturally introduced lead by significantly increased concentrations and a clearly distinguishable isotopic composition. Since the classic physical-oceanographic water parameters will also be measured during the trip, we can make clear statements as to where the dissolved lead in each examined body of water is derived from. Obtaining uncontaminated water samples for lead isotopic studies is very time-consuming and tedious, which requires the use of a special water sampler and work in clean room laboratories on the ship. This is the reason why there is almost no comparative data from the study area. The applicants were able to create the boundary conditions for this project through cooperation with scientists from the AWI Helmholtz Center for Polar and Marine Research, and the water samples obtained will be shared with international colleagues. A major focus will also be placed on the natural input behavior of dissolved lead via subglacial weathering below the Amery Ice Shelf in Prydz Bay (East Antarctica). These water samples will be compared with concentration and isotope data from sedimentary pore waters, which will also be obtained on the cruise. This part of the study will make it possible to depict the natural lead input and lead-specific exchange processes on the seabed and marine sediments. From this last aspect of the proposed project we hope to draw far-reaching conclusions for the interpretation of past hydrogenetic lead isotope data from sedimentary archives for paleo-climatic reconstructions.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
• International Connection: Australia, Netherlands
• Cooperation Partners: Dr. Laura Herraiz Borreguero; Professor Dr. Rob Middag
• Co-Investigators: Professorin Dr. Gesine Mollenhauer; Dr. Scarlett Trimborn