Nitrogen Reservoir Research Articles

Isotopically anomalous nitrogen in H-chondrite metal

The cause of the nitrogen isotopic anomalies observed by Hashizume and Sugiura (1995) among bulk equilibrated ordinary chondrites has been investigated. The bulk nitrogen isotopic anomalies can be explained by the isotopically anomalous nitrogen dissolved in taenite and/or tetra-taenite (γ/γ′ phase FeNi metal). Nitrogen concentrations in taenite range between 5 and 45 ppm, and in most of the samples within 10 ± 5 ppm. Nitrogen isotopic ratios trapped in taenite vary with samples in a range of −40 < δ 15 N < +120%o. No systematic correlation was observed between the amounts and the isotopic ratios. Another rather minor nitrogen reservoir seems to exist in nonmagnetic fractions, although the exact host phase has not yet been identified. The isotopic ratios of nitrogen trapped in nonmagnetic minerals generally do not coincide with those in taenite. We consider that the nitrogen dissolved in taenite was trapped there at the end of the thermal metamorphic event when the interior of the H-chondrite parent body was cooled down to 500°C, the closure temperature of nitrogen in γ-Fe,Ni. The concentration and isotopic ratios of nitrogen trapped in taenite reflect the nitrogen equilibrium system within the parent body at ⩾500°C. The nitrogen isotopic anomalies in taenite cannot be explained by an initially isotopically homogeneous nitrogen reservoir or by processes such as mass-dependent isotopic fractionation.

Partitioning of the reactive nitrogen reservoir in the lower stratosphere of the southern hemisphere: Observations and modeling

Measurements of nitric oxide (NO), nitrogen dioxide (NO2), and total reactive nitrogen (NOy = NO + NO2 + NO3 + HNO3 + ClONO2 + 2N2O5 + …) were made during austral fall, winter, and spring 1994 as part of the NASA Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft mission. Comparisons between measured NO2 values and those calculated using a steady state (SS) approximation are presented for flights at mid and high latitudes. The SS results agree with the measurements to within 8%, suggesting that the kinetic rate coefficients and calculated NO2 photolysis rate used in the SS approximation are reasonably accurate for conditions in the lower stratosphere. However, NO2 values observed in the Concorde exhaust plume were significantly less than SS values. Calculated NO2 photolysis rates showed good agreement with values inferred from solar flux measurements, indicating a strong self‐consistency in our understanding of UV radiation transmission in the lower stratosphere. Model comparisons using a full diurnal, photochemical steady state model also show good agreement with the NO and NO2 measurements, suggesting that the reactions affecting the partitioning of the NOy reservoir are well understood in the lower stratosphere.

Environmental degradation and rehabilitation of the landscape around Sudbury, a major mining and smelting area

A century of sulphur dioxide fumigation, copper and nickel particulate deposition, fire, soil erosion, and enhanced frost action has created 10 000 ha of barren land and 36 000 ha of stunted, open birch–maple woodland in the Sudbury area. The primary factor limiting plant colonization is the acidic and aluminum-, copper-, and nickel-toxic properties of the soils, although certain plant species survive the challenges through genetically based metal tolerance. In revegetation programs, the soil can be detoxified sufficiently to initiate colonization by the surface application of ground limestone. The drought vulnerability of seedlings, resulting from soil toxicity limiting root growth, is exacerbated by enhanced frost action resulting from the lack of leaf litter. Manual surface application of ground limestone, with or without an accompanying fertilizer and (or) grass–legume seed application, leads to immediate colonization by woody species including birch, aspen, and willows, and more than 3000 ha have been treated in this way by the Regional Municipality of Sudbury since 1978. Native coniferous species have also been planted in groups to form a seed source for future colonization. Most barren soils contain a substantial reservoir of phosphorus and nitrogen in the form of residual organic matter, but both rhizobial and actinorhizal species play an important role in dynamics, and the role of mycorrhizae is probably critical. The seed availability factor is rarely limiting; while the seed bank is small, in most sites the seed rain of light, wind-dispersed seeds is adequate to colonize soil detoxified by liming.Key words: Sudbury, pollution, revegetation, copper, nickel, toxicity.

Tissue-Specific Distribution of Glutamine Synthetase in Potato Tubers

Cytosolic isoforms of the enzyme glutamine synthetase (GS) located in the phloem have been implicated in the mobilization of nitrogen for intracellular transport in higher plants. The potato tuber represents an important reservoir of nitrogen and an approach was made to the characterization of GS in this organ, particularly at the stages of sprouting and of new tuber formation. By immunoblotting after SDS-PAGE, and by immunological tissue printing, it was possible to conclude that a cytosolic GS is present in tubers and sprouts, and that it is mainly expressed in the internal phloem, in a very precise tissue-specific pattern of distribution. These data provide additional clues to the interpretation of the functional role of GS in the mobilization of nitrogen and its utilization in growing parts of the plant. The importance of morphological data and localization studies in complementing molecular and biochemical work is emphasized. The proposed functional importance of the internal phloem in Solanum tuberosumorgans is also reinforced.

Interactions of wood decay fungi with other microorganisms, with emphasis on the degradation of cell walls

Interactions of two wood decay fungi, Lentinula edodes and Pleurotus ostreatus, with other wood inhabiting microorganisms were investigated on agar and in fagaceous wood, primarily by scanning electron microscopy. Micromorphologically, there were two principal modes of cell wall degradation: (i) selective removal of amorphous wall components, followed by the degradation of skeletal microfibrils, and (ii) simultaneous degradation of all wall components. These two modes were observed in three different degradation systems: (i) sapwood wall degradation by the wood decay fungi, (ii) hyphal wall degradation by mycoparasitic Trichoderma, and (iii) hyphal wall degradation by pathogenic bacteria. The simultaneous-type wall degradation in the systems i and ii was usually caused by hyphal tips. In addition to the three systems, bacteriolysis by the wood decay fungi was also studied. The bacterial cell walls, as well as microfibril bundles of wood cellulose and fungal chitin, were all fragmented into minute granules at later stages of microbial degradation and the granules were further degraded into smaller units. Frequency of occurrence and strength of mycoparasitic activity of Trichoderma harzianum were influenced by the degree of wood decay where the interaction occurred. Presence of both cellulose and chitin microfibrils apparently enhanced the mycoparasitic activity. In Quercus wood, P. ostreatus showed a unidirectional growth toward bacterial colonies, which formed as the result of decomposition of dead nematodes, and consumed the unidentified bacteria. In nitrogen-deficient wood, fungal and bacterial cell walls may serve as an important reservoir of nitrogen for wood inhabiting microorganisms. Key words: wood decay, mycoparasitism, bacteriolysis, cellulose, chitin.

Metabolism of [15N]Alanine in the Ectomycorrhizal Fungus Paxillus involutus

Chalot, M., Finlay, R. D., Ek, H., and Söderström, B. 1995. Metabolism of [15N]alanine in the ectomycorrhizal fungus Paxillus involutus. Experimental Mycology 19, 297-304. Alanine metabolism in the ectomycorrhizal fungus Paxillus involutus was investigated using [15N]alanine. Short-term exposure of mycelial discs to [15N]alanine showed that the greatest flow of 15N was to glutamate and to aspartate. Levels of enrichment were as high as 15-20% for glutamate and 13-18% for aspartate, whereas that of alanine reached 30%. Label was also detected in the amino-N of glutamine and in serine and glycine, although at lower levels. Preincubation of mycelia with aminooxyacetate, an inhibitor of transamination reactions. resulted in complete inhibition of the flow of the label to glutamate, aspartate, and amino-N of glutamine, whereas [15N]alanine rapidly accumulated. This evidence indicates the direct involvement of alanine aminotransferase for translocation of 15N from alanine to glutamate. Alanine may be a convenient reservoir of both nitrogen and carbon.

From stoichiometry to nitrogen in ilmenites

To determine if ilmenites are stoichiometric, the ratio of ferric to ferrous ions is measured by Mossbauer spectroscopy and the oxygen content by nuclear bombardment. This latter measurement implies also the determination of the nitrogen content, if any. It was surprisingly found that the five ilmenite crystals analyzed contain nitrogen from 0.51% to 2%. These exceed the values for most other minerals. Heating experiments suggest that the nitrogen is not located in fluid inclusions. These results suggest that ilmenite could be a major reservoir for nitrogen inside the earth.

The search for other planets: clues from the solar system.

Studies of element abundances and values of D/H in the atmospheres of the outer planets and Titan support a two-step model for the formation of these bodies. This model suggests that the dimensions of Uranus provide a good index for the sensitivity required to detect planets around other stars. The high proportion of N2 on the surfaces of Pluto and Triton indicates that this gas was the dominant reservoir of nitrogen in the early solar nebula. It should also be abundant on pristine comets. There is evidence that some of these comets may well have brought a large store of volatiles to the inner planets, while others were falling into the sun. In other systems, icy planetesimals falling into stars should reveal themselves through high values of D/H.

Nitrogen isotopic compositions of iron meteorites

Iron meteorites analyzed in this study have nitrogen concentrations ⪕-70 μg/g and δ 15 N from −90 to +150%.. Although the iron meteorites have a large range of δ 15 N, most have values more negative than −50%.. The nitrogen isotopic compositions were established by cosmochemical processes and were little modified by fractional crystallization or other chemical processes within the parent bodies. The data do not suggest the existence of a well-mixed solar nebular reservoir for nitrogen, as was already inferred from data from stony meteorites. The range of > 1100%. observed for δ 15 N in bulk meteorites is probably too large to be accounted for by physical and chemical mass-dependent fractionation processes in the solar nebula, and thus reflects nebular inhomogeneities of nucleosynthetic origin. Nitrogen isotopes may serve as fingerprints for different reservoirs, preserved in various parent bodies, in a manner similar to that observed for oxygen isotopes in stony meteorites, and oxygen-bearing phases of stony irons.

Biomass and production of heterotrophic bacterioplankton in the oceanic subarctic Pacific

As part of the Subarctic Pacific Ecosystem Research (SUPER) program, we measured the abundance and biomass production of heterotrophic bacterioplankton in the subarctic Pacific and compared these parameters with those of phytoplankton during four cruises in 1987 and 1988. Bacterial biomass was about equal to phytoplankton biomass during all cruises. Based on rates of bacterial biomass production and assuming a growth efficiency of 50%, we estimate that heterotrophic bacteria consumed 10% (June 1987) to 24% (August 1988) of primary production in the euphotic zone. These percentages are low compared with other aquatic ecosystems, apparently due to low bacterial growth rates (<0.1 day −1) iin the subarctic Pacific. In contrast, phytoplankton growth rates were much higher (0.1–8.8 day −1). Bacterial growth rates were limited by the supply of dissolved organic matter and temperature. Even with these low growth rates, however, bacterial biomass and rates of biomass production increased by 2–5-fold in May and August 1988, changes that were not obviously related to corresponding changes in phytoplankton biomass nor primary production. Heterotrophic bacterioplankton constitutes a large reservoir of carbon and nitrogen that needs to be considered in modelling ecosystem dynamics of the subarctic Pacific.

Measurements of jet aircraft emissions at cruise altitude I: The odd‐nitrogen gases NO, NO2, HNO2 and HNO3

Using a novel aircraft‐borne automatic mass spectrometer, the odd‐nitrogen gases NO, NO2, HNO2 and HNO3 were for the first time measured in a young exhaust‐trail of a jetliner at cruise‐altitude. The measurements, which took place at an altitude of 9.5 km and a distance of about 2 km from a DC‐9 jetliner, revealed NO and NO2 to be present with abundances as large as 780 and 150 ppbv, respectively. The acids HNO2 and HNO3 reached abundances of 0.52 and 0.46 ppbV, which implies that only about 0.05% of the emitted reactive nitrogen experienced rapid conversion to the stable odd nitrogen reservoir nitric acid. Hence, most of the emitted odd‐nitrogen remained in the reactive form NO and NO2, which affect ozone. Nitrous acid (HNO2) turns out to be an excellent tracer for young jet‐aircraft plumes since it is short‐lived and reaches only a very low atmospheric background abundance. The low HNO3‐emission implies that HNO3‐H2O nucleation and condensation in jet‐aircraft plumes is hardly favoured by the additional HNO3. However, it may still occur due to H2O emissions.

Clouds of ammonia ice: Laboratory measurements of the single-scattering properties

This work presents scattering measurements and photographs of ammonia ice crystals grown at temperatures from 130 to 180 K. The prime candidate for the material making up the visible clouds of Jupiter and Saturn is ammonia ice. Spacecraft observations of these planets have constrained the single-scattering properties of the cloud particles. To further investigate the nature of these particles, ammonia ice crystals were grown at temperatures occuring at the relevant levels of the atmospheres of Jupiter and Saturn. The experimental apparatus used to make these measurements has a glass-walled cylindrical chamber which permits measurement of the scattered light over a wide range of scattering angles and a temperature control system which uses a liquid nitrogen reservoir combined with heaters. The chamber is illuminated by a tungsten lamp through a rapidly spinning filter/polarizer wheel which yields measurements of intensity and linear polarization in each of three colors. A photographic record of the crystals is obtained with a microscope objective, and six linear array detectors measure the scattered light. Representative scattering measurements and photographs are presented, showing a variety of phase functions and crystal shapes. The data cannot be reproduced by theoretical calculations for ammonia clouds composed purely of cubic, tetrahedral, or octahedral crystals. The data appear similar to microwave analog measurements of the scattering by a mix of particles shapes and also by fluffy particles. The ammonia measurements fall into two groups: one has wavelength-dependent polarization and for size parameters up to about seven the scattering properties can be fit by Mie theory. The second group has wavelength-independent phase functions, implying size parameters of 10 to 50, and has a characteristic signature of polarization varying from - 10% to +10%. The data can be used to rule out some models for Jupiter's and Saturn's atmospheres and to guide future modeling efforts. For Jupiter, models with a cloud of ammonia crystals of size parameter equal to about 5 (in the red) are suggested. For Saturn, a model is suggested that has a thin layer of small ammonia crystals (in the Mie range) over a thicker ammonia cloud with the wavelength-independent polarization that is characteristic of larger crystals.

Low-temperature storage of bone marrow in nitrogen vapor-phase refrigerators: decreased temperature gradients with an aluminum racking system.

Large temperature gradients may exist in nitrogen vapor-phase refrigerators. Cryopreserved cells stored at higher levels may be considerably warmer than those stored closer to the liquid nitrogen reservoir. To decrease this temperature gradient, racking systems constructed of aluminum were placed in marrow storage refrigerators. The higher heat conductivity of aluminum resulted in a vapor-phase temperature gradient of only 5.9 degrees C at 22.5 inches above the liquid, as compared to the gradient of 86 degrees C seen with steel frames in a similar refrigerator. Temperature fluxes were minimal with lid opening or nitrogen filling. The thicker frame size and loss of the lowest storage level resulted in a storage capacity 63 percent of that achievable with steel frames and liquid immersion. Consumption of nitrogen was estimated to be 174 to 220 percent of the static usage in this model of refrigerator with 6 inches of nitrogen, but comparable to the consumption expected with full immersion of the racking system, regardless of frame construction. These data demonstrate the feasibility of achieving very low, stable, cryogenic temperatures in a vapor-phase refrigerator.

Photochemical partitioning of the reactive nitrogen and chlorine reservoirs in the high‐latitude stratosphere

Partitioning of the major components of the reactive nitrogen and inorganic chlorine reservoirs is derived from aircraft measurements in the lower stratosphere during the winter season in both hemispheres at latitudes of about 60° to 80°. The goal of this work is to exercise the power of the correlated set of measurements from polar missions of the NASA ER‐2 to extend what can be learned from looking at the measurements individually. The results provide a consistent method for comparing distributions, and hence the controlling processes, between different areas of the near‐polar regions. The analysis provides clear evidence of the effects of heterogeneous processes in the atmosphere. Values for NO2, ClONO2, N2O5, and Cl2O2 are derived in a simplified steady state model based on in situ NO, ClO, O3, temperature, and pressure measurements; laboratory‐measured reaction rates; and modeled photodissociation rates. Values for the reservoir totals are independently derived from measurements of N2O, organic chlorine, and total reactive nitrogen. The relative abundances of the measured and derived species within the reservoirs are calculated, and the longer‐lived species HCl and HNO3 are estimated as the residuals of their respective reservoirs. The resulting latitude distributions in the Arctic outside the vortex agree reasonably well with predictions of a two‐dimensional photochemical model, indicating that partitioning in this region is largely controlled by standard homogeneous gas phase chemistry. Inside the Arctic vortex a large fraction of the HCl has been converted to reactive chlorine species ClO and Cl2O2, consistent with the extensive action of known heterogeneous reactions, presumably occurring on the surfaces of polar stratospheric clouds formed in the cold temperatures of the vortex. The partitioning in the Antarctic suggests that nearly the entire range of latitudes sampled by the ER‐2 is affected by heterogeneous processes in situ, including that portion of the “collar” region equatorward of the nominal chemically perturbed region (CPR). Consideration of heterogeneous processing in the region outside the CPR is important in predicting the possible expansion of Antarctic ozone depletion and the transport of chemically perturbed air to lower latitudes.

Spring polar ozone behavior

It has been recognized since the commencement of Antarctic ozone measurements during the IGY that spring southern polar total ozone amount is less than spring northern polar total ozone amount. More importantly, since 1980 there has been a decline in the minimum spring total ozone value, from 250 DU in 1980 to 125 DU in 1987 and below 120 in 1991. This decline occurs within the winter polar vortex, which acts as a containment vessel preventing polar ozone from escaping to lower latitudes and excluding ozone-rich air from the polar region. Ozone decrease can be explained in terms of heterogeneous reactions of chlorine and nitrogen reservoir molecules on polar stratospheric clouds. These clouds form in the lower polar stratosphere during winter when temperatures in the Antarctic are sufficiently low to create water ice clouds. Clouds involving nitric acid form at higher temperatures. Chlorine reservoirs such as HCl are converted to Cl 2, which is photodissociated in the presence of sunlight. The resulting Cl reacts with O 3 to form ClO. Measurements of ClO and other species give agreement of theory and experiment within the uncertainties of the measurement. Heterogeneous chemistry accounts for most of the ozone hole. A small amount of ozone loss is also observed above the polar stratospheric cloud level, implying another mechanism, either chemical or dynamical. Above 25 km, formation of ozone-destroying odd nitrogen in the upper stratosphere by energetic electrons and the existence of any trend is still an open question. There is much less ozone depletion in the Arctic. This is the result of a less stable polar vortex and warmer temperatures, which reduce polar stratospheric cloud formation. There is strong evidence that tropospheric forcing within or just outside the vortex leads to adiabatic cooling with resulting cloud formation. During such events ozone-poor tropospheric air is transported into the stratosphere. In the Arctic this can result in the transport of long-lived hydrocarbons. Subsequent reactions lead to the formation of HCl, reducing the effect of Cl. There is also production of HO 2, which accelerates ozone loss due to chlorine. There are also small areas of large and rapid ozone depletion termed miniholes. Ozone-poor air from these regions can propagate to lower latitudes, as can the air from within the vortex, when it disintegrates in late spring. Data from the BUV ozone-measuring instrument on the Nimbus 4 satellite indicate the existence of October 1970 Antarctic ozone of only 250 DU. This is evidence of the existence of ozone loss with only CH 3Cl and low concentrations of CFCs as chlorine sources.

Sensitivity of stratospheric ozone to heterogeneous chemistry on sulfate aerosols

The effects of sulfate aerosols on stratospheric ozone have been studied with a 2D model. The model includes a comprehensive chemical code for homogeneous and heterogeneous reactions; both background and volcanic aerosols have been taken into account according to different scenarios. The basic temperature field is prescribed, while the perturbation introduced by the presence of volcanic aerosols is predicted. Increase of total chlorine in the stratosphere causes a well known ozone depletion by itself, but. the effects could be highly enhanced in presence of a large amount of volcanic aerosols that affect the balance of nitrogen and chlorine reservoirs through heterogeneous chemical reactions. For a volcanic eruption similar to El Chichon we show that the maximum O3 depletion (7% for a 2.5ppbv amount of stratospheric chlorine and 12% by doubling Cl) is to be expected at high latitudes in spring, because of a large chemical destruction acting in situ.

A Liquid Nitrogen Freeze-Branding Apparatus for Marking Fingerling Walleyes

Abstract Results of stocking fingerling walleyes (Stizostedion vitreum) were effectively evaluated with freeze branding, an inexpensive and dependable method of marking large numbers of fingerlings. The freeze brander evaluated consisted of brass nipples, bearing the character to be imprinted, connected directly to a reservoir of liquid nitrogen. The resulting brands were readily visible and persisted over several growing seasons.

High-resolution low-temperature scanning electron microscopy for observing intracellular structures of quick frozen biological specimens.

Intracellular structures of rapidly frozen biological tissues were observed in 3-D under a low-temperature scanning electron microscope using a newly developed side-entry type cryo-holder. The present low-temperature SEM is simple, easy to operate and effective for observing biological materials at high magnification. Biological tissues (the pancreas, small intestine, brown adipose tissue and Harderian gland) freshly removed from the mouse were immediately frozen in liquid propane cooled with liquid nitrogen, and their surfaces were manually fractured using a precooled razor blade in liquid nitrogen before introducing the cryo-holder into the SEM. When intracellular structures were revealed after appropriate sublimation, the specimens were coated with gold using a metal evaporator fitted to the side of the microscope column at one of the specimen chamber ports. The cryo-holder was connected to a copper braid coming from a liquid nitrogen reservoir to maintain a low temperature. Using this method, intracellular structures such as the mitochondria and endoplasmic reticulum were demonstrated at high magnifications. Ribosomal granules were discerned on the rough endoplasmic reticulum of the pancreatic acinar cells. Granular substances, presumably elementary particles, were also recognized on the mitochondrial cristae of the brown adipose tissue. The method was particularly effective for studying the 3-D configuration of lipid droplets which had been difficult to preserve by chemical fixation.

Intracellular structures of rapid frozen biological samples observed by high-resolution low-temperature Scanning Electron Microscopy

Low temperature scanning electron microscopy (LTSEM) is useful to avoid artifacts such as deformation and extraction, because specimens are not subjected to chemical fixation, dehydration and critical-point drying. Since Echlin et al developed a LTSEM, many techniques and instruments have been reported for observing frozen materials. However, intracellular structures such as mitochondria and endoplasmic reticulum have been unobservable by the method because of the low resolving power and inadequate specimen preparation methods. Recently, we developed a low temperature SEM that attained high resolutions. In this study, we introduce highly magnified images obtained by the newly developed LTSEM, especially intracellular structures which have been rapidly frozen without chemical fixation.[Specimen preparations] Mouse pancreas and brown adipose tissues (BAT) were used as materials. After the tissues were removed and cut into small pieces, the specimen was placed on a cryo-tip and rapidly frozen in liquid propane using a rapid freezing apparatus (Eiko Engineering Co. Ltd., Japan). After the tips were mounted on the specimen stage of a precooled cryo-holder, the surface of the specimen was manually fractured by a razor blade in liquid nitrogen. The cryo-holder was then inserted into the specimen chamber of the SEM (ISI DS-130), and specimens were observed at the accelerating voltages of 5-8 kV. At first the surface was slightly covered with frost, but intracellular structures were gradually revealed as the frost began to sublimate. Gold was then coated on the specimen surface while tilting the holder at 45-90°. The holder was connected to a liquid nitrogen reservoir by means of a copper braid to maintain low temperature.

Development of a Compact Electron Beam Ion Source Cooled with Liquid Nitrogen

A small-sized EBIS type ion source (mini-EBIS) for production of highly charged ions has been developed. The whole system, namely, the electron gun, ion drift tube, electron collector, ion extraction lens and liquid nitrogen reservoir containing solenoid coil is housed in a vacuum envelope, 150 mmφ in diameter and 500 mm in length. The idea of cooling the solenoid to 77 K has proved very effective to miniaturize the solenoid and its power supply. Moreover, the wall of the liquid nitrogen reservoir exhibits a cryogenic pumping function at the ionization region. In the DC ion extraction mode with an electron current of 15 mA at 2 keV, beam intensities obtained for C6+, N7+, O8+, Ne9+ and Ar16+ ions are at least 5×104, 3×104, 1×104, 5×103 and 3×103 counts per second, respectively.