Fate of mercury in tree litter during decomposition

We performed a controlled laboratory litter incubation study to assess changes in dry mass, carbon (C) mass and concentration, mercury (Hg) mass and concentration, and stoichiometric relations between elements during decomposition. Twenty-five surface litter samples each, collected from four forest stands, were placed in incubation jars open to the atmosphere, and were harvested sequentially at 0, 3, 6, 12, and 18 months. Using a mass balance approach, we observed significant mass losses of Hg during decomposition (5 to 23 % of initial mass after 18 months), which we attribute to gaseous losses of Hg to the atmosphere through a gas-permeable filter covering incubation jars. Percentage mass losses of Hg generally were less than observed dry mass and C mass losses (48 to 63 % Hg loss per unit dry mass loss), although one litter type showed similar losses. A field control study using the same litter types exposed at the original collection locations for one year showed that field litter samples were enriched in Hg concentrations by 8 to 64 % compared to samples incubated for the same time period in the laboratory, indicating strong additional sorption of Hg in the field likely from atmospheric deposition. Solubility of Hg, assessed by exposure of litter to water upon harvest, was very low (<0.22 ng Hg g<sup>−1</sup> dry mass) and decreased with increasing stage of decomposition for all litter types. Our results indicate potentially large gaseous emissions, or re-emissions, of Hg originally associated with plant litter upon decomposition. Results also suggest that Hg accumulation in litter and surface layers in the field is driven mainly by additional sorption of Hg, with minor contributions from "internal" accumulation due to preferential loss of C over Hg. Litter types showed highly species-specific differences in Hg levels during decomposition suggesting that emissions, retention, and sorption of Hg are dependent on litter type

Algebraically diverging modes upstream of a swept bluff body

International audienceClassical stability theory for swept leading-edge boundary layers predicts eigenmodes in the free stream with algebraic decay far from the leading edge. In this article, we extend the classical base flow solution by Hiemenz to a uniformly valid solution for the flow upstream of a bluff body, which includes a three-dimensional boundary layer, an inviscid stagnation-point flow and an outer parallel flow. This extended, uniformly valid base flow additionally supports modes which diverge algebraically outside the boundary layer. The theory of wave packet pseudomodes is employed to derive analytical results for the growth rates and for the eigenvalue spectra of this type of mode. The complete spectral analysis of the flow, including the algebraically diverging modes, will give a more appropriate basis for receptivity studies and will more accurately describe the interaction of perturbations in the free stream with disturbances in the boundary layer. © Cambridge University Press 2011

Toward real-time measurement of atmospheric mercury concentrations using cavity ring-down spectroscopy

Cavity ring-down spectroscopy (CRDS) is a direct absorption technique that utilizes path lengths up to multiple kilometers in a compact absorption cell and has a significantly higher sensitivity than conventional absorption spectroscopy. This tool opens new prospects for study of gaseous elemental mercury (Hg<sup>0</sup>) because of its high temporal resolution and reduced sample volume requirements (<0.5 l of sample air). We developed a new sensor based on CRDS for measurement of (Hg<sup>0</sup>) mass concentration. Sensor characteristics include sub-ng m<sup>−3</sup> detection limit and high temporal resolution using a frequency-doubled, tuneable dye laser emitting pulses at ~253.65 nm with a pulse repetition frequency of 50 Hz. The dye laser incorporates a unique piezo element attached to its tuning grating allowing it to tune the laser on and off the Hg<sup>0</sup> absorption line on a pulse-to-pulse basis to facilitate differential absorption measurements. Hg<sup>0</sup> absorption measurements with this CRDS laboratory prototype are highly linearly related to Hg<sup>0</sup> concentrations determined by a Tekran 2537B analyzer over an Hg<sup>0</sup> concentration range from 0.2 ng m<sup>−3</sup> to 573 ng m<sup>−3</sup>, implying excellent linearity of both instruments. The current CRDS instrument has a sensitivity of 0.10 ng Hg<sup>0</sup> m<sup>−3</sup> at 10-s time resolution. Ambient-air tests showed that background Hg<sup>0</sup> levels can be detected at low temporal resolution (i.e., 1 s), but also highlight a need for high-frequency (i.e., pulse-to-pulse) differential on/off-line tuning of the laser wavelength to account for instabilities of the CRDS system and variable background absorption interferences. Future applications may include ambient Hg<sup>0</sup> flux measurements with eddy covariance techniques, which require measurements of Hg<sup>0</sup> concentrations with sub-ng m<sup>−3</sup> sensitivity and sub-second time resolution

Factors affecting home delivery in rural Tanzania

BACKGROUND\ud \ud Studies of factors affecting place of delivery have rarely considered the influence of gender roles and relations within the household. This study combines an understanding of gender issues relating to health and help-seeking behaviour with epidemiological knowledge concerning place of delivery.\ud \ud METHODS\ud \ud In-depth interviews, focus group discussions and participant observation were used to explore determinants of home delivery in southern Tanzania. Quantitative data were collected in a cross-sectional survey of 21,600 randomly chosen households.\ud \ud RESULTS\ud \ud Issues of risk and vulnerability, such as lack of money, lack of transport, sudden onset of labour, short labour, staff attitudes, lack of privacy, tradition and cultures and the pattern of decision-making power within the household were perceived as key determinants of the place of delivery. More than 9000 women were interviewed about their most recent delivery in the quantitative survey. There were substantial variations between ethnic groups with respect to place of delivery (P<0.0001). Women who lived in male-headed households were less likely to deliver in a health facility than women in female-headed households (RR 0.86, 95% CI 0.80-0.91). Mothers with primary and higher education were more likely to deliver at a health facility (RR 1.30, 95% CI 1.23-1.38). Younger mothers and the least poor women were also more likely to deliver in a health facility compared with the older and the poorest women, respectively.\ud \ud CONCLUSIONS\ud \ud To address neonatal mortality, special attention should be paid to neonatal health in both maternal and child health programmes. The findings emphasize the need for a systematic approach to overcome health-system constraints, community based programmes and scale-up effective low-cost interventions which are already available

Touch, taste, & smell user interfaces: the future of multisensory HCI

The senses we call upon when interacting with technology are very restricted. We mostly rely on vision and audition, increasingly harnessing touch, whilst taste and smell remain largely underexploited. In spite of our current knowledge about sensory systems and sensory devices, the biggest stumbling block for progress concerns the need for a deeper understanding of people’s multisensory experiences in HCI. It is essential to determine what tactile, gustatory, and olfactory experiences we can design for, and how we can meaningfully stimulate such experiences when interacting with technology. Importantly, we need to determine the contribution of the different senses along with their interactions in order to design more effective and engaging digital multisensory experiences. Finally, it is vital to understand what the limitations are that come into play when users need to monitor more than one sense at a time. The aim of this workshop is to deepen and expand the discussion on touch, taste, and smell within the CHI community and promote the relevance of multisensory experience design and research in HCI

Use of a global model to understand speciated atmospheric mercury observations at five high-elevation sites

© 2015 Author(s). Atmospheric mercury (Hg) measurements using the Tekran® analytical system from five high-elevation sites (1400-3200 m elevation), one in Asia and four in the western US, were compiled over multiple seasons and years, and these data were compared with the GEOS-Chem global model. Mercury data consisted of gaseous elemental Hg (GEM) and "reactive Hg" (RM), which is a combination of the gaseous oxidized (GOM) and particulate bound ( < 2.5 μm) (PBM) fractions as measured by the Tekran® system. We used a subset of the observations by defining a "free tropospheric" (FT) data set by screening using measured water vapor mixing ratios. The oxidation scheme used by the GEOS-Chem model was varied between the standard run with Br oxidation and an alternative run with OH-O 3 oxidation. We used this model-measurement comparison to help interpret the spatio-temporal trends in, and relationships among, the Hg species and ancillary parameters, to understand better the sources and fate of atmospheric RM. The most salient feature of the data across sites, seen more in summer relative to spring, was that RM was negatively correlated with GEM and water vapor mixing ratios (WV) and positively correlated with ozone (O 3 ), both in the standard model and the observations, indicating that RM was formed in dry upper altitude air from the photo-oxidation of GEM. During a free tropospheric transport high RM event observed sequentially at three sites from Oregon to Nevada, the slope of the RM/GEM relationship at the westernmost site was-1020 ± 209 pg ng -1 , indicating near-quantitative GEM-to-RM photochemical conversion. An improved correlation between the observations and the model was seen when the model was run with the OH-O3 oxidation scheme instead of the Br oxidation scheme. This simulation produced higher concentrations of RM and lower concentrations of GEM, especially at the desert sites in northwestern Nevada. This suggests that future work should investigate the effect of Br-and O 3 -initiated gas-phase oxidation occurring simultaneously in the atmosphere, as well as aqueous and heterogeneous reactions to understand whether there are multiple global oxidants for GEM and hence multiple forms of RM in the atmosphere. If the chemical forms of RM were known, then the collection efficiency of the analytical method could be evaluated better.Taiwan. Environmental Protection Administratio

Mitigating the negative impacts of tall wind turbines on bats: Vertical activity profiles and relationships to wind speed.

Wind turbines represent a source of hazard for bats, especially through collision with rotor blades. With increasing technical development, tall turbines (rotor-swept zone 50-150 m above ground level) are becoming widespread, yet we lack quantitative information about species active at these heights, which impedes proposing targeted mitigation recommendations for bat-friendly turbine operation. We investigated vertical activity profiles of a bat assemblage, and their relationships to wind speed, within a major valley of the European Alps where tall wind turbines are being deployed. To monitor bat activity we installed automatic recorders at sequentially increasing heights from ground level up to 65 m, with the goal to determine species-specific vertical activity profiles and to link them to wind speed. Bat call sequences were analysed with an automatic algorithm, paying particular attention to mouse-eared bats (Myotis myotis and Myotis blythii) and the European free-tailed bat (Tadarida teniotis), three locally rare species. The most often recorded bats were the Common pipistrelle (Pipistrellus pipistrellus) and Savi's pipistrelle (Hypsugo savii). Mouse-eared bats were rarely recorded, and mostly just above ground, appearing out of risk of collision. T. teniotis had a more evenly distributed vertical activity profile, often being active at rotor level, but its activity at that height ceased above 5 ms-1 wind speed. Overall bat activity in the rotor-swept zone declined with increasing wind speed, dropping below 5% above 5.4 ms-1. Collision risk could be drastically reduced if nocturnal operation of tall wind turbines would be restricted to wind speeds above 5 ms-1. Such measure should be implemented year-round because T. teniotis remains active in winter. This operational restriction is likely to cause only small energy production losses at these tall wind turbines, although further analyses are needed to assess these losses precisely

Monitoring Cognitive and Emotional Processes Through Pupil and Cardiac Response During Dynamic Versus Logical Task

The paper deals with the links between physiological measurements and cognitive and emotional functioning. As long as the operator is a key agent in charge of complex systems, the definition of metrics able to predict his performance is a great challenge. The measurement of the physiological state is a very promising way but a very acute comprehension is required; in particular few studies compare autonomous nervous system reactivity according to specific cognitive processes during task performance and task related psychological stress is often ignored. We compared physiological parameters recorded on 24 healthy subjects facing two neuropsychological tasks: a dynamic task that require problem solving in a world that continually evolves over time and a logical task representative of cognitive processes performed by operators facing everyday problem solving. Results showed that the mean pupil diameter change was higher during the dynamic task; conversely, the heart rate was more elevated during the logical task. Finally, the systolic blood pressure seemed to be strongly sensitive to psychological stress. A better taking into account of the precise influence of a given cognitive activity and both workload and related task-induced psychological stress during task performance is a promising way to better monitor operators in complex working situations to detect mental overload or pejorative stress factor of error

Comparison of caffeine-induced changes in cerebral blood flow and middle cerebral artery blood velocity shows that caffeine reduces middle cerebral artery diameter

Changes in cerebral blood flow (CBF) can be assessed directly with xenon clearance (XeC) or indirectly by measuring changes in middle cerebral artery blood velocity (Vmca) with transcranial Doppler (TCD). The aim of this study was to compare the changes in CBF and Vmca following caffeine ingestion. Nineteen patients (age 48–86, recovering from an acute stroke) and ten controls (age 52–85) were each studied twice. Bilateral measurements of CBF and Vmca were made before and after ingestion of 250 mg caffeine or matched placebo. The percentage change in CBF and Vmca after caffeine was calculated. Full results (CBF and Vmca) were obtained from 14 patients and 9 controls. There was no significant difference between patients and controls, so results were combined. Caffeine reduced CBF by 22% (95% confidence interval (CI) = 17% to 28%) and reduced Vmca by 13% (95% CI = 10% to 17%). The fall in Vmca was significantly less than that in CBF (p = 0.0016), showing that caffeine reduces mca diameter. Analysis based on Poiseuille flow in the arterioles suggests that caffeine reduced arteriole diameter by 5.9% (95% CI = 4.6% to 7.3%) and mca diameter by 4.3% (95% CI = 2.0% to 6.6%). TCD is being used as an alternative to XeC for assessing the effect of vasoconstrictors and vasodilators on CBF. This study has demonstrated that mca diameter can be changed by the vasoactive agents, and that changes in Vmca do not necessarily reflect changes in CBF

Environmental risk assessment of genetically modified plants - concepts and controversies

Background and purpose: In Europe, the EU Directive 2001/18/EC lays out the main provisions of environmental risk assessment (ERA) of genetically modified (GM) organisms that are interpreted very differently by different stakeholders. The purpose of this paper is to: (a) describe the current implementation of ERA of GM plants in the EU and its scientific shortcomings, (b) present an improved ERA concept through the integration of a previously developed selection procedure for identification of non-target testing organisms into the ERA framework as laid out in the EU Directive 2001/18/EC and its supplement material (Commission Decision 2002/623/EC), (c) describe the activities to be carried out in each component of the ERA and (d) propose a hierarchical testing scheme. Lastly, we illustrate the outcomes for three different crop case examples. Main features: Implementation of the current ERA concept of GM crops in the EU is based on an interpretation of the EU regulations that focuses almost exclusively on the isolated bacteria-produced novel proteins with little consideration of the whole plant. Therefore, testing procedures for the effect assessment of GM plants on non-target organisms largely follow the ecotoxicological testing strategy developed for pesticides. This presumes that any potential adverse effect of the whole GM plant and the plant-produced novel compound can be extrapolated from testing of the isolated bacteriaproduced novel compound or can be detected in agronomic field trials. This has led to persisting scientific criticism. Results: Based on the EU ERA framework, we present an improved ERA concept that is system oriented with the GM plant at the centre and integrates a procedure for selection of testing organisms that do occur in the receiving environment. We also propose a hierarchical testing scheme from laboratory studies to field trials and we illustrate the outcomes for three different crop case examples. Conclusions and recommendations: Our proposed concept can alleviate a number of deficits identified in the current approach to ERA of GM plants. It allows the ERA to be tailored to the GM plant case and the receiving environment