Stable isotope analysis has emerged as one of the primary means for examining the structure and dynamics of food webs, and numerous analytical approaches are now commonly used in the field. ...Techniques range from simple, qualitative inferences based on the isotopic niche, to Bayesian mixing models that can be used to characterize food‐web structure at multiple hierarchical levels. We provide a comprehensive review of these techniques, and thus a single reference source to help identify the most useful approaches to apply to a given data set. We structure the review around four general questions: (1) what is the trophic position of an organism in a food web?; (2) which resource pools support consumers?; (3) what additional information does relative position of consumers in isotopic space reveal about food‐web structure?; and (4) what is the degree of trophic variability at the intrapopulation level? For each general question, we detail different approaches that have been applied, discussing the strengths and weaknesses of each. We conclude with a set of suggestions that transcend individual analytical approaches, and provide guidance for future applications in the field.
Trichlorofluoromethane (CFC-11), a widely used refrigerant throughout
much of the twentieth century and a very potent (stratospheric)
ozone-depleting substance (ODS), is now banned under the Montreal ...Protocol.
With a long atmospheric lifetime, it will only slowly degrade in the
atmosphere, so monitoring its vertical concentration profile using
infrared-sounding instruments, and thereby validating stratospheric loss
rates in atmospheric models, is of great importance; this in turn requires
high-quality laboratory spectroscopic data. This work describes new high-resolution infrared absorption cross sections of
trichlorofluoromethane/dry synthetic air over the spectral range
710–1290 cm−1, determined from spectra recorded using a
high-resolution Fourier transform spectrometer (Bruker IFS 125HR) and a
26 cm pathlength cell. Spectra were recorded at resolutions between 0.01 and
0.03 cm−1 (calculated as 0.9/MOPD; MOPD: maximum optical path
difference) over a range of temperatures and pressures (7.5–760 Torr and
192–293 K) appropriate for atmospheric conditions. This new cross-section
dataset improves upon the one currently available in the HITRAN (HIgh-resolution TRANsmission) and
GEISA (Gestion et Étude des Informations Spectroscopiques Atmosphériques) databases through an extension to the range of pressures and
temperatures, improved signal-to-noise
and wavenumber calibrations, the lack of channel fringing, the better
consistency in integrated band intensities, and additionally the coverage of
the weak combination band ν2+ν5.
CONTEXT Extracorporeal membrane oxygenation (ECMO) can support gas exchange in patients with severe acute respiratory distress syndrome (ARDS), but its role has remained controversial. ECMO was used ...to treat patients with ARDS during the 2009 influenza A(H1N1) pandemic. OBJECTIVE To compare the hospital mortality of patients with H1N1-related ARDS referred, accepted, and transferred for ECMO with matched patients who were not referred for ECMO. DESIGN, SETTING, AND PATIENTS A cohort study in which ECMO-referred patients were defined as all patients with H1N1-related ARDS who were referred, accepted, and transferred to 1 of the 4 adult ECMO centers in the United Kingdom during the H1N1 pandemic in winter 2009-2010. The ECMO-referred patients and the non–ECMO-referred patients were matched using data from a concurrent, longitudinal cohort study (Swine Flu Triage study) of critically ill patients with suspected or confirmed H1N1. Detailed demographic, physiological, and comorbidity data were used in 3 different matching techniques (individual matching, propensity score matching, and GenMatch matching). MAIN OUTCOME MEASURE Survival to hospital discharge analyzed according to the intention-to-treat principle. RESULTS Of 80 ECMO-referred patients, 69 received ECMO (86.3%) and 22 died (27.5%) prior to discharge from the hospital. From a pool of 1756 patients, there were 59 matched pairs of ECMO-referred patients and non–ECMO-referred patients identified using individual matching, 75 matched pairs identified using propensity score matching, and 75 matched pairs identified using GenMatch matching. The hospital mortality rate was 23.7% for ECMO-referred patients vs 52.5% for non–ECMO-referred patients (relative risk RR, 0.45 95% CI, 0.26-0.79; P = .006) when individual matching was used; 24.0% vs 46.7%, respectively (RR, 0.51 95% CI, 0.31-0.81; P = .008) when propensity score matching was used; and 24.0% vs 50.7%, respectively (RR, 0.47 95% CI, 0.31-0.72; P = .001) when GenMatch matching was used. The results were robust to sensitivity analyses, including amending the inclusion criteria and restricting the location where the non–ECMO-referred patients were treated. CONCLUSION For patients with H1N1-related ARDS, referral and transfer to an ECMO center was associated with lower hospital mortality compared with matched non–ECMO-referred patients.
High-resolution infrared absorption cross sections for 1,1,1,2-tetrafluoroethane have been determined over the spectral range 750–1600cm−1 from spectra recorded using a high-resolution FTIR ...spectrometer (Bruker IFS 125HR) and a 26-cm-pathlength cell. Spectra of 1,1,1,2-tetrafluoroethane/dry synthetic air mixtures were recorded at 0.015cm−1 resolution (calculated as 0.9/MOPD) at a number of temperatures and pressures (22–761Torr and 191–296K) appropriate for atmospheric conditions. Intensities were calibrated using composite 1,1,1,2-tetrafluoroethane spectra taken from the Pacific Northwest National Laboratory (PNNL) IR database. This cross section dataset is intended to replace what is currently available in the HITRAN/GEISA databases.
•1,1,1,2-Tetrafluoroethane (HFC-134a) infrared absorption cross sections have been determined from 750 to 1600cm−1.•They cover temperatures from 191 to 296K and appropriate atmospheric pressures.•These will allow the quantification of HFC-134a abundances from IR remote-sensing measurements.
Hydrogen cyanide (HCN) is an important tracer of biomass burning, but there are significant uncertainties in its atmospheric budget, especially its photochemical and ocean sinks. Here we use a tracer ...version of the TOMCAT global 3-D chemical transport model to investigate the physical and chemical processes driving the abundance of HCN in the troposphere and stratosphere over the period 2004–2016.
The modelled HCN distribution is compared with version 4.1 of the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) HCN satellite data, which provide profiles up to around 42 km, and with ground-based column measurements from the Network for the Detection of Atmospheric Composition Change (NDACC). The long-term ACE-FTS measurements reveal the strong enhancements in upper-tropospheric HCN due to large wildfire events in Indonesia in 2006 and 2015. Our 3-D model simulations confirm previous lower-altitude balloon comparisons that the currently recommended NASA Jet Propulsion Laboratory (JPL) reaction rate coefficient of HCN with OH greatly overestimates the HCN loss. The use of the rate coefficient proposed by Kleinböhl et al. (2006) in combination with the HCN oxidation by O(1D) gives good agreement between ACE-FTS observations and the model. Furthermore, the model photochemical loss terms show that the reduction in the HCN mixing ratio with height in the middle stratosphere is mainly driven by the O(1D) sink with only a small contribution from a reaction with OH.
From comparisons of the model tracers with ground-based HCN observations we test the magnitude of the ocean sink in two different published schemes (Li et al., 2000, 2003). We find that in our 3-D model the two schemes produce HCN abundances which are very different to the NDACC observations but in different directions. A model HCN tracer using the Li et al. (2000) scheme overestimates the HCN concentration by almost a factor of 2, while a HCN tracer using the Li et al. (2003) scheme underestimates the observations by about one-third. To obtain good agreement between the model and observations, we need to scale the magnitudes of the global ocean sinks by factors of 0.25 and 2 for the schemes of Li et al. (2000) and Li et al. (2003), respectively. This work shows that the atmospheric photochemical sinks of HCN now appear well constrained but improvements are needed in parameterizing the major ocean uptake sink.
Carbonyl sulfide (OCS) has emerged as a valuable proxy for photosynthetic uptake of carbon dioxide (CO.sub.2) and is known to be important in the formation of aerosols in the stratosphere. However, ...uncertainties in the global OCS budget remain large. This is mainly due to the following three flux terms: vegetation uptake, soil uptake and oceanic emissions. Bottom-up estimates do not yield a closed budget, which is thought to be due to tropical emissions of OCS that are not accounted for. Here we present a simulation of atmospheric OCS over the period 2004-2018 using the TOMCAT 3-D chemical transport model that is aimed at better constraining some terms in the OCS budget. Vegetative uptake of OCS is estimated by scaling gross primary productivity (GPP) output from the Joint UK Land Environment Simulator (JULES) using the leaf relative uptake (LRU) approach. The remaining surface budget terms are taken from available literature flux inventories and adequately scaled to bring the budget into balance.
The most widely used hydrochlorofluorocarbon (HCFC) commercially since the 1930s has been chloro-difluoromethane, or HCFC-22, which has the undesirable effect of depleting stratospheric ozone. As ...this molecule is currently being phased out under the Montreal Protocol, monitoring its concentration profiles using infrared sounders crucially requires accurate laboratory spectroscopic data. This work describes new high-resolution infrared absorption cross sections of chlorodifluoromethane over the spectral range 730–1380 cm−1, determined from spectra recorded using a high-resolution Fourier transform spectrometer (Bruker IFS 125HR) and a 26 cm pathlength cell. Spectra of chlorodifluoromethane/dry synthetic air mixtures were recorded at resolutions between 0.01 and 0.03 cm−1 (calculated as 0.9/MOPD; MOPD denotes the maximum optical path difference) over a range of temperatures and pressures (7.5–762 Torr and 191–295 K) appropriate for atmospheric conditions. This new cross-section dataset improves upon the one currently available in the HITRAN (HIgh-resolution TRANsmission) and GEISA (Gestion et Etude des Informations Spectroscopiques Atmosphériques) databases; in particular it provides coverage over a wider range of pressures and temperatures, has more accurate wavenumber scales, more consistent integrated band intensities, improved signal-to-noise, is free of channel fringing, and additionally covers the ν2 and ν7 bands.
Nitrogen oxides (NOx, NO + NO2) are potent air pollutants which directly impact on human health and which aid the formation of other hazardous pollutants such as ozone (O3) and particulate matter. In ...this study, we use satellite tropospheric column nitrogen dioxide (TCNO2) data to evaluate the spatiotemporal variability and magnitude of the United Kingdom (UK) bottom-up National Atmospheric Emissions Inventory (NAEI) NOx emissions. Although emissions and TCNO2 represent different quantities, for UK city sources we find a spatial correlation of∼0.5 between the NAEI NOx emissions and TCNO2 from the high-spatial-resolution TROPOspheric Monitoring Instrument (TROPOMI), suggesting a good spatial distribution of emission sources in the inventory. Between 2005 and 2015, the NAEI total UK NOx emissions and long-term TCNO2 record from the Ozone Monitoring Instrument (OMI), averaged over England, show annually decreasing trends of 4.4 % and 2.2 %, respectively. Top-down NOx emissions were derived in this study by applying a simple mass balance approach to TROPOMI-observed downwind NO2 plumes from city sources. Overall, these top-down estimates were consistent with the NAEI, but for larger cities such as London and Birmingham the inventory is significantly (>25 %) less than the top-down emissions.
High-resolution infrared absorption cross sections for trifluoromethane have been determined over the range 950–1500cm−1 from spectra recorded using a high-resolution FTIR spectrometer (Bruker IFS ...125HR) and a 26-cm-pathlength cell. Spectra of trifluoromethane/dry synthetic air mixtures were recorded at 0.015cm−1 resolution (calculated as 0.9/MOPD) at a number of temperatures and pressures (23–762Torr and 188–294K) appropriate for atmospheric conditions. Intensities were calibrated using composite trifluoromethane spectra taken from the Pacific Northwest National Laboratory (PNNL) IR database.
•Trifluoromethane infrared absorption cross sections have been determined from 950 to 1500cm−1.•They cover temperatures from 188 to 294K and appropriate atmospheric pressures.•They will allow retrievals of trifluoromethane abundances from IR remote-sensing instruments.
The ACE-FTS atlas of the infrared solar spectrum Hase, Frank; Wallace, Lloyd; McLeod, Sean D. ...
Journal of quantitative spectroscopy & radiative transfer,
03/2010, Letnik:
111, Številka:
4
Journal Article
Recenzirano
The ACE-FTS is a space-borne Fourier transform spectrometer onboard SCISAT-1. The satellite was launched in August 2003 and since February 2004 the ACE-FTS has been performing solar occultation ...measurements in order to infer the chemical composition of the terrestrial atmosphere. The individual spectra recorded at the highest limb tangent altitudes (above 160
km) are by definition “high sun” spectra and contain no atmospheric contribution. In this work, an empirical solar spectrum covering the 700 to 4430
cm
−1 spectral range has been constructed from an average of 224,782 individual ACE-FTS solar spectra. Line assignments have been made for about 12,000 lines. The spectrum and two line lists are provided in the supplemental material attached to this work. Due to the excellent noise level achieved in the ACE-FTS solar atlas presented here, numerous weak absorption features are assigned which were not detectable in the ATMOS solar observations.
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