Reexposure and advection of C-14-depleted organic carbon from old deposits at the upper continental slope

Outcrops of old strata at the shelf edge resulting from erosive gravity-driven flows have been globally described on continental margins. The reexposure of old strata allows for the reintroduction of aged organic carbon (OC), sequestered in marine sediments for thousands of years, into the modern carbon cycle. This pool of reworked material represents an additional source of C-14-depleted organic carbon supplied to the ocean, in parallel with the weathering of fossil organic carbon delivered by rivers from land. To understand the dynamics and implications of this reexposure at the shelf edge, a biogeochemical study was carried out in the Gulf of Lions (Mediterranean Sea) where erosive processes, driven by shelf dense water cascading, are currently shaping the seafloor at the canyon heads. Mooring lines equipped with sediment traps and current meters were deployed during the cascading season in the southwestern canyon heads, whereas sediment cores were collected along the sediment dispersal system from the prodelta regions down to the canyon heads. Evidence from grain-size, X-radiographs and Pb-210 activity indicate the presence in the upper slope of a shelly-coarse surface stratum overlying a consolidated deposit. This erosive discontinuity was interpreted as being a result of dense water cascading that is able to generate sufficient shear stress at the canyon heads to mobilize the coarse surface layer, eroding the basal strata. As a result, a pool of aged organic carbon (Delta C-14 = -944.5 +/- 24.7%; mean age 23,650 +/- 3,321 ybp) outcrops at the modern seafloor and is reexposed to the contemporary carbon cycle. This basal deposit was found to have relatively high terrigenous organic carbon (lignin = 1.48 +/- 0.14 mg/100 mg OC), suggesting that this material was deposited during the last low sea-level stand. A few sediment trap samples showed anomalously depleted radiocarbon concentrations (Delta C-14 = -704.4 +/- 62.5%) relative to inner shelf (Delta C-14 = -293.4 +/- 134.0%), mid-shelf (Delta C-14 = -366.6 +/- 51.1%), and outer shelf (Delta C-14 = -384 +/- 47.8%) surface sediments. Therefore, although the major source of particulate material during the cascading season is resuspended shelf deposits, there is evidence that this aged pool of organic carbon can be eroded and laterally advected downslope.

Differentiating bone osteonal turnover rates by density fractionation; validation using the bomb C-14 atmospheric pulse

The density (BSG) of bone increases, at the osteon scale, during lifetime aging within the bone. In addition, post-mortem diagenetic change due to microbial attack produces denser bioapatite. Thus, fractionation of finely powdered bone on the basis of density should not only enable younger and older populations of osteons to be separated but also make it possible to separate out a less diagenetically altered component. We show that the density fractionation method can be used as a tool to investigate the isotopic history within an individual's lifetime, both in recent and archaeological contexts, and we use the bomb C-14 atmospheric pulse for validating the method.

The joint effects of larval density and C-14-cypermethrin on the life history and population growth rate of the midge Chironomus riparius

1. Chemical effects on organisms are typically assessed using individual-level endpoints or sometimes population growth rate (PGR), but such measurements are generally made at low population densities. In contrast most natural populations are subject to density dependence and fluctuate around the environmental carrying capacity as a result of individual competition for resources. As ecotoxicology aims to make reliable population projections of chemical impacts in the field, an understanding of how high-density or resource-limited populations respond to environmental chemicals is essential. 2. Our objective was to determine the joint effects of population density and chemical stress on the life history and PGR of an important ecotoxicological indicator species, Chironomus riparius, under controlled laboratory conditions. Populations were fed the same ration but initiated at different densities and exposed to a solvent control and three concentrations of C-14-cypermethrin in a sediment-water test system for 67 days at 20 +/- 1 degreesC. 3. Density had a negative effect on all the measured life-history traits, and PGR declined with increasing density in the controls. Exposure to C-14-cypermethrin had a direct negative effect on juvenile survival, presumably within the first 24 h because the chemical rapidly dissipated from the water column. Reductions in the initial larval densities resulted in an increase in the available resources for the survivors. Subsequently, exposed populations emerged sooner and started producing offspring earlier than the controls. C-14-cypermethrin had no effect on estimated fecundity and adult body weight but interacted with density to reduce the time to first emergence and first reproduction. As a result, PGR increased with cypermethrin concentration when populations were initiated at high densities. 4. Synthesis and applications. The results showed that the effects of C-14-cypermethrin were buffered at high density, so that the joint effects of density and chemical stress on PGR were less than additive. Low levels of chemical stressors may increase carrying capacity by reducing juvenile competition for resources. More and perhaps fitter adults may be produced, similar to the effects of predators and culling; however, toxicant exposure may result in survivors that are less tolerant to changing conditions. If less than additive effects are typical in the field, standard regulatory tests carried out at low density may overestimate the effects of environmental chemicals. Further studies over a wide range of chemical stressors and organisms with contrasting life histories are needed to make general recommendations.

Pollen-based reconstructions of Japanese biomes at 0, 6000 and 18,000 14C yr bp

A biomization method, which objectively assigns individual pollen assemblages to biomes ( Prentice et al., 1996 ), was tested using modern pollen data from Japan and applied to fossil pollen data to reconstruct palaeovegetation patterns 6000 and 18,000 14C yr bp Biomization started with the assignment of 135 pollen taxa to plant functional types (PFTs), and nine possible biomes were defined by specific combinations of PFTs. Biomes were correctly assigned to 54% of the 94 modern sites. Incorrect assignments occur near the altitudinal limits of individual biomes, where pollen transport from lower altitudes blurs the local pollen signals or continuous changes in species composition characterizes the range limits of biomes. As a result, the reconstructed changes in the altitudinal limits of biomes at 6000 and 18,000 14C yr bp are likely to be conservative estimates of the actual changes. The biome distribution at 6000 14C yr bp was rather similar to today, suggesting that changes in the bioclimate of Japan have been small since the mid-Holocene. At 18,000 14C yr bp the Japanese lowlands were covered by taiga and cool mixed forests. The southward expansion of these forests and the absence of broadleaved evergreen/warm mixed forests reflect a pronounced year-round cooling.

TL, OSL and C-14 dating results of the sediments and bricks from mummified nuns' grave

Este artigo apresenta os resultados de datação por TL e OSL de solos, e fragmentos de tijolos de um túmulo, que foi ocupado por duas freiras mumificadas encontradas no Mosteiro da Luz, localizado no Estado de São Paulo, Brasil. As idades encontradas por TL e OSL foram comparadas às obtidas a partir de C-14 dos colágenos contidos em amostras de osso das múmias. A maioria das idades obtidas são do século XVIII. A espectroscopia de radiação-gama foi utilizada para avaliar concentrações de radioisótopos naturais nas amostras e para calcular as taxas de dose anual que resultaram em 3,0 a 5,3 Gy/kano. As concentrações radioativas são próximas daquelas obtidas através de Análise por Ativação de Nêutrons. Os conteúdos de elementos U, Th e Ce são superiores aos encontrados na maioria dos sedimentos.

Intraoperative Cardiac Arrest and Mortality in Trauma Patients. A 14-Yr Survey from a Brazilian Tertiary Teaching Hospital

Background: Little information on the factors influencing intraoperative cardiac arrest and its outcomes in trauma patients is available. This survey evaluated the associated factors and outcomes of intraoperative cardiac arrest in trauma patients in a Brazilian teaching hospital between 1996 and 2009.Methods: Cardiac arrest during anesthesia in trauma patients was identified from an anesthesia database. The data collected included patient demographics, ASA physical status classification, anesthesia provider information, type of surgery, surgical areas and outcome. All intraoperative cardiac arrests and deaths in trauma patients were reviewed and grouped by associated factors and also analyzed as totally anesthesia-related, partially anesthesia-related, totally surgery-related or totally trauma patient condition-related.Findings: Fifty-one cardiac arrests and 42 deaths occurred during anesthesia in trauma patients. They were associated with male patients (P<0.001) and young adults (18-35 years) (P = 0.04) with ASA physical status IV or V (P<0.001) undergoing gastroenterological or multiclinical surgeries (P<0.001). Motor vehicle crashes and violence were the main causes of trauma (P<0.001). Uncontrolled hemorrhage or head injury were the most significant associated factors of intraoperative cardiac arrest and mortality (P<0.001). All cardiac arrests and deaths reported were totally related to trauma patient condition.Conclusions: Intraoperative cardiac arrest and mortality incidence was highest in male trauma patients at a younger age with poor clinical condition, mainly related to uncontrolled hemorrhage and head injury, resulted from motor vehicle accidents and violence.

TL, OSL and C-14 dating results of the sediments and bricks from mummified nuns' grave

This paper presents the results of TL and OSL dating of soil and fragments of bricks from a grave, which was occupied by two mummified nuns, found at "Luz" Monastery, located in the state of São Paulo, Brazil. The TL and OSL ages were compared to C-14 dating ones obtained from bone collagens of the mummies. The majority of the ages is related to the eighteenth century. The gamma-ray spectroscopy was used to evaluate natural radioisotope concentrations in the samples, and by using these concentrations the annual dose rates, from 3.0 to 5.3 Gy/kyr, were obtained. Neutron activation analysis was performed and the radioisotope contents results are in agreement with those obtained by gamma-ray spectroscopy. The contents of U, Th and Ce elements were higher than those found in usual sediments.

Improving a gas ion source for C-14 AMS

For more than 4 years, gaseous samples of 1-50 mu g carbon have been routinely measured with the gas ion source of the small AMS (Accelerator Mass Spectrometer) facility MICADAS (Mini CArbon DAting System) at ETH Zurich. The applied measurement technique offers a simple and fast way of C-14 measurements without the need of sample graphitization. A major drawback of gaseous C-14 measurements, however, is the relatively low negative ion current, which results in longer measurement times and lower precision compared to graphitized samples. In December 2009, a new, improved Cs sputter ion source was installed at MICADAS and we began to optimize conditions for the measurement of gaseous samples. C-12(-) currents from the new ion source were improved from initially 3 to 12-15 mu A for routine measurements and the negative ion yield was increased by a factor of 2, reaching 8 on average during routine operation. Moreover, the new measurement settings enable a doubled CO2 flow, thus substantially reducing measurement times. The achieved performance allows closing the sample size gap between gaseous and solid samples and makes the gas ion source a promising tool for dating with a measurement precision of 5 parts per thousand on samples as small as 50 mu g carbon. (C) 2012 Elsevier B.V. All rights reserved.

Intercomparison of C-14 Analysis of Carbonaceous Aerosols: Exercise 2009

Radiocarbon analysis of the carbonaceous aerosol allows an apportionment of fossil and non-fossil sources of airborne particulate matter (PM). A chemical separation of total carbon (TC) into its subfractions organic carbon (OC) and elemental carbon (EC) refines this powerful technique, as OC and EC originate from different sources and undergo different processes in the atmosphere. Although C-14 analysis of TC, EC, and OC has recently gained increasing attention, interlaboratory quality assurance measures have largely been missing, especially for the isolation of EC and OC. In this work, we present results from an intercomparison of 9 laboratories for C-14 analysis of carbonaceous aerosol samples on quartz fiber filters. Two ambient PM samples and 1 reference material (RM 8785) were provided with representative filter blanks. All laboratories performed C-14 determinations of TC and a subset of isolated EC and OC for isotopic measurement. In general, C-14 measurements of TC and OC agreed acceptably well between the laboratories, i.e. for TC within 0.015-0.025 (FC)-C-14 for the ambient filters and within 0.041 (FC)-C-14 for RM 8785. Due to inhomogeneous filter loading, RM 8785 demonstrated only limited applicability as a reference material for C-14 analysis of carbonaceous aerosols. C-14 analysis of EC revealed a large deviation between the laboratories of 28-79 as a consequence of different separation techniques. This result indicates a need for further discussion on optimal methods of EC isolation for C-14 analysis and a second stage of this intercomparison.

C-14 Measurements of Ice Samples from the Juvfonne Ice Tunnel, Jotunheimen, Southern Norway-Validation of a C-14 Dating Technique for Glacier Ice

Establishing precise age-depth relationships of high-alpine ice cores is essential in order to deduce conclusive paleoclimatic information from these archives. Radiocarbon dating of carbonaceous aerosol particles incorporated in such glaciers is a promising tool to gain absolute ages, especially from the deepest parts where conventional methods are commonly inapplicable. In this study, we present a new validation for a published C-14 dating method for ice cores. Previously C-14-dated horizons of organic material from the Juvfonne ice patch in central southern Norway (61.676 degrees N, 8.354 degrees E) were used as reference dates for adjacent ice layers, which were C-14 dated based on their particulate organic carbon (POC) fraction. Multiple measurements were carried out on 3 sampling locations within the ice patch featuring modern to multimillennial ice. The ages obtained from the analyzed samples were in agreement with the given age estimates. In addition to previous validation work, this independent verification gives further confidence that the investigated method provides the actual age of the ice.