The Department of Environmental Services says a combination of pollution transported from surrounding areas, cold, calm air and temperature inversions limiting air movement is causing the problem Friday.

The department says much of the pollution is emitted from heating devices, especially wood-burning stoves and boilers. It gets trapped and concentrated near the ground. Communities in valleys or other low-lying areas are most prone to the conditions.

Officials say conditions are expected to improve late Saturday morning as wind speeds increase, resulting in better mixing and cleaner air.

Symptoms of particle pollution exposure for people with heart disease may include chest pain, palpitations, shortness of breath, and fatigue.

On Saturday, Beijing’s municipal government began publishing hourly measures of what are known as PM2.5 pollutants, or pollutants that measure less than 2.5 micrometers in diameter. But already the data (in Chinese) are showing discrepancies with another measure released hourly by the U.S. embassy in Beijing, long the favored source for air-pollution data for those able to circumvent the Chinese’s government’s Internet censorship efforts.

On Monday morning around 10 a.m., Beijing said PM2.5. levels were measured at about 30 micrograms per cubic meter, which the U.S. Environmental Protection Agency classifies as a “moderate” level of pollution. At roughly the same time Monday morning, the U.S. embassy measured PM2.5 levels of 66 micrograms per cubic meter, which is considered “unhealthy” by U.S. measurements.

Several reasons could help explain the discrepancy. U.S. and Chinese pollution monitoring locations are located across the city from one another. The U.S. measures PM2.5 levels from equipment at the embassy in eastern Beijing, near the heavily trafficked Third Ring Road. Meanwhile, Beijing’s government releases measurements from a monitoring site in the western Xicheng district, according to state media.

At least one environmental analyst has already begun raising questions about the data, in particular readings from Saturday that measured PM2.5 levels at an extremely low level of three micrograms per cubic meter.

“In all of 2010 and 2011, the U.S. embassy reported values at or below that level only 18 times out of over 15,000 hourly values,” said Steven Andrews, an environmental consultant who studies Beijing’s pollution data, according to the Associated Press. “PM2.5 concentrations vary by area so a direct comparison between sites isn’t possible, but the numbers being reported during some hours seem surprisingly low.”

Beijing has long worried about discrepancies between its data and U.S. pollution data raising suspicion among the Chinese public, and cables released by WikiLeaks have revealed at least one testy conversations between the embassy and Chinese officials, who lamented the U.S. data could confuse Chinese citizens.

State-run media have celebrated Beijing’s new data release as a sign of government openness and responsiveness to citizen demands. Nonetheless, the reliability of the Chinese data remains a question. Local and national officials have historically been accused of manipulating data on everything from food stockpiles to the country’s economic health.

The Chinese government had previously published PM10 pollution levels — that is, pollutants measuring between 2.5 and 10 micrometers in diameters. However, they didn’t previously release data for smaller PM2.5 pollutants, which are smaller and seen by some experts as more harmful to human health.

China hasn’t yet released targets for average annual PM2.5 levels, though the state-run Xinhua news agency in an article on Saturday said the the national standard could be set at 35 micrograms per cubic meter on average per year, citing hearings at the environment ministry from earlier this month.

Strong winds during the weekend blew off much of last week’s especially thick smog in Beijing, leaving behind a relatively rare stretch of consecutive blue sky days to welcome the new PM2.5 readings. It remains to be seen how the Chinese and U.S. data will compare when pollution levels pick up again — something that seems likely to happen before too long.

Both the U.S. Embassy and the Beijing monitoring station showed a massive spike in PM2.5 levels around midnight on Sunday. While it’s not entirely clear what caused the spike, Chinese Internet users speculated it could have something to do with city-wide launching of fireworks to ring in the Lunar New Year.

Source: http://blogs.wsj.com/

And although the process, which uses high-pressure liquid pumped deep underground to fracture shale rock and release gas, caused two earthquakes in Lancashire last year, they were too small to cause damage, they said.

Campaigners have called for a moratorium on fracking in the UK in the face of the earthquakes and amid fears it could lead to pollution of drinking water by methane gas or chemicals in the liquid used in the process.

Fracking has proved controversial in the US, where shale gas is already being exploited on a large scale and where footage has been captured of people able to set fire to the water coming out of their taps as a result of gas contamination.

But Professor Mike Stephenson, of the British Geological Survey, said most geologists thought it was a “pretty safe activity” and the risks associated with it were low. He said the distance between groundwater supplies around 40-50 metres below the surface and the deep sources of gas in the shale a mile or two underground, made it unlikely methane would leak into water as a result of fracking.

“Most geologists are pretty convinced that it is extremely unlikely contamination would occur,” he said.

There was no evidence in peer-reviewed literature of pollution of water by methane as a result of fracking, he said.

He also added that the presence of the gas in US water supplies was likely to be natural.

But a survey was currently being conducted in the UK, to establish a baseline of any gas naturally found in groundwater before drilling took place.

As you keep the lights ready this Diwali, perhaps it’s time to pause and reconsider your plans. For years, we’ve known that Diwali, as celebrated today, is not the easiest time for people with or without specific health challenges. However, we often overlook the suffering we inflict on other life forms.

Let there be less light

Govind Singh, director, Delhi Greens, an NGO, and PhD scholar, environmental department, University of Delhi, says, “Light pollution is an aspect of deepawali that often goes unnoticed.” For centuries, diyas (oil lamps) were the only lights set up on Diwali. These were also kinder to other living things.

Now, these range from candles to electric garlands of fairy lights (“tuni” lamps), strings of electric bulbs and even harsh spotlights. Many of these are strung on, or near, trees and plants.

Says Mumbai-based Deepa Katyal Engineer, veterinarian and trustee, People for Animals, an animal welfare non-profit, “Can you imagine how hot it must be getting for the tree and for the creatures living in it?” Harsh lights also disorient nocturnal creatures such as bats and owls. Daylight-loving birds, too, can’t sleep. The diurnal cycle of plants is disturbed too.

Don’t fan the flames

Both lighting and fireworks can damage plants. Ajay Mahajan, founder member of the Pune-based environmental organization Kalpavriksh, has seen many plants getting scorched during Diwali. “Plants register the presence or proximity to fire and they actually try to move away from the source of fire,” he says.

Since Diwali comes at the end of the peak growing season for most plants, leaf burn can set the plant back by months. Plus, if you peg fireworks to a tree, it injures the inner bark, a living part of the tree. “That’s where the nutrients and water move,” says Mahajan. “Stop treating trees like lamp posts or an inanimate trellis.” Fireworks performing aerial pyrotechnics can also singe insects, birds and arboreal animals such as squirrels.

Don’t raise a stink

Then there’s the more palpable air pollution. During Diwali, most of us are thankful for the plants, those great carbon sinks. They take in a lot of air pollution at a terrible price. Few new leaves sprout and existing leaves get caked with pollution. “I have noticed a black liquid drip from leaves around this time from pollution,” says Mahajan. “Unlike dust that just sits on the leaf, this sticks to it. It is also tougher to wash off.”

Fire crackers are made of potassium nitrate, sulphur and charcoal. When burnt, noxious fumes are released, including sulphur dioxide, carbon monoxide and carbon dioxide. These gases irritate the air passage of humans and animals. “If higher species like humans and dogs get respiratory allergies due to the pollution caused by crackers, do insects and birds stand a chance?” asks Dr Katyal Engineer.

In plants, these harmful chemicals are absorbed through the stomata (pores) and choke them. Vidya Subramanian, project manager, Delhi Greens, says, “Particulate matter like cement dust, magnesium dust and carbon soot on trees can inhibit the normal respiration and photosynthesis mechanisms within the leaf.” With the stomata choked, plants can’t breathe or feed. This can also lead to the death of the leaf tissue.

What doesn’t coat or choke the leaves falls on the soil or floats in the air. If there is rainfall soon after Diwali, this pollution may come down as acid rain, corroding plants, altering soil composition and upsetting water ecosystems. Says Mahajan, “We don’t much look at soil contamination, although it is much more difficult to rectify than air or water pollution.” If animals ingest the chemicals in fire crackers, these poison them.

Too big a bang

Animals, especially birds, are affected more than humans by the noise pollution. Says Dr Katyal Engineer: “The average animal has better hearing than humans. Dogs can hear seven times louder than humans. So if the fire cracker burst during Diwali deafens you, you can imagine its effect on them.” Often, they flee, which is why it’s common for pets to get lost during Diwali.

All in all, your Diwali celebration makes for a less than bright outlook for the neighbourhood’s flora and fauna.

The study links for the first time high levels of pollutants in the air with conditions that prevent the light kind of rainfall critical for agriculture. Led by atmospheric scientist Yun Qian at the Department of Energy’s Pacific Northwest National Laboratory, the study appears August 15 in the Journal of Geophysical Research-Atmospheres.

“People have long wondered if there was a connection, but this is the first time we’ve observed it from long-term data,” said Qian. “Besides the health effects, acid rain and other problems that pollution creates, this work suggests that reducing air pollution might help ease the drought in north China.”

Drier Times

China’s dramatic economic growth and pollution problems provide researchers an opportunity to study the connection between air quality and climate. Rain in eastern China — where most of the country’s people and pollution exist — is not like it used to be.

Over the last 50 years, the southern part of eastern China has seen increased amounts of total rainfall per year. The northern half has seen less rain and more droughts. But light rainfall that sustains crops has decreased everywhere. A group of climate researchers from the U.S., China and Sweden wanted to know why light rain patterns haven’t followed the same precipitation patterns as total rainfall.

Previous work has shown that pollution can interfere with light rain above oceans, so the team suspected pollution might have something to do with the changes over land. Light rain ranges from drizzles to 10 millimeters of accumulation per day and sustains agriculture. (Compared to heavy rain that causes floods, loss of light rain has serious consequences for crops.)

While the light rains have diminished, pollution has increased dramatically in China in the last half of the 20th century. For example, while China’s population rose two and a half times in size, the emissions of sulfur from fossil fuel burning outpaced that considerably — rising nine times.

Sky Gremlins

Air pollution contains tiny, unseen particles of gas, water and bits of matter called aerosols. Aerosols — both natural and human-caused (anthropogenic) — do contribute to rainfall patterns, but the researchers needed to determine if pollution was to blame for China’s loss of rain and how.

To find out, the team charted trends in rainfall from 1956 to 2005 in eastern China, which has 162 weather stations with complete data collected over the entire 50 years.

From this data, the team determined that both the north and south regions of eastern China had fewer days of light rain — those getting 10 millimeters per day or less — at the end of the 50 year timespan. The south lost more days — 8.1 days per decade — than the north did, at 6.9 days per decade. However, the drought-rattled north lost a greater percentage of its rainy days, about 25 percent compared to the south’s 21 percent.

“No matter how we define light rain, we can see a very significant decrease of light rain over almost every station,” said Qian.

Up Up & In the Way

To probe what caused the loss of rainfall, the team looked at how much water the atmosphere contained and where the water vapor traveled. Most parts of eastern China saw no significant change in the amount of water held by the atmosphere, even though light rains decreased. In addition, where the atmosphere transported water vapor didn’t coincide with light rain frequency.

These results suggested that changes in large-scale movement of water could not account for the loss of the precipitation. Some of pollution’s aerosols can seed clouds or form raindrops, depending on their size, composition and the conditions in which they find themselves. Because these skills likely contribute to rainfall patterns, the researchers explored the aerosols in more depth.

Cloud droplets form around aerosols, so the team determined the concentration of cloud droplets over China. They found higher concentrations of droplets when more aerosols were present. But more droplets mean that each cloud droplet is smaller, in the same way that filling 10 ice cream cones from a quart of ice cream results in smaller scoops than if the same amount were put in only five cones.

This result suggested that aerosols create smaller water droplets, which in turn have a harder time forming rainclouds. The team verified this with computer models of pristine, moderately polluted or heavily polluted skies. In the most heavily polluted simulation, rain fell at significantly lower frequencies than in the pristine conditions.

An examination of the cloud and rain drops showed that these water drops in polluted cases are up to 50 percent smaller than in clean skies. The smaller size impedes the formation of rain clouds and the falling of rain.

Qian said the next step in their research is to examine new data from the DOE’s Atmospheric Radiation Measurement Climate Research Facility in the central eastern Chinese city of Shouxian. The data was collected from April to December of 2008.

“This work is important because modeling studies of individual cases of pollution’s effect on convective clouds have shown varying results, depending on the environmental conditions,” said coauthor Ruby Leung. “The ARM data collected at Shouxian should provide more detailed measurements of both aerosols and clouds to enable us to quantify the impacts of aerosols on precipitation under different atmospheric and pollution conditions.”

The work was supported by the Office of Biological and Environmental Research within the DOE Office of Science under a bilateral agreement on regional climate research with the China Ministry of Science and Technology.

The atmosphere is a complex, dynamic natural gaseous system that is essential to support life on planet Earth. Stratospheric ozone depletion due to air pollution has long been recognized as a threat to human health as well as to the Earth’s ecosystems.

Pollutants

An air pollutant is known as a substance in the air that can cause harm to humans and the environment. Pollutants can be in the form of solid particles, liquid droplets, or gases. In addition, they may be natural or man-made.

Pollutants can be classified as either primary or secondary. Usually, primary pollutants are substances directly emitted from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories.

Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level ozone – one of the many secondary pollutants that make up photochemical smog.

Note that some pollutants may be both primary and secondary: that is, they are both emitted directly and formed from other primary pollutants.

About 4 percent of deaths in the United States can be attributed to air pollution, according to the Environmental Science Engineering Program at the Harvard School of Public Health.

Major primary pollutants produced by human activity include:

• Sulfur oxides (SOx) - especially sulfur dioxide, a chemical compound with the formula SO2. SO2 is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain. This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.
• Nitrogen oxides (NOx) - especially nitrogen dioxide are emitted from high temperature combustion. Can be seen as the brown haze dome above or plume downwind of cities.Nitrogen dioxide is the chemical compound with the formula NO2. It is one of the several nitrogen oxides. This reddish-brown toxic gas has a characteristic sharp, biting odor. NO2 is one of the most prominent air pollutants.
• Carbon monoxide - is a colourless, odourless, non-irritating but very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide.
• Carbon dioxide (CO2) - a greenhouse gas emitted from combustion but is also a gas vital to living organisms. It is a natural gas in the atmosphere.
• Volatile organic compounds - VOCs are an important outdoor air pollutant. In this field they are often divided into the separate categories of methane (CH4) and non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhanced global warming. Other hydrocarbon VOCs are also significant greenhouse gases via their role in creating ozone and in prolonging the life of methane in the atmosphere, although the effect varies depending on local air quality. Within the NMVOCs, the aromatic compounds benzene, toluene and xylene are suspected carcinogens and may lead to leukemia through prolonged exposure. 1,3-butadiene is another dangerous compound which is often associated with industrial uses.
• Particulate matter - Particulates, alternatively referred to as particulate matter (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas. In contrast, aerosol refers to particles and the gas together. Sources of particulate matter can be man made or natural. Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosols. Averaged over the globe, anthropogenic aerosols—those made by human activities—currently account for about 10 percent of the total amount of aerosols in our atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function and lung cancer.
• Toxic metals, such as lead, cadmium and copper.
• Chlorofluorocarbons (CFCs) - harmful to the ozone layer emitted from products currently banned from use.
• Ammonia (NH3) - emitted from agricultural processes. Ammonia is a compound with the formula NH3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceuticals. Although in wide use, ammonia is both caustic and hazardous.
• Odors – such as from garbage, sewage, and industrial processes
• Radioactive pollutants – produced by nuclear explosions, war explosives, and natural processes such as the radioactive decay of radon.

Secondary pollutants include:

• Particulate matter formed from gaseous primary pollutants and compounds in photochemical smog .Smog is a kind of air pollution; the word “smog” is a portmanteau of smoke and fog. Classic smog results from large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. Modern smog does not usually come from coal but from vehicular and industrial emissions that are acted on in the atmosphere by sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.
• Ground level ozone (O3) formed from NOx and VOCs. Ozone (O3) is a key constituent of the troposphere (it is also an important constituent of certain regions of the stratosphere commonly known as the Ozone layer). Photochemical and chemical reactions involving it drive many of the chemical processes that occur in the atmosphere by day and by night. At abnormally high concentrations brought about by human activities (largely the combustion of fossil fuel), it is a pollutant, and a constituent of smog.
• Peroxyacetyl nitrate (PAN) - similarly formed from NOx and VOCs.

Minor air pollutants include:

• A large number of minor hazardous air pollutants. Some of these are regulated in USA under the Clean Air Act and in Europe under the Air Framework Directive.
• A variety of persistent organic pollutants, which can attach to particulate matter.

Persistent organic pollutants (POPs) are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. Because of this, they have been observed to persist in the environment, to be capable of long-range transport, bioaccumulate in human and animal tissue, biomagnify in food chains, and to have potential significant impacts on human health and the environment.

Air Pollution Sources

Sources of air pollution refer to the various locations, activities or factors which are responsible for the releasing of pollutants in the atmosphere. These sources can be classified into two major categories which are:

Anthropogenic sources (human activity) mostly related to burning different kinds of fuel

• “Stationary Sources” include smoke stacks of power plants, manufacturing facilities (factories) and waste incinerators, as well as furnaces and other types of fuel-burning heating devices
• “Mobile Sources” include motor vehicles, marine vessels, aircraft and the effect of sound etc.
• Chemicals, dust and controlled burn practices in agriculture and forestry management. Controlled or prescribed burning is a technique sometimes used in forest management, farming, prairie restoration or greenhouse gas abatement. Fire is a natural part of both forest and grassland ecology and controlled fire can be a tool for foresters. Controlled burning stimulates the germination of some desirable forest trees, thus renewing the forest.
• Fumes from paint, hair spray, varnish, aerosol sprays and other solvents
• Waste deposition in landfills, which generate methane.Methane is not toxic; however, it is highly flammable and may form explosive mixtures with air. Methane is also an asphyxiant and may displace oxygen in an enclosed space. Asphyxia or suffocation may result if the oxygen concentration is reduced to below 19.5% by displacement
• Military, such as nuclear weapons, toxic gases, germ warfare and rocketry

Natural sources

• Dust from natural sources, usually large areas of land with little or no vegetation.
• Methane, emitted by the digestion of food by animals, for example cattle.
• Radon gas from radioactive decay within the Earth’s crust.Radon is a colorless, odorless, naturally occurring, radioactive noble gas that is formed from the decay of radium. It is considered to be a health hazard.Radon gas from natural sources can accumulate in buildings, especially in confined areas such as the basement and it is the second most frequent cause of lung cancer, after cigarette smoking.
• Smoke and carbon monoxide from wildfires.
• Volcanic activity, which produce sulfur, chlorine, and ash particulates.

Their research on the creation and effects of these chemicals, called epoxides, is being featured in the journal Science.

Paul Wennberg, the R. Stanton Avery Professor of Atmospheric Chemistry and Environmental Science and Engineering and director of the Ronald and Maxine Linde Center for Global Environmental Science at Caltech, and John Seinfeld, the Louis E. Nohl Professor and professor of chemical engineering, have been studying the role of biogenic emissions—organic carbon compounds given off by plants and trees—in the atmospheric chemical reactions that result in the creation of aerosols.

“If you mix emissions from the city with emissions from plants, they interact to alter the chemistry of the atmosphere,” Wennberg notes.

While there’s been plenty of attention paid to the effect of emissions from cars and manufacturing, less is understood about what happens to biogenic emissions, especially in places where there are relatively few man-made emissions. That situation is the focus of the research that led to this Science paper. “What we’re interested in,” Wennberg explains, “is what happens to the chemicals produced by trees once they are emitted into the atmosphere.”

In these studies, the research team focused on a chemical called isoprene, which is given off by many deciduous trees. “The king emitters are oaks,” Wennberg says. “And the isoprene they emit is one of the reasons that the Smoky Mountains appear smoky.”

Isoprene is no minor player in atmospheric chemistry, Wennberg notes. “There is much more isoprene emitted to the atmosphere than all of the gases—gasoline, industrial chemicals—emitted by human activities, with the important exceptions of methane and carbon dioxide,” he says. “And isoprene only comes from plants. They make hundreds of millions of tons of this chemical . . . for reasons that we still do not fully understand.”

“Much of the emission of isoprene occurs where anthropogenic emissions are limited,” adds Caltech graduate student Fabien Paulot, the paper’s first author. “The chemistry is very poorly understood.”

Once released into the atmosphere, isoprene gets “oxidized or chewed on” by free-radical oxidants such as OH, explains Wennberg. It is this chemistry that is the focus of this new study. In particular, the research was initiated to understand how the oxidation of isoprene can lead to formation of atmospheric particulate matter, so-called secondary organic aerosol. “A small fraction of the isoprene becomes secondary organic aerosol,” Seinfeld notes, “but because isoprene emissions are so large, even this small fraction is important.”

Up until now, the chemical pathways from isoprene to aerosol were not known. Wennberg, Seinfeld, and their colleagues discovered that this aerosol likely forms from chemicals known as an epoxides.

The name is apt. “These epoxides are nature’s glue,” says Wennberg. And, much like the epoxy you buy in a hardware store—which requires the addition of an acid for the compound to turn into glue—the epoxides found in the atmosphere also need an acidic kick in order to become sticky.

“When these epoxides bump into particles that are acidic, they make glue,” Wennberg explains. “The epoxides precipitate out of the atmosphere and stick to the particles, growing them and resulting in lowered visibility in the atmosphere.” Because the acidity of the aerosols is generally higher in the presence of anthropogenic activities, the efficiency of converting the epoxides to aerosol is likely higher in polluted environments, illustrating yet another complex interaction between emissions from the biosphere and from humans.

“Particles in the atmosphere have been shown to impact human health, as they are small enough to penetrate deep into the lungs of people. Also, aerosols impact Earth’s climate through the scattering and absorption of solar radiation and through serving as the nuclei on which clouds form. So it is important to know where particles come from,” notes Seinfeld.

The research team was able to make this scientific leap forward thanks to their development of a new type of chemical ionization mass spectrometry (CIMS), led by coauthor and Caltech graduate student John Crounse. “These new CIMS methods open up a very wide range of possibilities for the study of new sets of compounds that scientists have been largely unable to measure previously, mainly because they decompose when analyzed with traditional techniques.”

In general, molecules identified and quantified using mass spectroscopy must first be converted to charged ions. They are then directed into an electric field, where the ions are sorted by mass. The problem with traditional ionization techniques is that delicate molecules, such as those produced in the oxidation of isoprene, generally fragment during the ionization process, making their identification difficult or impossible. “This new method was originally developed in order to allow scientists to make atmospheric measurements from airplanes. It is able to ionize gasses, even fragile peroxide compounds, while still preserving information about the size or mass of the original molecule,” says Wennberg.

That makes determining the individual gases in a complex mixture much easier—especially when, as it turned out, you’re looking at a chemical you weren’t expecting to find.

Wennberg and colleagues also used oxygen isotopes—oxygen atoms with different numbers of neutrons in their nucleus, and thus different masses—to gain insight into the chemical mechanism yielding epoxides. Epoxides have remained unidentified so far because they have the same mass as another chemical that had been anticipated to form in isoprene oxidation, peroxide. “The oxygen isotopes separated the peroxides from epoxides and further showed that as the epoxides form, OH is recycled to the atmosphere,” comments Paulot. “Since OH is the atmosphere detergent, cleaning the atmosphere of many chemicals, the recycling has important implications for the overall oxidizing capacity of the atmosphere.”

The identification of a major photochemical pathway to formation of epoxides helps to explain just how tree emissions of organic carbon compounds influence the air in both city and rural settings. While trees aren’t exactly the “killers” that Ronald Reagan was once so famously derided for calling them, their isoprene emission levels can—and often probably should—”be a part of the criteria we use when buying and planting trees in a polluted urban setting,” notes Wennberg. In fact, he points out, the South Coast Air Quality Management District in Southern California already does this with its list of “approved” trees that don’t emit large amounts of organic carbon compounds into the atmosphere.

In addition to Wennberg, Paulot, Crounse, and Seinfeld, other authors on the Science paper are Henrik Kjaergaard of the University of Otago in New Zealand; former Caltech postdoctoral scholar Andreas Kürten, now at Goethe University in Germany; and Caltech postdoctoral scholar Jason St. Clair.

In the developing countries, it is the rural areas that face the greatest threat from indoor pollution, where some 3.5 billion people continue to rely on traditional fuels such as firewood, charcoal, and cowdung for cooking and heating. Concentrations of indoor pollutants in households that burn traditional fuels are alarming. Burning such fuels produces large amount of smoke and other air pollutants in the confined space of the home, resulting in high exposure. Women and children are the groups most vulnerable as they spend more time indoors and are exposed to the smoke. In 1992, the World Bank designated indoor air pollution in the developing countries as one of the four most critical global environmental problems. Daily averages of pollutant level emitted indoors often exceed current WHO guidelines and acceptable levels. Although many hundreds of separate chemical agents have been identified in the smoke from biofuels, the four most serious pollutants are particulates, carbon monoxide, polycyclic organic matter, and formaldehyde. Unfortunately, little monitoring has been done in rural and poor urban indoor environments in a manner that is statistically rigorous.

In urban areas, exposure to indoor air pollution has increased due to a variety of reasons, including the construction of more tightly sealed buildings, reduced ventilation, the use of synthetic materials for building and furnishing and the use of chemical products, pesticides, and household care products. Indoor air pollution can begin within the building or be drawn in from outdoors. Other than nitrogen dioxide, carbon monoxide, and lead, there are a number of other pollutants that affect the air quality in an enclosed space.

Volatile organic compounds originate mainly from solvents and chemicals. The main indoor sources are perfumes, hair sprays, furniture polish, glues, air fresheners, moth repellents, wood preservatives, and many other products used in the house. The main health effect is the imitation of the eye, nose and throat. In more severe cases there may be headaches, nausea and loss of coordination. In the long term, some of the pollutants are suspected to damage to the liver and other parts of the body.

Tobacco smoke generates a wide range of harmful chemicals and is known to cause cancer. It is well known that passive smoking causes a wide range of problems to the passive smoker (the person who is in the same room with a smoker and is not himself/herself a smoker) ranging from burning eyes, nose, and throat irritation to cancer, bronchitis, severe asthma, and a decrease in lung function.

Pesticides , if used carefully and the manufacturers, instructions followed carefully they do not cause too much harm to the indoor air.

Biological pollutants include pollen from plants, mite, hair from pets, fungi, parasites, and some bacteria. Most of them are allergens and can cause asthma, hay fever, and other allergic diseases.

Formaldehyde is a gas that comes mainly from carpets, particle boards, and insulation foam. It causes irritation to the eyes and nose and may cause allergies in some people.

Asbestos is mainly a concern because it is suspected to cause cancer.

Radon is a gas that is emitted naturally by the soil. Due to modern houses having poor ventilation, it is confined inside the house causing harm to the dwellers.

Toxic constituents depend upon the specific coal bed makeup, but may include one or more of the following elements or substances in quantities from trace amounts to several percent: arsenic, beryllium, boron, cadmium, chromium, chromium VI, cobalt, lead, manganese, mercury, molybdenum, selenium, strontium, thallium, and vanadium, along with dioxins and PAH compounds.

In the past, fly ash was generally released into the atmosphere, but pollution control equipment mandated in recent decades now require that it be captured prior to release. In the US, fly ash is generally stored at coal power plants or placed in landfills. About 43 percent is recycled, often used to supplement Portland cement in concrete production. Some have expessed health concerns about this. [4]Fly ash is increasingly finding use in the synthesis of geopolymers and zeolites.

Chemical Composition and Classification

Fly ash material solidifies while suspended in the exhaust gases and is collected by electrostatic precipitators or filter bags. Since the particles solidify while suspended in the exhaust gases, fly ash particles are generally spherical in shape and range in size from 0.5 µm to 100 µm. They consist mostly of silicon dioxide (SiO2), which is present in two forms: amorphous, which is rounded and smooth, and crystalline, which is sharp, pointed and hazardous; aluminium oxide (Al2O3) and iron oxide (Fe2O3). Fly ashes are generally highly heterogeneous, consisting of a mixture of glassy particles with various identifiable crystalline phases such as quartz, mullite, and various iron oxides.

Fly ash also contains environmental toxins in significant amounts, including arsenic (43.4 ppm); barium (806 ppm); beryllium (5 ppm); boron (311 ppm); cadmium (3.4 ppm); chromium (136 ppm); chromium VI (90 ppm); cobalt (35.9 ppm); copper (112 ppm); fluorine (29 ppm); lead (56 ppm); manganese (250 ppm); nickel (77.6 ppm); selenium (7.7 ppm); strontium (775 ppm); thallium (9 ppm); vanadium (252 ppm); and zinc (178 ppm).

Two classes of fly ash are defined by ASTM C618: Class F fly ash and Class C fly ash. The chief difference between these classes is the amount of calcium, silica, alumina, and iron content in the ash. The chemical properties of the fly ash are largely influenced by the chemical content of the coal burned (i.e., anthracite, bituminous, and lignite).

Not all fly ashes meet ASTM C618 requirements, although depending on the application, this may not be necessary. Ash used as a cement replacement must meet strict construction standards, but no standard environmental standards have been established in the United States. 75% of the ash must have a fineness of 45 µm or less, and have a carbon content, measured by the loss on ignition (LOI), of less than 4%. In the U.S., LOI needs to be under 6%. The particle size distribution of raw fly ash is very often fluctuating constantly, due to changing performance of the coal mills and the boiler performance. This makes it necessary that fly ash used in concrete needs to be processed using separation equipment like mechanical air classifiers. Especially important is the ongoing quality verification. This is mainly expressed by quality control seals like the Bureau of Indian Standards mark or the DCL mark of the Dubai Municipality.

Class F fly ash

The burning of harder, older anthracite and bituminous coal typically produces Class F fly ash. This fly ash is pozzolanic in nature, and contains less than 10% lime (CaO). Possessing pozzolanic properties, the glassy silica and alumina of Class F fly ash requires a cementing agent, such as Portland cement, quicklime, or hydrated lime, with the presence of water in order to react and produce cementitious compounds. Alternatively, the addition of a chemical activator such as sodium silicate (water glass) to a Class F ash can lead to the formation of a geopolymer.

Class C fly ash

Fly ash produced from the burning of younger lignite or subbituminous coal, in addition to having pozzolanic properties, also has some self-cementing properties. In the presence of water, Class C fly ash will harden and gain strength over time. Class C fly ash generally contains more than 20% lime (CaO). Unlike Class F, self-cementing Class C fly ash does not require an activator. Alkali and sulfate (SO4) contents are generally higher in Class C fly ashes.

Fly Ash Reuse

The reuse of fly ash as an engineering material primarily stems from its pozzolanic nature, spherical shape, and relative uniformity. Fly ash recycling, in descending frequency, includes usage in:

1. Portland cement and grout
2. Embankments and structural fill
3. Waste stabilization and solidification
4. Raw feed for cement clinkers
5. Mine reclamation
6. Stabilization of soft soils
7. Road subbase
8. Aggregate
9. Flowable fill
10. Mineral filler in asphaltic concrete
11. Other applications include cellular concrete, geopolymers, roofing tiles, paints, metal castings, and filler in wood and plastic products.

Environmental Problems

Present Production Rate of Fly Ash

In the United States about 131 million tons of fly ash are produced annually by 460 coal-fired power plants. A 2008 industry survey estimated that 43 percent of this ash is re-used.

Recently a new technology has appeared on the market, recycling 100% of both stockpiled and fresh fly ash, revolutionising the market. This is called Fly ash Beneficiation, created by the company RockTron.

Groundwater contamination

Since coal contains trace levels of arsenic, barium, beryllium, boron, cadmiium, chromium, thallium, selenium, molybdenum and mercury, its ash will continue to contain these traces and therefore cannot be dumped or stored where rainwater can leach the metals and move them to aquifers.

Spills of bulk storage

Where fly ash is stored in bulk, it is usually stored wet rather than dry so that fugitive dust is minimized. The resulting impoundments (ponds) are typically large and stable for long periods, but any breach of their dams or bunding will be rapid and on a massive scale.

In December 2008 the collapse of an embankment at an impoundment for wet storage of fly ash at the Tennessee Valley Authority’s Kingston Fossil Plant resulted in a major release of 5.4 millon cubic yards of coal fly ash, damaging 3 homes and flowing into the Emory River. Cleanup costs may exceed $100 million. This spill was followed a few weeks later by a smaller TVA-plant spill in Alabama, which contaminated Widows Creek and the Tennessee River.

Contaminants

Fly ash contains trace concentrations of heavy metals and other substances that are known to be detrimental to health in sufficient quantities. Potentially toxic trace elements in coal include arsenic, beryllium, cadmium, barium, chromium, copper, lead, mercury, molybdenum, nickel, radium, selenium, thorium, uranium, vanadium, and zinc. Approximately 10 percent of the mass of coals burned in the United States consists of unburnable mineral material that becomes ash, so the concentration of most trace elements in coal ash is approximately 10 times the concentration in the original coal. A 1997 analysis by the U.S. Geological Survey (USGS) found that fly ash typically contained 10 to 30 ppm of uranium, comparable to the levels found in some granitic rocks, phosphate rock, and black shale.

In 2000, the United States Environmental Protection Agency? (EPA) said that coal fly ash did not need to be regulated as a hazardous waste. Studies by the U.S. Geological Survey and others of radioactive elements in coal ash have concluded that fly ash compares with common soils or rocks and should not be the source of alarm. However, community and environmental organizations have documented numerous environmental contamination and damage concerns.

A revised risk assessment approach may change the way coal combustion wastes (CCW) are regulated, according to an August 2007 EPA notice in the Federal Register. In June 2008, the U.S. House of Representatives held an oversight hearing on the Federal government’s role in addressing health and environmental risks of fly ash.

Contamination in Byker

In the 1980s and 1990s, around 2,000 tons of fly ash from local incinerators (used to burn garbage – not coal) were used by the local council deliberately to surface footpaths around the Byker and Walker districts of Newcastle upon Tyne, England. Considerable concern was raised in the local community when this was discovered. Later studies found contamination by dioxins and furans from this fly ash, although no strong evidence for heavy metals (the area has an industrial past that may itself explain the levels that were found).

Acid rain causes extensive damage to water, forest, soil resources and even human health. Many lakes and streams have been contaminated and this has led to the disappearance of some species of fish in Europe, USA and Canada as also extensive damage to forests and other forms of life. It is said that it can corrode buildings and be hazardous to human health. Because the contaminants are carried long distances, the sources of acid rain are difficult to pinpoint and hence difficult to control. For example, the acid rain that may have damaged some forest in Canada could have originated in the industrial areas of USA. In fact, this has created disagreements between Canada and the United States and among European countries over the causes of and solutions to the problem of acid rain.

The international scope of the problem has led to the signing of international agreements on the limitation of sulphur and nitrogen oxide emissions.