Effects of nutrients and turbulence on the production of transparent exopolymer particles: a mesocosm study

The production of transparent exopolymer particles (TEP) in response to several environmental variables was studied in 2 mesocosm experiments. The first (Expt 1) examined a gradient of 4 nutrient levels; the second (Expt 2) examined different conditions of silicate availability and zooplankton presence. Tanks were separated in 2 series, one subjected to turbulence and the other not influenced by turbulence. In tanks with nutrient addition, TEP were rapidly formed, with net apparent production rates closely linked to chl a growth rates, suggesting that phytoplankton cells were actively exuding TEP precursors. High nutrient availability increased the absolute concentration of TEP; however, the relative quantity of TEP produced was found to be lower, as TEP concentration per unit of phytoplankton biomass was inversely related to the initial nitrate dose. In Expt 1, an increase in TEP volume (3 to 48 µm equivalent spherical diameter) with nutrient dose was observed; in Expt 2, both silicate addition and turbulence enhanced TEP production and favored aggregation to larger TEP (>48 µm). The presence of zooplankton lowered TEP concentration and changed the size distribution of TEP, presumably by grazing on TEP or phytoplankton. For lower nutrient concentrations, the ratio of particulate organic carbon (POC) to particulate organic nitrogen (PON) followed the Redfield ratio. At higher nutrient conditions, when nutrients were exhausted during the post-bloom, a decoupling of carbon and nitrogen dynamics occurred and was correlated to TEP formation, with a large flow of carbon channeled toward the TEP pool in turbulent tanks. TEP accounted for an increase in POC concentration of 50% in high-nutrient and turbulent conditions. The study of TEP dynamics is crucial to understanding the biogeochemical response of the aquatic system to forcing variables such as nutrient availability and turbulence intensity.

Transcutaneous carbon dioxide pressure for monitoring patients with severe croup.

In a prospective investigation of 17 children with severe croup, we analyzed the effect of epinephrine inhalations and mild sedation with chloral hydrate on transcutaneous carbon dioxide pressure (tcPCO2), pulse oximetry measurements, and croup scores. There was a highly significant reduction (p less than 0.001) in the tcPCO2 values and croup scores after inhalation of epinephrine. The changes in the tcPCO2 values correlated with the clinical findings. Mild sedation also significantly improved the croup scores but failed to influence the tcPCO2 values. There was not statistically significant difference in pulse oximetry saturation, fraction of administered oxygen, heart rate, or respiratory rate before and after inhalation of epinephrine or chloral hydrate administration. Monitoring tcPCO2 appears to be a reliable and objective tool for managing patients with upper airway obstruction, whereas croup scores may be misleading.

Migration of dissolved organic carbon in biochars and biochar-mineral complexes

The objective of this work was to determine the contribution of dissolved organic carbon (DOC) from a biochar mineral complex (BMC), so as to better understand the interactions between DOC, biochar, clay, and minerals during thermal treatment, and the effects of BMC on amended soils. The BMC was prepared by heating a mixture of a H3PO4-treated saligna biochar from Acacia saligna, clays, other minerals, and chicken manure. The BMC was applied to a sandy loam soil in Western Australia, where wheat was grown. Liquid chromatography-organic carbon detection (LC-OCD) tests were carried out on water extracts from the untreated biochar, the BMC, the BMC-amended soil, and on a control soil to measure the DOC concentration. LC-OCD tests provide a fingerprint of the DOC, which allows the fractions of DOC to be determined. Thermal processing enhanced the reaction of the A. saligna biochar with manure, clays and minerals, and affected the distribution of the DOC fractions. Notably, the process leads to immobilization of hydrophobic DOC and to an increase in the concentration of low-molecular-weight neutrals in the BMC. The application of the BMC to soil increases the DOC in the amended soil, especially the biopolymer fraction.

Carbon-isotope stratigraphy and ammonite faunal turnover for the Middle Jurassic in the Southern Iberian palaeomargin

Variations in the stable carbon-isotope ratio of marine and continental sediments can reflect changes in sink and flux modifications of the palaeocarbon cycle. Here we report carbon-isotope compositions of Middle Jurassic marine carbonates from the Betic Cordillera (southern Spain), which represents an ideal region to link the stable carbon-isotope curves directly to ammonite zones and subzones, and thereby for the first time achieve an accurate chronostratigraphic calibration. The five sections studied represent basin and high swell deposits of the Southern Iberian palaeomargin. We find a similar delta C-13 of carbonates between different oceanic areas, suggesting a homogeneous carbon-isotope oceanic reservoir through the Middle Jurassic. The Aalenian-Bajocian transition is a critical period in ammonite evolution; hence the Early Jurassic fauna are replaced by new ammonite families which become dominant throughout the Middle and Late Jurassic. For this reason, we compared the delta C-13 values of carbonates with ammonite diversity and extinction rates at different taxonomical levels in order to explore the possible relationship between the carbon cycle and ammonite evolution. The carbon-isotope values of carbonates are not exactly linearly correlated with the extinction rate and ammonite diversity, but the main faunal turnovers follow minimum delta C-13 values, where extinct taxa are replaced by new ones. Likewise, radiation episodes are associated with increasing delta C-13 values and with transgressive sea-level rise. All these data support the idea that perturbations in the global carbon cycle reflect rapid palaeoenvironmental changes. We made detailed analyses of these faunal turnovers, using them as a proxy to identify major palaeoenvironmental crises in their ecosystems forced by modification in the carbon cycle. (c) 2006 Elsevier B.V All rights reserved.

Tracing of the Rhône River, wastewater, and mixing within Lake Geneva : stable isotope compositions of water and dissolved inorganic carbon

This study presents an evaluation of the stable isotopic composition of water (hydrogen and oxygen) and dissolved inorganic carbon (DIC) of Lake Geneva, a deep, peri-alpine lake situated at the border between Switzerland and France. The research goal is to apply vertical and seasonal variations of the isotope compositions to evaluate mixing processes of pollutants, nutrients and oxygen. Depth profiles were sampled at different locations throughout Lake Geneva on a monthly and seasonal basis over the course of three years (2009-2011). The results of the oxygen isotopic composition indicate a Rhône River interflow, which can be traced for about 55 km throughout the lake during summer. The Rhône River interflow is 7 to 15 m thick and the molar fraction of Rhône water is estimated to amount up to 37 %. Calculated density of the water and measured isotopic compositions demonstrate that the interflow depth changes in conjunction with the density gradient in the water column during fall. Partial pressure of CO2 indicates that the epilimnion is taking up CO2 from the atmosphere between spring and fall. The epilimnion is most enriched in 13CDIC in September and a progressive depletion of 13CDIC can be observed in the metalimnion from spring to late fall. This stratification is dependent on the local density stratification and the results demonstrate that parameters, which are indicating photosynthesis, are not necessarily linked to δ13CDIC values. In addition, the amount of primary production shows a strong discrepancy between summer 2009 and 2010, but δ13CDIC values of the epilimnion and metalimnion do not indicate variations. In the hypolimnion of the deep lake δ13CDIC values are constant and the progressive depletion allows tracing remineralization processes. The combination of stable carbon and oxygen isotopic compositions allows furthermore tracing Rhône River water fractions, as well as wastewater, stormwater and anthropogenic induced carbon in the water column of the shallow Bay of Vidy. In combination with the results of measured micropollutants, the study underlines that concentrations of certain substances may be related to the Rhône River interflow and/or remineralization of particulate organic carbon. Water quality monitoring and research should therefore be extended to the metalimnion as well as sediment water interface.

Carbon isotope fractionation for cotton genotype selection

The objective of this work was to evaluate the carbon isotope fractionation as a phenomic facility for cotton selection in contrasting environments and to assess its relationship with yield components. The experiments were carried out in a randomized block design, with four replicates, in the municipalities of Santa Helena de Goiás (SHGO) and Montividiu (MONT), in the state of Goiás, Brazil. The analysis of carbon isotope discrimination (Δ) was performed in 15 breeding lines and three cultivars. Subsequently, the root growth kinetic and root system architecture from the selected genotypes were determined. In both locations, Δ analyses were suitable to discriminate cotton genotypes. There was a positive correlation between Δ and seed-cotton yield in SHGO, where water deficit was more severe. In this site, the negative correlations found between Δ and fiber percentage indicate an integrative effect of gas exchange on Δ and its association with yield components. As for root robustness and growth kinetic, the GO 05 809 genotype performance contributes to sustain the highest values of Δ found in MONT, where edaphoclimatic conditions were more suitable for cotton. The use of Δ analysis as a phenomic facility can help to select cotton genotypes, in order to obtain plants with higher efficiency for gas exchange and water use.

Kinetics of selective oxidation of lactose to lactobionic acid over Pd-active carbon catalyst

Laktoosi eli maitosokeri on tärkein ainesosa useimpien nisäkkäiden tuottamassa maidossa. Sitä erotetaan herasta, juustosta ja maidosta. Laktoosia käytetään elintarvike- ja lääketeollisuuden raaka-aineena monissaeri tuotteissa. Lääketeollisuudessa laktoosia käytetään esimerkiksi tablettien täyteaineena. Hapettamalla laktoosia voidaan valmistaa laktobionihappoa, 2-keto-laktobionihappoa ja laktuloosia. Laktobionihappoa käytetään biohajoavien pintojen ja kosmetiikkatuotteiden valmistuksessa, sekä sisäelinten säilöntäliuoksissa, joissa laktobionihappo estää happiradikaalien aiheuttamien kudosvaurioiden syntymistä. Tässä työssä laktoosia hapetettiin laktobionihapoksi sekoittimella varustetussa laboratoriomittakaavaisessa panosreaktorissa käyttäenkatalyyttinä palladiumia aktiivihiilellä. Muutamissa kokeissa katalyytin promoottorina käytettiin vismuttia, joka hidastaa katalyytin deaktivoitumista. Työn tarkoituksena oli saada lisää tietoa laktoosin hapettamisen kinetiikasta. Laktoosin hapettumisessa laktobionihapoksi havaittiin selektiivisyyteen vaikuttavan muunmuassa reaktiolämpötila, paine, pH ja käytetyn katalyytin määrä. Katalyyttiä kierrättämällä eri kokeiden välillä saatiin paremmat konversiot, selektiivisyydet ja saannot. Parhaat koetulokset saatiin hapetettaessa synteettisellä ilmalla 60 oC lämpötilassa ja 1 bar paineessa. Tehdyissä kokeissa pH:n säätö tehtiin manuaalisesti, joten pH ei pysynyt koko ajan haluttuna. Laktoosin konversio oli parhaimmillaan 95 %. Laktobionihapon suhteellinen selektiivisyys oli 100% ja suhteellinen saanto 100 %. Kinetiikan matemaattinen mallinnus tehtiin Modest-ohjelmalla käyttäen kokeista saatuja mittaustuloksia.Ohjelman avulla estimoitiin parametreja ja saatiin matemaattinen malli reaktorille. Tässä työssä tehtiin kineettinen mallinnus myös ravistelureaktorissa tehdyille laktoosin hapetuskokeille, missä pH pysyi koko ajan haluttuna 'in-situ' titrauksen avulla. Työn yhteydessä selvitettiin myös mahdollisuutta käyttää monoliittikatalyyttejä laktoosin hapetusreaktiossa.

Carbon-isotope stratigraphy of the Liesberg Beds Member (Oxfordian, Swiss Jura) using echinoids and crinoids

The Liesberg Beds form the transition between the lower Oxfordian dark coloured marls (Renggeri Member and the Terrain a Chailles Member) and the middle Oxfordian reefal limestones (St-Ursanne Formation). Both lithofacies and biofacies are diverse and evolve rapidly up-section. Stable isotope studies of whole-rock samples are therefore excluded. In search for a convenient isotopic marker, we measured carbon isotope compositions of several fossil groups and chose crinoid stems of Millericrinus spp and echinoid spines of Paracidaris spp because of their abundance throughout the section and the small variations of delta(13)C within one fossil and between fossils from the same stratigraphic level. The delta(13)C values of echinoderms largely reflect earliest diagenetic conditions at the seawatersediment interface. The porous stereome structure secreted of high Mg-calcite by echinoderms has a high reactive surface/volume ratio, which triggers the precipitation of very early syntaxial cements. In the four studied sections reproducible carbon isotope shifts were observed both for Millericrinus spp stems and Paracidaris spp spines. A negative delta(13)C shift of 1-1.5 parts per thousand was observed near the base of the section, just above the transition from Terrain a Chailles Member, where the first corals occur. In the middle and upper part of the four sections, characterised by a stepwise increase of corals and the macrofossils, a positive delta(13)C Shift of about 2 parts per thousand was observed. Despite the highly variable lithologic composition of the Liesberg Beds;Member, carbon isotope shifts seem to be consistent and warrant an interpretation as an original signal, controlled by the isotopic composition of dissolved carbonic acid in seawater. We explain the heavy delta(13)C values (approximate to 2-2.3 parts per thousand) in the lower Liesberg Beds as a transition from an oxygen-limited environment (Terrain a Chailles Member) to the Liesberg Beds Member. The lowest delta(13)C values (approximate to 1-1.5 parts per thousand) correspond to a large input of dissolved nutrients to the platform under oxidizing conditions. The ensuing positive shift (between 2.5 and 3.5 parts per thousand), however, seems to correspond to a general trend of opening up of the platform and connection to open marine waters. Positive delta(13)C values in the upper Liesberg Beds is interpreted as a result of important accelareted extraction of organic carbon from the ocean reservoir, that occurred possibly during periods of warm and humid climate.

Carbon and nitrogen cycling in an integrated soybean-beef cattle production system under different grazing intensities

Abstract:The objective of this work was to evaluate the effect of grazing intensity on the decomposition of cover crop pasture, dung, and soybean residues, as well as the C and N release rates from these residues in a long-term integrated soybean-beef cattle system under no-tillage. The experiment was initiated in 2001, with soybean cultivated in summer and black oat + Italian ryegrass in winter. The treatments consisted of four sward heights (10, 20, 30, and 40 cm), plus an ungrazed area, as the control. In 2009-2011, residues from pasture, dung, and soybean stems and leaves were placed in nylon-mesh litter bags and allowed to decompose for up to 258 days. With increasing grazing intensity, residual dry matter of the pasture decreased and that of dung increased. Pasture and dung lignin concentrations and C release rates were lower with moderate grazing intensity. C and N release rates from soybean residues are not affected by grazing intensity. The moderate grazing intensity produces higher quality residues, both for pasture and dung. Total C and N release is influenced by the greater residual dry matter produced when pastures were either lightly grazed or ungrazed.

Graphitized carbon black in quartz tubes for the sampling of indoor air nicotine and analysis by microwave thermal desorption-capillary gas chromatography

Nicotine in a smoky indoor air environment can be determined using graphitized carbon black as a solid sorbent in quartz tubes. The temperature stability, high purity, and heat absorption characteristics of the sorbent, as well as the permeability of the quartz tubes to microwaves, enable the thermal desorption by means of microwaves after active sampling. Permeation and dynamic dilution procedures for the generation of nicotine in the vapor phase at low and high concentrations are used to evaluate the performances of the sampler. Tube preparation is described and the microwave desorption temperature is measured. Breakthrough volume is determined to allow sampling at 0.1-1 L/min for definite periods of time. The procedure is tested for the determination of gas and paticulate phase nicotine in sidestream smoke produced in an experimental chamber.