Table of Contents

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

Sediment samples were collected via a 4-barrel multi-corer (R/V Endeavor) and box corer (GeoB; samples previously collected from the Department of Geosciences at Bremen University, see MARUM GeoB Core Re­pos­it­ory https://www.marum.de/en/Infrastructure/MARUM-GeoB-Core-Repository.html). Sediments collected on the R/V Endeavor were segmented into 1-2 cm sections, dried in a drying oven (35°C) and homogenized via mortar and pestle; sediments from GeoB had previously been segmented into 1-10cm sections, freeze-dried and ground with a mortar and pestle.

Instruments:
Homogenized sediments were extracted with an accelerated solvent extractor (Dionex ASE 350) in 6 cycles at 150°C using a 50/50 mix of hexane and acetone. Prior to extraction, d10-acenapthene, d10-phenanthrene, d12-chrysene, and d12-perylene were added to each sample to assess recovery. Solvent extracts were evaporated to 1 mL using a rotary evaporator and purified through a column containing 2 mg of activated silica with 45 mL of a 30/70 solvent mixture of dichloromethane and hexane. Extracts were evaporated with N2 gas to 50 μL and an injection surrogate of p-terphenyl was added before analysis on an Agilent 6890 Series gas chromatograph coupled to a 5973 Mass Selection Detector (GC-MS).

Location: 
Amazon Delta (approximately: 4 N, 47 W; 2400-3500m); Sierra Leone Rise (approximately: 7 N, 20 W; 2800-3800m), Niger Delta (approximately: 1 N, 8 E; 1200-3000m), Senegal Delta (approximately: 17 N, 17 W; 330 m), and Northwest Argentina Basin (approximately: 37 S, 39 W; 5000m)

Cruise or Deployment:R/V Endeavor (EN-480, EN-481; July/August 2010); GeoB (4901, 4903, 4904, 4905, 4907, 4908; February/March 1998), GeoB (9501; April/May 2003), GeoB (2814, July/August 1994)

* R/V Endeavor cruises were attached to this dataset as "Deployments."
​* Collection information for the GeoB samples previously collected from the Department of Geosciences at Bremen University can be found in table "Atlantic Sediment Cruise Information" in the Supplemental Files section of this dataset.

24 PAH analyzes were quantified using ChemStation software.

* 5 sheets named by location name in "Atlantic_Sediment_PAH.xlsx" were imported into the BCO-DMO data system.
* Individual location tables were combined into one table with an additional column "Location" to capture the site name provided by the sheet name.
* PAH values rounded to two decimal places as discussed with the submitter. There was variable formatting imported from the original excel file so two decimal place format was used.

* Column names adjusted to conform to BCO-DMO naming conventions designed to support broad re-use by a variety of research tools and scripting languages. [Only numbers, letters, and underscores. Can not start with a number]
** example: column "1,5-Dimethyl Napthalene" became "Napthalene_1_5_Dimethyl" with column description "Polycyclic aromatic hydrocarbon (PAH) 1,5-Dimethyl Napthalene"

* Date format converted to ISO 8601 format.

NSF Award Abstract:
Black carbon is formed during the incomplete burning of fuels (e.g., the black clouds of smoke emitted by buses and trucks). Black carbon does not degrade easily in the environment and can be transported long distances, even reaching the seafloor. Yet the fluxes of black carbon in the environment are not well known, particularly in the oceans. Rivers are considered the dominant source of black carbon to the oceans. However, recent results suggest that there may be regions of the ocean where the atmospheric delivery of black carbon may be important. This study investigates whether biomass burning (e.g., wildfires) in Africa is a source of black carbon to the tropical Atlantic Ocean. The unique molecular and isotopic properties of black carbon will be used to identify black carbon in the atmosphere, water and sediment in the study region. Sediment, water column and atmospheric particles will be collected during a 3-week research cruise across the tropical Atlantic Ocean. Two different approaches will be used to quantify black carbon in the environment. The research is relevant and timely for our understanding of the carbon cycle, a key component of our ability to forecast climate and its change. The project supports a graduate student and provide opportunities for high school students participating in the SMILE Program (Science and Math Investigative Learning Experiences). This project is jointly funded by the Chemical Oceanography Program and the Established Program to Stimulate Competitive Research (EPSCoR).

Surface sediment samples will be collected at ten sites across the tropical Atlantic Ocean in a region known to be impacted by biomass burning events (wildfires) in Africa. Appropriate locations for sediment sampling will be identified using state-of-the-art ship equipment to ensure a successful coring operation. Once collected, the black carbon and organic carbon fractions of the sediment will be isolated and measured. A range of isotopic and molecular marker approaches will be used to identify the likely source of these carbon fractions. The central hypothesis is that the black carbon residing in the sediment of the tropical Atlantic Ocean is derived from biomass burning and delivered through atmospheric deposition. Carbon derived from recent biomass burning contains C-14 isotopes that indicate 'young' (or recently produced) carbon, while carbon from fossil fuels ('old carbon') has no C-14 due to radioactive decay. To further assess the origin of the black carbon in the region, water column and atmospheric particles will be collected during the research cruise. The origin of the atmospheric black carbon particles (biomass burning or fossil fuel emissions) will be established through a collaboration with colleagues in Sweden. The broader impacts of this research include the engagement of high school students through The SMILE Program (Science and Math Investigative Learning Experiences) at the University of Rhode Island. The project also provides training opportunities for graduate and undergraduate students, with a focus on recruitment of students from under-represented groups.

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.

NSF abstract:
This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

In this study, researchers at the University of Rhode Island will attempt to determine the origin and fluxes of black carbon (BC) in marine sediments from the South Atlantic. Black carbon in the atmosphere is a key driver of global climate change; it is second only to CO2 in its contribution to global warming. The proposed work is thus relevant and timely for our understanding of the carbon cycle, a key component of our ability to forecast climate and its change. The major sources of BC on the global scale are fossil fuel and biomass burning, which are both prominent in Africa and South America. Hence, it is proposed to account for soot BC, char and charcoal residing in sediments from the South Atlantic by combining thermal, chemical and petrographic isolation methods.

This project has three main hypotheses: (1) Soot BC constitutes a significant fraction of the total organic carbon in deep sea sediments of the South Atlantic, and dominates total BC in those sediments; (2) Biomass burning is the dominant source of the soot BC present in deep sea sediments of the South Atlantic; and (3) For the South Atlantic, atmospheric deposition of soot BC is as important as riverine inputs.

This study represents a first attempt to account for BC sinks on an Ocean scale. It thus holds promise to make a major step forward towards being able to mass balance sources and sinks of BC. Previous studies suggest that BC reaches the oceans predominantly from riverine sources. In the case of the South Atlantic, the research team hypothesizes that atmospheric transport and deposition is at least as important. The proposed research will compare different BC determination procedures for deep sea sediments, thereby improving our understanding of the different constituents of the BC cycle. Similarly, organic marker molecules are often used for source apportionment. This study will explore if this still holds true for deep sea sediment samples, as preliminary data found discrepancies arising from molecular marker analysis and isotopic analysis. Lastly, accounting for soot BC in deep sea sediments will also aid in identifying more of the uncharacterized sedimentary OC .

Broader Impacts: The results of this work are expected to aid atmospheric and earth system science modelers in refining their atmospheric and oceanic transport models for BC, including its relation to global climate change. The project will enhance infrastructure for research and education by establishing research collaboration between URI and international partners at the University of Bremen, the MPI for Meteorology, Hamburg, and the University of Tuebingen.