Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Program Information
• Funding

This dataset contains. DI water soluble trace element concentrations from bulk aerosol samples collected during the 2013 US GEOTRACES EPZT section cruise (TN303). Samples were analyzed at the Skidaway Institute of Oceanography.

Samples were collected using Florida State University's high vol aerosol sampler (Tisch Environmental TSP TE5170V), located on the 03 deck, forward railings. Samples were collected at the rate of 1 cubic meter per minute on Whatman 41, 47 mm discs (cellulose esters; W41) and were acid cleaned.

Methods are described in:
C.Buck et al., 2006, G^3, doi:10.1029/2005GC000977;
C.Buck et al., 2010, Mar. Chem., doi:10.1016/j.marchem.2008.08.003;
Morton et al., 2013, Limnol and Oceanogr.: Methods, doi: 10.4319/lom.2013.11.62;
Shelley, R. et al., 2015, DSR-II, doi: 10.1016/j.dsr2.2014.12.005

Data have been corrected for field and analytical blank. All reported trace element concentration values have been normalized to the volume of air filtered during that sample collection. Each sample collection period (n = 17) produced 36 replicate filters. Three of those filters were extracted with ultrapure DI water producing three replicate measurements. In the majority of cases, the three replicates agreed well. In a small number of cases, one replicate differed from the others and these data are marked as described in the datasheet. In all cases, data from the three replicates were averaged and reported along with the standard deviation.

Results of analysis of NASS-6 certified reference materials are available (PDF).

Quality flag codes:
BDL = below detection limit;
0 = No QC performed;
1 = Good data;
2 = Probably good data;
3 = Probably bad data that is potentially correctable;
4 = Bad data;
5 = Value changed;
6 = Sample < blank;
8 = Interpolated value;
​9 = Missing value.

BCO-DMO Processing:
- modified parameter names to conform with BCO-DMO naming convetions;
- replaced missing data and "no value" with "nd";
- added ISO_DateTime fields using date and time fields provided in original dataset;
- joined to the BCO-DMO master file to add station, event, etc. fields;
- 13 June 2017: changed parameter original named "nss_SO4_DI_S_Conc_Aerosol" to "SO4_DI_S_Conc_Aerosol"; re-named associated variance and QF columns as well.

Additional GEOTRACES Processing:
As was done for the GEOTRACES-NAT data, BCO-DMO added standard US GEOTRACES information, such as the US GEOTRACES event number, to each submitted dataset lacking this information. To accomplish this, BCO-DMO compiled a 'master' dataset composed of the following parameters:

cruise_id, EXPOCODE,SECT_ID, STNNBR, CASTNO, GEOTRC_EVENTNO, GEOTRC_SAMPNO, GEOTRC_INSTR, SAMPNO, GF_NO, BTLNBR, BTLNBR_FLAG_W, DATE_START_EVENT, TIME_START_EVENT, ISO_DATETIME_UTC_START_EVENT, EVENT_LAT, EVENT_LON, DEPTH_MIN, DEPTH_MAX, BTL_DATE, BTL_TIME, BTL_ISO_DATETIME_UTC, BTL_LAT, BTL_LON, ODF_CTDPRS, SMDEPTH, FMDEPTH, BTMDEPTH, CTDPRS, CTDDEPTH.

This added information will facilitate subsequent analysis and inter comparison of the datasets.

Bottle parameters in the master file were taken from the GT-C_Bottle and ODF_Bottle datasets. Non-bottle parameters, including those from GeoFish tows, Aerosol sampling, and McLane Pumps, were taken from the TN303 Event Log (version 30 Oct 2014). Where applicable, pump information was taken from the PUMP_Nuts_Sals dataset.

A standardized BCO-DMO method (called "join") was then used to merge the missing parameters to each US GEOTRACES dataset, most often by matching on sample_GEOTRC or on some unique combination of other parameters.

If the master parameters were included in the original data file and the values did not differ from the master file, the original data columns were retained and the names of the parameters were changed from the PI-submitted names to the standardized master names. If there were differences between the PI-supplied parameter values and those in the master file, both columns were retained. If the original data submission included all of the master parameters, no additional columns were added, but parameter names were modified to match the naming conventions of the master file.

See the dataset parameters documentation for a description of which parameters were supplied by the PI and which were added via the join method.

From the NSF Award Abstract
The mission of the International GEOTRACES Program (https://www.geotraces.org/), of which the U.S. chemical oceanography research community is a founding member, is "to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions" (GEOTRACES Science Plan, 2006). In the United States, ocean chemists are currently in the process of organizing a zonal transect in the eastern tropical South Pacific (ETSP) from Peru to Tahiti as the second cruise of the U.S.GEOTRACES Program. This Pacific section includes a large area characterized by high rates of primary production and particle export in the eastern boundary associated with the Peru Upwelling, a large oxygen minimum zone that is a major global sink for fixed nitrogen, and a large hydrothermal plume arising from the East Pacific Rise. This particular section was selected as a result of open planning workshops in 2007 and 2008, with a final recommendation made by the U.S.GEOTRACES Steering Committee in 2009. It is the first part of a two-stage plan that will include a meridional section of the Pacific from Tahiti to Alaska as a subsequent expedition.

This award provides funding for management of the U.S.GEOTRACES Pacific campaign to a team of scientists from the University of Southern California, Old Dominion University, and the Woods Hole Oceanographic Institution. The three co-leaders will provide mission leadership, essential support services, and management structure for acquiring the trace elements and isotopes samples listed as core parameters in the International GEOTRACES Science Plan, plus hydrographic and nutrient data needed by participating investigators. With this support from NSF, the management team will (1) plan and coordinate the 52-day Pacific research cruise described above; (2) obtain representative samples for a wide variety of trace metals of interest using conventional CTD/rosette and GEOTRACES Sampling Systems; (3) acquire conventional JGOFS/WOCE-quality hydrographic data (CTD, transmissometer, fluorometer, oxygen sensor, etc) along with discrete samples for salinity, dissolved oxygen (to 1 uM detection limits), plant pigments, redox tracers such as ammonium and nitrite, and dissolved nutrients at micro- and nanomolar levels; (4) ensure that proper QA/QC protocols are followed and reported, as well as fulfilling all GEOTRACES Intercalibration protocols; (5) prepare and deliver all hydrographic-type data to the GEOTRACES Data Center (and US data centers); and (6) coordinate cruise communications between all participating investigators, including preparation of a hydrographic report/publication.

Broader Impacts: The project is part of an international collaborative program that has forged strong partnerships in the intercalibration and implementation phases that are unprecedented in chemical oceanography. The science product of these collective missions will enhance our ability to understand how to interpret the chemical composition of the ocean, and interpret how climate change will affect ocean chemistry. Partnerships include contributions to the infrastructure of developing nations with overlapping interests in the study area, in this case Peru. There is a strong educational component to the program, with many Ph.D. students carrying out thesis research within the program.

Figure 1. The 2013 GEOTRACES EPZT Cruise Track. [click on the image to view a larger version]

During the 2013 GEOTRACES Eastern Pacific zonal transect, a gradient in aerosol inputs to surface waters will be encountered with higher inputs near Peru and decreasing offshore. This zonal section contrasts sharply to the high aerosol deposition areas found and sampled during the GEOTRACES North Atlantic Zonal Section in the fall of 2010 and 2011. As such, this Pacific section represents a unique opportunity to characterize aerosol and rainfall chemistry in a low deposition environment. Scientists from the University of Alaska and Florida State University plan to collect and characterize aerosol and rainfall samples along this transect, as well as distribute samples to the community. Bulk and size-fractionated aerosol samples collected on a 24 to 48-hour integrated basis and event-based rain samples will be analyzed for trace elements and isotopes (TEIs) to quantify their atmospheric input. The TEIs to be analyzed will be aluminum, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium, lead, and thorium, as well as the major ions sodium, magnesium, potassium, calcium, nitrate, phosphate, chlorine, and fluorine. Other efforts to be carried out as part of this study include (1) aerosol leaches to determine seawater-soluble and ultrapure-water-soluble TEI fractions: (2) determine the size fractionation and redox speciation of seawater-soluble iron: (3) obtain subsamples of water column samples from other GEOTRACES scientists for the analysis of the TEIs of interest to help interpret the atmospheric deposition data; and (4) collaborate with researchers from other institutions to characterize and constrain estimates of atmospheric deposition. This project will contribute towards the overall goal of the GEOTRACES Program by establishing the range of fractional aerosol solubility and better quantify deposition across the global ocean.

One graduate student from the University of Alaska would be supported and trained as part of this project. Relying on a cruise blog, email, and project website updates, the scientist from the University of Alaska plans to continue her interactions with students in Alaska, Arizona, and Florida and results from the study would be incorporated into class curricula, as well as disseminated via public outreach and web dissemination.

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.