Extraction-scintillation medium and method of use

An extraction-scintillation medium of substantially free-flowing, porous, solid particulate matter having one or more fluors retained within the particulate matter and an extraction agent adsorbed on or bound to the surface of the particulate matter. The medium is capable of extracting one of a selected radionuclide from an aqueous stream and permits transmission of light therethrough, which light is emitted from the one or more fluors in response to radiation absorbed thereby from the selected radionuclide. A sensor system using the extraction-scintillation medium for real-time or near real-time detection of the selected radionuclide is also disclosed

Coastal versus open-ocean denitrification in the Arabian Sea

International audienceThe Arabian Sea contains one of the three major open-ocean denitrification zones in the world. In addition, pelagic denitrification also occurs over the inner and mid-shelf off the west coast of India. The major differences between the two environments are highlighted using the available data. The perennial open-ocean system occupies two orders of magnitude larger volume than the seasonal coastal system, however, the latter offers more extreme conditions (greater nitrate consumption leading to complete anoxia). Unlike the open-ocean system, the coastal system seems to have undergone a change (i.e., it has intensified) over the past few decades presumably due to enhanced nutrient loading from land. The two systems also differ from each other with regard to the modes of nitrous oxide (N2O) production: In the open-ocean suboxic zone, an accumulation of secondary nitrite (NO2?) is invariably accompanied by depletion of N2O whereas in the coastal suboxic zone high NO2? and very high N2O concentrations frequently co-occur, indicating, respectively, net consumption and net production of N2O by denitrifiers. The extents of heavier isotope enrichment in the combined nitrate and nitrite (NO3?+NO2?) pool and in N2O in reducing waters appear to be considerably smaller in the coastal region, reflecting more varied sources/sinks and/or different isotopic fractionation factors

Metal Reduction at Cold Temperatures by Shewanella Isolates from Various Marine Environments

Members of the genus Shewanella capable of reducing metals and forming minerals under cold-temperature conditions were isolated from 3 distinct marine habitats (the coast of Wash- ington State, the Puget Sound, and an iron-rich microbial mat off Hawaii). Cultures of microorgan- isms were isolated at 8°C on nutrient agar medium prepared in artificial seawater. Isolates in this study could use a wide variety of electron acceptors such as oxygen, nitrate, and metals, and reduce various metals coupled to the oxidation of several organic acids, glucose or hydrogen at temperatures down to 0°C. Akaganeite was reduced to either magnetite or siderite, depending on the test condi- tions. The geochemical profiles at the sample sites from which these strains were isolated spanned a temperature range of 1.8 to 11°C, and all showed active oxygen and nitrate reduction as well as metal reduction. This confirms previous reports that sediment microorganisms participating in biogeo- chemical cycles remain active at low temperatures

Denitrification rates and excess nitrogen gas concentrations in the Arabian Sea oxygen deficient zone

Rates of canonical, i.e. heterotrophic, water-column denitrification were measured by 15N incubation techniques at a number of coastal and open ocean stations in the Arabian Sea. Measurements of N2:Ar gas ratios were also made to obtain independent estimates of N2 excess resulting from denitrification. Measured denitrification rates (15NO3-→15-14N2) at open ocean stations averaged 9.1±1.0 nmol N l-1 d-1 (n=15), and coastal rates averaged 33.2±12.4 nmol N l-1 d-1 (n=18). When extrapolated to the entire Arabian Sea, deep measurements within the offshore perennial suboxic zone indicate an overall denitrification rate of 41 Tg N a-1±18 Tg N a-1, which is within the range (10-44 Tg N a-1) of previous estimates for canonical denitrification in the region based on stoichiometric calculations and electron transport system activity. Nitrogen excess gas measurements predict a larger nitrogen anomaly than estimated by classical stoichiometric methods (maximum anomaly=23 μg at N l-1 vs. 13 μg at N l-1, respectively). This mismatch may result from incorrect assumptions of Redfield stoichiometry inherent in the nitrate deficit calculation, inputs of new nitrogen through N-fixation, N2 contributions from sedimentary denitrification along continental margins, the anammox reaction, and metal catalyzed denitrification reactions. Nevertheless, if denitrification is defined as the conversion of combined nitrogen to a gaseous end product, then the data suggest that denitrification in the Arabian Sea may have been underestimated so far

Elevated Concentrations of Primordial Radionuclides in Sediments from the Reedy River and Surrounding Creeks in Simpsonville, South Carolina

A gamma-ray survey and analysis of sixteen riverbed samples from the Reedy River watershed near Simpsonville, SC were conducted and compared with national and international studies of primordial radionuclides. The study reported here follows on a recent discovery of anomalously high uranium concentrations in several private well waters in the area near Simpsonville, SC. A HPGe spectrometer was used for quantification of gamma emitting radionuclides in the sediments. All sediments contained radionuclides from the uranium and thorium series as well as {sup 40}K. Uranium-238 concentrations in sediment samples ranged from 11.1 to 74.2 Bq kg{sup -1}. The measured radionuclide concentrations were compared with data from UNSCEAR and NURE reports. The river and stream sediment data were augmented by in situ NaI(Tl) gamma-ray spectrometer measurements. Comparisons between the ex-situ and in-situ measurements indicate equivalently distributed uranium in the surface soils and stream sediments, the source of which is likely attributed to the monazite belts that are known to exist in the area

Lake ecosystems of the Lake Washington drainage basin

p.333-386 from Analysis of coniferous forest ecosystems in the Western United States

Retrospective studies in scleroderma: Effect of potassium para-aminobenzoate on survival

Demographic and survival data are presented for 390 patients with scleroderma. For the entire group An estimated, 81.4% survived 5 years from diagnosis and 69.4% survived 10 years. Life-table analyses revealed that adequate treatment with potassium para-aminobenzoate (Potaba(R) KPAB) was associated with improved survival (p per se as a prognostic indicator: the greater the extent of skin involvement the poorer prognosis. Time from first diagnosis to first University Hospital visit or admission when included as a covariate did not influence survival.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27502/1/0000546.pd

Large emissions from floodplain trees close the Amazon methane budget

Wetlands are the largest global source of atmospheric methane (CH4), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain, the largest natural geographic source of CH4 in the tropics, consistently underestimate the atmospheric burden of CH4 determined via remote sensing and inversion modelling, pointing to a major gap in our understanding of the contribution of these ecosystems to CH4 emissions. Here we report CH4 fluxes from the stems of 2,357 individual Amazonian floodplain trees from 13 locations across the central Amazon basin. We find that escape of soil gas through wetland trees is the dominant source of regional CH4 emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests6 and tropical peat swamp forests, representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (δ13C) of −66.2 ± 6.4 per mil, consistent with a soil biogenic origin. We estimate that floodplain trees emit 15.1 ± 1.8 to 21.2 ± 2.5 teragrams of CH4 a year, in addition to the 20.5 ± 5.3 teragrams a year emitted regionally from other sources. Furthermore, we provide a ‘top-down’ regional estimate of CH4 emissions of 42.7 ± 5.6 teragrams of CH4 a year for the Amazon basin, based on regular vertical lower-troposphere CH4 profiles covering the period 2010–2013. We find close agreement between our ‘top-down’ and combined ‘bottom-up’ estimates, indicating that large CH4 emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH4 budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH4 emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH4 source when trees are combined with other emission sources

Nacre tablet thickness records formation temperature in modern and fossil shells

Nacre, the iridescent outer lining of pearls and inner lining of many mollusk shells, is composed of periodic, parallel, organic sheets alternating with aragonite (CaCO_3) tablet layers. Nacre tablet thickness (TT) generates both nacre's iridescence and its remarkable resistance to fracture. Despite extensive studies on how nacre forms, the mechanisms controlling TT remain unknown, even though they determine the most conspicuous of nacre's characteristics, visible even to the naked eye. Thermodynamics predicts that temperature (T) will affect both physical and chemical components of biomineralized skeletons. The chemical composition of biominerals is well-established to record environmental parameters, and has therefore been extensively used in paleoclimate studies. The physical structure, however, has been hypothesized but never directly demonstrated to depend on the environment. Here we observe that the physical TT in nacre from modern and fossil shallow-water shells of the bivalves Pinna and Atrina correlates with T as measured by the carbonate clumped isotope thermometer. Based on the observed TT vs. T correlation, we anticipate that TT will be used as a paleothermometer, useful to estimate paleotemperature in shallow-water paleoenvironments. Here we successfully test the proposed new nacre TT thermometer on two Jurassic Pinna shells. The increase of TT with T is consistent with greater aragonite growth rate at higher T, and with greater metabolic rate at higher T. Thus, it reveals a complex, T-dependent biophysical mechanism for nacre formation

Nitrogen isotopic studies in the suboxic Arabian Sea

Measurements of 15N/14N in dissolved molecular nitrogen (N2), nitrate (NO3- ) and nitrous oxide (N2O) and 18O/16O in N2O [expressed as δ15N and δ18O, relative to atmospheric N2 and oxygen (O2), respectively] have been made in water column at several locations in the Arabian Sea, a region with one of the thickest and most intense O2 minima observed in the open ocean. Microbially-mediated reduction of NO3- to N2 (denitrification) in the oxygen minimum zone (OMZ) appears to greatly affect the natural isotopic abundances. The δ15N of NO3- increases from 6‰ in deep waters (2500 m) to 15‰ within the core of the denitrifying layer (250-350 m); the δ15N of N2 concurrently decreases from 0.6‰ to 0.20‰ Values of the isotopic fractionation factor (e) during denitrification estimated using simple advection-reaction and diffusion-reaction models are 22‰ and 25‰, respectively. A strong decrease in δ15N of NO3- is observed from ~ 200m (> 11‰) to 80m (~ 6‰); this is attributed to the input of isotopically light nitrogen through nitrogen fixation. Isotopic analysis of N2O reveals extremely large enrichments of both 15N and 18O within the OMZ, presumably due to the preferential reduction of lighter N2O to N2. However, isotopically light N2O is observed to accumulate in high concentrations above the OMZ indicating that the N2O emitted to the atmosphere from this region cannot be very heavy. The isotope data from the intense upwelling zone off the southwest coast of India, where some of the highest concentrations of N2O ever found at the sea surface are observed, show moderate depletion of 15N, but slight enrichment of 18O relative to air. These results suggest that the ocean-atmosphere exchange cannot counter inputs of heavier isotopes (particularly 18O) associated with the stratospheric back flux, as proposed by previous workers. This calls for additional sources and/or sinks of N2O in the atmosphere. Also, the N2O isotope data cannot be explained by production through either nitrification or denitrification, suggesting a possible coupling between the two processes as an important mechanism of N2O production