Carbon sources in suspended particles and surface sediments from the Beaufort Sea revealed by molecular lipid biomarkers and compound-specific isotope analysis

27 pages, 12 figures, 13 tablesMolecular lipid biomarkers (hydrocarbons, alcohols, sterols and fatty acids) and compound-specific isotope analysis of suspended particulate organic matter (SPM) and surface sediments of the Mackenzie Shelf and slope (southeast Beaufort Sea, Arctic Ocean) were studied in summer 2009. The concentrations of the molecular lipid markers, characteristic of known organic matter sources, were grouped and used as proxies to evaluate the relative importance of fresh algal, detrital algal, fossil, C3 terrestrial plants, bacterial and zooplankton material in the organic matter (OM) of this area. Fossil and detrital algal contributions were the major fractions of the freshwater SPM from the Mackenzie River with ~34% each of the total molecular biomarkers. Fresh algal, C3 terrestrial, bacterial and zooplanktonic components represented much lower percentages, 17, 10, 4 and 80%), with a minor contribution of fossil and C3 terrestrial biomarkers. Characterization of the sediments revealed a major sink of refractory algal material mixed with some fresh algal material, fossil hydrocarbons and a small input of C3 terrestrial sources. In particular, the sediments from the shelf and at the mouth of the Amundsen Gulf presented the highest contribution of detrital algal material (60–75%), whereas those from the slope contained the highest proportion of fossil (40%) and C3 terrestrial plant material (10%). Overall, considering that the detrital algal material is marine derived, autochthonous sources contributed more than allochthonous sources to the OM lipid pool. Using the ratio of an allochthonous biomarker (normalized to total organic carbon, TOC) found in the sediments to those measured at the river mouth water, we estimated that the fraction of terrestrial material preserved in the sediments accounted for 30–40% of the total carbon in the inner shelf sediments, 17% in the outer shelf and Amundsen Gulf and up to 25% in the slope sediments. These estimates are low compared to other studies conducted 5–20 yr earlier, and they support the increase in primary production during the last decade mainly because of the increase in the number of ice-free days and due to the strength and persistence of winds favouring upwellingThe IAEA is grateful for the support provided to the Environment Laboratories by the Government of the Principality of Monaco. This study was conducted as part of the Malina Scientific Program funded by ANR (Agence nationale de la recherche), INSU-CNRS (Institut national des sciences de l’univers – Centre national de la recherche scientifique), CNES (Centre national d’etudes spatiales) and ESA (European Space Agency). The authors would like to thank M. Babin, chief scientist of the cruise and coordinator of the Malina program, A. Forest, H. Link and G. Chaillou and three anonymous reviewers for their constructive commentsPeer reviewe

On-line SPE LC-MS/MS for the quantification of Δ9-tetrahydrocannabinol (THC) and its two major metabolites in human peripheral blood by liquid chromatography tandem mass spectrometry

A universal and robust analytical method for the determination of Δ9-tetrahydrocannabinol (THC) and two of its metabolites Δ9-(11-OH)-tetrahydrocannabinol (11-OH-THC) and 11-nor-Δ9-carboxy-tetrahydrocannabinol (THC-COOH) in human whole blood was developed and validated for use in forensic toxicology. Protein precipitation, integrated solid phase extraction and on-line enrichment followed by high-performance liquid chromatography separation and detection with a triple quadrupole mass spectrometer were combined. The linear ranges used for the three cannabinoids were from 0.5 to 20ng/mL for THC and 11-OH-THC and from 2.5 to 100ng/mL for THC-COOH, therefore covering the requirements for forensic use. Correlation coefficients of 0.9980 or better were achieved for all three analytes. No relevant hydrolysis was observed for THC-COOH glucuronide with this procedure — in contrast to our previous GC-MS procedure, which obviously lead to an artificial increase of the THC-COOH concentration due to the hydrolysis of the glucuronide-conjugate occurring at high pH during the phase-transfer catalyzed methylation ste

Refixation stability in shoulder hemiarthroplasty in case of four-part proximal humeral fracture

Primary stability of refixated fractures in case of shoulder hemiarthroplasty is a prerequisite to restore physiological glenohumeral joint function. Clinical observations often show a secondary dislocation and subsequent resorption of the bony anchor points like the greater and lesser tuberosity at the rotator cuff tendons. This failed integration leads to impaired glenohumeral load transmission and subsequent reduction of mobility. As a consequence, the optimisation of refixation methods is crucial for a better clinical outcome. To prove the stability of refixation techniques, a Finite Element fracture model was built. Resulting stresses at the bone surface and fragment migration relative to the prosthesis shaft were studied. The results of the calculations show that the isolated tuberosities show unstressed bone regions compared to the intact model. This circumstance may explain the clinically detected bone resorption due to the absence of mechanical stimuli. Furthermore, a cable guidance through lateral holes in the middle part of the proximal prosthesis results in a lower fragment displacement than a circumferential fixation method surrounding the entire proximal bon

Effects of 238U variability and physical transport on water column 234Th downward fluxes in the coastal upwelling system off Peru

The eastern boundary region of the southeastern Pacific Ocean hosts one of the world's most dynamic and productive upwelling systems with an associated oxygen minimum zone (OMZ). The variability in downward export fluxes in this region, with strongly varying surface productivity, upwelling intensities and water column oxygen content, is however poorly understood. Thorium-234 (234Th) is a powerful tracer to study the dynamics of export fluxes of carbon and other elements, yet intense advection and diffusion in nearshore environments impact the assessment of depth-integrated 234Th fluxes when not properly evaluated. Here we use vessel-mounted acoustic Doppler current profiler (VmADCP) current velocities, satellite wind speed and in situ microstructure measurements to determine the magnitude of advective and diffusive fluxes over the entire 234Th flux budget at 25 stations from 11 to 16∘ S in the Peruvian OMZ. Contrary to findings along the GEOTRACES P16 eastern section, our results showed that weak surface wind speed during our cruises induced low upwelling rates and minimal upwelled 234Th fluxes, whereas vertical diffusive 234Th fluxes were important only at a few shallow shelf stations. Horizontal advective and diffusive 234Th fluxes were negligible because of small alongshore 234Th gradients. Our data indicated a poor correlation between seawater 238U activity and salinity. Assuming a linear relationship between the two would lead to significant underestimations of the total 234Th flux by up to 40 % in our study. Proper evaluation of both physical transport and variability in 238U activity is thus crucial in coastal 234Th flux studies. Finally, we showed large temporal variations on 234Th residence times across the Peruvian upwelling zone and cautioned future carbon export studies to take these temporal variabilities into consideration while evaluating carbon export efficiency

Controls on redox-sensitive trace metals in the Mauritanian oxygen minimum zone

The availability of the micronutrient iron (Fe) in surface waters determines primary production, N2 fixation, and microbial community structure in large parts of the world's ocean, and thus it plays an important role in ocean carbon and nitrogen cycles. Eastern boundary upwelling systems and the connected oxygen minimum zones (OMZs) are typically associated with elevated concentrations of redox-sensitive trace metals (e.g., Fe, manganese (Mn), and cobalt (Co)), with shelf sediments typically forming a key source. Over the last 5 decades, an expansion and intensification of OMZs has been observed and this trend is likely to proceed. However, it is unclear how trace-metal (TM) distributions and transport are influenced by decreasing oxygen (O2) concentrations. Here we present dissolved (d; 0.2 µm) TM data collected at seven stations along a 50 km transect in the Mauritanian shelf region. We observed enhanced concentrations of Fe, Co, and Mn corresponding with low O2 concentrations (<50 µmol kg−1), which were decoupled from major nutrients and nutrient-like and scavenged TMs (cadmium (Cd), lead (Pb), nickel (Ni), and copper (Cu)). Additionally, data from repeated station occupations indicated a direct link between dissolved and leachable particulate Fe, Co, Mn, and O2. An observed dFe (dissolved iron) decrease from 10 to 5 nmol L−1 coincided with an O2 increase from 30 to 50 µmol kg−1 and with a concomitant decrease in turbidity. The changes in Fe (Co and Mn) were likely driven by variations in their release from sediment pore water, facilitated by lower O2 concentrations and longer residence time of the water mass on the shelf. Variations in organic matter remineralization and lithogenic inputs (atmospheric deposition or sediment resuspension; assessed using Al as indicator for lithogenic inputs) only played a minor role in redox-sensitive TM variability. Vertical dFe fluxes from O2-depleted subsurface-to-surface waters (0.08–13.5 µmol m−2 d−1) driven by turbulent mixing and vertical advection were an order of magnitude larger than atmospheric deposition fluxes (0.63–1.43 µmol m−2 d−1; estimated using dAl inventories in the surface mixed layer) in the continental slope and shelf region. Benthic fluxes are therefore the dominant dFe supply to surface waters on the continental margins of the Mauritanian upwelling region. Overall, our results indicated that the projected future decrease in O2 concentrations in OMZs may result in increases in Fe, Mn, and Co concentrations

Carbon sources in the Beaufort Sea revealed by molecular lipid biomarkers and compound specific isotope analysis

61 pages, 12 figures, 13 tablesMolecular lipid biomarkers (hydrocarbons, alcohols, sterols and fatty acids) and compound specific isotope analysis of suspended particulate organic matter (SPM) and surface sediments of the Mackenzie Shelf and slope (Southeast Beaufort Sea, Arctic Ocean), were studied in summer 2009. The concentrations of the molecular lipid markers, characteristic of known organic matter sources, were grouped and used as proxies to evaluate the relative importance of fresh algal, detrital algal, fossil, C3 terrestrial plants, bacterial and zooplankton material in the sedimentary organic matter (OM). Fossil and detrital algal contributions were the major fractions of the freshwater SPM from the Mackenzie River with ~34% each of the total molecular biomarkers. Fresh algal, C3 terrestrial, bacterial and zooplanktonic components represented much lower percentages, 17, 10, 4 and 80%) with a minor contribution of fossil and C3 terrestrial biomarkers. Characterization of the sediments revealed a major sink of refractory algal material mixed with some fresh algal material, fossil hydrocarbons and a small input of C3 terrestrial sources. In particular, the sediments from the shelf and at the mouth of the Amundsen Gulf presented the highest contribution of detrital algal material (60–75%) whereas those from the slope contained the highest proportion of fossil (40%) and C3 terrestrial plant material (10%). Overall, considering that the detrital algal material is marine derived, autochthonous sources contributed more than allochthonous sources to the OM lipid pool. Using the ratio of an allochthonous biomarker (normalized to total organic carbon, TOC) found in the sediments to those measured at the river mouth water, we estimated that the fraction of terrestrial material preserved in the sediments accounted for 30–40% of the total carbon in the inner shelf sediments, 17% in the outer shelf and Amundsen Gulf and up to 25% in the slope sedimentsThe IAEA is grateful for the support provided to the Environment Laboratories by the Government of the Principality of Monaco. This study was conducted as part of the Malina Scientific Program funded by ANR (Agence nationale de la recherche), INSU-CNRS (Institut national des sciences de l’univers – Centre national de la recherche scientifique), CNES (Centre national d’ etudes spatiales) and ESA (European Space Agency)Peer reviewe

On-line SPE LC-MS/MS for the quantification of Δ9-tetrahydrocannabinol (THC) and its two major metabolites in human peripheral blood by liquid chromatography tandem mass spectrometry

A universal and robust analytical method for the determination of Δ9-tetrahydrocannabinol (THC) and two of its metabolites Δ9-(11-OH)-tetrahydrocannabinol (11-OH-THC) and 11-nor-Δ9-carboxy-tetrahydrocannabinol (THC-COOH) in human whole blood was developed and validated for use in forensic toxicology. Protein precipitation, integrated solid phase extraction and on-line enrichment followed by high-performance liquid chromatography separation and detection with a triple quadrupole mass spectrometer were combined. The linear ranges used for the three cannabinoids were from 0.5 to 20 ng/mL for THC and 11-OH-THC and from 2.5 to 100 ng/mL for THC-COOH, therefore covering the requirements for forensic use. Correlation coefficients of 0.9980 or better were achieved for all three analytes. No relevant hydrolysis was observed for THC-COOH glucuronide with this procedure--in contrast to our previous GC-MS procedure, which obviously lead to an artificial increase of the THC-COOH concentration due to the hydrolysis of the glucuronide-conjugate occurring at high pH during the phase-transfer catalyzed methylation step

Refixation stability in shoulder hemiarthroplasty in case of four-part proximal humeral fracture

ISSN:0140-0118ISSN:1741-044

Carbon Fluxes and Sources of Organic Matter in Late Summer in the Southern Beaufort Sea

IPY2012 Conference Montréal. From Knowledge to Action, 22-27 April 2012, Montréal, CanadaClimate change is expected to deeply affect the Arctic pelagic ecosystems via ice cover reduction and increase of freshwater discharge. Important but mostly unknown consequences are to follow for the downward export of particulate matter and the carbon cycling in general. This situation has caused a growing need of field observations to monitor the complex and rapidly changing Arctic environment and to enlarge the dataset available to modelers. In the framework of the international multidisciplinary project MALINA, an intensive survey in the Beaufort Sea off the Mackenzie River Delta was done during August 2009. The vertical flux of particulate material and carbon was measured and characterized. The sources of the organic carbon pool was also identified by analysis of lipid biomarkers and their δ13C in both suspended particles and surface sediments in order to identify the terrestrial, marine and bacterial sources of carbon and the processes of transport and degradation in the water column. Downward particle and carbon flux was measured directly by means of sediment traps (Technicap PPS3) attached to a drifting line. Traps were deployed at 4 depths (40, 85, 145 and 200 m) along with current-meters. The drifting array was deployed at selected sites of the Canadian Beaufort Sea between 14 and 25 August 2009. Mooring deployments lasted for 28-50 hours and targeted the shelfbreak and the slope along the Beaufort-Mackenzie continental margin, as well as the edge between the Mackenzie Shelf and the Amundsen Gulf. The measured fluxes were relatively low (in the range of 9-56 mg m-2 d-1 for the total mass and 1-15 mg C m-2 d-1 for carbon). Overall, the magnitude and composition of the particulate flux suggests post-bloom conditions during the survey. Particulate organic carbon export was also estimated through natural radionuclide disequilibria (234Th/238U) used as a proxy for POC flux. Water column profiles of total 234Th were obtained from 2 L of seawater (small volume technique) sampled by a CTD-Rosette, and particulate 234Th was measured at selected depths using large volume Challenger in-situ pumps. Derived fluxes were relatively low during the sampled period and consistent with the direct flux measurements. The analysis of molecular and isotopic lipid biomarkers in suspended particulate matter in the water column from the Mackenzie Shelf to the edge of the Amundsen Gulf showed a predominant biogenic and fossil composition, while surface sediments revealed that sinking material was relatively fresh and of marine organic source, mixed with a fossil hydrocarbon background and a small input of terrestrial sources. Altogether, the results highlight that despite the importance of the Mackenzie river outflow in the southern Beaufort Sea, the sinking particle dynamics in the open shelf is largely marinePeer Reviewe