Climate Puzzle Over Origins of Life On Earth

The mystery of why life on Earth evolved when it did has deepened with the publication of a new study in the latest edition of the journal Science.

Scientists at the CRPG-CNRS University of Lorraine, The University of Manchester and the Institut de Physique du Globe de Paris have ruled out a theory as to why the planet was warm enough to sustain the planet's earliest life forms when the Sun's energy was roughly three-quarters the strength it is today.

Life evolved on Earth during the Archean, between 3.8 and 2.4 billion years ago, but the weak Sun should have meant the planet was too cold for life to take hold at this time; scientists have therefore been trying to find an explanation for this conundrum, what is dubbed the 'faint, young Sun paradox'.

"During the Archean the solar energy received at the surface of the Earth was about 20 to 25 % lower than present," said study author, Dr Ray Burgess, from Manchester's School of Earth, Atmospheric and Environmental Sciences. "If the greenhouse gas composition of the atmosphere was comparable to current levels then the Earth should have been permanently glaciated but geological evidence suggests there were no global glaciations before the end of the Archean and that liquid water was widespread."

One explanation for the puzzle was that greenhouse gas levels -- one of the regulators of Earth's climate -- were significantly higher during the Archean than they are today.

"To counter the effect of the weaker Sun, carbon dioxide concentrations in the Earth's atmosphere would need to have been 1,000 times higher than present," said lead author Professor Bernard Marty, from the CRPG-CNRS University of Lorraine. "However, ancient fossil soils -- the best indicators of ancient carbon dioxide levels in the atmosphere -- suggest only modest levels during the Archean. Other atmospheric greenhouse gases were also present, in particular ammonia and methane, but these gases are fragile and easily destroyed by ultraviolet solar radiation, so are unlikely to have had any effect."

But another climate-warming theory -- one the team wanted to test -- is that the amount of nitrogen could have been higher in the ancient atmosphere, which would amplify the greenhouse effect of carbon dioxide and allow Earth to remain ice-free.

The team analysed tiny samples of air trapped in water bubbles in quartz from a region of northern Australia that has extremely old and exceptionally well-preserved rocks.

"We measured the amount and isotopic abundances of nitrogen and argon in the ancient air," said Professor Marty. "Argon is a noble gas which, being chemically inert, is an ideal element to monitor atmospheric change. Using the nitrogen and argon measurements we were able to reconstruct the amount and isotope composition of the nitrogen dissolved in the water and, from that, the atmosphere that was once in equilibrium with the water."

 

The researchers found that the partial pressure of nitrogen in the Archean atmosphere was similar, possibly even slightly lower, than it is at present, ruling out nitrogen as one of the main contenders for solving the early climate puzzle.

Dr Burgess added: "The amount of nitrogen in the atmosphere was too low to enhance the greenhouse effect of carbon dioxide sufficiently to warm the planet. However, our results did give a higher than expected pressure reading for carbon dioxide -- at odds with the estimates based on fossil soils -- which could be high enough to counteract the effects of the faint young Sun and will require further investigation."

Source:Science Daily

R.S

Study Could Help Improve Nuclear Waste Repositories

Here’s the question faced by a team of Sandia National Laboratories researchers: How fast will iodine-129 released from spent nuclear fuel move through a deep, clay-based geological repository?

Understanding that process is crucial as countries worldwide consider underground clay formations for nuclear waste disposal, because clay offers low permeability and high radionuclide retention. Even when a repository isn’t sited in clay, engineered barriers often include a compacted buffer of bentonite, a common type of clay, to improve waste isolation.

Iodine-129, a radioactive isotope with a half-life of 15.7 million years, is an important fission product in spent nuclear fuel and a major contributor to the predicted total radiation dose from a deep geological repository. So even a small improvement in the ability of clay to retain iodine-129 can make a difference in total dose predictions.

Some evidence indicates weak interaction between clay and iodide — a negatively charged predominant chemical species of iodine in geologic repositories, said researcher Yifeng Wang, who leads the study. Computer models haven’t been able to adequately explain clay’s chemical behavior with iodide, and the mechanism is difficult to study because the faint interaction is easily masked by measurement uncertainties.

 “It seems there’s some kind of previously unrecognized mechanism that accounts for that kind of interaction,” said Wang, co-principal investigator for the Laboratory Directed Research and Development project to study radionuclide-clay interaction, now in its third and final year.

His team concluded the interaction, often disregarded as experimental noise, is real and that there might be engineering ways to improve clay’s ability to retain iodide.

The team — Wang and former co-principal investigator Andy Miller, who recently left Sandia; technician Hernesto Tellez; and year-round interns Jessica Kruichak and Melissa Mills — developed experiments with different clays, focusing on their structural characteristics. Past studies of iodide retention in clay concentrated on bentonite. Wang’s team instead studied several different clays, five with the same type of layered structure as bentonite.

Although industries are accustomed to using the plentiful and oft-studied bentonite, the team’s experiments show other clays have higher radionuclide retention capability and might isolate spent fuel waste better. Kaolinite had the best iodide retention of the five clays with layering properties. Wang said the team believes its work “can help us select a better clay material or combination of clay materials.”

Team members believe they discovered a mechanism for iodide-clay interactions that allows more accurate prediction of iodine-129 movement in a geologic repository. The finding was presented in May to the International High Level Radioactive Waste Management Conference in Albuquerque and was published in the conference proceeding.

 

The experimental data indicate iodide directly interacts with the tiny spaces between the layers of clay, called clay interlayer sites. That raises the question of how negatively charged iodide gets into those negatively charged interlayer sites, since like charges repel each other, similar to magnets of the same polarity. “So that contradicts the conventional concept,” Wang said.

The team got clues about what was going on by studying the problem at the nanoscale, 100,000 times smaller than the diameter of a human hair. At that scale, Wang said, the property of water changes in a way that enhances the pairing of ions.

Source:Science Daily

Sh/Kh

Experiment to Produce Bio-Gas

DAMASCUS, (ST) - Minister of State for Environmental Affairs, Dr. Nazira Sarkis, recently affirmed the ministry's keenness to cooperate with all public bodies and civil society organizations to take advantage of experiments and projects aimed at reducing the pollution of the environment and reduce greenhouse gas emissions.


It showed the minister Sarkis By launching an experiment to produce bio-gas by the Society for the Protection of Environment and Sustainable Development in Damascus, Dr. Sarkis clarified  the need to use this technology as a distinctive experience to increase the use of waste, noting the importance of circulating this experience in order to meet the growing needs for energy and educate citizens to use and benefit of the economic and environmental advantage and energy-saving.

For his part, Head of the Association of Environmental Protection and Sustainable Development, Dr. Yahya Owaida, showed the importance of the project, especially in the current circumstances and the search for alternative means of energy, pointing out that the most important goal of the project is to protect the environment and support the government's efforts in this regard and educate citizens about the use of this technique.

The experiment, carried out by the Society of Environment Protection and Sustainable Development funded by the Global Environment Utility, relies on biogas production from animal dung on an anaerobic fermentation tank, bag for gas storage and pump gas in addition to a solar charger and gas pipeline. This experiment quickly and easily install and weight removable and multiple materials used to generate gas such as food waste, grass and straw used as fermentation materials as well as characterized by the production of gas.

 

Sh Kh.

Scientists Relate Urban Population to Air Pollution

Live in a large city like New York, London, Beijing or Mumbai, and you are likely exposed to more air pollution than people in smaller cities in surrounding areas. But exactly how a city's pollution relates to the size of its population has never been measured, until now.

Using satellite observations, NASA scientists directly measured air pollution's dependence on population in four of the planet's major air pollution regions: the United States, Europe, China and India.

The study shows that the pollution-population relationship varies by region. For example, a city of 1 million people in Europe experiences six times higher nitrogen dioxide pollution than an equally populated city of 1 million people in India, according to the research led by Lok Lamsal, of NASA's Goddard Space Flight Center in Greenbelt, Md. The variation is a reflection of regional differences such as industrial development, per capita emissions and geography. The study was published June 13 in Environmental Science & Technology.

Previously, researchers have measured the relationship between population and several urban characteristics, such as infrastructure, employment and innovation. "We show that the relationship is also applicable to pollution," Lamsal said. "Measurement of that relationship is potentially useful for developing future inventories and formulating air pollution control policies."

The researchers focused on nitrogen dioxide, or NO2, a common pollutant from the burning of fossil fuels. The gas is a precursor to the formation of near-ground ozone, which can cause respiratory problems and is a problem in many major metropolitan areas. NO2 is also unhealthy to breathe in high concentrations. One feature of the gas, however, is that it's a good proxy for urban air quality.

Lok and colleagues studied data collected by the Ozone Monitoring Instrument on NASA's Aura satellite, which measures NO2 throughout the atmosphere in the afternoon around the world. Next they used an air quality computer model to derive from the satellite data the annual mean concentration of the gas near the ground in some of the Northern Hemisphere's major polluting regions, excluding hotspots such as power plants that could skew the urban relationship. By overlaying pollution concentration with population density data, the researchers could examine the relationship.

Results across the different regions showed divergent NO2 surface concentrations in urban areas of 1 million people: 0.98 parts per billion (U.S.), 1.33 ppb (Europe), 0.68 ppb (China) and 0.23 ppb (India). The same regions saw various degrees of pollution increases in cities with population of 10 million people: 2.55 ppb (U.S.), 3.86 ppb (Europe), 3.13 ppb (China) and 0.53 ppb (India).

The contribution to air pollution from surface-level NO2 in each region more than doubled when cities increased in population from 1 million to 10 million people, although in China the increase was much larger, by about a factor of five.

Even though larger cities are typically more energy efficient with lower per-capita emissions, more people still translates to more pollution. But the study reveals some noteworthy regional differences.

"Energy usage patterns and per capita emissions differ greatly between India and Europe," Lamsal said. "Despite large populations, Indian cities seem cleaner in terms of NO2 pollution than the study's other regions."

The researchers say that further investigation is needed in order to clarify the causes behind the regional differences.

N.H.Khider

Source :Science daily

Traffic Pollution and Wood Smoke Increases Asthma in Adults

Asthma sufferers frequently exposed to heavy traffic pollution or smoke from wood fire heaters, experienced a significant worsening of symptoms, a new University of Melbourne led study has found.

The study is the first of its kind to assess the impact of traffic pollution and wood smoke from heaters on middle-aged adults with asthma.

The results revealed adults who suffer asthma and were exposed to heavy traffic pollution experienced an 80 per cent increase in symptoms and those exposed to wood smoke from wood fires experienced an 11 per cent increase in symptoms.

Asthma affects more than 300 million people worldwide and is one of the most chronic health conditions.

Dr John Burgess of the School of Population Health at the University of Melbourne and a co-author on the study said "it is now recommended that adults who suffer asthma should not live on busy roads and that the use of old wood heaters should be upgraded to newer heaters, to ensure their health does not worsen."

In the study, a cohort of 1383 44-year old adults in the Tasmanian Longitudinal Health Study were surveyed for their exposure to smoke from wood fires and traffic pollution. Participants were asked to rate their exposure.

The survey asked for exposure to the frequency of heavy traffic vehicles near homes and the levels of ambient wood smoke in winter.

Results were based on the self-reporting of symptoms and the number of flare-ups or exacerbations in a 12-month period. Participants reported from between two to three flare-ups (called intermittent asthma) to more than one flare-up per week (severe persistent asthma) over the same time.

Traffic exhaust is thought to exacerbate asthma through airway inflammation. Particles from heavy vehicles exhaust have been shown to enhance allergic inflammatory responses in sensitized people who suffer asthma.

"Our study also revealed a connection between the inhalation of wood smoke exposure and asthma severity and that the use of wood for heating is detrimental to health in communities such as Tasmania where use of wood burning is common," Dr Burgess said.

"Clean burning practices and the replacement of old polluting wood stoves by new ones are likely to minimise both indoor and outdoor wood smoke pollution and improve people's health," he said.

"These findings may have particular importance in developing countries where wood smoke exposure is likely to be high in rural communities due to the use of wood for heating and cooking, and the intensity of air pollution from vehicular traffic in larger cities is significant."

The study revealed no association between traffic pollution and wood smoke and the onset of asthma

N.H.Khider

Source : Science Daily