69 research outputs found
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Speciation, Mobility and Fate of Actinides in the Groundwater at the Hanford Site
Plutonium and other actinides represent important contaminants in the groundwater and vadose zone at Hanford and other DOE sites. The distribution and migration of these actinides in groundwater must be understood so that these sites can be carefully monitored and effectively cleaned up, thereby minimizing risks to the public. The objective of this project was to obtain field data on the chemical and physical forms of plutonium in groundwater at the Hanford site. We focused on the 100-k and 100-n areas near the Columbia River, where prior reactor operations and waste storage was in close proximity to the river. In particular, a unique set of technical approaches were combined to look at the details of Pu speciation in groundwater, as thus its chemical affinity for soil surfaces and solubility in groundwater, as these impact directly the migration rates off site and possible mitigation possibilities one might undertake to control, or at least better monitor these releases
Seasonal occurrence of anoxygenic photosynthesis in Tillari and Selaulim reservoirs, Western India
© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 9 (2012): 2485-2495, doi:10.5194/bg-9-2485-2012.Phytoplankton and bacterial pigment compositions were determined by high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) in two freshwater reservoirs (Tillari Dam and Selaulim Dam), which are located at the foothills of the Western Ghats in India. These reservoirs experience anoxia in the hypolimnion during summer. Water samples were collected from both reservoirs during anoxic periods while one of them (Tillari Reservoir) was also sampled in winter, when convective mixing results in well-oxygenated conditions throughout the water column. During the period of anoxia (summer), bacteriochlorophyll (BChl) e isomers and isorenieratene, characteristic of brown sulfur bacteria, were dominant in the anoxic (sulfidic) layer of the Tillari Reservoir under low light intensities. The winter observations showed the dominance of small cells of Chlorophyll b-containing green algae and cyanobacteria, with minor presence of fucoxanthin-containing diatoms and peridinin-containing dinoflagellates. Using total BChl e concentration observed in June, the standing stock of brown sulfur bacteria carbon in the anoxic compartment of Tillari Reservoir was estimated to be 2.27 gC m−2, which is much higher than the similar estimate for carbon derived from oxygenic photosynthesis (0.82 gC m−2. The Selaulim Reservoir also displayed similar characteristics with the presence of BChl e isomers and isorenieratene in the anoxic hypolimnion during summer. Although sulfidic conditions prevailed in the water column below the thermocline, the occurrence of photo-autotrophic bacteria was restricted only to mid-depths (maximal concentration of BChl e isomers was detected at 0.2% of the surface incident light). This shows that the vertical distribution of photo-autotrophic sulfur bacteria is primarily controlled by light penetration in the water column where the presence of H2S provides a suitable biogeochemical environment for them to flourish.Financial
support for this work was provided by the Council of Scientific
& Industrial Research (CSIR) and Ministry of Earth Sciences
(MoES). S. Kurian acknowledges POGO-SCOR for financial
support to visit WHOI. R. Roy, G. Narvenkar and A. Sarkar
received fellowship support from CSIR. D. Repeta acknowledges
support from US National Science Foundation Center Award
EF0424599 to the Center for Microbial Oceanography: Research
and Education (C-MORE)
Daily changes in phytoplankton lipidomes reveal mechanisms of energy storage in the open ocean
© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 5179, doi:10.1038/s41467-018-07346-z.Sunlight is the dominant control on phytoplankton biosynthetic activity, and darkness deprives them of their primary external energy source. Changes in the biochemical composition of phytoplankton communities over diel light cycles and attendant consequences for carbon and energy flux in environments remain poorly elucidated. Here we use lipidomic data from the North Pacific subtropical gyre to show that biosynthesis of energy-rich triacylglycerols (TAGs) by eukaryotic nanophytoplankton during the day and their subsequent consumption at night drives a large and previously uncharacterized daily carbon cycle. Diel oscillations in TAG concentration comprise 23 ± 11% of primary production by eukaryotic nanophytoplankton representing a global flux of about 2.4 Pg C yr−1. Metatranscriptomic analyses of genes required for TAG biosynthesis indicate that haptophytes and dinoflagellates are active members in TAG production. Estimates suggest that these organisms could contain as much as 40% more calories at sunset than at sunrise due to TAG production.This work was supported by a grant from the Simons Foundation, and is a contribution of the Simons Collaboration on Ocean Processes and Ecology (SCOPE award # 329108, B.A.S.V.M.). K.W.B. was further supported by the Postdoctoral Scholarship Program at Woods Hole Oceanographic Institution & U.S. Geological Survey
Discovery of chlorophyll d: isolation and characterization of a far-red cyanobacterium from the original site of manning and strain (1943) at Moss Beach, California
© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kiang, N. Y., Swingley, W. D., Gautam, D., Broddrick, J. T., Repeta, D. J., Stolz, J. F., Blankenship, R. E., Wolf, B. M., Detweiler, A. M., Miller, K. A., Schladweiler, J. J., Lindeman, R., & Parenteau, M. N. Discovery of chlorophyll d: isolation and characterization of a far-red cyanobacterium from the original site of manning and strain (1943) at Moss Beach, California. Microorganisms, 10(4), (2022): 819, https://doi.org/10.3390/microorganisms10040819.We have isolated a chlorophyll-d-containing cyanobacterium from the intertidal field site at Moss Beach, on the coast of Central California, USA, where Manning and Strain (1943) originally discovered this far-red chlorophyll. Here, we present the cyanobacterium’s environmental description, culturing procedure, pigment composition, ultrastructure, and full genome sequence. Among cultures of far-red cyanobacteria obtained from red algae from the same site, this strain was an epiphyte on a brown macroalgae. Its Qyin vivo absorbance peak is centered at 704–705 nm, the shortest wavelength observed thus far among the various known Acaryochloris strains. Its Chl a/Chl d ratio was 0.01, with Chl d accounting for 99% of the total Chl d and Chl a mass. TEM imagery indicates the absence of phycobilisomes, corroborated by both pigment spectra and genome analysis. The Moss Beach strain codes for only a single set of genes for producing allophycocyanin. Genomic sequencing yielded a 7.25 Mbp circular chromosome and 10 circular plasmids ranging from 16 kbp to 394 kbp. We have determined that this strain shares high similarity with strain S15, an epiphyte of red algae, while its distinct gene complement and ecological niche suggest that this strain could be the closest known relative to the original Chl d source of Manning and Strain (1943). The Moss Beach strain is designated Acaryochloris sp. (marina) strain Moss Beach.N.Y.K., M.N.P. and R.E.B. were supported by the NASA Virtual Planetary Laboratory team (VPL), which was funded under NASA Astrobiology Institute Cooperative Agreement Number NNA13AA93A, and Grant Number 80NSSC18K0829. This work also benefited from participation in the NASA Nexus for Exoplanet Systems Science (NExSS) research coordination network (RCN). W.D.S, N.Y.K. and M.N.P. were also supported by a NASA Exobiology grant No. 80NSSC19K0478. J.TB. was supported by the NASA Postdoctoral Program (NPP) award number NPP168014S. N.Y.K. received training support from the NASA Goddard Space Flight Center Training Office to take the Microbial Diversity course at the Marine Biological Laboratory, Woods Hole, MA, USA
Seasonal and annual fluxes of nutrients and organic matter from large rivers to the Arctic Ocean and surrounding seas
Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Estuaries and Coasts 35 (2012): 369-382, doi:10.1007/s12237-011-9386-6.River inputs of nutrients and organic matter impact the biogeochemistry of arctic
estuaries and the Arctic Ocean as a whole, yet there is considerable uncertainty about the
magnitude of fluvial fluxes at the pan-arctic scale. Samples from the six largest arctic
rivers, with a combined watershed area of 11.3 x 106 km2, have revealed strong seasonal
variations in constituent concentrations and fluxes within rivers as well as large
differences among the rivers. Specifically, we investigate fluxes of dissolved organic
carbon, dissolved organic nitrogen, total dissolved phosphorus, dissolved inorganic
nitrogen, nitrate, and silica. This is the first time that seasonal and annual constituent
fluxes have been determined using consistent sampling and analytical methods at the pan
arctic scale, and consequently provide the best available estimates for constituent flux
from land to the Arctic Ocean and surrounding seas. Given the large inputs of river water
to the relatively small Arctic Ocean, and the dramatic impacts that climate change is
having in the Arctic, it is particularly urgent that we establish the contemporary river
fluxes so that we will be able to detect future changes and evaluate the impact of the
changes on the biogeochemistry of the receiving coastal and ocean systems.This work was supported by the National Science Foundation through grants
OPP-0229302, OPP-0519840, OPP-0732522, and OPP-0732944. Additional support was
provided by the U. S. Geological Survey (Yukon River) and the Department of Indian
and Northern Affairs (Mackenzie River)
Extracellular enzyme activity in anaerobic bacterial cultures: evidence of pullulanase activity among mesophilic marine bacteria.
The extracellular enzymatic activity of a mixed culture of anaerobic marine bacteria enriched on pullulan [alpha(1,6)-linked maltotriose units] was directly assessed with a combination of gel permeation chromatography (GPC) and nuclear magnetic resonance spectroscopy (NMR). Hydrolysis products of pullulan were separated by GPC into three fractions with molecular weights of > or = 10,000, approximately 5,000, and < or = 1,200. NMR spectra of these fractions demonstrated that pullulan was rapidly and specifically hydrolyzed at alpha(1,6) linkages by pullulanase enzymes, most likely type II pullulanase. Although isolated pullulanase enzymes have been shown to hydrolyze pullulan completely to maltotriose (S. H. Brown, H. R. Costantino, and R. M. Kelly, Appl. Environ. Microbiol. 56:1985-1991, 1990; M. Klingeberg, H. Hippe, and G. Antranikian, FEMS Microbiol. Lett. 69:145-152, 1990; R. Koch, P. Zablowski, A. Spreinat, and G. Antranikian, FEMS Microbiol. Lett. 71:21-26, 1990), the smallest carbohydrate detected in the bacterial cultures consisted of two maltotriose units linked through one alpha(1,6) linkage. Either the final hydrolysis step was closely linked to substrate uptake, or specialized porins similar to maltoporin might permit direct transport of large oligosaccharides into the bacterial cell. This is the first report of pullulanase activity among mesophilic marine bacteria. The combination of GPC and NMR could easily be used to assess other types of extracellular enzyme activity in bacterial cultures
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Speciation and structural characterization of plutonium and actinide-organic complexes in surface and ground waters. Annual progress report, September 1996--September 1997
'The authors proposed research is designed to study the association of actinides with dissolved organic complexes in subsurface waters. Actinide-humic matter associations in natural waters have been investigated previously, but the authors have postulated that much of the actinide binding activity may be supported by colloidal biopolymers. To investigate this, they are developing techniques to sample and identify organic constituents in groundwater, and to measure the Pu associated with different fractions of organic matter. Year 1 activities have focused on: (1) sampling techniques to minimize contamination and artifact formation, and to establish mass balances, (2) separation of Pu isotopes by oxidation state, and (3) analytical development of techniques for separation and identification of organic constituents from natural waters. The authors proposed research calls for field work at the Savannah River and Hanford Sites (SRS and HS, respectively). Towards this, they have been working on establishing protocols for ultra-clean (fg level) cross-flow filtration (CFF) techniques suitable for thermal ionization mass spectrometric (TIMS) analysis. A series of tests have been completed and the results have shown no Pu contamination from the CFF system was observable as long as the system is rigorously cleaned with acid, base and nano-pure water (Table 1). They have also collected a water sample from a pond near the laboratory in Woods Hole, MA to test blank conditions in the field, and to determine system mass balances. Blank levels were found to be satisfactory, and the mass balance is 100 \261 10% for both {sup 239}Pu and {sup 240}Pu, the only two isotopes measurable in the sample. This is one of the major assurances for the success of the project because CFF will be the major sampling tool the authors will use to study natural Pu-organic complexes. Another important result from the field test is that > 80% of the dissolved Pu (based on the TIMS measurements) is in colloidal form.
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