This project involved measuring the aerosol trace element concentrations, aerosol fractional solubility, and atmospheric deposition of bio-essential trace elements on a cruise of opportunity, collaborating in a multidisciplinary project studying trace element sources, transformations, and sinks in the Indian Ocean sector of the Southern Ocean, an area that has been relatively under-studied from a biogeochemical perspective. The cruise track crossed the currents and oceanographic fronts that are major pathways of the general circulation in the region and allowed us to quantify the atmospheric deposition of bioactive trace elements in a region with multiple possible aerosol sources, and where aerosol iron (Fe) deposition and rainfall rates are predicted to range over 1-2 orders of magnitude.

Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Curation Notes
• Data Files
• Supplemental Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Program Information
• Funding

Aerosol samples were collected according to protocols in the GEOTRACES cookbook using a Tisch TE-5170V-BL high-volume aerosol sampler modified to collect 12 replicate samples on 47-millimeter (mm) diameter Whatman-41 (W-41) filters. In order to minimize filter blanks, the W-41 filters were pre-cleaned inside a HEPA-filtered laminar flow hood using three cycles of leaching with 0.5M HCl (Optima) and then rinsing with ultra-high purity water (UHP water) according to trace element protocols. Sector control, which was accomplished via a Campbell Scientific data logger, was set such that the sampler would only operate during winds of >0.5 meters per second (m/s) and from ± 60° of the ship's bow to avoid sampling air influenced by the ship's exhaust.

Briefly, a W41 filter aerosol sample was digested and dried down three times in a 15-milliliter (mL) flat-bottom/round-interior Teflon jar (Savillex: 200-015-20 and 600-033-01); first with HNO3, next with HNO3 and HF, and finally with HNO3 only (all acids were Fisher Optima grade). All filter digestions were performed under a continuous flow of HEPA-filtered air within a Class-1000 clean room.

ICPMS data (raw counts) for each isotope were drift corrected and converted to element mass using calibration curves generated from high-purity ICPMS standards of known concentrations. Element masses were then divided by the volume of air filtered over each deployment.

Quality Flags:
The dataset includes quality flags applied following the GEOTRACES recommendations found at https://www.geotraces.org/geotraces-quality-flag-policy/, where 2 = probably good value, and 9 = missing value.

This section documents curation actions performed prior to publication review with the submitter, and additional information relevant to understanding and reusing this dataset. It distinguishes changes made to the submitted (meta)data from unresolved issues and/or enhancements that improve future reuse and interoperability.

CURATION ACTIONS PERFORMED ON DATA

- Imported original file "template_MD229 SWINGS aerosol data.xlsx" (sheet 4) into the BCO-DMO processing system.
- Treated "-999.000" as a missing data value (missing data are empty/blank in the final CSV file).
- Renamed data columns to comply with BCO-DMO naming conventions.
- Converted Start_Date_UTC + Start_Time_UTC into Start_ISO_DateTime_UTC (ISO 8601, UTC) and End_Date_UTC + End_Time_UTC into End_ISO_DateTime_UTC (ISO 8601, UTC).
- Deleted the following empty/unused columns: Station_ID, Rosette_Position, Sample_ID, Sample_Depth.
- Saved the final file as "1008364_v1_gs02_swings_aerosols.csv".

CURATION ACTIONS PERFORMED ON METADATA

- BCO-DMO's standard metadata entry and text formatting steps were performed. See: https://www.bco-dmo.org/how-to/standard-curation-edits

ISSUES POTENTIALLY IMPACTING REUSE

- N/A

Coverage: Southwest Indian Ocean

NSF Award Abstract:
Marine phytoplankton (microscopic photosynthetic algae) produce about half of the oxygen we breath and remove billions of tons of carbon dioxide from the atmosphere each year. This primary productivity plays a central role in controlling atmospheric carbon dioxide (pCO2) levels and the global climate. Yet, phytoplankton productivity is limited by lack of iron (an essential trace element) in about 40% of the global ocean. While phytoplankton productivity helps remove carbon dioxide from the atmosphere, it also removes iron and other essential trace elements (like manganese, cobalt, copper, and zinc) from the upper ocean. One critical issue is, "What are the sources for these essential trace elements that are needed to replace those removed by phytoplankton to keep the annual productivity cycles going?" This is especially important in the waters of the Southern Ocean around Antarctica, where ocean circulation brings deep water to the surface; water that is enriched in nutrients like nitrate and phosphate but depleted in essential trace elements. The main source for iron in the open ocean is from desert dust deposition. In this project, scientists will collect aerosols (fine particles in the air) and rain samples over the Southern Ocean to measure how much iron (and the other essential trace elements) is depositing to surface waters. Other scientists will be measuring how fast phytoplankton are growing, and together we will learn how the input of trace elements from dust helps to remove carbon dioxide from the atmosphere. This information can then be used to help predict the future of Earth’s climate. The scientists will communicate results of their study to the public via open house events at their respective campuses, as well as through online forums. One undergraduate student from Florida International University, a leading minority serving university, would be supported and trained as part of this project.

The project will measure the aerosol fractional solubility and atmospheric deposition of bio-essential trace elements as part of a multidisciplinary project studying trace element sources, transformations and sinks in the Indian Ocean sector of the Southern Ocean. The research cruise track will cross the currents and oceanographic fronts that are major pathways of the general circulation in the region where we expect to find multiple possible aerosol sources, and where aerosol Fe deposition and rainfall rates are predicted to range over 1-2 orders of magnitude. Aerosol samples (bulk and size-fractionated) will be collected on a daily basis and event-based rain samples to be analyzed for total and soluble major and trace elements including nitrate, phosphate, silicate, chloride, sulfate, Na, Mg, Al, V, Mn, Fe, Co, Ni, Cu, Zn, and Cd. In addition, scientists will analyze the water-soluble organic compounds in aerosols, focusing on compounds such as oxalate and methane-sulfonic acid (MSA) that enhance aerosol trace element solubility. Scientists will use Be-7 concentrations in aerosols and the upper water column to calculate aerosol bulk deposition velocities and test whether the relationship between rainfall rate and bulk deposition velocity that we have previously published can be applied on a more global basis. Further, scientists will use the trace element concentration data along with air-mass back trajectory analysis to apportion the aerosols between anthropogenic and natural sources, and study how aerosol sources affect the fractional solubility. Aerosol and rain subsamples will be provided to collaborators on the cruise for the analysis of additional important parameters.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Website: http://www.geotraces.org/

Coverage: Global

GEOTRACES is a SCOR sponsored program; and funding for program infrastructure development is provided by the U.S. National Science Foundation.

GEOTRACES gained momentum following a special symposium, S02: Biogeochemical cycling of trace elements and isotopes in the ocean and applications to constrain contemporary marine processes (GEOSECS II), at a 2003 Goldschmidt meeting convened in Japan. The GEOSECS II acronym referred to the Geochemical Ocean Section Studies To determine full water column distributions of selected trace elements and isotopes, including their concentration, chemical speciation, and physical form, along a sufficient number of sections in each ocean basin to establish the principal relationships between these distributions and with more traditional hydrographic parameters;

* To evaluate the sources, sinks, and internal cycling of these species and thereby characterize more completely the physical, chemical and biological processes regulating their distributions, and the sensitivity of these processes to global change; and

* To understand the processes that control the concentrations of geochemical species used for proxies of the past environment, both in the water column and in the substrates that reflect the water column.

GEOTRACES will be global in scope, consisting of ocean sections complemented by regional process studies. Sections and process studies will combine fieldwork, laboratory experiments and modelling. Beyond realizing the scientific objectives identified above, a natural outcome of this work will be to build a community of marine scientists who understand the processes regulating trace element cycles sufficiently well to exploit this knowledge reliably in future interdisciplinary studies.

Expand "Projects" below for information about and data resulting from individual US GEOTRACES research projects.