Multilevel samplers as microcosms to assess microbial response to biostimulation

Passive multilevel samplers (MLS) containing a solid matrix for microbial colonization were used as in situ microcosms in conjunction with a push-pull biostimulation experiment designed to promote biological U(VI) and Tc(VII) reduction. MLS were deployed at 24 elevations in the injection well and two downgradient wells to investigate the spatial variability in microbial community composition and growth prior to and following biostimulation. The microbial community was characterized by real-time quantitative polymerase chain reaction (Q-PCR) quantification of bacteria, NO(3)(-)-reducing bacteria (nirS and nirK), delta-proteobacteria, Geobacter sp., and methanogens (mcrA). Pretest cell densities were low overall but varied substantially with significantly greater bacterial populations detected at circumneutral pH (t-test, alpha= 0.05), suggesting carbon substrate and low pH limitations of microbial activity. Although pretest cell densities were low, denitrifying bacteria were dominant members of the microbial community. Biostimulation with an ethanol-amended ground water resulted in concurrent NO(3)(-) and Tc(VII) reduction, followed by U(VI) reduction. Q-PCR analysis of MLS revealed significant (1 to 2 orders of magnitude, Mann-Whitney U-test, alpha= 0.05) increases in cell densities of bacteria, denitrifiers, delta-proteobacteria, Geobacter sp., and methanogens in response to biostimulation. Traditionally, characterization of sediment samples has been used to investigate the microbial community response to biostimulation; however, collection of sediment samples is expensive and not conducive to deep aquifers or temporal studies. The results presented demonstrate that push-pull tests with passive MLS provide an inexpensive approach to determine the effect of biostimulation on contaminant concentrations, geochemical conditions, and the microbial community composition and function.     

Relative risk assessment of cruise ships biosolids disposal alternatives

A relative risk assessment of biosolids disposal alternatives for cruise ships is presented in this paper. The area of study encompasses islands and marine waters of the Caribbean Sea. The objective was to evaluate relative human health and ecological risks of (a) dewatering/incineration, (b) landing the solids for disposal, considering that in some countries land-disposed solids might be discharged in the near-shore environment untreated, and (c) deep ocean disposal. Input to the Bayesian assessment consisted of professional judgment based on available literature and modeling information, data on constituent concentrations in cruise ship biosolids, and simulations of constituent concentrations in Caribbean waters assuming ocean disposal. Results indicate that human health and ecological risks associated with land disposal and shallow ocean disposal are higher than those of the deep ocean disposal and incineration. For incineration, predicted ecological impacts were lower relative to deep ocean disposal before considering potential impacts of carbon emissions.     

Push-pull tests for assessing in situ aerobic cometabolism

Three types of single-well push-pull tests were developed for use in assessing the feasibility of in situ aerobic cometabolism of chlorinated aliphatic hydrocarbons (CAHs). These included transport tests, biostimulation tests, and activity tests. Transport tests are conducted to evaluate the mobility of solutes used in subsequent tests. These included bromide or chloride (conservative tracers), propane (growth substrate), ethylene, propylene (CAH surrogates), dissolved oxygen (electron acceptor), and nitrate (a minor nutrient). Tests were conducted at an experimental wellfield of Oregon State University. At this site, extraction phase breakthrough curves for all solutes were similar, indicating apparent conservative transport of the dissolved gases and nitrate prior to biostimulation. Biostimulation tests were conducted to stimulate propane-utilizing activity of indigenous microorganisms and consisted of sequential injections of site ground water containing dissolved propane and oxygen. Biostimulation was detected by the increase in rates of propane and oxygen utilization after each injection. Activity tests were conducted to quantify rates of substrate utilization and to confirm that CAH-transforming activity had likely been stimulated. In particular, the transformation of injected CAH surrogates ethylene and propylene to the cometabolic byproducts ethylene oxide and propylene oxide provided evidence that activity of the monooxygenase enzyme system, responsible for aerobic cometabolic transformations of CAHs, had likely also been stimulated. Estimated zero-order transformation rates decreased in the order propane > ethylene > propylene. The series of push-pull tests developed and field tested in this study should prove useful for conducting rapid, low-cost feasibility assessments for in situ aerobic cometabolism of CAHs.     

New emission features in the 11-13 micron region and their relationship to polycyclic aromatic hydrocarbons

If the "11.3 microns" emission feature seen in the spectra of many planetary nebulae, H II regions, and reflection nebulae is due to polycyclic aromatic hydrocarbons (PAHs), then additional features should be present between 11.3 and 13.0 microns (885 and 770 cm-1). Moderate-resolution spectra of NGC 7027, HD 44179, IRAS 21282+5050, and BD + 30 degrees 3639 are presented which show that the "11.3 microns" feature actually peaks at 11.22 microns (891 cm-1). The spectra also show evidence of new emission features near 11.9 and 12.7 microns (840 and 787 cm-1). These are consistent with an origin from PAHs and can be used to constrain the molecular structure of the family of PAHs responsible for the infrared features. The observed asymmetry of the "11.3 microns" band is consistent with the slight anharmonicity expected in the C--H out-of-plane bending mode in PAHs. Laboratory experiments show that the intensity of this mode relative to the higher frequency modes depends on the extent of molecular "clustering." The observed strengths of the "11.3 microns" interstellar bands relative to the higher frequency bands are most consistent with the features originating from free molecular PAHs. The intensity and profile of the underlying broad structure, however, may well arise from PAH clusters and amorphous carbon particles. Analysis of the 11-13 microns (910-770 cm-1) emission suggests that the molecular structures of the most intensity emitting free PAHs vary somewhat between the high-excitation environment in NGC 7027 and the low-excitation but high-flux environment close to HD 44179. Finally, a previously undetected series of regularly spaced features between 10 and 11 microns (1000 and 910 cm-1) in the spectrum of HD 44179 suggests that a simple polyatomic hydride is present in the gas phase in this object.     

Infrared emission from comets

A brief discussion of the infrared observations from 4 to 20 micrometers of seven comets is presented. The observed infrared emission from comets depends primarily on their heliocentric distance. A model based on grain populations composed of a mixture of silicate and amorphous carbon particles in the mass ratio of about 40 to 1, with a power-law size distribution similar to that inferred for comet Halley, is applied to the observations. The model provides a good match to the observed heliocentric variation of both the 10 micrometers feature and the overall thermal emission from comets West and Halley. Matches to the observations of comet IRAS-Araki-Alcock and the antitail of comet Kohoutek require slightly larger grains. While the model does not match the exact profile and position of the 3.4 micrometers feature discovered in comet Halley, it does produce a qualitative fit to the observed variation of the feature's strength as a function of heliocentric distance. The calculations predict that the continuum under the 3.4 micrometers feature is due primarily to thermal emission from the comet dust when the comet is close to the Sun and to scattered solar radiation at large heliocentric distances, as is observed. A brief discussion of the determination of cometary grain temperatures from the observed infrared emission is presented. It is found that the observed shape of the emission curve from about 4 to 8 micrometers provides the best spectral region for estimating the cometary grain temperature distribution.     

Depuration dynamics of oysters (Crassostrea gigas) artificially contaminated by Salmonella enterica serovar Typhimurium

The State of Santa Catarina produces the greatest quantity of edible mollusks in Brazil. To guarantee sanitary qualify, mollusk cultures should be monitored for contamination by pathogenic microorganisms. A self-purification or "depuration" system that eliminates Salmonella enterica serovar Typhimurium contamination from oysters has been developed and evaluated. The depuration process occurred within a closed system, in which 1000 L of water was recirculated for 24 h. The water was sterilized with ultraviolet (UV) light, chlorine, or both together. Oysters (Crassostrea gigas) artificially contaminated with S. typhimurium were harvested every 6 h. Samples of oyster tissue were excised and both the presence and numbers of bacteria were determined. Combined UV light and chlorine treatments resulted in total elimination of bacteria within 12 h. Polymerase chain reaction detected bacteria in water exposed to the three treatments. This pioneering study is the first of its kind in Brazil and represents a major contribution to commercial mollusk culture in this country.     

Whole-bird models for the magnetic cleansing of oiled feathers

Iron powder, a promising dry-cleansing agent for oiled feathers where both the contaminant and the cleansing agent may be harvested magnetically, has been tested on the plumage of whole-bird models. The breast and back plumage of Mallard Duck (Anas platyrhynchos) and Little Penguin (Eudyptula minor) carcasses were patch-contaminated with commercial-grade engine oil, three different crude oils, and an oil/seawater emulsion. The plumage was then subjected to a magnetic cleansing protocol. The contaminant removal was assessed gravimetrically and was found to reflect the outcomes for a previously reported in vitro study using feather clusters. Between 92-98% of the contaminants, and effectively all of the cleansing agent, were removed from the feathers.     

The atmospheric lead record preserved in lagoon sediments at a remote equatorial Pacific location: Palmyra Atoll, northern Line Islands

Anthropogenic lead (Pb) inputs to the atmosphere increased greatly over the past century and now dominate Pb supply to the oceans. However, the Pb content of sediments across the equatorial Pacific region is relatively unknown, and data exist only for deep sea sites where Pb deposition lags surface water inputs by up to a century. Here we present ICP-MS analyses of Pb of a core from a lagoon at Palmyra Atoll, northern Line Islands, that spans approximately the past 160 years. The non-bioturbated sediments of the euxinic lagoon, coupled with rapid rates of deposition, provide a unique fine-scale record of atmospheric Pb supply at a remote Pacific location. These first observations of historic Pb sedimentation in an atoll lagoon reveal a 63-fold increase in Pb flux to sediments during the past century and correlate directly with the North American consumption of leaded gasoline that began in 1926.