Mineralogy, geochemistry, isotopic ratios and foraminifer occurrence in ODP Hole 183-1139A

Mixed terrigenous-pelagic sediments from the Oligocene-lower Miocene interval of Hole 1139A accumulated on the flank of an eroded alkalic volcano, Skiff Bank. In this study, I explore relationships among sediment fluxes, especially of organic carbon and the clay mineral by-products of silicate weathering, and lithologic, tectonic, climatic, and biologic forcing factors. Benthic foraminifers indicate that Skiff Bank had subsided to lower bathyal depths (1000-2000 m) by the Oligocene. Two prominent maxima in noncarbonate concentration at 28 and 22 Ma correspond to peaks in the terrigenous flux; also, high noncarbonate concentrations are associated with larger grain sizes (silt) and higher opal concentrations. These and higher-frequency variations of noncarbonate concentration were probably controlled by glacioeustatic/climatic changes, with higher noncarbonate concentrations caused by increased erosion during glacial lowstands. Around 27 Ma, benthic foraminiferal d18O values decreased 0.7 per mil as the noncarbonate concentration decreased after the 28-Ma maximum. A paucity of clay-sized sediment and clay minerals suggests that physical erosion, by waves and/or ice, predominated under weathering-limited conditions. Low organic carbon concentrations (~0.13 wt%) also suggest a harsh environment and/or poor preservation in coarse (>2 µm) sediments that were extensively bioturbated below the oxygen minimum zone.

Carbon and nitrogen content of marine pore waters

We have developed sampling methods and an analytical system to determine the concentration of dissolved organic C (DOC) in marine pore waters. Our analytical approach is a modification of recently developed high-temperature, Pt-catalyzed oxidation methods; it uses Chromatographic trapping of the DOC-derived CO2 followed by reduction to CH4 and flame ionization detection. Sampling experiments with nearshore sediments indicate that pore-water separation by whole-core squeezing causes artificially elevated DOC concentrations, while pore-water recovery by sectioning and centrifugation does not appear to introduce DOC artifacts. Results from a set of northwestern Atlantic continental slope cores suggest that net DOC production accounts for >50% of the organic C that is recycled at the sediment-water interface.

(Table 1) Boron concentration and d11B ratios of ODP Hole 130-803D

The pH of the surface ocean is a sensitive function of its alkalinity and total inorganic carbon concentration, properties which also control the partial pressure of atmospheric carbon dioxide (Broecker and Peng, 1982). Thus, an accurate proxy for past ocean pH could yield information about variations in atmospheric CO2. Recently, it has been suggested that the boron isotopic composition of foraminiferal tests depends on the pH of sea water as well as its isotopic composition (Vengosh et al., 1991, doi:10.1016/0016-7037(91)90139-V; Hemming and Hanson, 1992, doi:10.1016/0016-7037(92)90151-8). Here we present boron isotope and elemental data for sedimentary pore fluids and isotope data for bulk foraminiferal samples from a deep-sea sediment core. The composition of the pore waters implies that sea water boron concentrations and isotopic composition have been constant during the past 21 Myr, allowing us to reconstruct past ocean pH directly from the foraminiferal isotope data. We find that 21 Myr ago, surface ocean pH was only 7.4 ±0.2, but it then increased to 8.2 ±0.2 (roughly the present value) about 7.5 Myr ago. This is consistent with suggestions (Popp et al., 1989; Cerling, 1991; Arthur et al., 1991) that atmospheric CO2 concentrations may have been much higher 21 Myr ago than today.

Major and trace element concentration of melt inclusions from Zhupanovsky volcano, Kamchatka

The paper presents data on naturally quenched melt inclusions in olivine (Fo 69-84) from Late Pleistocene pyroclastic rocks of Zhupanovsky volcano in the frontal zone of the Eastern Volcanic Belt of Kamchatka. The composition of the melt inclusions provides insight into the latest crystallization stages (~70% crystallization) of the parental melt (~46.4 wt % SiO2, ~2.5 wt % H2O, ~0.3 wt % S), which proceeded at decompression and started at a depth of approximately 10 km from the surface. The crystallization temperature was estimated at 1100 ± 20°C at an oxygen fugacity of deltaFMQ = 0.9-1.7. The melts evolved due to the simultaneous crystallization of olivine, plagioclase, pyroxene, chromite, and magnetite (Ol: Pl: Cpx : (Crt-Mt) ~ 13 : 54 : 24 : 4) along the tholeiite evolutionary trend and became progressively enriched in FeO, SiO2, Na2O, and K2O and depleted in MgO, CaO, and Al2O3. Melt crystallization was associated with the segregation of fluid rich in S-bearing compounds and, to a lesser extent, in H2O and Cl. The primary melt of Zhupanovsky volcano (whose composition was estimated from data on the most primitive melt inclusions) had a composition of low-Si (~45 wt % SiO2) picrobasalt (~14 wt % MgO), as is typical of parental melts in Kamchatka and other island arcs, and was different from MORB. This primary melt could be derived by ~8% melting of mantle peridotite of composition close to the MORB source, under pressures of 1.5 ± 0.2 GPa and temperatures 20-30°C lower than the solidus temperature of 'dry' peridotite (1230-1240°C). Melting was induced by the interaction of the hot peridotite with a hydrous component that was brought to the mantle from the subducted slab and was also responsible for the enrichment of the Zhupanovsky magmas in LREE, LILE, B, Cl, Th, U, and Pb. The hydrous component in the magma source of Zhupanovsky volcano was produced by the partial slab melting under water-saturated conditions at temperatures of 760-810°C and pressures of ~3.5 GPa. As the depth of the subducted slab beneath Kamchatkan volcanoes varies from 100 to 125 km, the composition of the hydrous component drastically changes from relatively low-temperature H2O-rich fluid to higher temperature H2O-bearing melt. The geothermal gradient at the surface of the slab within the depth range of 100-125 km beneath Kamchatka was estimated at 4°C/km.

Biogeochemistry of the Eastern Weddell Gyre

The Southern Ocean (SO) plays a key role in modulating atmospheric CO2 via physical and biological processes. However, over much of the SO, biological activity is iron-limited. New in situ data from the Antarctic zone south of Africa in a region centered at -20°E - 25°E reveal a previously overlooked region of high primary production, comparable in size to the northwest African upwelling region. Here, sea ice together with enclosed icebergs is channeled by prevailing winds to the eastern boundary of the Weddell Gyre, where a sharp transition to warmer waters causes melting. This cumulative melting provides a steady source of iron, fuelling an intense phytoplankton bloom that is not fully captured by monthly satellite production estimates. These findings imply that future changes in sea-ice cover and dynamics could have a significant effect on carbon sequestration in the SO.

Characterization of carbon molecular sieves using methane and carbon dioxide as adsorptive probes

Nitrogen adsorption at 77 K is the current standard means for pore size determination of adsorbent materials. However, nitrogen adsorption reaches limitations when dealing with materials such as molecular sieving carbon with a high degree of ultramicroporosity. In this investigation, methane and carbon dioxide adsorption is explored as a possible alternative to the standard nitrogen probe. Methane and carbon dioxide adsorption equilibria and kinetics are measured in a commercially derived carbon molecular sieve over a range of temperatures. The pore size distribution is determined from the adsorption equilibrium, and the kinetics of adsorption is shown to be Fickian for carbon dioxide and non-Fickian for methane. The non-Fickian response is attributed to transport resistance at the pore mouth experienced by the methane molecules but not by the carbon dioxide molecules. Additionally, the change in the rate of adsorption with loading is characterized by the Darken relation in the case of carbon dioxide diffusion but is greater than that predicted by the Darken relation for methane transport. Furthermore, the proposition of inkbottle-shaped micropores in molecular sieving carbon is supported by the determination of the activation energy for the transport of methane and subsequent sizing of the pore-mouth barrier by molecular potential calculations.

Electronic nose evaluation of onion headspace volatiles and bulb quality as affected by nitrogen, sulphur and soil type

Edaphic factors affect the quality of onions (Allium cepa). Two experiments were carried out in the field and glasshouse to investigate the effects of N (field: 0, 120 kg ha(-1); glasshouse: 0, 108 kg ha(-1)), S (field: 0, 20 kg ha(-1); glasshouse: 0, 4.35 kg ha(-1)) and soil type (clay, sandy loam) on onion quality. A conducting polymer sensor electronic nose (E-nose) was used to classify onion headspace volatiles. Relative changes in the E-nose sensor resistance ratio (%dR/R) were reduced following N and S fertilisation. A 2D Principal Component Analysis (PCA) of the E-nose data sets accounted for c. 100% of the variations in onion headspace volatiles in both experiments. For the field experiment, E-nose data set clusters for headspace volatiles for no N-added onions overlapped (D-2 = 1.0) irrespective of S treatment. Headspace volatiles of N-fertilised onions for the glasshouse sandy loam also overlapped (D-2 = 1.1) irrespective of S treatment as compared with distinct separations among clusters for the clay soil. N fertilisation significantly (P < 0.01) reduced onion bulb pyruvic acid concentration (flavour) in both experiments. S fertilisation increased pyruvic acid concentration significantly (P < 0.01) in the glasshouse experiment, especially for the clay soil, but had no effect on pyruvic acid concentration in the field. N and S fertilisation significantly (P < 0.01) increased lachrymatory potency (pungency), but reduced total soluble solids (TSS) content in the field experiment. In the glasshouse experiment, N and S had no effect on TSS. TSS content was increased on the clay by 1.2-fold as compared with the sandy loam. Onion tissue N:water-soluble SO42- ratios of between five and eight were associated with greater %dR/R and pyruvic acid concentration values. N did not affect inner bulb tissue microbial load. In contrast, S fertilisation reduced inner bulb tissue microbial load by 80% in the field experiment and between 27% (sandy loam) and 92% (clay) in the glasshouse experiment. Overall, onion bulb quality discriminated by the E-nose responded to N, S and soil type treatments, and reflected their interactions. However, the conventional analytical and sensory measures of onion quality did not correlate with %dR/R.

Effects of phosphorus on the growth and nitrogen fixation rates of Lyngbya majuscula: implications for management in Moreton Bay, Queensland

Significant acetylene reduction and therefore N-2 fixation was observed for Lyngbya majuscula only during dark periods, which suggests that oxygenic photosynthesis and N-2 fixation are incompatible processes for this species. Results from a series of batch and continuous-flow-culture reactor studies showed that the specific growth rate and N-2 fixation rate of L, majuscula increased with phosphate (P-PO4) concentration up to a maximum value and thereafter remained constant. The P-PO4 concentrations corresponding to the maximum N-2 fixation and maximum growth rates were -0.27 and -0.18 muM respectively and these values are denoted as the saturation values for N-2 fixation and growth respectively. Regular monitoring studies in Moreton Bay, Queensland, show that concentrations Of P-PO4 generally exceed these saturation values over a large portion of the Bay and therefore, the growth of the bloom-forming L, majuscula is potentially maximised throughout much of the Bay by the elevated P-PO4 concentrations. Results from other studies suggest that the elevated P-PO4 concentrations in the Bay can be largely attributed to discharges from waste-water treatment plants (WWTPs), and thus it is proposed that the control of the growth of L. majuscula in Moreton Bay will require a significant reduction in the P load from the WWTP discharges. If the current strategy of N load reduction for these discharges is maintained in the absence of substantial P load reduction, it is hypothesised that the growth of L, majuscula and other diazotrophs in Moreton Bay will increase in the future.

Multicomponent adsorption on activated carbons under supercritical conditions

Adsorption of binary mixtures onto activated carbon Norit R1 for the system nitrogen-methane-carbon dioxide was investigated over the pressure range up to 15 MPa. A new model is proposed to describe the experimental data. It is based on the assumption that an activated carbon can be characterized by the distribution function of elements of adsorption volume (EAV) over the solid-fluid potential. This function may be evaluated from pure component isotherms using the equality of the chemical potentials in the adsorbed phase and in the bulk phase for each EAV. In the case of mixture adsorption a simple combining rule is proposed, which allows determining the adsorbed phase density and its composition in the EAV at given pressure and compositions of the bulk phase. The adsorbed concentration of each adsorbate is the integral of its density over the set of EAV. The comparison with experimental data on binary mixtures has shown that the approach works reasonably well. In the case of high-pressure binary mixture adsorption, when only total amount adsorbed was measured, the proposed model allows reliably determining partial amounts of the adsorbed components. (C) 2004 Elsevier Inc. All rights reserved.

Adsorption of quadrupolar, diatomic nitrogen onto graphitized thermal carbon black and in slit-shaped carbon pores. Effects of surface mediation

In this paper, we study the effect of solid surface mediation on the intermolecular potential energy of nitrogen, and its impact on the adsorption of nitrogen on a graphitized carbon black surface and in carbon slit-shaped pores. This effect arises from the lower effective interaction potential energy between two particles close to the surface compared to the potential energy of the same two particles when they are far away from the surface. A simple equation is proposed to calculate the reduction factor and this is used in the Grand Canonical Monte Carlo (GCMC) simulation of nitrogen adsorption on graphitized thermal carbon black. With this modification, the GCMC simulation results agree extremely well with the experimental data over a wide range of pressure; the simulation results with the original potential energy (i.e. no surface mediation) give rise to a shoulder in the neighbourhood of monolayer coverage and a significant over-prediction of the second and higher layer coverages. The influence of this surface mediation on the dependence of the pore-filling pressure on the pore width is also studied. It is shown that such surface mediation has a significant effect on the pore-filling pressure. This implies that the use of the local isotherms obtained from the potential model without surface mediation could give rise to a serious error in the determination of the pore-size distribution.

Effects of surface heterogeneity on the adsorption of nitrogen on graphitized thermal carbon black

In this paper, we study the surface heterogeneity and the surface mediation on the intermolecular potential energy for nitrogen adsorption on graphitized thermal carbon black (GTCB). The surface heterogeneity is modeled as the random distribution of effective carbonyl functional groups on the graphite surface. The molecular parameters and the discrete charges of this carbonyl group are taken from Jorgensen, et al. (J. Am. Chem. Soc., (1984) 106, 6638) while those for nitrogen (dispersive parameters and discrete charges) are taken from Murthy et al. (Mol. Phys., (1983) 50, 531) in our Grand Canonical Monte Carlo (GCMC) simulation. The solid surface mediation in the reduction of intermolecular potential energy between two fluid molecules was taken from a recent work by Do et al. (Langmuir, (2004) 20, 7623). Our simulation results accounting for the surface heterogeneity and surface mediation on intermolecular potential energy were compared with the experimental data of nitrogen at 77 and 90 K. The solid-fluid dispersive parameters are determined from the Lorentz-Berthelot (LB) rule. The fraction of the graphite surface covered with carbonyl functional groups was then derived from the consideration of the Henry constant, and for the data of Kruk et al. (Langmuir, (1999) 15, 1435) we have found that 1% of their GTCB surface is covered with effective carbonyl functional groups. The damping constant, due to surface mediation, was determined from the consideration of the portion of the adsorption isotherm where the first layer is being completed, and it was found to take a value of 0.0075. With these parameters, we have found that the GCMC simulation results describe the data over the complete range of pressure substantially better than any other MC models in the literature. The implication of this work is demonstrated with local adsorption isotherms of 10 and 20 A slit pores. One was obtained without allowance for surface mediation, while the other correctly accounts for these factors. The two local isotherms differ substantially, and the implication is that if we used incorrect local isotherms (i.e. without the surface mediation) the pore size distribution would be incorrectly derived.

Piggery pond sludge as a nitrogen source for crops - 2. Assay of wet and stockpiled piggery pond sludge by successive cereal crops or direct measurement of soil available N

The appropriate use of wastes is a significant issue for the pig industry due to increasing pressure from regulatory authorities to protect the environment from pollution. Nitrogen contained in piggery pond sludge ( PPS) is a potential source of supplementary nutrient for crop production. Nitrogen contribution following the application of PPS to soil was obtained from 2 field experiments on the Darling Downs in southern Queensland on contrasting soil types, a cracking clay ( Vertosol) and a hardsetting sandy loam (Sodosol), and related to potentially mineralisable N from laboratory incubations conducted under controlled conditions and NO3- accumulation in the field. Piggery pond sludge was applied as-collected ( wet PPS) and following stockpiling to dry ( stockpiled PPS). Soil NO3- levels increased with increased application rates of wet and stockpiled PPS. Supplementary N supply from PPS estimated by fertiliser equivalence was generally unsatisfactory due to poor precision with this method, and also due to a high level of NO3- in the clay soil before the first assay crop. Also low recoveries of N by subsequent sorghum ( Sorghum bicolor) and wheat ( Triticum aestivum) assay crops at the 2 sites due to low in-crop rainfall in 1999 resulted in low apparent N availability. Over all, 29% ( range 12 - 47%) of total N from the wet PPS and 19% ( range 0 - 50%) from the stockpiled PPS were estimated to be plant-available N during the assay period. The high concentration of NO3- for the wet PPS application on sandy soil after the first assay crop ( 1998 barley, Hordeum vulgare) suggests that leaching of NO3- could be of concern when high rates of wet PPS are applied before infrequent periods of high precipitation, due primarily to the mineral N contained in wet PPS. Low yields, grain protein concentrations, and crop N uptake of the sorghum crop following the barley crop grown on the clay soil demonstrated a low residual value of N applied in PPS. NO3- in the sandy soil before sowing accounted for 79% of the variation in plant N uptake and was a better index than anaerobically mineralisable N ( 19% of variation explained). In clay soil, better prediction of crop N uptake was obtained when both anaerobically mineralisable N (39% of variation explained) and soil pro. le NO3- were used in combination (R-2 = 0.49).

Effect of nitrogen supply on leaf appearance, leaf growth, leaf nitrogen economy and photosynthetic capacity in maize (Zea mays L.)

Leaf area growth and nitrogen concentration per unit leaf area, N-a (g m(-2) N) are two options plants can use to adapt to nitrogen limitation. Previous work indicated that potato (Solanum tuberosum L.) adapts the size of leaves to maintain Na and photosynthetic capacity per unit leaf area. This paper reports on the effect of N limitation on leaf area production and photosynthetic capacity in maize, a C4 cereal. Maize was grown in two experiments in pots in glasshouses with three (0.84-6.0 g N pot(-1)) and five rates (0.5-6.0 g pot(-1)) of N. Leaf tip and ligule appearance were monitored and final individual leaf area was determined. Changes with leaf age in leaf area, leaf N content and light-saturated photosynthetic capacity, P a,, were measured on two leaves per plant in each experiment. The final area of the largest leaf and total plant leaf area differed by 16 and 29% from the lowest to highest N supply, but leaf appearance rate and the duration of leaf expansion were unaffected. The N concentration of expanding leaves (N-a or %N in dry matter) differed by at least a factor 2 from the lowest to highest N supply. A hyperbolic function described the relation between P-max and N-a. The results confirm the 'maize strategy': leaf N content, photosynthetic capacity, and ultimately radiation use efficiency is more sensitive to nitrogen limitation than are leaf area expansion and light interception. The generality of the findings is discussed and it is suggested that at canopy level species showing the 'potato strategy' can be recognized from little effect of nitrogen supply on radiation use efficiency, while the reverse is true for species showing the 'maize strategy' for adaptation to N limitation. (c) 2004 Elsevier B.V. All rights reserved.