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31.
Petroleum Hydrocarbon Bioventing Kinetics Determined in Soil Core, Microcosm, and Tubing Cluster Studies 总被引:2,自引:0,他引:2
Ellen E. Moyer David W. Ostendorf Robin J. Richards Steve Goodwin 《Ground Water Monitoring & Remediation》1996,16(1):141-153
Aerobic biodegradation of vapor-phase petroleum hydrocarbons was evaluated in an intact soil core from the site of an aviation gasoline release. An unsaturated zone soil core was subjected to a flow of nitrogen gas, oxygen, water vapor, and vapor-phase hydrocarbons in a configuration analogous to a biofilter or an in situ bioventing or sparging situation. The vertical profiles of vapor-phase hydrocarbon concentration in the soil core were determined by gas chromatography of vapor samples. Biodegradation reduced low influent hydrocarbon concentrations by 45 to 92 percent over a 0.6-m interval of an intact soil core. The estimated total hydrocarbon concentration was reduced by 75 percent from 26 to 7 parts per million. Steady-state concentrations were input to a simple analytical model balancing advection and first-order biodegradation of hydrocarbons. First-order rate constants for the major hydrocarbon compounds were used to calibrate the model to the concentration profiles. Rate constants for the seven individual hydrocarbon compounds varied by a factor of 4. Compounds with lower molecular weights, fewer methyl groups, and no quaternary carbons tended to have higher rate constants. The first-order rate constants were consistent with kinetic parameters determined from both microcosm and tubing cluster studies at the field site. 相似文献
32.
Sunil Bharati Richard L. Patience Steve R. Larter Guy Standen Iain J. F. Poplett 《Organic Geochemistry》1995,23(11-12)
The significance and validity of integrating data obtained from a variety of analytical techniques to understand, elucidate and model kerogen's complex chemical structure is reported here using degradative (open and closed system pyrolysis, chemical oxidation), non-degradative (13C CP/MAS NMR) and optical (incident white light and blue light) methods. Seven Cambrian Alum Shale samples, ranging in maturity from immature to post-mature with respect to petroleum generation, were studied and were chosen for their simple geological history, uniform organic matter type and high organic carbon content. The Alum Shale kerogens, which primarily consist of algal organic matter, liberate low molecular weight gaseous and aromatic compounds on pyrolysis and give mostly branched dicarboxylic acids on chemical oxidation. 13C NMR spectroscopy shows that the Alum Shale kerogens are anomalously rich in oxygen-bearing functional groups (such as C = O, ArCO, CHO, CHxO), most of which apparently remain intact within the kerogen macro-molecule (KMM) through the diagenetic and catagenetic stages. Fragments released by different degradative techniques are quantified and the aromaticity (fa), O/C and relative proportions of various carbon types estimated by 13C NMR. A synthesis of these data has allowed us to better understand the chemistry of the Alum Shale kerogen. 相似文献
33.
Ho KT Burgess RM Pelletier MC Serbst JR Ryba SA Cantwell MG Kuhn A Raczelowski P 《Marine pollution bulletin》2002,44(4):286-293
The identification of toxicants affecting aquatic benthic systems is critical to sound assessment and management of our nation's waterways. Identification of toxicants can be useful in designing effective sediment remediation plans and reasonable options for sediment disposal. Knowledge of which contaminants affect benthic systems allows managers to link pollution to specific dischargers and prevent further release of toxicant(s). In addition, identification of major causes of toxicity in sediments may guide programs such as those developing environmental sediment guidelines and registering pesticides, while knowledge of the causes of toxicity which drive ecological changes such as shifts in benthic community structure would be useful in performing ecological risk assessments. To this end, the US Environmental Protection Agency has developed tools (toxicity identification and evaluation (TIE) methods) that allow investigators to characterize and identify chemicals causing acute toxicity in sediments and dredged materials. To date, most sediment TIEs have been performed on interstitial waters. Preliminary evidence from the use of interstitial water TIEs reveals certain patterns in causes of sediment toxicity. First, among all sediments tested, there is no one predominant cause of toxicity; metals, organics, and ammonia play approximately equal roles in causing toxicity. Second, within a single sediment there are multiple causes of toxicity detected; not just one chemical class is active. Third, the role of ammonia is very prominent in these interstitial waters. Finally, if sediments are divided into marine or freshwater, TIEs perforMed on interstitial waters from freshwater sediments indicate a variety of toxicants in fairly equal proportions, while TIEs performed on interstitial waters from marine sediments have identified only ammonia and organics as toxicants, with metals playing a minor role. Preliminary evidence from whole sediment TIEs indicates that organic compounds play a major role in the toxicity of marine sediments, with almost no evidence for either metal or ammonia toxicity. However, interpretation of these results may be skewed because only a small number of interstitial water (n = 13) and whole sediment (n = 5) TIEs have been completed. These trends may change as more data are collected. 相似文献
34.
Nathan Roche Steve Eales & Hans Hippelein 《Monthly notices of the Royal Astronomical Society》1998,295(4):946-958
We investigate the angular correlation function, ο(θ), of the galaxies detected in the 2.1-μm K ' band in 17 fields (101.5 arcmin2 in total), each containing a z ∼1.1 radio galaxy. There is a significant detection of galaxy clustering at a limit of K ∼20, with a ο(θ) amplitude similar to that estimated by Carlberg et al. at K =21.5. The ο(θ) amplitudes of these K -limited samples are higher than expected from the faint galaxy clustering in the blue and red passbands, but consistent with a pure luminosity evolution model if clustering is stable (ε=0) and the correlation function of early-type galaxies is steeper than that of spirals.
We do not detect a significant cross-correlation between the radio galaxies and the other galaxies in these fields. The upper limits on the cross-correlation are consistent with a mean clustering environment of Abell class 0 for z ∼1.1 radio galaxies, similar to that observed for radio galaxies at z ∼0.5, but would argue against an Abell class 1 or richer environment. As Abell 0 clustering around the radio galaxies would not significantly increase the ο(θ) amplitude of galaxies in these fields, stable clustering with a steep ξ( r ) for E/S0 galaxies appears to remain the most likely interpretation of the ο(θ) amplitude.
At K ≤20, the number of galaxy–galaxy pairs of 2–3 arcsec separation exceeds the random expectation by a factor of 2.15±0.26. The excess of close pairs is comparable to that previously reported for R -band data, and consistent with a ∼(1+ z )2 evolution of the galaxy merger rate. 相似文献
We do not detect a significant cross-correlation between the radio galaxies and the other galaxies in these fields. The upper limits on the cross-correlation are consistent with a mean clustering environment of Abell class 0 for z ∼1.1 radio galaxies, similar to that observed for radio galaxies at z ∼0.5, but would argue against an Abell class 1 or richer environment. As Abell 0 clustering around the radio galaxies would not significantly increase the ο(θ) amplitude of galaxies in these fields, stable clustering with a steep ξ( r ) for E/S0 galaxies appears to remain the most likely interpretation of the ο(θ) amplitude.
At K ≤20, the number of galaxy–galaxy pairs of 2–3 arcsec separation exceeds the random expectation by a factor of 2.15±0.26. The excess of close pairs is comparable to that previously reported for R -band data, and consistent with a ∼(1+ z )
35.
36.
Mock 2dF and SDSS galaxy redshift surveys 总被引:1,自引:0,他引:1
37.
Marek J. Kukula James S. Dunlop David H. Hughes & Steve Rawlings 《Monthly notices of the Royal Astronomical Society》1998,297(2):366-382
Although radio-quiet quasars (RQQs) constitute ≳ 90 per cent of optically identified quasar samples, their radio properties are only poorly understood. In this paper we present the results of a multi-frequency VLA study of 27 low-redshift RQQs. We detect radio emission from 20 objects, half of which are unresolved (≤ 0.24 arcsec). In cases where significant structure can be resolved, double, triple and linear radio sources on scales of a few kpc are found. The radio emission (typically) has a steep spectrum (α ∼ 0.7, where S ∝ ν−α ), and high brightness temperatures ( T B ≥ 105 K) are measured in some of the radio components. The RQQs form a natural extension to the radio luminosity–absolute magnitude distribution of nearby Seyfert 1s. We conclude that a significant fraction of the radio emission in RQQs originates in a compact nuclear source directly associated with the quasar. There are no significant differences between the radio properties of RQQs with elliptical hosts and those in disc galaxies within the current sample. 相似文献
38.
Alfonso V. Botello Enrique F. Mandelli Steve Macko Patrick L. Parker 《Geochimica et cosmochimica acta》1980,44(3):557-559
The stable carbon isotope composition sedimentary organic carbon was determined in the sediments of seven coastal lagoons of the Gulf of Mexico, Mexico. For most of the lagoons the δ13C values for sediments ranged from ?20.1 to ?23.9%. Anomalously low values, ?26.8 to 29.3%. were determined in sediments of two of the studied lagoons, probably due to the presence of organic carbon from anthropogenic sources, naturally absent in these environments. The δ13C values determined in the tissues of oysters collected at the same time in the different lagoons were very similar to those recorded in the sediments. 相似文献
39.
40.
The WFD has introduced an international commitment to assess the ecological status of transitional waters (TWs), within which fish communities are a key biological monitoring component. The Transitional Fish Classification Index (TFCI) outlined in this paper uses 10 ecological measures to analyse fish populations caught from various ecological niches using a variety of gear types within the Thames estuary. These reach and method-specific communities are then compared to a reference population created from a 'healthy' population from TWs of a similar type. The results indicate a progressive downstream increase the quality of fish communities, consistent with previous work; variation between methods can be accounted for by gear selectivity. Overall, the TFCI is an effective communication tool for converting ecological information into an easily understood format for managers, policy makers and the general public. 相似文献