Richard B. Coffin

The Naval Research Laboratory contributed to an international research expedition to determine the association of methane (CH4) hydrate dissociation with pockmark formation on the Chatham Rise (New Zealand) during previous climate cycles. Piston coring and multi-coring was conducted at four locations with different seismic, multibeam, and physical profiles. Prior to SO226, seismic and multibeam data were obtained by the University of Auckland and IFM-Geomar which helped to identify broad study areas. Seismic and multibeam data collected on Leg 1 (SO226-1) helped to identify specific coring locations. These target areas were determined based on the seafloor morphology and seismic data interpretation of shallow sediments. More specifically, coring locations were selected where seismic profiles suggested high vertical CH4 fluxes to the shallow sediment and at sites that were predicted to have low or nonexistent vertical CH4 fluxes. Sediment cores were also collected in the same locations for paleogeochemical analyses which will be completed by Helen Neil at National Institute of Water and Atmospheric Research, Ltd. (NIWA) in Wellington, NZ. The final assessment of these sediments will require integration of geophysical, geological, and geochemical data.

Dissolved CO₂ radiocarbon and stable carbon isotope ratios were measured in groundwater from a fuel contaminated site at the North Island Naval Air Station in San Diego, CA (USA). A background groundwater sampling well and 16 wells in the underground fuel contamination zone were evaluated. For each sample, a two end-member isotopic mixing model was used to determine the fraction of CO₂ derived from fossil fuel. The CO₂ fraction from fossil sources ranged from 8 to 93% at the fuel contaminated site, while stable carbon isotope values ranged from −14 to +5‰_VPDB. Wells associated with highest historical and contemporary fuel contamination showed the highest fraction of CO₂ derived from petroleum (fossil) sources. Stable carbon isotope ratios indicated sub-regions on-site with recycled CO₂ (δ¹³CO₂ as high as +5‰_VPDB) – most likely resulting from methanogenesis. Ancillary measurements (pH and cations) were used to determine that no fossil CaCO₃, for instance limestone, biased the analytical conclusions. Radiocarbon analysis is verified as a viable and definitive technique for confirming fossil hydrocarbon conversion to CO₂ (complete oxidation) at hydrocarbon-contaminated groundwater sites. The technique should also be very useful for assessing the efficacy of engineered remediation efforts and by using CO₂ production rates, contaminant mass conversion over time and per unit volume.

The IRMS Data Processing software package is designed to allow easy stable isotope data entry and multivariate data analysis. When comparing two of more hydrocarbon samples using compound-specific isotope ratio mass spectrometry, an analyst obtains multiple data variables for each sample. Multivariate statistics allows rigorous comparison(s) to determine if the samples are in fact different and if so, how closely related they are. This software uses three main types of data analyses: Multiple Analysis of Variance (MAN0VA), Principal Components Analysis (PCA), and Cluster Analysis. The layout is a standard Windows interface which should be usable to anyone familiar with modem operating system software.

The program for International Collaboration on CO{sub 2} Ocean Sequestration was initiated December 1997. Preliminary steps involved surveying a suite of biogeochemical parameters off the coast of Kona on the Big Island of Hawaii. The preliminary survey was conducted twice, in 1999 and 2000, to obtain a thorough data set including measurements of pH, current profiles, CO{sub 2} concentrations, microbial activities, and water and sediment chemistries. These data were collected in order to interpret a planned CO{sub 2} injection experiment. After these preliminary surveys were completed, local environment regulation forced moving the project to the coast north east of Bergen, Norway. The preliminary survey along the Norwegian Coast was conducted during 2002. However, Norwegian government revoked a permit, approved by the Norwegian State Pollution Control Authority, for policy reasons regarding the CO{sub 2} injection experiment. As a result the research team decided to monitor the natural CO{sub 2} flow off the southern coast of the Big Island. From December 3rd-13th 2002 scientists from four countries representing the Technical Committee of the International Carbon Dioxide Sequestration Experiment examined the hydrothermal venting at Loihi Seamount (Hawaiian Islands, USA). Work focused on tracing the venting gases, the impacts of the vent fluids onmore » marine organisms, and CO{sub 2} influence on biogeochemical cycles. The cruise on the R/V Ka'imikai-O-Kanaloa (KOK) included 8 dives by the PISCES V submarine, 6 at Loihi and 2 at a nearby site in the lee of the Big Island. Data for this final report is from the last 2 dives on Loihi. « less

Benzene, toluene, ethylbenzene, and xylene (BTEX) hydrocarbons are typically the most abundant carbon source for bacteria in gasoline‐contaminated ground water. In situ bioremediation strategies often involve stimulating bacterial heterotrophic production in an attempt to increase carbon demand of the assemblage. This may, in turn, stimulate biodegradation of contaminant hydrocarbons. In this study, ground water circulation wells (GCWs) were used as an in situ treatment for a fuel‐contaminated aquifer to stimulate bacterial production, purportedly by increasing oxygen transfer to the subsurface, circulating limiting nutrients, enhancing bioavailability of hydrocarbons, or by removing metabolically inhibitory volatile organics. Bacterial production, as measured by rates of bacterial protein synthesis, was stimulated across the zone of influence (ZOI) of a series of GCWs. Productivity increased from ∼10 ² to >10 ⁵ ng C/L hour across the ZOI, suggesting that treatment stimulated overall biodegradation of carbon sources present in the ground water. However, even if BTEX carbon met all bacterial carbon demand, biodegradation would account for <4.3% of the total estimated BTEX removed from the ground water. Although bacterial productivity measurements alone cannot prove the effectiveness of in situ bioremediation, they can estimate the maximum amount of contaminant that may be biodegraded by a treatment system.

Data from a combination of laboratory and fieldwork is presented to initiate testing of stable carbon and nitrogen isotope ratios to trace sources of TNT in contaminated soil and groundwater. Evaluation of these extraction methods resulted in 99.9 and 99.8% recovery of TNT with Soxhlet and solid-phase extraction (SPE), respectively. As a result of the high extraction efficiency, isotope fractionation did not occur, thus providing an accurate stable isotope value on TNT from laboratory and field samples. Subsequent experiments evaluated the stability of isotope signatures through incubations lasting up to four weeks with a 70% decline in the TNT concentration. During these experiments, no significant variation in stable carbon and nitrogen isotope ratios was measured. Five different sources of TNT, compared for stable carbon and nitrogen isotope ratios, showed a range of 4.2 and 15%, respectively. This large range in the isotope ratios suggests excellent potential to trace sources in a complex environment. Finally, a site was surveyed for concentrations and isotope values of TNT extracted from groundwaters. Values from this site were substantially different relative to the variation measured on standards and in laboratory incubation experiments. The data set indicates good potential to use stable isotopes to determine TNT sources and fate in the environment.

Stable carbon isotope (δ¹³C) analysis was used in the Peridido Estuary, Florida U.S. to determine the predominant carbon source that supports the bacterial assemblage. Stable carbon isotope values were measured in the suspended particulate matter (SPM), dissolved organic and inorganic matter, and bacteria. Stable nitrogen isotope (δ¹⁵N) ratios were measured in SPM and nitrate to assist in understanding carbon cycling through the estuary. Analyses were conducted on samples from riverine, coastal, and anthropogenic sources and compared with samples from the bay. Stable isotope ratio analysis was coupled with estimates of mixing of riverine and coastal waters into the bay. Preliminary observation of the °¹³C data indicates that terrestrial organic matter is the primary carbon source that is assimilated by bacteria in the ecosystem. Stable isotope data from carbon and nitrogen pools in combination with analysis of estuarine current velocities indicates that primary production is an important factor in the carbon cycle. This study demonstrates the importance of stable isotope analysis of multiple carbon and nitrogen pols to assess sources and cycling of organic matter.

The results of a three-year study funded by the Department of Defense under the Strategic Environmental Research and Development Program (SERDP) to couple modem geochemical techniques with biological and chemical methods to determine the efficacy of bioremediation strategies for fossil fuels are reported. The objective of this project was to directly measure the catabolic activity of indigenous soil microflora on the contaminants of interest. The combination of stable isotope measurements, contaminant concentration analysis and measurement of bacterial production rates in the different matrices accomplished the objective as follows. The monitoring of a bioremediation technology assessed the effectiveness of these strategies on diverse contamination problems. In addition, the suitability of delta13 C stable isotope measurements of multiple carbon pools as an indication of bioremediation was assessed.

Stable isotope analysis of bacterial nucleic acids can be used to trace carbon that is assimilated and respired by the bacterioplankton in aquatic ecosystems. However, in sediment and soil environments humic acids co-extract with the nucleic acids, resulting in inaccurate isotope analysis. In this study we have examined the use of amino acids found in bacterial cell walls as biomarkers to trace carbon sources that support growth. In the development of the method, peptidoglycan from laboratory grown Pseudomonas sp. was hydrolyzed to amino acids. Stable carbon isotope ratios (δ¹³C) were analyzed with a dual mass spectrometer, ion trap and isotope ratio, equipped with a gas chromatograph sample inlet (GC/ITMS/IRMS). Comparisons of δ¹³C values of whole cells, cell wall peptidoglycan and the amino acids d-alanine and diaminopimelic acid from the cell wall were made using different carbon substrates and through different stages of growth to determine isotopic fractionation of these compounds. The δ¹³C values of whole cells, peptidoglycan and d-alanine and the substrate sources (glucose, glutamic acid, isoleucine, lysine, phenylalanine) were similar. The δ¹³C values of the d-alanine were within 0.5‰ of the substrate. In comparison, diaminopimelic acid was enriched in ¹³C by 10.3‰ relative to the whole cells, peptidoglycan and substrate. Additional laboratory experiments also demonstrated that the δ¹³C of d-alanine did not vary significantly relative to the whole cell and substrate through different growth stages. Stable carbon isotope analysis of the bacterial amino acids was determined at two field locations, water from Santa Rosa Sound, Florida, a humic rich estuarine ecosystem, and jet-fuel contaminated soils of Tyndall Air Force Base, Florida. d-alanine and diaminopimelic acid were isolated from these water and soil samples and the amino acids were analyzed for purity after extraction and for their δ¹³C values relative to organic matter in the environments. In the Santa Rosa Sound the δ¹³C value of d-alanine was −27.6±0.6‰. This value is in the range of δ¹³C values of bacteria and organic matter previously measured in the system, −24.0 to −27.0‰. The δ¹³C value of d-alanine in soil samples from Tyndall Air Force Base was −20.5±1.7‰ (n=4) similar to ranges of values measured for spilled jet-fuel and CO₂ respired from the soil at this site. Results from this study demonstrate that d-alanine can be used as a biomarker for analysis of carbon sources that are assimilated by bacteria in soils and sediments.