scholarly journals Global Emissions of Perfluorocyclobutane (PFC-318, c-C<sub>4</sub>F<sub>8</sub>) Resulting from the Use of Hydrochlorofluorocarbon-22 (HCFC-22) Feedstock to Produce Polytetrafluoroethylene (PTFE) and related Fluorochemicals

2021 ◽  
Author(s):  
Jens Mühle ◽  
Lambert J. M. Kuijpers ◽  
Kieran M. Stanley ◽  
Matthew Rigby ◽  
Luke M. Western ◽  
...  
Keyword(s):  
Developing Countries ◽  
Emission Factor ◽  
Climate Impact ◽  
Manufacturing Processes ◽  
Atmospheric Measurements ◽  
Global Emission ◽  
Facility Level ◽  
Highly Correlated ◽  
Almost All ◽  
Global Emissions

Abstract. Emissions of the potent greenhouse gas perfluorocyclobutane (c-C4F8, PFC-318, octafluorocyclobutane) into the global atmosphere inferred from atmospheric measurements have been increasing sharply since the early 2000s. We find that these inferred emissions are highly correlated with the production of hydrochlorofluorocarbon-22 (HCFC-22, CHClF2) for feedstock (FS) uses, because almost all HCFC-22 FS is pyrolyzed to produce (poly)tetrafluoroethylene ((P)TFE, Teflon) and hexafluoropropylene (HFP), a process in which c-C4F8 is a known by-product, causing a significant fraction of global c-C4F8 emissions. We find a global emission factor of ~0.003 kg c-C4F8 per kg of HCFC-22 FS pyrolyzed. Mitigation of these c-C4F8 emissions, e.g., through process optimization, abatement, or different manufacturing processes, such as electrochemical fluorination, could reduce the climate impact of this industry. While it has been shown that c-C4F8 emissions from developing countries dominate global emissions, more atmospheric measurements and/or detailed process statistics are needed to quantify country to facility level c-C4F8 emissions.

scholarly journals Global biogenic volatile organic compound emissions in the ORCHIDEE and MEGAN models and sensitivity to key parameters

2016 ◽  
Vol 16 (22) ◽  
pp. 14169-14202 ◽  
Author(s):  
Palmira Messina ◽  
Juliette Lathière ◽  
Katerina Sindelarova ◽  
Nicolas Vuichard ◽  
Claire Granier ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Regional Scale ◽  
High Sensitivity ◽  
Geographical Differences ◽  
Area Index ◽  
Tropical Regions ◽  
Global Emission ◽  
Volatile Organic ◽  
Almost All ◽  
Global Emissions

Abstract. A new version of the biogenic volatile organic compounds (BVOCs) emission scheme has been developed in the global vegetation model ORCHIDEE (Organizing Carbon and Hydrology in Dynamic EcosystEm), which includes an extended list of biogenic emitted compounds, updated emission factors (EFs), a dependency on light for almost all compounds and a multi-layer radiation scheme. Over the 2000–2009 period, using this model, we estimate mean global emissions of 465 Tg C yr−1 for isoprene, 107.5 Tg C yr−1 for monoterpenes, 38 Tg C yr−1 for methanol, 25 Tg C yr−1 for acetone and 24 Tg C yr−1 for sesquiterpenes. The model results are compared to state-of-the-art emission budgets, showing that the ORCHIDEE emissions are within the range of published estimates. ORCHIDEE BVOC emissions are compared to the estimates of the Model of Emissions of Gases and Aerosols from Nature (MEGAN), which is largely used throughout the biogenic emissions and atmospheric chemistry community. Our results show that global emission budgets of the two models are, in general, in good agreement. ORCHIDEE emissions are 8 % higher for isoprene, 8 % lower for methanol, 17 % higher for acetone, 18 % higher for monoterpenes and 39 % higher for sesquiterpenes, compared to the MEGAN estimates. At the regional scale, the largest differences between ORCHIDEE and MEGAN are highlighted for isoprene in northern temperate regions, where ORCHIDEE emissions are higher by 21 Tg C yr−1, and for monoterpenes, where they are higher by 4.4 and 10.2 Tg C yr−1 in northern and southern tropical regions compared to MEGAN. The geographical differences between the two models are mainly associated with different EF and plant functional type (PFT) distributions, while differences in the seasonal cycle are mostly driven by differences in the leaf area index (LAI). Sensitivity tests are carried out for both models to explore the response to key variables or parameters such as LAI and light-dependent fraction (LDF). The ORCHIDEE and MEGAN emissions are differently affected by LAI changes, with a response highly depending on the compound considered. Scaling the LAI by a factor of 0.5 and 1.5 changes the isoprene global emission by −21 and +8 % for ORCHIDEE and −15 and +7 % for MEGAN, and affects the global emissions of monoterpenes by −43 and +40 % for ORCHIDEE and −11 and +3 % for MEGAN. Performing a further sensitivity test, forcing ORCHIDEE with the MODIS LAI, confirms the high sensitivity of the ORCHIDEE emission module to LAI variation. We find that MEGAN is more sensitive to variation in the LDF parameter than ORCHIDEE. Our results highlight the importance and the need to further explore the BVOC emission estimate variability and the potential for using models to investigate the estimated uncertainties.

Methyl mercury in the dutch rhine delta

1994 ◽  
Vol 30 (10) ◽  
pp. 213-219 ◽  
Author(s):  
Hendrik Pieters ◽  
Victor Geuke
Keyword(s):  
Suspended Matter ◽  
Methyl Mercury ◽  
Mercury Contamination ◽  
Benthic Organisms ◽  
Considerable Decrease ◽  
Continuous Sedimentation ◽  
Highly Correlated ◽  
High Level ◽  
Almost All

Samples of yellow eel from various locations in the Dutch Rhine area have been analyzed for trend monitoring of mercury since 1977. In the western Rhine delta mercury levels in eels have hardly changed since the seventies, whereas in the eastern part of the Dutch Rhine area a considerable decrease of mercury concentrations in eel has occurred. Because of continuous sedimentation of contaminated suspended matter transported from upstream regions, accumulation rates and concentrations of mercury in eel in the western Rhine delta remained at a relatively high level. Analyses of methyl mercury in biota have been performed to elucidate the role of methyl mercury in the mercury contamination of the Dutch Rhine ecosystem. Low percentages of methyl mercury were observed in zooplankton (3 to 35%). In benthic organisms (mussels) percentages of methyl mercury ranged from 30 to 57%, while in fish species and liver of aquatic top predator birds almost all the mercury was present in the form of methyl mercury (&gt; 80%). During the period 1970-1990 mercury concentrations of suspended matter in the eastern Rhine delta have drastically decreased. These concentrations seemed to be highly correlated with mercury concentrations of eel (R = 0.84). The consequences of this relation are discussed.

scholarly journals Emissions of halocarbons from India inferred through atmospheric measurements

2019 ◽  
Vol 19 (15) ◽  
pp. 9865-9885 ◽  
Author(s):  
Daniel Say ◽  
Anita L. Ganesan ◽  
Mark F. Lunt ◽  
Matthew Rigby ◽  
Simon O'Doherty ◽  
...  
Keyword(s):  
Rapid Growth ◽  
Central India ◽  
Fold Increase ◽  
Montreal Protocol ◽  
Emission Rates ◽  
Atmospheric Measurements ◽  
Modelling Framework ◽  
Global Emission ◽  
Atmospheric Measurement ◽  
Ozone Depleting Substances

Abstract. As the second most populous country and third fastest growing economy, India has emerged as a global economic power. As such, its emissions of greenhouse and ozone-depleting gases are of global significance. However, unlike neighbouring China, the Indian sub-continent is very poorly monitored by atmospheric measurement networks. India's halocarbon emissions, here defined as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs) and chlorocarbons, are not well-known. Previous measurements from the region have been obtained at observatories many hundreds of kilometres from source regions, or at high altitudes, limiting their value for the estimation of regional emission rates. Given the projected rapid growth in demand for refrigerants and solvents in India, emission estimates of these halocarbons are urgently needed to provide a benchmark against which future changes can be evaluated. In this study, we report atmospheric-measurement-derived halocarbon emissions from India. With the exception of dichloromethane, these top-down estimates are the first for India's halocarbons. Air samples were collected at low altitude during an aircraft campaign in June and July 2016, and emissions were derived from measurements of these samples using an inverse modelling framework. These results were evaluated to assess India's progress in phasing out ozone-depleting substances under the Montreal Protocol. India's combined CFC emissions are estimated to be 54 (27–86) Tg CO2 eq. yr−1 (5th and 95th confidence intervals are shown in parentheses). HCFC-22 emissions of 7.8 (6.0–9.9) Gg yr−1 are of similar magnitude to emissions of HFC-134a (8.2 (6.1–10.7) Gg yr−1). We estimate India's HFC-23 emissions to be 1.2 (0.9–1.5) Gg yr−1, and our results are consistent with resumed venting of HFC-23 by HCFC-22 manufacturers following the discontinuation of funding for abatement under the Clean Development Mechanism. We report small emissions of HFC-32 and HFC-143a and provide evidence to suggest that HFC-32 emissions were primarily due to fugitive emissions during manufacturing processes. A lack of significant correlation among HFC species and the small emissions derived for HFC-32 and HFC-143a indicate that in 2016, India's use of refrigerant blends R-410A, R-404A and R-507A was limited, despite extensive consumption elsewhere in the world. We also estimate emissions of the regulated chlorocarbons carbon tetrachloride and methyl chloroform from northern and central India to be 2.3 (1.5–3.4) and 0.07 (0.04–0.10) Gg yr−1 respectively. While the Montreal Protocol has been successful in reducing emissions of many ozone-depleting substances, growth in the global emission rates of the unregulated very short-lived substances poses an ongoing threat to the recovery of the ozone layer. Emissions of dichloromethane are found to be 96.5 (77.8–115.6) Gg yr−1, and our estimate suggests a 5-fold increase in emissions since the last estimate derived from atmospheric data in 2008. We estimate perchloroethene emissions from India and chloroform emissions from northern–central India to be 2.9 (2.5–3.3) and 32.2 (28.3–37.1) Gg yr−1 respectively. Given the rapid growth of India's economy and the likely increase in demand for halocarbons such as HFCs, the implementation of long-term atmospheric monitoring in the region is urgently required. Our results provide a benchmark against which future changes to India's halocarbon emissions may be evaluated.

Sensitivity to binaural intensity and phase difference cues in kitten inferior colliculus

1990 ◽  
Vol 64 (2) ◽  
pp. 582-597 ◽  
Author(s):  
B. J. Blatchley ◽  
J. F. Brugge
Keyword(s):  
Auditory Cortex ◽  
Inferior Colliculus ◽  
Phase Difference ◽  
Central Nucleus ◽  
Intensity Difference ◽  
Monotonic Functions ◽  
Age Related ◽  
Highly Correlated ◽  
Intensity Functions ◽  
Almost All

1. Responses of single neurons to monaural or binaural CF tones delivered through a closed and calibrated sound delivery system were studied in the central nucleus of the inferior colliculus (ICC) in ketamine and barbiturate-anesthetized kittens 4-105 days old. 2. Neurons from young kittens had elevated thresholds, some greater than 100 dB in the youngest kittens tested. Average thresholds in the ICC matched those previously measured in the auditory nerve (AN), cochlear nuclei (CN), and auditory cortex (CTX), suggesting that the drop in threshold as a function of age is primarily determined by development at the periphery. 3. Minimal first-spike latencies were relatively long in the youngest kittens, approaching adult values by the end of the third postnatal week. Latencies were distributed between values previously determined for the CN and auditory cortex and can be attributed to the centripetal development of the auditory system. 4. The range of frequencies that were effective in exciting ICC neurons was restricted in young kittens. Neurons having characteristic frequencies (CFs) greater than 7 kHz were not recorded before postnatal day 10. CF distribution matched that obtained in previous experiments from AN, CN, and CTX, reflecting the development of the cochlea. 5. Both monotonic and nonomonotonic spike count-versus-intensity functions were found in the youngest kittens. There was a tendency for monotonic functions from the youngest kittens to be steeper than those from older kittens. No age-related changes in the shapes of non-monotonic functions were found. 6. Sensitivity to interaural intensity difference (IID), tested by holding the intensity to the excitatory ear at a suprathreshold level and increasing the intensity of the stimulus to the inhibitory ear, was exhibited as early as 8 days after birth. The majority of the cells exhibiting sensitivity to IID (89.5%) were classified as EI cells, and almost all IID sensitive cells had CFs between 3 and 25 kHz. Within our sample the shapes of IID functions, as well as the operating range of the IID functions, closely resembled those obtained from the adult cat. Thresholds of excitation and of inhibition were highly correlated, suggesting that the ipsilateral and contralateral inputs to the ICC develop as a matched set. 7. Sensitivity to interaural phase difference (IPD), tested either by shifting the onset phase of a CF tone to one ear relative to the other or by presenting tones of slightly different frequency to the two ears, was present as early as 12 days after birth.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Atmospheric abundance and global emissions of perfluorocarbons CF<sub>4</sub>, C<sub>2</sub>F<sub>6</sub> and C<sub>3</sub>F<sub>8</sub> since 1900 inferred from ice core, firn, air archive and in situ measurements

2016 ◽  
Author(s):  
Cathy M. Trudinger ◽  
Paul J. Fraser ◽  
David M. Etheridge ◽  
William T. Sturges ◽  
Martin K. Vollmer ◽  
...  
Keyword(s):  
World War Ii ◽  
Global Financial Crisis ◽  
Ice Core ◽  
Emission Factors ◽  
Smelting Process ◽  
Atmospheric Measurements ◽  
Temporary Reduction ◽  
Aluminium Production ◽  
The Impact ◽  
Global Emissions

Abstract. Perfluorocarbons (PFCs) are very potent and long-lived greenhouse gases in the atmosphere, released predominantly during aluminium production and semiconductor manufacture. They have been targeted for emission controls under the United Nations Framework Convention on Climate Change. Here we present the first continuous records of the atmospheric abundance and global emissions of CF4 (PFC-14), C2F6 (PFC-116) and C3F8 (PFC-218) from 1900 to 2014. The records are derived from high precision measurements of PFCs in air extracted from polar firn or ice at six sites (DE08, DE08-2, DSSW20K, EDML, NEEM and South Pole) and air archive tanks and atmospheric air sampled from both hemispheres. We take proper account of the age characteristics of the firn and ice core air samples and demonstrate excellent consistency between the ice core, firn and atmospheric measurements. In addition to an inversion for global emissions from 1900 to 2014, we also formulate the inversion to directly infer emission factors for PFC emissions due to aluminium production prior to the 1980s. We show that the late-Holocene pre-industrial level was 34.05 &amp;pm; 0.33 ppt for CF4, and below detection limits of 0.002 ppt and 0.01 ppt for C2F6 and C3F8, respectively. We find a significant peak in CF4 and C2F6 emissions around 1940, most likely due to the high demand for aluminium during World War II, for example for construction of aircraft. The PFC emission factors for aluminium production in the early twentieth century were significantly higher than today, but have decreased since then due to improvements and better control of the smelting process. We see a temporary reduction of around 15 % in CF4 emissions in 2009, presumably associated with the impact of the Global Financial Crisis on aluminium and semiconductor production.

Estimating arterial resistance and compliance during transient conditions in humans

1989 ◽  
Vol 257 (1) ◽  
pp. H190-H197 ◽  
Author(s):  
F. C. Yin ◽  
Z. R. Liu
Keyword(s):  
Pressure Difference ◽  
Arterial Compliance ◽  
Quantitative Difference ◽  
Peripheral Resistance ◽  
Aortic Pressure ◽  
Hemodynamic Parameters ◽  
Windkessel Model ◽  
Total Arterial Compliance ◽  
Highly Correlated ◽  
Almost All

Almost all existing methods for estimating hemodynamic parameters are valid only during steady-state conditions. There is often a need, however, for estimating peripheral resistance and total arterial compliance during beat-to-beat transients such as during atrial fibrillation. During such transients the pressure at the onset and end of a cardiac cycle usually differ. This pressure difference necessitates a modification of usual methods used for estimating these hemodynamic parameters. In this paper we formulate a method for estimating resistance and total arterial compliance during such beat-to-beat transients. For simplicity the expressions are derived for a two-element windkessel model of the circulation. The method is a generalization of one we previously proposed. Rather than using parameter estimation techniques or having to assume a monoexponential pressure decay during diastole, our method uses the areas under the systolic and diastolic portions of the aortic pressure versus time tracing to obtain explicit expressions for compliance; both for the case where it is constant and when it is assumed to be nonlinear (exponential) function of pressure. Aortic pressure and flow data from patients undergoing cardiac catheterization are employed to illustrate the method. Results illustrate the quantitative difference between uncorrected and corrected estimates of both resistance and compliance as a function of the pressure difference between the onset and end of each beat. The uncorrected parameters were found to be linearly and highly correlated with these pressure differences. Regressions of pressure difference against normalized values revealed that the pooled data for all patients defined a single relationship.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Do contemporary (1980–2015) emissions determine the elemental carbon deposition trend at Holtedahlfonna glacier, Svalbard?

2017 ◽  
Vol 17 (20) ◽  
pp. 12779-12795 ◽  
Author(s):  
Meri M. Ruppel ◽  
Joana Soares ◽  
Jean-Charles Gallet ◽  
Elisabeth Isaksson ◽  
Tõnu Martma ◽  
...  
Keyword(s):  
Elemental Carbon ◽  
Transport Model ◽  
Ice Core ◽  
Climate Impact ◽  
The Arctic ◽  
Chemical Transport Model ◽  
Atmospheric Measurements ◽  
Atmospheric Concentration ◽  
Scavenging Efficiency ◽  
Firn Core

Abstract. The climate impact of black carbon (BC) is notably amplified in the Arctic by its deposition, which causes albedo decrease and subsequent earlier snow and ice spring melt. To comprehensively assess the climate impact of BC in the Arctic, information on both atmospheric BC concentrations and deposition is essential. Currently, Arctic BC deposition data are very scarce, while atmospheric BC concentrations have been shown to generally decrease since the 1990s. However, a 300-year Svalbard ice core showed a distinct increase in EC (elemental carbon, proxy for BC) deposition from 1970 to 2004 contradicting atmospheric measurements and modelling studies. Here, our objective was to decipher whether this increase has continued in the 21st century and to investigate the drivers of the observed EC deposition trends. For this, a shallow firn core was collected from the same Svalbard glacier, and a regional-to-meso-scale chemical transport model (SILAM) was run from 1980 to 2015. The ice and firn core data indicate peaking EC deposition values at the end of the 1990s and lower values thereafter. The modelled BC deposition results generally support the observed glacier EC variations. However, the ice and firn core results clearly deviate from both measured and modelled atmospheric BC concentration trends, and the modelled BC deposition trend shows variations seemingly independent from BC emission or atmospheric BC concentration trends. Furthermore, according to the model ca. 99 % BC mass is wet-deposited at this Svalbard glacier, indicating that meteorological processes such as precipitation and scavenging efficiency have most likely a stronger influence on the BC deposition trend than BC emission or atmospheric concentration trends. BC emission source sectors contribute differently to the modelled atmospheric BC concentrations and BC deposition, which further supports our conclusion that different processes affect atmospheric BC concentration and deposition trends. Consequently, Arctic BC deposition trends should not directly be inferred based on atmospheric BC measurements, and more observational BC deposition data are required to assess the climate impact of BC in Arctic snow.

Prospects for Employment Opportunities in the 1970s

1971 ◽  
Vol 9 (2) ◽  
pp. 283-291
Author(s):  
Archibald Callaway
Keyword(s):  
Economic Growth ◽  
Developing Countries ◽  
Labour Force ◽  
Employment Opportunities ◽  
Cambridge University ◽  
Development Committee ◽  
Almost All ◽  
Distribution Of Income ◽  
Overseas Development ◽  
Key Questions

Unemployment – and underemployment – of large proportions of the labour force is a central factor in almost all of today's developing countries. For many, this situation has steadily worsened despite the achievement during the last decade of relatively high rates of economic growth. Poverty and malaise characterise wide areas of the countryside as well as large sectors of major cities. These problems were explored by the eighth in the series of international conferences on development, sponsored by Cambridge University Overseas Development Committee. Key questions were posed: What are the facts of unemployment and underemployment? What are its causes? What measures should be taken to generate more employment opportunities and to reduce, simultaneously, the more glaring inequalities in the distribution of income?

Cognitive Abilities and Their Interplay

2006 ◽  
Vol 27 (2) ◽  
pp. 57-72 ◽  
Author(s):  
Markus Buehner ◽  
Stefan Krumm ◽  
Matthias Ziegler ◽  
Tonja Pluecken
Keyword(s):  
Working Memory ◽  
Sustained Attention ◽  
Cognitive Abilities ◽  
Latent Variables ◽  
Common Variance ◽  
Crystallized Intelligence ◽  
The Common ◽  
Highly Correlated ◽  
Almost All ◽  
And Storage

The aim of this study was to confirm that coordination and storage in the context of processing are significant predictors of reasoning even if crystallized intelligence is controlled for. It was also expected that sustained attention and coordination would be highly correlated. Therefore, 20 working memory tests, 2 attention tests, and 18 intelligence subtests were administered to 121 students. We were able to replicate results indicating that storage in the context of processing and coordination are significant predictors of reasoning. Controlling for crystallized intelligence did not decrease the common variance between working memory and reasoning. The study also revealed that the factors coordination and sustained attention were highly correlated. Finally, a model is presented with the latent variables speed and g, which can explain almost all of the common variance of the applied aggregates. A detailed discussion of the results supports the view that working memory and intelligence share about 70% of the common variance.

scholarly journals Food and Nutrition in Pakistan (A Cross-regional Study)

1987 ◽  
Vol 26 (4) ◽  
pp. 485-498 ◽  
Author(s):  
Shaheen A. But ◽  
Tallat Mahmood
Keyword(s):  
Developing Countries ◽  
Nutritional Status ◽  
Family Size ◽  
Large Family ◽  
Mirror Image ◽  
Nutritional Deficiencies ◽  
Regional Study ◽  
Negative Effect ◽  
Per Capita ◽  
Almost All

Though the nutritional status of an individual is the outcome of complex interaction of a host of environmental factors, income is the mirror-image of a household's purchasing capacity. Another major factor in determining nutritional status in developing countries is considered to be the family size. Higher income levels are regarded as a prerequisite for the improved nutritional status of household [Berg (1973); Levinson and Morinda (1974); Seyoam, Kindaue and Gebru (1986)]. It is posited that, with improvement in a household's income, the absolute expenditure on food is likely to go up as also the intake of four essential nutrients.1 It has been observed in various studies that food intake level in developing countries varies significantly across income classes (Seyoam, Kindaue and Gebru (1986). A World Bank. study underscored the fact that serious and intensive nutritional deficiencies that exist in almost all developing countries are largely a reflection of poverty (World Development Report 1980). A large family size may adversely affect the nutritional status of every member of a household because it may be associated with decreased per capita human impact i.e. the allocation of food per member is likely to decrease with the increase in the number of household members which, in turn, may have a negative effect on per capita nutrient intake.

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