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A primary purpose of this report is to provide documentation for the new isotopic and chemical particulate carbon data for certified, reference and information values in Tables 12 and 13 of the Certificate of Analysis. Supporting this is a critical review of underlying international intercomparison data and methodologies, provided by 18 teams of analytical experts from 11 institutions. Key results of the intercomparison are: (1) a new, Certified Value for total carbon (TC) in SRM 1649a; (2) 14C Reference Values for total carbon and a number of organic species, including 8 individual PAH; and (3) elemental carbon Information Values for 13 analytical methods applied to elemental carbon (EC). Elemental carbon comprised a special focus of the intercomparison. The results are diverse, reflecting the confounding of methodological-matrix effect artifacts, and information on different regions of the black carbon spectrum representing more or less refractory forms of this universal product of combustion. These data can be described in terms of three clusters, centered at EC/TC ratios of 0.075, 0.28, and 0.46. Availability of both chemical and 14C speciation data for SRM 1649a holds great promise for improved analytical insight through comparative analysis (e.g., fossil/biomass partition in EC compared to PAH), and through the application of the principle of isotopic mass balance.

The objective of this study was to evaluate the chemical composition of meat from three portions of the carcass of kids raised in range conditions and slaughtered at 8-9 or 11-12 months old. The trial was conducted in the region of Alto Camaquã and had 15 animals per group. Chemical composition of the carcass (moisture, protein, ashes, fats, and cholesterol) was determined from the shoulder, loin, and legs. Kids slaughtered younger had higher moisture and ash content in all three portions (p<0.05) when compared to older animals. Fat levels only were higher in kids slaughtered at an older age (p<0.05). Cholesterol content only on the leg, was lesser than the two other portions in younger animals (p<0.05). There were no differences observed between the three portions on the older animals. Older kids at slaughter had higher content of protein and fat but cholesterol remained unchanged. The three portions of the carcass had distinct chemical composition. Our results suggest that in range conditions the slaughter of animals should occur at 11-12 months old, resulting in meat with higher nutritional content in all portions of the carcass. [ABSTRACT FROM AUTHOR]

In Lake Matano, Indonesia, the world's largest known ferruginous basin, more than 50% of authigenic organic matter is degraded through methanogenesis, despite high abundances of Fe (hydr)oxides in the lake sediments. Biogenic CH accumulates to high concentrations (up to 1.4 mmol L) in the anoxic bottom waters, which contain a total of 7.4 × 10 tons of CH. Profiles of dissolved inorganic carbon (ΣCO) and carbon isotopes (δC) show that CH is oxidized in the vicinity of the persistent pycnocline and that some of this CH is likely oxidized anaerobically. The dearth of NO and SO in Lake Matano waters suggests that anaerobic methane oxidation may be coupled to the reduction of Fe (and/or Mn) (hydr)oxides. Thermodynamic considerations reveal that CH oxidation coupled to Fe(III) or Mn(III/IV) reduction would yield sufficient free energy to support microbial growth at the substrate levels present in Lake Matano. Flux calculations imply that Fe and Mn must be recycled several times directly within the water column to balance the upward flux of CH. 16S gene cloning identified methanogens in the anoxic water column, and these methanogens belong to groups capable of both acetoclastic and hydrogenotrophic methanogenesis. We find that methane is important in C cycling, even in this very Fe-rich environment. Such Fe-rich environments are rare on Earth today, but they are analogous to conditions in the ferruginous oceans thought to prevail during much of the Archean Eon. By analogy, methanogens and methanotrophs could have formed an important part of the Archean Ocean ecosystem. [ABSTRACT FROM AUTHOR]

Methane (CH4) concentration and stable isotope (δ²H-CH4 and δ13C-CH4) depth distributions show large differences in the water columns of the Earth's largest CH4-containing anoxic basins, the Black Sea and Cariaco Basin. In the deep basins, the between-basin stable isotope differences are large, 83‰ for δ²H-CH4 and 9‰ for δ13C-CH4, and the distributions are mirror images of one another. The major sink in both basins, anaerobic oxidation of CH4, results in such extensive isotope fractionation that little direct information can be obtained regarding sources. Recent measurements of natural 14C-CH4 show that the CH4 geochemistry in both basins is dominated (~64 to 98%) by inputs of fossil (radiocarbon-free) CH4 from seafloor seeps. We derive open-system kinetic isotope effect equations and use a one-dimensional (vertical) stable isotope box model that, along with isotope budgets developed using radiocarbon, permits a quantitative treatment of the stable isotope differences. We show that two main factors control the CH4 concentration and stable isotope differences: (1) the depth distributions of the input of CH4 from seafloor seeps and (2) anaerobic oxidation of CH4 under open-system steady state conditions in the Black Sea and open-system non- steady-state conditions in the Cariaco Basin. [ABSTRACT FROM AUTHOR]

The primary objective of the research reported here has been the development of a hybrid reference material (RM) to serve as a test of accuracy for elemental carbon (EC) isotopic (14C) speciation measurements. Such measurements are vital for the quantitative apportionment of fossil and biomass sources of "soot" (EC), the tracer of fire that has profound effects on health, atmospheric visibility, and climate. Previous studies of 14C-EC measurement quality, carried out with NIST SRM 1649a (Urban Dust), showed a range of results, but since the "truth" was not known for this natural matrix RM, one had to rely on isotopic-chemical consistency evidence (14C in PAH, EC) of measurement validity (Currie et al., 2002). Components of the new Hybrid RM (DiesApple), however, have known 14C and EC composition, and they are nearly orthogonal (isotopically and chemically). NIST SRM 2975 (Forklift Diesel Soot) has little or no 14C, and its major compositional component is EC; SRM 1515 (Apple Leaves) has the 14C content of biomass-C, and it has little or no EC. Thus, the Hybrid RM can serve as an absolute isotopic test for the absence of EC-mimicking pyrolysis-C (char) from SRM 1515 in the EC isolate of the Hybrid RM, as well as a test for conservation of its dominant soot fraction throughout the isolation procedure. The secondary objective was to employ the Hybrid RM for the comparative evaluation of the thermal optical kinetic (TOK) and thermal optical transmission (TOT) methods for the isolation of EC for micro-molar carbon accelerator mass spectrometry (AMS). As part of this process, the relatively new TOK method was subjected to a critical evaluation and significant development. Key findings of our study are: (1) both methods exhibited biomass-C "leakage"; for TOT, the EC fraction isolated for AMS contained about 8% of the original biomass-C; for TOK, the refractory carbon (RC) isolated contained about 3% of the original biomass-C.; (2) the initial isothermal oxidation stage of the TOK method substantially reduced the transfer of artifact char to the RC fraction, improving isolation capabilities; (3) the Hybrid RM was not equal to the sum of its parts, with matrix interactions inducing premature loss of EC which, however, could be quantified and minimized; (4) the three-stage TOK method provided a superior capability for carbonate quantification at the submicromolar level, with "reagent-free" removal of carbonate- C from EC -- essential for low-level EC-14C AMS. [ABSTRACT FROM AUTHOR]

The primary objective of the research reported here has been the development of an hybrid reference material (RM) to serve as a test of accuracy for elemental carbon (EC) isotopic (14C) speciation measurements. Such measurements are critically important for the quantitative apportionment of fossil and biomass sources of "soot" (EC), the tracer of fire that has profound effects on health, atmospheric visibility, and climate. Previous studies of 14C-EC measurement quality, carried out with NIST SRM 1649a (Urban Dust), showed a range of results, but since the "truth" was not known for this natural matrix RM, one had to rely on isotopic-chemical consistency evidence (14C in PAH, EC) of measurement validity (Currie et al., 2002). Components of the new Hybrid RM (DiesApple), however, have known 14C and EC composition, and they are nearly orthogonal (isotopically and chemically). NIST SRM 2975 (Forklift Diesel Soot) has little or no 14C, and its major compositional component is EC. SRM 1515 (Apple Leaves) has the 14C content of biomass-C, and it has little or no EC. Thus, the hybrid RM can serve as an absolute isotopic test for the absence of EC-mimicking pyrolysis-C from SRM 1515 in the EC isolate of the hybrid RM, together with testing for conservation of its dominant soot fraction through the isolation procedure. A secondary objective was the use of the hybrid RM for the comparative evaluation of the thermal optical transmission (TOT) and thermal optical kinetic (TOK) methods for the isolation of EC for micro-molar carbon accelerator mass spectrometry (AMS). Key findings were: that both methods exhibited biomass-C "leakage" into the fossil EC fraction, with substantially more for the TOT method; that the initial isothermal oxidation stage of the TOK method substantially reduced charring, improving isolation capabilities; that the hybrid RM was not equal to the sum of its parts, with matrix interactions yielding premature loss of EC which, however, could be quantified and minimized; and that the three-stage TOK method provided a superior capability for carbonate quantification at the sub-micromolar level, with "reagent-free" removal of carbonate-C from EC -- essential for low-level EC-14C AMS. [ABSTRACT FROM AUTHOR]

Increasing atmospheric CO2 is promoting ocean acidification and higher global temperatures and has been suggested as a possible factor for shifts in marine phytoplankton composition to more harmful species. Karenia brevis is the major harmful algal species in the Gulf of Mexico producing potent neurotoxins known as brevetoxins. We examined how changes in ocean inorganic carbon chemistry associated with pre-industrial (250 ppm), recent (350 ppm), and predicted at 2100 (1000 ppm) pCO2 levels and increased temperature affect growth rates and brevetoxin production in K. brevis. At the predicted pCO2 levels for 2100, growth rate of K. brevis Wilson clone increased substantially by 46% at 25 °C (0.43 ± 0.01 d-1) compared to recent and pre-industrial levels (0.29 ± 0.01 d-1). Growth rates also increased for a low brevetoxin-producing clone, SP1, from 0.24 ± 0.02 d-1 at lower pCO2 levels to 0.33 ± 0.003 d-1 at a pCO2 of 1000 ppm. When grown at a higher temperature (30 °C), growth rates for the Wilson clone significantly decreased at all three pCO2 by approximately 30%. However, even at the higher temperature, K. brevis growth rate significantly increased by 30% (0.30 ± 0.01 d-1) at the 1000 ppm CO2 level when compared to recent and pre-industrial CO2 levels (0.21 ± 0.01 d-1). Although K. brevis growth rate decreased at higher temperatures, the growth rate at pCO2 level of 1000 and 30 °C was slightly higher than at current conditions (pCO2 level of 350 and 25 °C). Modification of pCO2 levels and temperatures did not have an effect on total brevetoxin production or brevetoxin profiles in either clone examined. Due to the increased growth rate, total brevetoxin production was significantly higher at the pCO2 level of 1000. Finally, from these results we conclude there is no connection between growth rate and brevetoxin per cell. Although neither pCO2 nor temperature influenced brevetoxin production per cell, we suggest that under predicted future climate conditions K. brevis blooms have the potential to produce higher cell concentrations and increased brevetoxin concentrations, which will pose an increased risk for ecosystem and human health. [ABSTRACT FROM AUTHOR]

Because of increased interest in the marine and atmospheric sciences in elemental carbon (EC), or black carbon (BC) or soot carbon (SC), and because of the difficulties in analyzing or even defining this pervasive component of particulate carbon, it has become quite important to have appropriate reference materials for intercomparison and quality control. The NIST "urban dust" Standard Reference Material(®) SRM 1649a is useful in this respect, in part because it comprises a considerable array of inorganic and organic species, and because it exhibits a large degree of ((14)C) isotopic heterogeneity, with biomass carbon source contributions ranging from about 2 % (essentially fossil aliphatic fraction) to about 32 % (polar fraction). A primary purpose of this report is to provide documentation for the new isotopic and chemical particulate carbon data for the most recent (31 Jan. 2001) SRM 1649a Certificate of Analysis. Supporting this is a critical review of underlying international intercomparison data and methodologies, provided by 18 teams of analytical experts from 11 institutions. Key results of the intercomparison are: (1) a new, Certified Value for total carbon (TC) in SRM 1649a; (2) (14)C Reference Values for total carbon and a number of organic species, including for the first time 8 individual PAHs; and (3) elemental carbon (EC) Information Values derived from 13 analytical methods applied to this component. Results for elemental carbon, which comprised a special focus of the intercomparison, were quite diverse, reflecting the confounding of methodological-matrix artifacts, and methods that tended to probe more or less refractory regions of this universal, but ill-defined product of incomplete combustion. Availability of both chemical and (14)C speciation data for SRM 1649a holds great promise for improved analytical insight through comparative analysis (e.g., fossil/biomass partition in EC compared to PAH), and through application of the principle of isotopic mass balance.