93 research outputs found
Conflicting estimates of natural geologic methane emissions
Global bottom-up and top-down estimates of natural, geologic methane (CH4) emissions (average approximately 45 Tg yrâ1) have recently been questioned by near-zero (approximately 1.6 Tg yrâ1) estimates based on measurements of 14CH4 trapped in ice cores, which imply that current fossil fuel industries' CH4 emissions are underestimated by 25%â40%. As we show here, such a global near-zero geologic CH4 emission estimate is incompatible with multiple independent, bottom-up emission estimates from individual natural geologic seepage areas, each of which is of the order of 0.1â3 Tg yrâ1. Further research is urgently needed to resolve the conundrum before rejecting either method or associated emission estimates in global CH4 accounting
Chemical Recycling of Carbon Dioxide to Methanol and Dimethyl Ether: From Greenhouse Gas to Renewable, Environmentally Carbon Neutral Fuels and Synthetic Hydrocarbons
Inventory of current EU paediatric vision and hearing screening programmes
Background: We examined the diversity in paediatric vision and hearing screening
programmes in Europe.
Methods: Themes relevant for comparison of screening programmes were derived from
literature and used to compile three questionnaires on vision, hearing and public-health
screening. Tests used, professions involved, age and frequency of testing seem to influence
sensitivity, specificity and costs most. Questionnaires were sent to ophthalmologists,
orthoptists, otolaryngologists and audiologists involved in paediatric screening in all EU fullmember,
candidate and associate states. Answers were cross-checked.
Results: Thirty-nine countries participated; 35 have a vision screening programme, 33 a
nation-wide neonatal hearing screening programme. Visual acuity (VA) is measured in 35
countries, in 71% more than once. First measurement of VA varies from three to seven years
of age, but is usually before the age of five. At age three and four picture charts, including Lea
Hyvarinen are used most, in children over four Tumbling-E and Snellen. As first hearing
screening test otoacoustic emission (OAE) is used most in healthy neonates, and auditory
brainstem response (ABR) in premature newborns. The majority of hearing testing
programmes are staged; children are referred after one to four abnormal tests. Vision
screening is performed mostly by paediatricians, ophthalmologists or nurses. Funding is
mostly by health insurance or state. Coverage was reported as >95% in half of countries, but
reporting was often not first-hand.
Conclusion: Largest differences were found in VA charts used (12), professions involved in
vision screening (10), number of hearing screening tests before referral (1-4) and funding
sources (8)
Global methane emission through mud volcanoes and its past and present impact on the Earth's climate. Comment.
The role of mud volcanoes (MVs) as a source of methane(CH4) flux to the atmosphere and the ocean has been increasingly recognised in the last several years (Milkov
2000; Dimitrov 2002, 2003; Etiope and Klusman 2002; Kopf 2002, 2003; Milkov et al. 2003; Etiope and Milkov
2004). In one of the most recent papers, Kopf (2003) claims to report a reliable estimate of the global CH4 emission from MVs. However, the significance and
usefulness of the estimate presented by Kopf (2003) are rather poor. The used dataset is smaller than in previous
studies (although the author makes a reverse claim), and
some previously published works are misquoted and misinterpreted. Numerous arithmetic mistakes made
during simple calculations and data manipulations lead to confusing results and conclusions. In this comment,
we highlight some of the most significant problems with the estimates published by Kopf (2003).Published490-4924.5. Degassamento naturaleJCR Journalreserve
Global methane emission through mud volcanoes and its past and present impact on the Earth's climate. Comment.
The role of mud volcanoes (MVs) as a source of methane(CH4) flux to the atmosphere and the ocean has been increasingly recognised in the last several years (Milkov
2000; Dimitrov 2002, 2003; Etiope and Klusman 2002; Kopf 2002, 2003; Milkov et al. 2003; Etiope and Milkov
2004). In one of the most recent papers, Kopf (2003) claims to report a reliable estimate of the global CH4 emission from MVs. However, the significance and
usefulness of the estimate presented by Kopf (2003) are rather poor. The used dataset is smaller than in previous
studies (although the author makes a reverse claim), and
some previously published works are misquoted and misinterpreted. Numerous arithmetic mistakes made
during simple calculations and data manipulations lead to confusing results and conclusions. In this comment,
we highlight some of the most significant problems with the estimates published by Kopf (2003)
Measurement of Nasal Mucociliary Clearance by Saccharin Test
The nasal mucosa lines the entry of the respiratory tract and is in constant contact with a great variety of inhaled microbial antigens and allergens. Mucociliary clearance is defined as cleaning of upper and lower airway by interaction of nasal mucus and ciliary beating. Inhaled particles, bacteria and virus are trapped in the mucus and are transported by the beat of the cilia to the pharynx where they are either swallowed or coughed up.The main purpose of this study is to examine the capabilities of the saccharin test and its application in determination of the modified mucociliary clearance time (MTC) by obstructive nasal breathing, caused by different local pathology. The essence of the test is that a small amount of saccharin is placed approximately 1 cm behind the anterior end of the inferior turbinate. In the presence of normal mucociliary action, the saccharin will be swept backwards to the nasopharynx and a sweet taste perceived.15 healthy volunteers and 15 patients with obstructive nasal breathing were tested with the saccharin test. Most of the similar studies indicate different clearance times as normal, averaging between 5 and 19 minutes (max. 36 minutes). Results, out of the norm, were registered in cases with present nasal breathing disorder. Our research does not show considerable difference in this respect.Regardless of whether normal or pathological mucociliary clearance is concerned, the saccharin test appears to be simple, inexpensive and reproducible examination, appropriate for quick and reliable valuation of mucociliary function or dysfunction
Did geologic emissions of methane play any role in Quaternary climate change?
The âmethane-led hypothesesâ assume that gas hydrates and marine seeps are the sole geologic factors controlling Quaternary atmospheric and climate changes. Nevertheless, a wider class of geologic sources of methane exist which could have played a role in past climate changes. Beyond
offshore seepage, relevant geologic emissions of methane (GEM) are from onshore seepage, including mud volcanism, microseepage and
geothermal flux; altogether GEM are the second most important natural source of atmospheric methane at present. The amount of methane entering the atmosphere from onshore GEM seems to prevail on that from offshore seepage. Onshore sources inject a predominantly isotopically heavy (13C-enriched) methane into the atmosphere. They are controlled mainly by endogenic (geodynamic) processes, which induce large-scale gas flow variations over geologic and millennial time scales, and only partially by exogenic (surface) conditions, so that they are not affected by negative feedbacks. The eventual influence on atmospheric methane concentration does not necessarily require catastrophic or abrupt releases, as proposed for the âclathrate gun hypothesisâ. Enhanced degassing from these sources could have contributed to the methane trends observed in the ice core records, and could explain the late Quaternary peaks of increased methane concentrations accompanied by the enrichment of isotopically heavy methane, as recently observed. This hypothesis shall be tested by means of robust multidisciplinary studies, mainly based on a series of atmospheric, biologic and geologic proxies
Methane emission from mud volcanoes in eastern Azerbaijan
Methane (CH4) flux to the atmosphere was measured from gas vents and, for the first
time, from soil microseepage at four quiescent mud volcanoes and one ââeverlasting fireââ
in eastern Azerbaijan. Mud volcanoes show different activity of venting craters, gryphons,
and bubbling pools, with CH4 fluxes ranging from less than one to hundreds of tons per
year. Microseepage CH4 flux is generally on the order of hundreds of milligrams per
square meter per day, even far away from the active centers. The CH4 flux near the
everlasting fires (on the order of 105 mg·m22·d21) represents the highest natural CH4
emission from soil ever measured. The specific CH4 flux to the atmosphere, between 102
and 103 t·km22·yr21, was similar to specific flux from other mud volcanoes in Europe. At
least 1400 tons of CH4 per year are released from the investigated areas. It is conservatively
estimated that all onshore mud volcanoes of Azerbaijan, during quiescent activity,
may still emit ;0.3â0.9 3 106 t of CH4 per year into the atmosphere. The new data fill a
significant gap in the worldwide data set and confirm the importance of geologic sources
of greenhouse CH4, although they are not yet considered in the climate-study budgets of atmospheric CH4 sources and sinks.Published465-468reserve
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