Artist’s impression of a massive asteroid impact, such as the one over three billion years ago, that may have splintered Earth’s crust
One of the things that distinguishes Earth from other planets is its plate tectonics. But how did this moving jigsaw surface begin? New research suggests that a 3.26 billion-year-old asteroid impact may have kick-started the process.
The impact crater has long since gone (recycled by plate tectonics), but Norman Sleep and Donald Lowe, both at Stanford University, have been able to study this cataclysmic event by looking at the fall-out it produced: tiny spherical rocks which rained down into an ocean, in what is now South Africa. These little grains, and the shattered rocks surrounding them, tell the story of what was probably one of the last major asteroid impacts during Earth’s violent early history.
And what an impact it was. Hurtling in at 72,000km per hour, this 37km wide asteroid (four times larger than the one that wiped out the dinosaurs) smashed into Earth, vaporising rock and creating a 500km wide crater. The impact triggered magnitude 10.8 earthquakes (100 times larger than the 2011 Japanese earthquake), set off tsunamis, and heated the atmosphere enough to make oceans boil.
Crucially the findings, published in the journal Geochemistry, Geophysics, Geosystems, also indicate that the impact could have initiated plate tectonics. Since then the heat from Earth’s mantle has kept the plates in a state of continuous agitation. Without that impact Earth’s surface might be more akin to Mars or Venus. And without the constant chemical recycling that plate tectonics brings (which stabilises Earth’s climate) we probably wouldn’t be here.
Note : The above story is based on materials provided by Kate Ravilious “The Guardian”
William Philipps, a UB geology graduate researcher, examines Greenland’s terrain as part of research on deglaciation and global climate change. Credit: Jason Briner
After one of the snowiest winters in recent history, William Philipps will forego the beach to spend the summer studying glaciers at the world’s northernmost university.
The University at Buffalo geology graduate student and self-proclaimed “nerd who likes rocks” will travel to the University Centre on Svalbard (UNIS) in Norway to collect data that proves the Svalbard-Barents Sea Ice-Sheet’s (SBSIS) time of deglaciation – the point when the ice began to melt – is older than its suggested age of 12,000 years.
Philipps, an Amherst native, will travel to Svalbard on July 12 through the UNIS’s Icebound Project, funded by the ConocoPhillips and Lundin Petroleum arctic research program, which seeks to improve understanding of the region for petroleum exploration. He will spend three months completing a mix of courses and research on global climate change.
The Norwegian archipelago of Svalbard is not the average study abroad or research experience. Philipps will visit during the region’s midnight sun season, a period when the sun is visible 24 hours a day. He will also undergo survival training that includes strapping on an insulated suit and learning to withstand the chilly artic water.
Fortunately, Philipps is familiar with the experience. A member of the paleoclimatology research group under Jason Briner, PhD, associate professor in the UB Department of Geology in the UB College of Arts and Sciences, he conducted similar research in Greenland as an undergraduate.
“I am incredibly fortunate to be where I am in life,” says Philipps. “I get to work in the most breathtaking settings in the world on complex scientific problems and learn from some of the foremost research scientists in my field.”
At their maximum extent, as long ago as 25,000 years ago, the SBSIS and other ice sheets – some over a mile thick – engulfed the northern hemisphere. But over time, the ice eroded, transporting pieces of rock, known as glacial erratics, up to hundreds of miles into different geologic areas.
Once the ice melted, the rocks were exposed to the sun and bombarded with cosmic radiation, causing a nuclear chemical reaction that produces beryllium. Through cosmogenic exposure dating, researchers measure the ratios of beryllium to determine the time of deglaciation.
The material used to date the SBSIS’s deglaciation were pieces of driftwood found on Kongsøya and Hopen, two of Svalbard’s eastern most islands. However, the conditions for the wood to be deposited on the islands indicate that the time between the ice beginning to drift and when the wood was deposited may be thousands of years off, says Philipps.
After collecting samples from several locations that are fractions of a gram in weight and about the size of a pinhead, the researchers will send the erratics to a mass spectrometer facility to measure their age.
The study’s results will increase the understanding of the SBSIS’s behavior and can potentially help predict the future behavior of the West Antarctic Ice Sheet.
Determining the age of the erratics will also improve constraints of glacial isostatic adjustment (GIA) values for the region, which detail the rise of land masses that were suppressed by the weight of ice sheets during a glacial period, says Philipps.
Note : The above story is based on materials provided by University at Buffalo
Chemical Formula: NaCaB5O7(OH)4·3H2O Locality: Boron, Kern Co., California. Name Origin: Named for Frank H. Probert (1876-1940), University of California, who discovered the mineral.
Cartoon of the wind intensification/upwelling process. Increasing winds and upwelling may increase nutrients in the lighted upper ocean, enhancing primary productivity, but excessive upwelling may increase turbulence, acidification and de-oxygenation of the photic zone. The ecological impacts of upwelling intensification are difficult to predict. Credit: Steve Ravenscraft for The Pew Charitable Trusts
Summer winds are intensifying along the west coasts of North and South America and southern Africa and climate change is a likely cause, a new study says.
The winds, which blow parallel to the shore and draw cold, nutrient-rich water from the deep ocean to the surface in a process known as coastal upwelling, have increased over the last 60 years in three out of five regions of the world, according to an analysis published Thursday in the journal Science.
Stronger winds have the potential to benefit coastal areas by bringing a surge of nutrients and boosting populations of plankton, fish and other species. But they could also harm marine life by causing turbulence in surface waters, disrupting feeding, worsening ocean acidification and lowering oxygen levels, the study says.
The shift could already be having serious effects on some of the world’s most productive marine fisheries and ecosystems off California, Peru and South Africa.
At this point “we don’t know what the implications are,” said William Sydeman, president of the Farallon Institute for Advanced Ecosystem Research in Petaluma, Calif., who led the study by seven scientists in the U.S. and Australia. “On the one hand it could be good. On the other hand, it could be really bad.”
The windier conditions are occurring in important currents along the eastern edges of the Pacific and Atlantic oceans. In those areas, the influx of nutrients from coastal upwelling fuels higher production of phytoplankton, tiny plant-like organisms that are eaten by fish, which in turn feed populations of seabirds, whales and other marine life.
Scientists said their results lend support to a hypothesis made more than two decades ago by oceanographer Andrew Bakun. He suggested that rising temperatures from the human-caused buildup of greenhouse gases, by causing steeper atmospheric pressure gradients between oceans and continents, would produce stronger winds during summer and drive more coastal upwelling.
To test that claim, researchers reviewed and analyzed 22 published studies that tracked winds in the world’s five major coastal upwelling regions using data from the 1940s to the mid-2000s.
Scientists found a trend of windier conditions in the California Current along the west coast of North America, the Humboldt Current off Peru and Chile and the Benguela Current off the west coast of southern Africa. In the Canary and Iberian currents off northern Africa and Spain, however, they found no clear signs of increasing winds.
Researchers can’t say for sure that human-caused climate change is to blame, but they said finding a pattern that was consistent across several parts of the planet gives a strong indication it is a factor. The study also found that the increase in winds was more pronounced at higher latitudes, which is in line with other observed effects of climate change.
The study’s conclusions are controversial among ocean scientists. They say the records used in the analysis do not go back far enough in time to rule out naturally occurring climate cycles such as the Pacific Decadal Oscillation, which shifts between warm and cool phases about every 20 to 30 years and also influences atmospheric conditions.
“It doesn’t prove that global warming is driving this,” said Art Miller, a climate scientist at Scripps Institution of Oceanography who was not involved in the study.
Similar limitations in the data have made it difficult for other researchers to link increases in coastal upwelling to climate change.
A study published last year by Canadian researchers, for instance, found huge year-to-year changes in coastal winds and the timing and intensity of upwelling from Vancouver Island to Northern California and urged caution in analyzing trends over short time periods.
“We found it extremely difficult to capture a climate change signal,” said Brian Bylhouwer, an environmental scientist with Stantec Consulting in Dartmouth, Canada, who led that study.
Sydeman acknowledged that scientists need more time and data to firmly establish that shifting winds are the result of climate change and not natural cycles.
He said future research will examine the mechanism behind the increase in coastal winds and study how a boost in upwelling might be affecting fish and seabirds off California and South Africa.
More information:
Climate change and wind intensification in coastal upwelling ecosystems, Science 4 July 2014: Vol. 345 no. 6192 pp. 77-80. DOI: 10.1126/science.1251635
Map of the Amazon Basin with the Mamoré River highlighted
The Mamoré is a large river in Bolivia and Brazil, which unites with the Beni to form the Madeira, one of the largest tributaries of the Amazon. It rises on the northern slope of the Sierra de Cochabamba, east of the city of Cochabamba, and is known as the Chimoré down to its junction with the Chapare. Its larger tributaries are the Chapare, Secure, Apere, and Yacuma from the west, and the Ichilo, Guapay, Ivari, Manique, and Guapore from the east.
Taking into account its length only, the Guapay should be considered the upper part of the Mamore; but it is shallow and obstructed, and carries a much smaller volume of water. The Guapore also rivals the Mamore in length and volume, having its source in the Parecis plateau, Mato Grosso, Brazil, a few miles from streams flowing north-ward to the Tapajos and Amazon, and southward to the Paraguay and Paraná rivers. The Mamore is interrupted by rapids a few miles above its junction with the Beni, but a railway 300 km long has been undertaken from below the rapids of the Madeira. Above the rapids the river is navigable to Chimore, at the foot of the sierra, and most of its tributaries are navigable for long distances. In 1874, Franz Keller gave the outflow of the Mamoré at mean water level, and not including the Guapore, as 41,459 cm3/sec (2,530 cub. in. per second), and the area of its drainage basin, also not including the Guapore, as 24,299 km2 (9,382 square miles).
Note : The above story is based on materials provided by Wikipedia
Chemical Formula: Ca2Al2Si3O10(OH)2 Locality: Haslach, Harzburg and Oberstein, Germany. Name Origin: Named after the Dutch Colonel, H. Von Prehn (1733-1785).Prehnite is a inosilicate of calcium and aluminium with the formula: Ca2Al2Si3O10(OH)2. Limited Fe3+ substitutes for aluminium in the structure. Prehnite crystallizes in the orthorhombic crystal system, and most oftens forms as stalactitic or botryoidal aggregates, with only just the crests of small crystals showing any faces, which are almost always curved or composite. Very rarely will it form distinct, well individualized crystals showing a square-like cross-section, like those found at the Jeffrey Mine in Asbestos, Quebec, Canada. It is brittle with an uneven fracture and a vitreous to pearly lustre. Its hardness is 6-6.5, its specific gravity is 2.80-2.90 and its color varies from light green to yellow, but also colorless, blue or white. In April 2000, a rare orange Prehnite was discovered at the famous Kalahari Manganese Fields in South Africa. It is mostly translucent, and rarely transparent.
Though not a zeolite, it is found associated with minerals such as datolite, calcite, apophyllite, stilbite, laumontite, heulandite etc. in veins and cavities of basaltic rocks, sometimes in granites, syenites, or gneisses. It is an indicator mineral of the prehnite-pumpellyite metamorphic facies.
It was first described in 1788 for an occurrence in the Karoo dolerites of Cradock, Eastern Cape Province, South Africa. It was named for Colonel Hendrik Von Prehn (1733–1785), commander of the military forces of the Dutch colony at the Cape of Good Hope from 1768 to 1780.
Extensive deposits of gem quality prehnite occur in the basalt tableland surrounding Wave Hill Station in the central Northern Territory, of Australia.
Authors : WERNER Discovery date : 1788 Town of Origin : CAP DE BONNE ESPERANCE Country of Origin: AFRIQUE DU SUD
Optical properties
Optical and misc. Properties : Macles possibles – Fragile, cassant – Transparent – Translucide – Gemme, pierre fine – Refractive Index : from 1,61 to 1,66 Axial angle 2V: 65-69°
Physical properties
Hardness : from 6,00 to 6,50 Density : from 2,80 to 2,95 Color : yellow; grey; white; colorless; pale green; dark green; green; greenish yellow; yellowish green; pink Luster : vitreous; nacreous Streak: white Break: irregular Cleavage: yes
The new (eleventh) specimen of Archaeopteryx. Credit: H. Tischlinger
Paleontologists of Ludwig-Maximilians-Universitaet (LMU) in Munich are currently studying a new specimen of Archaeopteryx, which reveals previously unknown features of the plumage. The initial findings shed light on the original function of feathers and their recruitment for flight.
A century and a half after its discovery and a mere 150 million years or so since it took to the air, Archaeopteryx still has surprises in store: The eleventh specimen of the iconic “basal bird” so far discovered turns out to have the best preserved plumage of all, permitting detailed comparisons to be made with other feathered dinosaurs. The fossil is being subjected to a thorough examination by a team led by Dr. Oliver Rauhut, a paleontologist in the Department of Earth and Environmental Sciences at LMU Munich, who is also affiliated with the Bavarian State Collection for Paleontology and Geology in Munich. The first results of their analysis of the plumage are reported in the latest issue of Nature. The new data make a significant contribution to the ongoing debate over the evolution of feathers and its relationship to avian flight. They also imply that the links between feather development and the origin of flight are probably much more complex than has been assumed up to now.
“For the first time, it has become possible to examine the detailed structure of the feathers on the body, the tail and, above all, on the legs,” says Oliver Rauhut. In the case of this new specimen, the feathers are, for the most part, preserved as impressions in the rock matrix. “Comparisons with other feathered predatory dinosaurs indicate that the plumage in the different regions of the body varied widely between these species. That suggests that primordial feathers did not evolve in connection with flight-related roles, but originated in other functional contexts,” says Dr. Christian Foth of LMU and the Bavarian State Collection for Paleontology and Geology in Munich, first author on the new paper.
To keep warm and to catch the eye
Predatory dinosaurs (theropods) with body plumage are now known to predate Archaeopteryx, and their feathers probably provided thermal insulation. Advanced species of predatory dinosaurs and primitive birds with feathered forelimbs may have used them as balance organs when running, like ostriches do today. Moreover, feathers could have served useful functions in brooding, camouflage and display. Indeed, the feathers on the tail, wings and hind-limbs most probably fulfilled functions in display, although it is very likely that Archaeopteryx was also capable of flight. “Interestingly, the lateral feathers in the tail of Archaeopteryx had an aerodynamic form, and most probably played an important role in its aerial abilities,” says Foth.
On the basis of their investigation of the plumage of the new fossil, the researchers have been able to clarify the taxonomical relationship between Archaeopteryx and other species of feathered dinosaur. Here, the diversity in form and distribution of the feather tracts is particularly striking. For instance, among dinosaurs that had feathers on their legs, many had long feathers extending to the toes, while others had shorter down-like plumage. “If feathers had evolved originally for flight, functional constraints should have restricted their range of variation. And in primitive birds we do see less variation in wing feathers than in those on the hind-limbs or the tail,” explains Foth.
These observations imply that feathers acquired their aerodynamic functions secondarily: Once feathers had been invented, they could be co-opted for flight. “It is even possible that the ability to fly evolved more than once within the theropods,” says Rauhut. “Since the feathers were already present, different groups of predatory dinosaurs and their descendants, the birds, could have exploited these structures in different ways.” The new results also contradict the theory that powered avian flight evolved from earlier four-winged species that were able to glide.
Archaeopteryx represents a transitional form between reptiles and birds and is the best-known, and possibly the earliest, bird fossil. It proves that modern birds are directly descended from predatory dinosaurs, and are themselves essentially modern-day dinosaurs. The many new fossil species of feathered dinosaurs discovered in China in recent years have made it possible to place Archaeopteryx within a larger evolutionary context. However, when feathers first appeared and how often flight evolved are matters that are still under debate.
The eleventh known specimen of Archaeopteryx is still in private hands. Like all other examples of the genus, it was found in the Altmühl valley in Bavaria, which in Late Jurassic times lay in the northern tropics, and at the bottom of a shallow sea, as all Archaeopteryx fossils found so far have been recovered from limestone deposits.
Note : The above story is based on materials provided by Ludwig-Maximilians-Universitaet Muenchen (LMU).
Scientists at Rice have reported the results of their decadelong effort to build a two-dimensional mathematical model that will help identify rich pockets of gas hydrate under the ocean floor. The model shows where hydrates – the “ice that burns” – are likely to be found based on extrapolating data from core samples, seismic signals and other geologic data. Click for larger image. Credit: Sayantan Chatterjee
A decade of research by Rice University scientists has produced a two-dimensional model to prove how gas hydrate, the “ice that burns,” is formed under the ocean floor.Gas hydrate—basically methane frozen under high pressures and low temperatures—has potential as a source of abundant energy, if it can be extracted and turned into usable form.
It also has potential to do great harm, if global warming results in melting hydrate that releases methane, a powerful greenhouse gas, into the atmosphere.
The award-winning mathematical model created by Rice alumnus Sayantan Chatterjee, who earned his doctorate in chemical engineer George Hirasaki’s group, is intended to help pinpoint abundant pockets of hydrate by extrapolating data from several sources: one-dimensional core samples, seismic surveys that image the fractures as well as stratified layers of sand and clay that build up over millennia, and the geochemistry of sediment and water near the ocean floor, which offers chemical clues to what lies beneath.
The research was published by the Journal of Geophysical Research – Solid Earth.
There’s a lot at stake for energy producers—and consumers—in finding hydrates in high concentrations, with as much as 20 trillion tons of methane under the sea. Japanese researchers are already testing production techniques in the Pacific, but extraction without reliable exploration tools is too expensive, Chatterjee said.
The Rice researchers’ two-dimensional model draws upon a variety of survey techniques to envision a more accurate slice of the deep-sea formation.
“Our modeling incorporates geologic processes like sedimentation and compaction that enable methane-rich fluids to flow through porous media,” Chatterjee said. Methane degraded by microbes from organic matter or rising from the depths turns into hydrate when it encounters the necessary pressure, temperature and salinity conditions in the gas hydrate stability zone, which can be as shallow as a few hundred meters.
“High-saturation hydrate deposits preferentially occur in fracture networks within fine-grained sediment and interbedded, permeable sand sequences, and we’re looking for such lithologic sweet spots,” he said.
Chatterjee explained the complex stratigraphy and lack of homogeneity of subsea formations limits the ability of one-dimensional modeling and core samples to scan a potential hydrate reservoir isolated in permeable sand sequences between dense layers of clay. “Marine lithologic layering is very complex, and we can’t replicate it in our models. But we have developed techniques to compute local fluid flow in lithologically complex reservoirs, which we correlate to local hydrate saturation,” he said.
“When people seismically image the submarine formations and recover sediment cores dominated with faults and fractures, they find these fractures to be filled with hydrates,” Chatterjee said. “Our model has explained this observation. It shows that these fracture networks and sand layers are the sweet spots for hydrate occurrence, the ones we want to pinpoint when it comes to exploration.”
The Rice team intends the model to locate these hydrate-rich pockets and estimate how saturated they’re likely to be based on the geologic setting and history. “Only when a pore space is highly saturated with hydrate is it economically feasible to drill at that location to extract these trapped hydrocarbons,” he said. “But first we have to estimate the fluid flow. No flow, no hydrates.”
More information:
Sayantan Chatterjee, Gaurav Bhatnagar, Brandon Dugan, Gerald R. Dickens, Walter G. Chapman and George J. Hirasaki “The Impact of Lithologic Heterogeneity and Focused Fluid Flow upon Gas Hydrate Distribution in Marine Sediments” Journal of Geophysical Research: Solid Earth. Accepted manuscript online: 25 JUN 2014 DOI: 10.1002/2014JB011236
Note : The above story is based on materials provided by Rice University
Chemical Formula: Ca(MoO4) Locality: Peacock Mine, Cuprum, Seven Devils District, Adams Co., Idaho, USA Name Origin: Named after the American geologist, John Westly Powell (1834-1902).Powellite is a calcium molybdate mineral with formula Ca(MoO4). Powellite crystallizes with tetragonal – dipyramidal crystal structure as transparent adamantine blue, greenish brown, yellow to grey typically anhedral forms. It exhibits distinct cleavage and has a brittle to conchoidal fracture. It has a Mohs hardness of 3.5 to 4 and a specific gravity is 4.25. It forms a solid solution series with scheelite (calcium tungstate, CaWO4). It has refractive index values of nω=1.974 and nε=1.984.Powellite was first described by William Harlow Melville in 1891 for an occurrence in the Peacock Mine, Adams County, Idaho and named for American explorer and geologist, John Wesley Powell (1834–1902).
It occurs in hydrothermal ore deposits of molybdenum within the near surface oxidized zones. It also appears as a rare mineral phase in pegmatite, tactite and basalt. Minerals found in association with powellite include molybdenite, ferrimolybdite, stilbite, laumontite and apophyllite.
A team of scientists has discovered that a giant ‘burp’ of carbon dioxide (CO2) from the North Pacific Ocean helped trigger the end of last ice age, around 17,000 years ago.
A recent study, led by Dr James Rae of the University of St Andrews, found that changes in ocean circulation in the North Pacific caused a massive ‘burp’ of CO2 to be released from the deep ocean into the atmosphere, helping to warm the planet sufficiently to trigger the end of the ice age.
Previously, scientists have suggested that the Antarctic Ocean and North Atlantic were the only places likely to release deglacial CO2, due to their deep water formation. However, a change in rainfall over the North Pacific region, caused by the East Asian monsoon and the Westerly storm track, made the ocean surface saltier and less buoyant, allowing it to form deep water. This allowed CO2 stored in the deep Pacific to be released to the atmosphere, where it helped warm the planet and melt back the ice sheets that covered much of the Northern Hemisphere.
Dr James Rae, of the University’s Department of Earth and Environmental Sciences, explained:
“Our study shows that North Pacific deep water penetrated all the way into the deep ocean, allowing it to release deep ocean CO2. We tested this idea further with a climate model, which showed that deep water formation in the North Pacific causes ocean CO2 release, large enough to drive the atmospheric CO2 rise recorded at the start of the deglaciation.
The results of our study came as a big surprise, as we were expecting to see a signature of CO2 release from the ocean around Antarctica, which has been the leading hypothesis for deglacial CO2 rise. Instead we found a signal we can only explain with CO2 release from the North Pacific.”
The team of scientists from the University of St Andrews, University of Bristol and University of Kiel, Germany, made a series of chemical measurements on minuscule fossil shells to trace ocean CO2 storage and circulation patterns up to two miles beneath the ocean’s surface.
Dr Gavin Foster, of the University of Southampton, added; “This study is only really possible thanks to new developments in geochemistry, that allow us to reconstruct the pH of the ocean in the past for the first time, giving an accurate measurement of how ocean CO2 is stored and released”.
The new findings will help scientists understand how the earth’s climate can operate, and the different ways in which the ocean and atmosphere can exchange CO2.
Dr Rae concluded:
“Although the CO2 rise caused by this process was dramatic in geological terms, it happened very slowly compared to modern man-made CO2 rise. Humans have driven CO2 rise in the atmosphere as large as the CO2 rise that helped end the last ice age, but the man-made CO2 rise has happened 100 times faster. This will have a huge effect on the climate system, and one that we are only just starting to see.”
More information:
Rae, J. W. B., M. Sarnthein, G. L. Foster, A. Ridgwell, P. M. Grootes, and T. Elliott (2014), “Deep water formation in the North Pacific and deglacial CO2 rise,” Paleoceanography, 29, DOI: 10.1002/2013PA002570.
Note : The above story is based on materials provided by University of St Andrews
Iron is an essential element in all living creatures, and its availability in seawater can have a profound effect on phytoplankton growth and, consequently, the earth’s carbon cycle. In the journal Nature, Seth John and Tim Conway have just published an assessment of the various sources of dissolved iron in the north Atlantic Ocean.
Iron is present in tiny concentrations in seawater. On the order of a few billionths of a gram in a liter.
“I did a calculation once on a ton of ocean water,” says Seth John, an assistant professor in the department of marine science at the University of South Carolina. “The amount of iron in that ton of water would weigh about as much as a single eyelash.”
Given that there is so little iron in seawater, one might conclude that its presence there is inconsequential.
Hardly. Iron is one of the essential elements of life. Found in enzymes like myoglobin and hemoglobin and cytochrome P450, iron is an essential cog in the biomachinery of every living cell. And its scarcity in the ocean, the earth’s wellspring of life, only magnifies its importance.
“The key reason that everybody cares about iron is because it limits the growth of phytoplankton, such as algae, in maybe a fifth of the ocean,” says John, a researcher in the School of Earth, Ocean and Environment in South Carolina’s College of Arts and Sciences.
In those iron-poor places, there’s plenty of everything else that phytoplankton, the base of the food web, need to grow—sunlight, carbon, fixed nitrogen, water. Just a small change in the amount of iron that finds its way there can have a dramatic impact on the growth of photosynthetic organisms and their concomitant uptake of carbon dioxide.
When algae and other phytoplankton grow, they take carbon dioxide out of the atmosphere, converting it into proteins and other carbon-based molecules that constitute living cells. And it takes very little iron to keep this process going—in a typical cell, for every atom of iron, there are about a million atoms of carbon, says John. A little iron goes a long way in allowing phytoplankton to grow and pull carbon dioxide out of the air.
Knowing how iron moves into the oceans is thus crucial for scientists to fully understand the details of the carbon cycle on earth.
John and his colleagues have spent the past several years working to fill in those details. They’ve been collecting ocean samples and developing their analytical techniques for quantifying different natural isotopes of iron in seawater, which is one means of tracking the origins of the dissolved metal.
Iron finds its way into seawater from a variety of sources. The ratio of the stable natural isotopes iron-56 and iron-54 from these sources can differ from the ratio in the earth’s crust because a number of chemical processes change the ratio by favoring the release of one of the two isotopes. The processes controlling release of iron from distinct sources vary, and so different sources can have characteristic iron-56/iron-54 ratios. Tiny variations in this ratio in seawater samples thus provide insight into the origin of the iron found there.
For example, one source is sediments from the ocean’s floor, from which iron is typically released into the ocean under very low-oxygen (anoxic) conditions, and release of ‘light’ iron-54 is favored. Another source is dust from the atmosphere, from which Fe is typically released into the ocean with processes favoring ‘heavy’ iron-56. Using this information, the researchers were able to establish, for the first time, where dissolved iron in seawater had originated.
John and postdoctoral associate Tim Conway have developed a high-throughput means of purifying seawater samples and determining the iron-56/iron-54 ratio, a method capable of handling the nearly 600 samples they collected in a high-resolution transect of the north Atlantic Ocean on a GEOTRACES cruise.
From those samples, they were able to show in a paper published in the journal Nature that the largest source of iron in the north Atlantic, somewhere between 70 and 90 percent, comes from dust that blows in from the Sahara desert.
The results are helping define a very poorly understood but essential component of the carbon cycle.
“It could help us understand past climate change, like glacial-interglacial cycles,” says John. “There would have been huge changes in dust fluxes to the ocean in glacial times, and so understanding how much iron comes from dust in the modern day helps us figure out whether that was an important driver of glacial-interglacial cycles.”
The breakdown of the sources might surprise many, according to John and Conway.
“I think that a lot of people thought that there would be a lot of dust in the north Atlantic, and so while it’s very satisfying to have proved that, it’s perhaps more surprising that there’s 20 percent that comes from other sources,” says John. “I think before we published this paper, you would have found many, many people who would have guessed that that was zero percent or very close to zero percent.”
“That’s one interesting thing that the iron isotopes really show on the east margin,” says Conway. “Off the coast of Africa you have really high iron, and in the past most people attributed that just to dust. We can show from the iron isotopes that there’s actually iron coming from sediments.
“People have always argued whether it was dust or sediments. This is one of the first studies to really show clearly that sediments are important as well.”
Chemical Formula: KNa2B3Si12O30 Locality: From Mont Saint-Hilaire, Quebec, Canada. Name Origin: Named for the Poudrette family, operators of the quarry where type material was discovered.
Poudretteite is an extremely rare mineral and gemstone that was first discovered as minute crystals in Mont St. Hilaire, Quebec, Canada, during the 1960s. The mineral was named for the Poudrette family because they operated a quarry in the Mont St. Hilaire area where poudretteite was originally found.
When the 1893 World’s Fair opened in Chicago, fairgoers aboard the world’s first Ferris wheel soared high enough to compare two cities: the White City—gleaming whitewashed architecture built for the massive fair—and its dark twin, the blackened, soot-stained buildings of the Loop just a few miles to the north.
Chicago, like many industrialized cities in the 19th century, lay under a thick layer of soot of its own making. Dirt from trains and factories soiled linen shirts and blew into homes past tightly shut windows. Across the Atlantic in London, residents lit lamps at midday to wade through pea-soup fogs, yellow with sulfur, that lingered over the city for days.
Nineteenth-century meteorologist Luke Howard called London “the volcano of a hundred thousand mouths,” referring to the city’s factories and engines that constantly exhaled soot, which is mostly made up of tiny particles of black carbon. Black carbon is released when things burn: coal and other fuels, bush fires, and the combustion that powers diesel engines and generators.
In the 20th century, scientists began to learn exactly how bad soot is for human health—it accelerates heart failure and burrows into lung tissue, aggravating asthma and respiratory conditions. More recently, scientists have started to realize that carbon particulates play a second unwelcome role: the second largest contributor to climate change.
Environmental regulations have helped to clear the skies over many cities. Yet the U.S., along with other countries around the world, still releases particles of carbon from trucks and generators, and we still don’t really understand what happens to it once it leaves the exhaust pipe.
But there is one bright spot in the study of soot. Unlike carbon dioxide, which will remain for hundreds of years, it can cycle out of the atmosphere within weeks. Whatever harm carbon particulates do to the atmosphere is temporary, at least theoretically. That is, if we could only stop.
“Changing habits is perhaps the most difficult challenge of all,” said Argonne scientist Rao Kotamarthi.
Carbon dioxide has long been established as the most notorious contributor to climate change. But aerosolized carbon particles floating around in the atmosphere also influence climate, although their combined effect is substantially more complex. For example, aerosols can scatter incoming solar radiation away from Earth—fling it back into space—which cools the Earth. Or they can absorb solar radiation, which contributes to global warming.
Though they by and large tend to absorb heat, carbon particles are big enough to serve as nuclei for cloud formation. And clouds reflect more sunlight, which cools the Earth. However, there’s some evidence that clouds formed around black carbon don’t last as long; the dark nucleus absorbs heat and evaporates the cloud.
Researchers try to understand this massive puzzle by building extremely detailed virtual models of the atmosphere. At Argonne, climate scientists like Yan Feng pack all the data they can get their hands on into an elaborate working picture of the atmosphere and how it behaves.
To make sure that the model’s analyses line up with the real world, scientists go through a process called “ground-truthing.” “We compare our model’s results to measurements taken at actual sites and see how they compare,” Feng said.
Once they know the model is reliable, Feng and her colleagues can run models forward in time to see what might happen in 10, 25, 100 years, depending on whether we cut aerosol emissions or let them run wild.
“It’s an extremely complex puzzle, but we can address it by looking carefully at problems one by one,” said Rao Kotamarthi, who manages a climate modeling program at Argonne.
Carbon aerosols are in some ways more difficult to model than carbon dioxide. Whereas carbon dioxide spreads fairly evenly around the world, black carbon tends to affect weather more locally. Carbon particulates often linger in the same region where they are emitted because the particles are too heavy to mix into the atmosphere but not as easily washed out in raindrops as other aerosols. A lot of carbon aerosol modeling, therefore, relies heavily on meteorology: charting the local ebb and flow of wind and water and temperature to map how the particles travel. “For example, large-scale meteorology, like a big cold front, can wipe out some of the carbon’s effects—but not all,” Feng said.
In the past few years, Feng has turned her attention to a second type of carbon in the atmosphere, called brown carbon. These are organic particles with different chemical compositions; they can be tar balls or fats. Long, smoldering fires give off brown carbon; hot fires release black.
There’s a lot more brown carbon in the atmosphere by mass, but it can’t trap as much heat by mass as black carbon—”Think of wearing a black shirt in the sun,” Kotamarthi said—so it’s largely been overlooked.
Only recently have researchers at Argonne and elsewhere begun to explore brown carbon’s effects and habits more closely. “We have a little idea of how black carbon behaves,” Feng said. “But brown carbon was only identified as a potentially significant factor in the past several years.”
Feng, along with Kotamarthi and Professor V. Ramanathan at the Scripps Institution of Oceanography, recently published the first global model study to estimate how much heat brown carbon traps in the atmosphere. “Our model shows how carbon is distributed across the atmosphere,” she said. “We can use that to predict how much solar radiation is being trapped in the atmosphere, and from that we can estimate how much the global temperature may rise.” Feng thinks that brown carbon could turn out to be a significant factor in how aerosols affect Earth’s climate.
There are still a lot of uncertainties in the model, though. “Getting more data is the biggest problem,” Kotamarthi said.
That’s where Argonne environmental scientist David Streets comes in. Streets specializes in collecting data on emissions; he modeled Beijing’s air quality before it hosted the 2008 Summer Olympics. In 2005, along with Professor Tami Bond of the University of Illinois, he published the gold standard figures for soot sources now used by modelers around the world.
“We tell them what’s being emitted into the air,” Streets said. “They use meteorology to get where it winds up and how it affects weather and climate.”
To ensure the accuracy of his data, Streets works with collaborators all over the world, including rapidly industrializing countries like China and India.
Climate modelers also keep an eye on a number of different global economic indicators, because the health of the world’s economies significantly affects emissions. In 2008, scientists saw the economic crash written out in the sky. Aerosols dropped noticeably. The skies cleared over Greece in 2010 as the debt crisis squeezed its citizens below.
This is a central reason why aerosol emissions control is so hard. Carbon, like carbon dioxide, tends to ride piggyback on economic development. In particular, developing countries—where the electricity sometimes goes out because the power infrastructure hasn’t quite kept up with demand—tend to rely heavily on diesel generators. They produce a lot of black carbon.
And aerosols are a major human health problem in developing countries. The World Health Organization puts smoke from solid fuels as the 10th major mortality risk factor globally; it estimates that smoke contributes to approximately two million deaths annually, particularly affecting women and children. Urban air pollution ranks among the top 10 risk factors in middle and developed countries too.
We’ve succeeded in reducing emissions from factories and other sources in developed countries like the U.S. and Europe; in many places, black carbon emission levels are lower than they’ve been in decades, if not centuries. In Chicago, cleaners scrubbed a century’s worth of soot off several buildings in the Loop to discover stone and brick underneath in shades of delicate pastels that probably hadn’t been seen since the last tourists left the World’s Fair more than 100 years ago.
“Purely from a technical standpoint, we could do this,” Streets said. “We have the technology.”
Note : The above story is based on materials provided by Argonne National Laboratory
Soot, a.k.a. black carbon, is finding its way to snow-covered peaks and glaciers around the world. Primarily the result of particulate emissions from burning fossil fuels, such as coal-fired power plants and diesel engines, soot has an impact on the regional and global climate. In the Arctic, soot increases ice and snow melt, causing a series of events that are heating up the climate.
No one but a Grinch enjoys black snow—it has no redeeming qualities. Yet scientists at Pacific Northwest National Laboratory trained their sights on soot to understand its undesirable effects on the Arctic environment. Using global climate model simulations, they evaluated soot’s effects in Northern China and the Arctic against measurements over the region. PNNL and a University of Michigan collaborator found key model parameters that correctly spot soot buildup and melt-away in a complex seasonal and latitudinal dependence swing. Their study will help the climate modeling community better understand soot’s great influence on regional and global climate.
Soot, a.k.a. black carbon, may have a greater impact on the fast-retreating Arctic snow pack and glaciers than any other human-caused climate-warming agent. Soot is black, and black draws and holds heat from the sun. Soot from combustion of fossil fuels, such as diesel and coal, as well as forest fires and other organic burning, travels through the atmosphere and falls on snow and glacier ice pack. Like a dark blanket, it heats up the snow and ice and also reduces the amount of the sun’s rays normally reflected back into space from bright, white snow. It’s a one-two punch for the world’s store of ice and snow. This study helps researchers understand how black carbon’s impacts are registered and reproduced in climate models, providing valuable information in predicting the future of the Arctic climate.
The research team led by Dr. Yun Qian at PNNL evaluated the simulated black carbon on snow against measurements collected from multiple field campaigns over the Arctic and Northern China. They conducted a series of sensitivity experiments using the newly improved Community Atmosphere Model version 5 (CAM5) to examine the impact of several key parameters. They looked at the impact of snow aging, and the melt-water scavenging efficiency parameters on black carbon’s concentration and radiative forcing in the model. They also compared the uncertainty (the range of possible answers), resulting from the black carbon deposition, with the uncertainty related to how snow-aging and melt-water scavenging is treated for black carbon in the model.
The sensitivity simulations in CAM5 indicated that the melt-water scavenging efficiency parameter plays an important role in regulating black carbon concentrations in the Arctic through the post-depositional enrichment, which not only drastically changes the amplitude but also shifts the seasonal cycle of the black carbon in snow concentration and its radiative forcing in the Arctic. They found that the improvements of black carbon transport and deposition in CAM5 have a stronger influence on black carbon in snow than perturbations of the two snow model parameters over Northern China.
Scientists are planning research that will explore the limitations of simulating black carbon in snow that were highlighted in this study, including in situ observations and laboratory studies with a focus on snow aging and melt-water scavenging of black carbon.
More information:
Qian Y, H Wang, R Zhang, M Flanner, and PJ Rasch. 2014. “A Sensitivity Study on Modeling the Black Carbon in Snow and its Radiative Forcing over the Arctic and Northern China.” Environmental Research Letters 9:064001. DOI: 10.1088/1748-9326/9/6/064001
Note : The above story is based on materials provided by Pacific Northwest National Laboratory
Polybasite with Chalcopyrite Chispas Mine (Pedrazzini mine), Arizpe, Mun. de Arizpe, Sonora, Mexico Miniature, 5.5 x 4.3 x 3.2 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
Chemical Formula: [(Ag,Cu)6(Sb,As)2S7][Ag9CuS4] Name Origin: From the Greek, poly, “many” and basis, “a base” in allusion to the basic character of the compound.
Polybasite is a sulfosalt mineral of silver, copper, antimony and arsenic. Its chemical formula is [(Ag,Cu)6(Sb,As)2S7][Ag9CuS4].It forms black monoclinic crystals (thin, tabular, with six corners) which can show dark red internal reflections. It has a Mohs hardness of 2.5 to 3. It is found worldwide and is an ore of silver. The name comes from the number of base metals in the mineral.
Discovery date : 1829 Town of Origin : GUARISAMEY, DURANGO Country of Origin : MEXIQUE
Optical properties
Optical and misc. Properties: Translucide – Opaque Reflective Power: 30,2-31,7% (580) Refractive Index: from 2,72 to 2,73 Axial angle 2V : 22°
Physical properties
Hardness : from 2,00 to 3,00 Density: 6,10 Color : iron black; steel black; black grey Luster: metallic; adamantine; unpolished Streak : reddish black; dark red; black Break : irregular Cleavage : yes
Researchers found that Titan’s ice shell, which overlies a very salty ocean, varies in thickness around the moon, suggesting the crust is in the process of becoming rigid. Credit: NASA/JPL -Caltech/SSI/Univ. of Arizona/G. Mitri/University of Nantes
Scientists analyzing data from NASA’s Cassini mission have firm evidence the ocean inside Saturn’s largest moon, Titan, might be as salty as Earth’s Dead Sea.
The new results come from a study of gravity and topography data collected during Cassini’s repeated flybys of Titan during the past 10 years. Using the Cassini data, researchers presented a model structure for Titan, resulting in an improved understanding of the structure of the moon’s outer ice shell. The findings are published in this week’s edition of the journal Icarus.
“Titan continues to prove itself as an endlessly fascinating world, and with our long-lived Cassini spacecraft, we’re unlocking new mysteries as fast as we solve old ones,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, who was not involved in the study.
Additional findings support previous indications the moon’s icy shell is rigid and in the process of freezing solid. Researchers found that a relatively high density was required for Titan’s ocean in order to explain the gravity data. This indicates the ocean is probably an extremely salty brine of water mixed with dissolved salts likely composed of sulfur, sodium and potassium. The density indicated for this brine would give the ocean a salt content roughly equal to the saltiest bodies of water on Earth.
“This is an extremely salty ocean by Earth standards,” said the paper’s lead author, Giuseppe Mitri of the University of Nantes in France. “Knowing this may change the way we view this ocean as a possible abode for present-day life, but conditions might have been very different there in the past.”
Cassini data also indicate the thickness of Titan’s ice crust varies slightly from place to place. The researchers said this can best be explained if the moon’s outer shell is stiff, as would be the case if the ocean were slowly crystalizing and turning to ice. Otherwise, the moon’s shape would tend to even itself out over time, like warm candle wax. This freezing process would have important implications for the habitability of Titan’s ocean, as it would limit the ability of materials to exchange between the surface and the ocean.
A further consequence of a rigid ice shell, according to the study, is any outgassing of methane into Titan’s atmosphere must happen at scattered “hot spots” — like the hot spot on Earth that gave rise to the Hawaiian Island chain. Titan’s methane does not appear to result from convection or plate tectonics recycling its ice shell.
How methane gets into the moon’s atmosphere has long been of great interest to researchers, as molecules of this gas are broken apart by sunlight on short geological timescales. Titan’s present atmosphere contains about five percent methane. This means some process, thought to be geological in nature, must be replenishing the gas. The study indicates that whatever process is responsible, the restoration of Titan’s methane is localized and intermittent.
“Our work suggests looking for signs of methane outgassing will be difficult with Cassini, and may require a future mission that can find localized methane sources,” said Jonathan Lunine, a scientist on the Cassini mission at Cornell University, Ithaca, New York, and one of the paper’s co-authors. “As on Mars, this is a challenging task.”
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA’s Science Mission Directorate in Washington.
Note : The above story is based on materials provided by NASA/Jet Propulsion Laboratory.
The Madeira River is a major waterway in South America, approximately 3,250 km (2,020 mi) long. The Madeira is one of the biggest tributaries of the Amazon. A map from Emanuel Bowen in 1747, held by the David Rumsey Map Collection, refers to the Madeira by the pre-colonial, indigenous name Cuyari:
“The River of Cuyari, called by the Portuguese Madeira or the Wood River, is formed by two great rivers, which join near its mouth. It was by this River, that the Nation of Topinambes passed into the River Amazon.”
The mean inter-annual precipitations on the great basins vary from 750 to 3,000 millimetres (30 to 118 in), the entire upper Madeira basin receiving 1,705 millimetres (67.1 in). The greatest extremes of rainfall are between 490 to 7,000 millimetres (19 to 276 in). At its head, the Madeira on its own is still one of the largest rivers of the world, with a mean inter-annual discharge of 18,000 cubic metres per second (640,000 cu ft/s), i.e. 536 cubic kilometres (129 cu mi)/yr, approximately half the discharge of the Congo River. The mean inter-annual contribution of the Bolivian Andes is 4,170 cubic metres per second (147,000 cu ft/s), i.e. 132 cubic kilometres (32 cu mi)yr, representing 25% of the discharge of the entire upper Madeira basin. On the further course towards the Amazon, the mean discharge of the Madeira increases up to 31,200 cubic metres per second (1,100,000 cu ft/s).
Course
Between Guajará-Mirim and the falls of Teotônio, the Madeira receives the drainage of the north-eastern slopes of the Andes from Santa Cruz de la Sierra to Cuzco, the whole of the south-western slope of Brazilian Mato Grosso and the northern slope of the Chiquitos sierras. In total, the catchment area is 850,000 km2, almost equal in area to France and Spain combined. The waters flow into the Madeira from many large rivers, the principal of which, (from east to west), are the Guaporé or Itenez, the Baures and Blanco, the Itonama or San Miguel, the Mamoré, Beni, and Mayutata or Madre de Dios, all of which are reinforced by numerous secondary but powerful affluents. The climate of the upper catchment area varies from humid in the western edge with the origin of the river’s main stem by volume (Río Madre de Dios, Río Beni) to semi arid in the southernmost part with the andine headwaters of the main stem by length (Río Caine, Río Rocha, Río Grande, Mamoré).
All of the upper branches of the river Madeira find their way to the falls across the open, almost level Mojos and Beni plains, 90,000 km2 (35,000 sq mi) of which are yearly flooded to an average depth of about 3 feet (0.91 m) for a period of from three to four months.
The falls of Teotônio and of San Antonio exceed the more famous Boyoma Falls in Africa by volume and total drop. From these rapids, the Madeira flows northward forming the border between Bolivia and Brazil for approximately 100 km (62 mi). Below the confluence of the Rio Abunã, the Madeira meanders north-eastward through the Rondônia and Amazonas states of north west Brazil to its junction with the Amazon. At its mouth is Ilha Tupinambaranas, an extensive marshy region formed by the Madeira’s distributaries.
Note : The above story is based on materials provided by Wikipedia
Chemical Formula: PbO2 Locality: Leadhills, Lanark, Scotland Name Origin: Named after the German metallurgist, K. F. Plattner (1800-1858).Plattnerite is an oxide mineral and is the beta crystalline form of lead dioxide (β-PbO2), scrutinyite being the other, alpha form. It was first reported in 1845 and named after German mineralogist Karl Friedrich Plattner. Plattnerite forms bundles of dark needle-like crystals on various minerals; the crystals are hard and brittle and have tetragonal symmetry.
Plattnerite is found in numerous arid locations in North America (US and Mexico), most of Europe, Asia (Iran and Russia), Africa (Namibia) and Southern and Western Australia. It occurs in weathered hydrothermal base-metal deposits as hay-like bundles of dark prismatic crystals with a length of a few millimeters; the bundles grow on, or sometimes within various minerals, including cerussite, smithsonite, hemimorphite, leadhillite, hydrozincite, rosasite, aurichalcite, murdochite, limonite, pyromorphite, wulfenite, calcite and quartz.
History
Discovery date : 1845 Town of Origin : LEADHILLS, LANARKSHIRE Country of Origin : ECOSSE
Optical properties
Optical and misc. Properties : Fragile, cassant – Opaque – Translucide – Macles possibles – Reflective Power : ~13%
Physical properties
Hardness : 5,50 Density : 9,42 Color : black; brownish black; black grey Luster : bright metallic; adamantine; unpolished Streak : brown Break : conchoidal Cleavage : NO
This is an atom probe tomography, or APT, analysis result showing the sub-nanoscale elemental distribution within a single aerosol particle. Credit: Arun Devaraj, EMSL
Dust storms, volcanic eruptions and hurricanes are tangible events that send particles of sand, soot and salt into the atmosphere. These particles can alter the climate cycles that heat and cool the Earth. Less obvious sources of aerosols affect these cycles, too; the sea salt sprayed off breaking waves or volatile organic compounds emitted from trees. But nearly untraceable chemical transformations also lead to the birth of new atmospheric particles. Accounting for these newborn particles and their role in cloud formation is key to improving climate models. Scientists recently gathered at EMSL to discuss ways to more accurately chronicle the clandestine lives of these aerosols in the lab and the field.
The precise processes that govern how new particles are created out of vapor, then grow and nucleate clouds – enticing other organic molecules into chemical reactions – largely remains a mystery. Increasingly sophisticated instruments provide scientists with new details about these transformations; they also point out big gaps between theoretical models and field findings.
“We discovered nucleation is an important source of atmospheric particles more than 20 years ago. And ever since we’ve been trying to figure out the chemical and physical processes that lead to their creation,” says Peter McMurry, a professor at the University of Minnesota. “The goal is to achieve closure between the rates observed in the atmosphere and those predicted by models. This will lead to more credible climate models. Right now we can’t do that.”
Part of the problem is catching the particles in the act of doing whatever it is they do. Researchers spend weeks in the field stalking new particle formation events. With little lead time the particles are born. Within a few hours they grow to sizes large enough to serve as cloud condensation nuclei, sending a brief bloom of data across suites of specialized sampling instruments. “It’s a challenge,” says McMurry. “Some of the species that lead to particle formation are found in almost unimaginably low concentrations. Sometimes it’s like trying to pick out one person in a thousand or a million Earths.”
From Field to Lab: An Inside Job
For the last 15 years Alexander Laskin, an atmospheric aerosol chemist at EMSL, and collaborators have been using the unique analytical chemistry capabilities of EMSL on particle samples collected from test facilities, laboratory studies and far-flung field sites. A variety of off-line chemical imaging techniques have been advanced at EMSL – including mass spectrometry, spectroscopy, microscopy and microanalysis methods – to probe the composition and properties of these particles. But there’s no single technique in existence that gives us all the information we need to know. says Laskin”
The ability to run multi-modal analyses on the same sample is a particular strength at EMSL. But even interrogating particles with multiple techniques can’t answer some of the pressing questions. So EMSL researchers are devising new strategies in collaboration with scientists across the country.
Laskin and his colleagues want to understand the physical and chemical properties of aerosols that nucleate ice clouds. Although ice nucleation has been studied for more than two decades, much about the process remains unknown.
“In the traditional view of ice nucleation events, there are very few particles in the atmosphere with the right properties to become ice nuclei,” says Laskin. “But now there’s growing evidence that’s not always case,” he says. “Particles with mediocre ice nucleation propensity – but present at high number concentrations – can play an equivalently important role. So the big question is how to delineate the two scenarios: Under which conditions would different nucleation particles prevail?”
It would be easier to figure out if they could visualize nucleation events, says Bingbing Wang, a postdoctoral researcher at EMSL. To see which individual particles nucleate ice first, he started a project coupling ice nucleation experiments with scanning electron microscopy, complemented with particle spectro-microscopy. Then he can probe the composition of the instigating particles. “From that knowledge we can achieve better understanding of heterogeneous ice nucleation. Then with further data analysis we can provide better parameterizations for cloud and climate models,” says B. Wang.
The study involves a group of Pacific Northwest National Laboratory experts in collaboration with Daniel Knopf of Stony Brook University and Mary Gilles at Lawrence Berkeley National Laboratory.
An Outside Approach
Another way to analyze these perplexing particles is to look at them one by one. To accomplish this, transmission electron microscopy, or TEM, is the technique of choice for Peter Buseck, a professor at Arizona State University who attended the recent user meeting at EMSL. “We want to know the intimate details about these aerosol particles,” he says. “TEM has been used on a larger scale, but now the technique is needed on a nanometer scale because there’s a whole range of particle sizes in the atmosphere.”
Although Buseck already has the TEM capabilities he needs, EMSL could devise novel ways to combine electron microscopy with instruments such as the helium ion microscope in EMSL’s Quiet Wing. No one’s doing that now with aerosols, says Buseck.
Probing the Surface
It’s not just the particles that need to be accounted for.
“An intrinsic scientific problem is how reactions occur and the particle surface is key for those. From mass spectrometry you can find out what kind of molecules are in aerosols, but you don’t know how they are arranged on the particle surface,” says Hongfei Wang, a chief scientist at EMSL.
To get at the structure of the surface, in 2011 H. Wang and his colleagues developed a unique high-resolution sum frequency generation, or HR-SFG, spectrometer to discern surface particle reactions with a resolution 10 times better than any other instruments out there. That kind of resolution was critical for Sergey Nizkorodov who studies aerosol photochemistry in his laboratory at the University of California at Irvine and then sends samples to H. Wang for high-resolution studies at the surface.
“We want to be able to detect minor species that might be important for controlling reactions,” says H. Wang. “We’ve improved resolution, but the sensitivity of the signal needs to be improved for field measurements. It’s possible – but will take at least several years. It will be a real milestone to do this.”
Another pioneer in applying SFG spectroscopy to aerosol particles is Franz Geiger of Northwestern University. After meeting H. Wang at an American Chemical Society conference two years ago, he started using the high-resolution instrument to study alpha-pinene, one of the main components of secondary organic aerosol particles. EMSL’s HR-SFG gave Geiger a significant improvement in his analytics, getting resolution from standard values of about 10 wave numbers down to 0.6 wave numbers.
To bridge the gap between particle analysis in the lab and the field, Geiger is working with Northwestern colleague Regan Thomson, Victor Batista of Yale University and Scot Martin at Harvard University on an EMSL user project and with matching funds from Northwestern (and he hopes, the National Science Foundation).
Geiger is focused on the organic emissions of trees, namely pinene, that react with ozone at the ground level. The resulting cascades of reactions create aerosols that can interact with water vapor and ultimately make clouds. The questions he wants to answer are: Will future, possibly warmer, climates lead to faster emission rates of pinene over the Northern hemisphere? And if more organic particles form, potentially leading to more clouds, would this cause a negative feedback mechanism to cool our planet?
The answers to how these particles form will be found on their surfaces, thinks Geiger. But it’s hard to analyze what’s never been identified before. So the collaborators are creating synthetic compounds they surmise could be created when pinene reacts with ozone and are also surface reactive. By analyzing the chemical signatures of these lab-made components they’ll build a reference library to help identify the unknown surface components they discover on these particles.
“There’s no silver bullet,” says Geiger. “But more current tools will give us a more complete understanding.”
Helping Solve Problems
Aerosol research may also get a boost with instruments that haven’t traditionally been used for studies in this field. In the past, the tiny sample sizes and filter collection methods for aerosol particles have hampered efforts to use analytic techniques such as nuclear magnetic resonance, or NMR, spectroscopy. But at the recent EMSL user meeting, NMR lead scientist Karl Mueller told researchers they’re building smaller and better tools to aid aerosol research.
“NMR is phenomenal for determining chemical structure,” says Nancy Washton, the capability lead for EMSL’s NMR group. “But it’s considered an insensitive technique because it requires such a large sample size – I want a vial full of stuff, about 20 milligrams.”
Now Mueller and Washton are working with a team of scientists to make very small volume NMR detectors. “We’re combining our abilities as ‘spin jocks’ with miniaturization and microfabrication capabilities to work with picoliter amounts more suitable for aerosol studies. Success here would be a real breakthrough,” says Mueller.
Washton anticipates they’ll be able to run aerosol samples within the year. The possibilities have already enticed collaborators to send samples and she thinks NMR will be very useful for scientists who are synthetically producing atmospheric molecules.
Another technique that might prove useful is atom probe tomography, or APT. EMSL Scientist Arun Devaraj thinks APT could provide a way to visualize the three-dimensional element distribution within a single aerosol particle at sub-nanometer spatial resolution.
“Even if a potential user doesn’t quite know what capabilities they need, the staff at EMSL can discuss their needs and provide guidance,” says Alex Guenther, the lead scientist for atmospheric aerosol science at EMSL. The staff will make extraordinary efforts to understand what scientists need for their research and how the laboratory’s capabilities can be applied to answer their scientific questions, he says.
Although new tools are nice, Nicole Riemer, a computer modeler at Illinois University, thinks researchers may squeeze more information out of the tools already on hand. “As modelers, we are using different tools from the researchers in the lab who measure these things,” says Riemer. “But we’re trying to solve the same problems.”
The aerosols are really, really small. So it’s difficult to develop equations that reflect the complexity of those minuscule – but critical – interactions without bogging down the ability to scale up to global proportions. Riemer believes careful, repeated experiments under varied conditions, using the equipment already in EMSL laboratories, can provide key details needed to derive more accurate aerosol predictions. For example, our models are based on particles with spherical shapes, says Riemer. Yet Laskin’s work shows particle morphology changes. “Is that important?” she says. “If it is, we need to know how it changes over time so we can incorporate it into our equations.”
Gathering Better Field Samples
But even the best available laboratory instruments don’t really capture the conditions in the atmosphere. So, Guenther invited scientists to brainstorm better ways to get samples from the field. Among the more immediately feasible possibilities discussed were ways to build a better Orbitrap.
“I was excited to hear discussions about making a smaller high-resolution mass spectrometer to carry around in a truck or plane,” says Nizkorodov. “If there’s a way to get those measurements in real time, that would be a big step forward.”
With that kind of innovation, Franz Geiger may one day realize a decades-old research dream: to analyze aerosol particle surfaces without plucking them out of the air. “People once said we couldn’t study aerosols from ships or planes and now we do that all the time,” he says. “It’s not impossible.”
Note : The above story is based on materials provided by Environmental Molecular Sciences Laboratory
Map of the combined Tigris–Euphrates drainage basin (in yellow)
The Euphrates is the longest and one of the most historically important rivers of Western Asia. Together with the Tigris, it is one of the two defining rivers of Mesopotamia. Originating in eastern Turkey, the Euphrates flows through Syria and Iraq to join the Tigris in the Shatt al-Arab, which empties into the Persian Gulf.
The Ancient Greek form Euphrátēs (Ancient Greek: Εὐφράτης) was borrowed from Old Persian Ufrātu, itself from Elamite ú-ip-ra-tu-iš. In Akkadian the river was similarly called Purattu, which has been perpetuated in Semitic languages (cf. Syriac P(ə)rāṯ, Arabic al-Furrāt) and in other nearby languages of the time (cf. Hurrian Puranti, Sabarian Uruttu). The Elamite, Akkadian, and possibly Sumerian forms are from an unrecorded substrate language.
The earliest references to the Euphrates come from cuneiform texts found in Shuruppak and pre-Sargonic Nippur in southern Iraq and date to the mid-3rd millennium BCE. In these texts, written in Sumerian, the Euphrates is called Buranuna (logographic: UD.KIB.NUN). The name could also be written KIB.NUN.(NA) or dKIB.NUN, with the prefix “d” indicating that the river was a divinity. In Sumerian, the name of the city of Sippar in modern-day Iraq was also a written UD.KIB.NUN, indicating a historically strong relationship between the city and the river.
Course
The Euphrates is the longest river of Western Asia. It emerges from the confluence of the Kara Su or Western Euphrates (450 kilometres (280 mi)) and the Murat Su or Eastern Euphrates (650 kilometres (400 mi)) 10 kilometres (6.2 mi) upstream from the town of Keban in southeastern Turkey.Daoudy and Frenken put the length of the Euphrates from the source of the Murat River to the confluence with the Tigris at 3,000 kilometres (1,900 mi), of which 1,230 kilometres (760 mi) falls in Turkey, 710 kilometres (440 mi) in Syria and 1,060 kilometres (660 mi) in Iraq. The same figures are given by Isaev and Mikhailova. The length of the Shatt al-Arab, which connects the Euphrates and the Tigris with the Persian Gulf, is given by various sources as 145–195 kilometres (90–121 mi).
Both the Kara Su and the Murat Su rise northwest from Lake Van at elevations of 3,290 metres (10,790 ft) and 3,520 metres (11,550 ft) amsl, respectively. At the location of the Keban Dam, the two rivers, now combined into the Euphrates, have dropped to an elevation of 693 metres (2,274 ft) amsl. From Keban to the Syrian–Turkish border, the river drops another 368 metres (1,207 ft) over a distance of less than 600 kilometres (370 mi). Once the Euphrates enters the Upper Mesopotamian plains, its grade drops significantly; within Syria the river falls 163 metres (535 ft) while over the last stretch between Hīt and the Shatt al-Arab the river drops only 55 metres (180 ft).
Discharge of the Euphrates
The Euphrates receives most of its water in the form of rainfall and melting snow, resulting in peak volumes during the months April through May. Discharge in these two months accounts for 36 percent of the total annual discharge of the Euphrates, or even 60–70 percent according to one source, while low runoff occurs in summer and autumn. The average natural annual flow of the Euphrates has been determined from early- and mid-twentieth century records as 20.9 cubic kilometres (5.0 cu mi) at Keban, 36.6 cubic kilometres (8.8 cu mi) at Hīt and 21.5 cubic kilometres (5.2 cu mi) at Hindiya. However, these averages mask the high inter-annual variability in discharge; at Birecik, just above the Syro–Turkish border, annual discharges have been measured that ranged from a low volume of 15.3 cubic kilometres (3.7 cu mi) in 1961 to a high 42.7 cubic kilometres (10.2 cu mi) in 1963.
The discharge regime of the Euphrates has changed dramatically since the construction of the first dams in the 1970s. Data on Euphrates discharge collected after 1990 show the impact of the construction of the numerous dams in the Euphrates and of the increased withdrawal of water for irrigation. Average discharge at Hīt after 1990 has dropped to 356 cubic metres (12,600 cu ft) per second (11.2 cubic kilometres (2.7 cu mi) per year). The seasonal variability has equally changed. The pre-1990 peak volume recorded at Hīt was 7,510 cubic metres (265,000 cu ft) per second, while after 1990 it is only 2,514 cubic metres (88,800 cu ft) per second. The minimum volume at Hīt remained relatively unchanged, rising from 55 cubic metres (1,900 cu ft) per second before 1990 to 58 cubic metres (2,000 cu ft) per second afterward.
Tributaries
In Syria, three rivers add their water to the Euphrates; the Sajur, the Balikh and the Khabur. These rivers rise in the foothills of the Taurus Mountains along the Syro–Turkish border and add comparatively little water to the Euphrates. The Sajur is the smallest of these tributaries; emerging from two streams near Gaziantep and draining the plain around Manbij before emptying into the reservoir of the Tishrin Dam. The Balikh receives most of its water from a karstic spring near ‘Ayn al-‘Arus and flows due south until it reaches the Euphrates at the city of Ar-Raqqah. In terms of length, drainage basin and discharge, the Khabur is the largest of these three. Its main karstic springs are located around Ra’s al-‘Ayn, from where the Khabur flows southeast past Al-Hasakah, where the river turns south and drains into the Euphrates near Busayrah. Once the Euphrates enters Iraq, there are no more natural tributaries to the Euphrates, although canals connecting the Euphrates basin with the Tigris basin exist.
Watershed
The drainage basins of the Kara Su and the Murat River cover an area of 22,000 square kilometres (8,500 sq mi) and 40,000 square kilometres (15,000 sq mi), respectively. The estimates that have been made for the area of the Euphrates drainage basin vary widely; from a low 233,000 square kilometres (90,000 sq mi) to a high 766,000 square kilometres (296,000 sq mi). Recent estimates put the basin area at 388,000 square kilometres (150,000 sq mi), 444,000 square kilometres (171,000 sq mi) and 579,314 square kilometres (223,674 sq mi). The greater part of the Euphrates basin is located in Turkey, Syria and Iraq. According to both Daoudy and Frenken, Turkey’s share is 28 percent, Syria’s is 17 percent and that of Iraq is 40 percent. Isaev and Mikhailova estimate the percentages of the drainage basin lying within Turkey, Syria and Iraq at 33, 20 and 47 percent respectively. Some sources estimate that approximately 15 percent of the drainage basin is located within Saudi Arabia, while a small part falls inside the borders of Kuwait. Finally, some sources also include Jordan in the drainage basin of the Euphrates; a small part of the eastern desert (220 square kilometres (85 sq mi)) drains toward the east rather than to the west.
Note : The above story is based on materials provided by Wikipedia
