Lori A. Ziolkowski

Aged black carbon identified in marine dissolved organic carbon

GEOPHYSICAL RESEARCH LETTERS, VOL. 37, L16601, doi:10.1029/2010GL043963, 2010 Aged black carbon identified in marine dissolved organic carbon L. A. Ziolkowski 1,2 and E. R. M. Druffel 1 Received 13 May 2010; revised 17 June 2010; accepted 1 July 2010; published 17 August 2010. [ 1 ] Produced on land by incomplete combustion of organic matter, black carbon (BC) enters the ocean by aerosol and river deposition. It has been postulated that BC resides in the marine dissolved organic carbon (DOC) pool before sedimentary deposition and may attribute to its great 14 C age (1500–6500 14 C years). Here we report the first radiocarbon measurements of BC in high molecular weight DOC (UDOM). BC exported from rivers is highly aromatic and 50,000 years (the detection limit). In contrast, BC recently produced from biomass burning has a C content equal to that in the contemporary biosphere C (D 14 C = 0 to 200‰). Here we present the distribution of BPCAs in conjunction with radiocarbon measurements of Auxiliary materials are available in the HTML. doi:10.1029/ 2010GL043963. L16601 1 of 4

Blank Assessment for Ultra-Small Radiocarbon Samples: Chemical Extraction and Separation Versus AMS

The Keck Carbon Cycle AMS facility at the University of California, Irvine (KCCAMS/UCI) has developed protocols for analyzing radiocarbon in samples as small as ~0.001 mg of carbon (C). Mass-balance background corrections for modern and 14C-dead carbon contamination (MC and DC, respectively) can be assessed by measuring 14C-free and modern standards, respectively, using the same sample processing techniques that are applied to unknown samples. This approach can be validated by measuring secondary standards of similar size and 14C composition to the unknown samples. Ordinary sample processing (such as ABA or leaching pretreatment, combustion/graphitization, and handling) introduces MC contamination of ~0.6 ± 0.3 μg C, while DC is ~0.3 ± 0.15 μg C. Today, the laboratory routinely analyzes graphite samples as small as 0.015 mg C for external submissions and =0.001 mg C for internal research activities with a precision of ~1% for ~0.010 mg C. However, when analyzing ultra-small samples isolated by a series of complex chemical and chromatographic methods (such as individual compounds), integrated procedural blanks may be far larger and more variable than those associated with combustion/graphitization alone. In some instances, the mass ratio of these blanks to the compounds of interest may be so high that the reported 14C results are meaningless. Thus, the abundance and variability of both MC and DC contamination encountered during ultra-small sample analysis must be carefully and thoroughly evaluated. Four case studies are presented to illustrate how extraction chemistry blanks are determined.

Aged black carbon in marine sediments and sinking particles

PUBLICATIONS Geophysical Research Letters RESEARCH LETTER 10.1002/2013GL059068 Key Points: • Multipool black carbon data set of Δ C values, BC/OC%, and BPCA abundances • A significant fraction of biomass-derived BC is transported to sediments by particulate organic carbon • Our BC flux estimate represents ~8–16% of the global OC burial flux to sediments Supporting Information: • Readme • Figure S1 • Table S1 • Table S2 • Equation S1 Correspondence to: A. I. Coppola, acoppola@uci.edu Aged black carbon in marine sediments and sinking particles Alysha I. Coppola 1 , Lori A. Ziolkowski 2 , Caroline A. Masiello 3 , and Ellen R. M. Druffel 1 Department of Earth System Science, University of California, Irvine, California, USA, 2 Marine Science Program and Department of Earth and Ocean Sciences, University of South Carolina, Columbia, South Carolina, USA, 3 Department of Earth Science and Department of Chemistry, Rice University, Houston, Texas, USA Abstract We report measurements of oceanic black carbon (BC) to determine the sources of BC to abyssal marine sediments in the northeast Pacific Ocean. We find that the average 14 C age of BC is older (by 6200 ± 2200 14 C years) than that of the concurrently deposited non-BC sedimentary organic carbon. We investigate sources of aged BC to sediments by measuring a sample of sinking particulate organic carbon (POC) and find that POC may provide the main transport mechanism of BC to sediments. We suggest that aged BC is incorporated into POC from a combination of resuspended sediments and sorption of ancient dissolved organic carbon BC onto POC. Our BC flux estimate represents ~8–16% of the global burial flux of organic carbon to abyssal sediments and constitutes a minimum long-term removal estimate of 6–32% of biomass-derived BC using the present day emission flux. 1. Introduction Citation: Coppola, A. I., L. A. Ziolkowski, C. A. Masiello, and E. R. M. Druffel (2014), Aged black carbon in marine sediments and sinking particles, Geophys. Res. Lett., 41, doi:10.1002/2013GL059068. Received 18 DEC 2013 Accepted 3 FEB 2014 Accepted article online 5 FEB 2014 Black carbon (BC), formed by incomplete combustion of organic matter, cycles on annual to millennial time scales [Masiello and Druffel, 1998; Middelburg et al., 1999]. Black carbon is defined as a continuum from slightly charred plant material to highly graphitized soot [Goldberg, 1985; Schmidt and Noack, 2000; Masiello, 2004]. Char BC is produced by the incomplete combustion of biomass, coals, and other materials, while soot BC is formed from the condensation of combustion gases. Black carbon has been found in marine dissolved organic carbon (DOC) [Dittmar, 2008; Ziolkowski and Druffel, 2010a], particulate organic carbon (POC) [Lohmann et al., 2009; Zigah et al., 2012; Flores-Cervantes et al., 2010], and sedimentary organic carbon (SOC) [Goldberg, 1985; Masiello and Druffel, 2003; Ohkouchi and Eglinton, 2006]. Black carbon enters the ocean by rivers and atmospheric deposition. Modern biomass-derived BC is mainly transported by surface erosion of soils and rivers, delivered to watersheds, and then to the ocean [Foereid et al., 2011; Major et al., 2010; Rumpel et al., 2006; Hockaday et al., 2007; Jaffe et al., 2013]. Because of its submicron size, soot BC can travel long distances before it is deposited into the ocean [Lohmann et al., 2009; Posfai and Buseck, 2010; Gustafsson and Gschwend, 1998; Ohkouchi and Eglinton, 2006]. Once BC enters the ocean’s DOC pool, its chemical and isotopic composition (as measured in ultrafiltered, high molecular weight DOC) dramatically changes between coastal and open ocean regions, suggesting that there are BC loss processes from the marine DOC pool [Ziolkowski and Druffel, 2010a, 2010b; Ward et al., 2014]. Two proposed loss processes are photochemical oxidation in the sea surface [Stubbins et al., 2012] and transport to sediments via sorption to POC [Flores-Cervantes et al., 2010; Zigah et al., 2012]. Marine sediments contain a significant amount of BC in organic carbon, with BC/OC% values ranging from 15 ± 2% to 21 ± 6% in abyssal sediments and up to 50 ± 40% in coastal sediments [Verardo and Ruddiman, 1996; Masiello and Druffel, 1998, 2003; Gustafsson and Gschwend, 1998; Middelburg et al., 1999; Lohmann et al., 2009]. The variability of sediment BC/OC% values is partly due to differences in methods used to quantify BC and to environmental transformations not accounted for by the analytical method used [Hammes et al., 2007; Currie et al., 2002]. Masiello and Druffel [1998] measured 15 ± 2% BC/OC in sediment (0–50 cm) from the northeast Pacific, with 14 C ages of the SOC BC 2400 ± 120 to 5400 ± 520 14 C years older than concurrently deposited non-BC SOC. This suggested that BC is preaged for thousands of years prior to deposition in the sediments. Here we report that BC is removed from seawater via sorption to marine POC and subsequently transported to sediments. We compare BC concentration, 14 C analyses, and qualitative BC structural information to COPPOLA ET AL. ©2014. American Geophysical Union. All Rights Reserved.

The feasibility of isolation and detection of fullerenes and carbon nanotubes using the benzene polycarboxylic acid method.

The incorporation of fullerenes and carbon nanotubes into electronic, optical and consumer products will inevitably lead to the presence of these anthropogenic compounds in the environment. To date, there have been few studies isolating these materials from environmental matrices. Here we report a method commonly used to quantify black carbon (BC) in soils, the benzene polycarboxylic acid (BPCA) method, for measurement of two types of single walled carbon nanotubes (SWCNTs), two types of fullerenes and two forms of soot. The distribution of BC products (BPCAs) from the high pressure and high temperature oxidation illustrates the condensed nature of these compounds because they form predominantly fully substituted mellitic acid (B6CA). The conversion of carbon nanoparticles to BPCAs was highest for fullerenes (average of 23.2+/-4.0% C recovered for both C(60) and C(70)) and lowest for non-functionalized SWCNTs (0.5+/-0.1% C). The recovery of SWCNTs was 10 times higher when processed through a cation-exchange column, indicating the presence of metals in SWCNTs compromises the oxidation chemistry. While mixtures of SWCNTs, soot and sediment revealed small losses of black carbon during sample processing, the method is suitable for quantifying total BC. The BPCA distribution of mixtures did not agree with theoretical mixtures using model polyaromatic hydrocarbons, suggesting the presence of a matrix effect. Future work is required to quantify different types of black carbon within the same sample.

Quantification of Extraneous Carbon during Compound Specific Radiocarbon Analysis of Black Carbon

Radiocarbon ((14)C) is a radioactive isotope that is useful for determining the age and cycling of carbon-based materials in the Earth system. Compound specific radiocarbon analysis (CSRA) provides powerful insight into the turnover of individual components that make up the carbon cycle. Extraneous or nonspecific background carbon (C(ex)) is added during sample processing and subsequent isolation of CSRA samples. Here, we evaluate the quantity and radiocarbon signature of C(ex) added from two sources: preparative capillary gas chromatography (PCGC, C(PCGC)) and chemical preparation of CSRA of black carbon samples (C(chemistry)). We evaluated the blank directly using process blanks and indirectly by quantifying the difference in the isotopic composition between processed and unprocessed samples for a range of sample sizes. The direct and indirect assessment of C(chemistry+PCGC) agree, both in magnitude and radiocarbon value (1.1 +/- 0.5 microg of C, fraction modern = 0.2). Half of the C(ex) is introduced before PCGC isolation, likely from coeluting compounds in solvents used in the extraction method. The magnitude of propagated uncertainties of CSRA samples are a function of sample size and collection duration. Small samples collected for a brief amount of time have a smaller propagated (14)C uncertainty than larger samples collected for a longer period of time. CSRA users are cautioned to consider the magnitude of uncertainty they require for their system of interest, to frequently evaluate the magnitude of C(ex) added during sampling processing, and to avoid isolating samples < or = 5 microg of carbon.

COMPOUND-SPECIFIC RADIOCARBON ANALYSES OF PHOSPHOLIPID FATTY ACIDS AND n -ALKANES IN OCEAN SEDIMENTS

We report compound-specific radiocarbon analyses of organic matter in ocean sediments from the northeast Pacific Ocean. Chemical extractions and a preparative capillary gas chromatograph (PCGC) were used to isolate phospholipid fatty acids (PLFA) and n-alkanes from 3 cores collected off the coast of California, USA. Mass of samples for accelerator mass spectrometry (AMS) 14C analysis ranged from 13-100 μg C. PLFA extracted from anaerobic sediments in the Santa Barbara Basin (595 m depth) had modern ∆14C values (-20 to +54‰), indicating bacterial utilization of surface-produced, post-bomb organic matter. Lower ∆14C values were obtained for n-alkanes and PLFA from coast (92 m depth) and continental slope (1866 m) sediments, which reflect sources of old organic matter and bioturbation. We present a brief analysis of the blank carbon introduced to samples during chemical processing and PCGC isolation.

Preparation for radiocarbon analysis

This chapter presents an overview of the steps required to prepare a sample for radiocarbon (14C) measurement by accelerator mass spectrometry (AMS). These include: (1) collection of an appropriate sample that can answer the question being asked; (2) pretreatment of samples to isolate a the most representative fraction of the bulk carbon (C) or to separate total C into different components; (3) conversion of C in the sample to CO2 and/or graphite for measurement by AMS; and (4) assessing errors, especially those associated with 14C contamination that occur during processing.

Ongoing biodegradation of Deepwater Horizon oil in beach sands: Insights from tracing petroleum carbon into microbial biomass.

Heavily weathered petroleum residues from the Deepwater Horizon (DwH) disaster continue to be found on beaches along the Gulf of Mexico as oiled-sand patties. Here, we demonstrate the ongoing biodegradation of weathered Macondo Well (MW) oil residues by tracing oil-derived carbon into active microbial biomass using natural abundance radiocarbon (14C). Oiled-sand patties and non-oiled sand were collected from previously studied beaches in Mississippi, Alabama, and Florida. Phospholipid fatty acid (PLFA) analyses illustrated that microbial communities present in oiled-sand patties were distinct from non-oiled sand. Depleted 14C measurements of PLFA revealed that microbes on oiled-sand patties were assimilating MW oil residues five years post-spill. In contrast, microbes in non-oiled sand assimilated recently photosynthesized carbon. These results demonstrate ongoing biodegradation of weathered oil in sand patties and the utility of 14C PLFA analysis to track the biodegradation of MW oil residues long after other indicators of biodegradation are no longer detectable.

Radiocarbon in the Oceans

This chapter reviews how radiocarbon (14C) in dissolved inorganic carbon (DIC) has been used to determine the cycling time of water within the world ocean, and how 14C in dissolved organic carbon (DOC) is being used to reveal the sources and cycling of this largest organic carbon pool in the ocean. In addition, recent studies that reveal the concentration and 14C values of black carbon in DOC in the oceans are presented.