 |
|
Tracking Down the Menace in Mexico City Smog
September 08, 2008A new report by scientists who are part of the international MILAGRO Campaign indicates that some of the most harmful air pollution in Mexico City may not come from motor vehicles but instead originates with industrial sources - and that the culprit may be garbage incineration.
The MILAGRO Campaign (Megacity Initiative: Local and Global Research Observations) monitored air quality in the Mexico City Metropolitan Area throughout the month of March, 2006. Headed by the Molina Center for Energy and the Environment in La Jolla, California, MILAGRO - the acronym means "miracle" in Spanish - is an international scientific collaboration supported by the U.S. Department of Energy, the National Science Foundation, NASA, and other agencies in the U.S., Mexico, and Europe. Five DOE labs contributed to the study, including Lawrence Berkeley National Laboratory.
Beamline 11.0.2 at Berkeley Lab's Advanced Light Source (ALS) was used for scanning transmission x-ray microscopy (STXM) of aerosol particles, in work led by Mary Gilles of the Lab's Chemical Sciences Division. Ryan Moffet, now a Seaborg Postdoctoral Fellow at Berkeley Lab, was a member of a team monitoring a rooftop collection station at the Mexican Institute of Petroleum in the northern part of Mexico City, a site designated T0 (T-zero); the evidence gathered there was among that analyzed by Gilles and her colleagues.
"The T0 site is in the industrial heart of the city, but the neighborhood is also a densely populated residential area. Children who live here have 11 percent higher levels of lead in their blood than children from the opposite side of town," says Moffet, who was a doctoral student at the University of California at San Diego during the MILAGRO Campaign. Moffet is first author of a report in Environmental Science & Technology on the research at the T0 site. "Although researchers had noted the high levels of lead, no one before us had analyzed the aerosol compounds for clues to its origins."
Airborne particles of varying size, shape, and chemical composition are an important constituent of the smog in Mexico City, one of the largest cities in the world and one of the most polluted. The aerosols come from motor vehicles, industries, and residences; their sources include the burning of fossil fuels and biomass, and industrial emissions. Because of the city's high elevation in a basin walled by mountains, air pollution in the metropolitan area is often trapped in the basin and chemically altered by ultraviolet radiation and other processes.
Metal-containing aerosols in particular are implicated in adverse effects on health. Size and solubility affect their mobility in the body; for example, small particles with compact shapes penetrate deep into the lungs, where they are likely to stay. Soluble compounds readily enter the bloodstream. And a metal's oxidation state affects its toxicity.
Measuring airborne particles
Many different instruments were used to collect the aerosol samples at several sites: one, a Davis Rotating Drum, captured particles of three different sizes on Teflon tapes; another, a Time Resolved Aerosol Impactor, collected single particles. In situ measurements were made with an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS), which sucked particles into a vacuum chamber, determined their size, and analyzed the mass spectra of their constituent chemicals on the fly, by zapping each with a laser pulse.
Spectra from tens of thousands of particles were stored for later analysis. The rotating drum and ATOFMS yielded time series, allowing the researchers to determine how size, shape, chemical composition, and the changing mix of chemicals in the aerosol particles varied with the time of day and other factors like weather.
"When we started the study, we were interested in what fraction of the aerosols was from traffic, since many scientists believed that traffic was the worst source of the pollution," says Moffet. "But when I looked at the mass spectrometry data, the first thing that jumped at me was the lead spikes. We wondered what the source of the lead was. Lead has been completely banned in gasoline sold in the city since 1997, which meant the aerosols were coming from something else."
Many anthropogenic (human caused) sources contribute to the metal-containing aerosols in Mexico City air. Nickel and vanadium are associated in particles from fossil-fuel burning. Smelting and other metallurgical processes produce emissions rich in heavy metals. Burning waste emits particles containing lead, zinc, and many other metals, plus chlorine. Activities like construction and traffic stir up dust and send large metal-containing particles into the atmosphere. All these sources can be identified by their characteristic compositions.
"In many of the spikes the lead was associated with chlorine and zinc," Moffet says. "The nature of the chemical associations of these metals could give us valuable clues as to the origin of the particles and their subsequent processing."
Mass spectrometry results were available on the spot, while additional informative data came from later laboratory analyses, including proton-induced x-ray emission and computer-controlled scanning electron microscopy directed by Alexander Laskin at the W. R. Wiley Environmental Molecular Sciences Laboratory at DOE's Pacific Northwest National Laboratory in Washington State, the STXM studies by Mary Gilles at Berkeley Lab's ALS, and other researchers using additional techniques.
Narrowing the suspects
By comparing the mixing of lead, zinc, and chloride in the T0 particles to previous studies characterizing the sources of metal-containing aerosols, clues to the source of the Mexico City particles quickly emerged. Both nonferrous (non-iron) smelters and municipal waste incinerators emit particles that contain lead and zinc, and both have similar compositions - except that smelter particles do not contain phosphorus and chlorine, while incinerator particles do.
The particles that contained lead and zinc in the T0 aerosols did contain phosphorus and chlorine, and had other species in common with incinerator samples, including soot. Particles from smelting typically have more iron; moreover, smelter emissions do not have large amounts of chlorine but do have high concentrations of sulfates, which were missing in the T0 samples.
ALS beamline 11.0.2 helped further zero in on the chemical makeup of particles containing zinc. Incinerators produce metal chlorides, which in the atmosphere can react with acidic gases and become other species like nitrates: many of the zinc-containing particles from T0 were zinc nitrates, suggesting their origin in incinerator emissions. Zinc oxides were also among the particles collected at T0; nitrates, chlorides, and sulfates are partitioned on zinc oxide surfaces, and all are found in the lead and zinc-rich aerosols from T0.
The occurrence of lead and zinc particles at different times of day - and even different days of the month - added more evidence for incineration as the principal source of the airborne metals. On most days, metal-rich particles at the T0 site peaked early in the morning, as early morning air masses from the northeastern part of the city carried them to other neighborhoods. The lag time of metal nitrates behind metal chlorides matched the time needed for reactions with nitric acid in the air. Perhaps most telling, during the month-long collection, the lowest concentration of metal-rich particles occurred on a holiday weekend when most industrial processes were shut down.
The lead-bearing aerosol particles found in Mexico City are small, many of them needle-shaped, making them easy to inhale and likely to stay in the lungs. As time passes, the initial metal chlorides are converted to lead nitrates, which are soluble and readily enter the blood stream.
Can garbage incineration be unequivocally identified as the source of the worst pollution in the Mexico City Metropolitan Area? Not quite yet, says Moffet.
"At present the government is not keeping track of emissions from incinerators, and incineration is not even listed in the emissions inventory for the metropolitan area," he says, "although we saw garbage incinerators in the northern part of Mexico City. But even short of absolute proof of bad health effects, incineration - especially of discarded electronics, which are loaded with heavy metals and chlorine - is a dangerous process and a growing problem in developing countries."
"Characterization of aerosols containing Zn, Pb, and Cl from an industrial region of Mexico City," by Ryan Moffet, Yuri Desyaterik, Rebecca Hopkins, Alexei Tivanski, Mary Gilles, Vaithiyalingam Shutthanandan, Luisa Molina, R. Gonzalez Abraham, Kenneth Johnson, Violeta Mugica, Mario Molina, Alexander Laskin, and Kimberly Prather, appears in Environmental Science & Technology and is available to subscribers at http://dx.doi.org/10.1021/es7030483
Lawrence Berkeley National Laboratory
"The T0 site is in the industrial heart of the city, but the neighborhood is also a densely populated residential area. Children who live here have 11 percent higher levels of lead in their blood than children from the opposite side of town," says Moffet, who was a doctoral student at the University of California at San Diego during the MILAGRO Campaign. Moffet is first author of a report in Environmental Science & Technology on the research at the T0 site. "Although researchers had noted the high levels of lead, no one before us had analyzed the aerosol compounds for clues to its origins."
Airborne particles of varying size, shape, and chemical composition are an important constituent of the smog in Mexico City, one of the largest cities in the world and one of the most polluted. The aerosols come from motor vehicles, industries, and residences; their sources include the burning of fossil fuels and biomass, and industrial emissions. Because of the city's high elevation in a basin walled by mountains, air pollution in the metropolitan area is often trapped in the basin and chemically altered by ultraviolet radiation and other processes.
Metal-containing aerosols in particular are implicated in adverse effects on health. Size and solubility affect their mobility in the body; for example, small particles with compact shapes penetrate deep into the lungs, where they are likely to stay. Soluble compounds readily enter the bloodstream. And a metal's oxidation state affects its toxicity.
Measuring airborne particles
Many different instruments were used to collect the aerosol samples at several sites: one, a Davis Rotating Drum, captured particles of three different sizes on Teflon tapes; another, a Time Resolved Aerosol Impactor, collected single particles. In situ measurements were made with an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS), which sucked particles into a vacuum chamber, determined their size, and analyzed the mass spectra of their constituent chemicals on the fly, by zapping each with a laser pulse.
Spectra from tens of thousands of particles were stored for later analysis. The rotating drum and ATOFMS yielded time series, allowing the researchers to determine how size, shape, chemical composition, and the changing mix of chemicals in the aerosol particles varied with the time of day and other factors like weather.
"When we started the study, we were interested in what fraction of the aerosols was from traffic, since many scientists believed that traffic was the worst source of the pollution," says Moffet. "But when I looked at the mass spectrometry data, the first thing that jumped at me was the lead spikes. We wondered what the source of the lead was. Lead has been completely banned in gasoline sold in the city since 1997, which meant the aerosols were coming from something else."
Many anthropogenic (human caused) sources contribute to the metal-containing aerosols in Mexico City air. Nickel and vanadium are associated in particles from fossil-fuel burning. Smelting and other metallurgical processes produce emissions rich in heavy metals. Burning waste emits particles containing lead, zinc, and many other metals, plus chlorine. Activities like construction and traffic stir up dust and send large metal-containing particles into the atmosphere. All these sources can be identified by their characteristic compositions.
"In many of the spikes the lead was associated with chlorine and zinc," Moffet says. "The nature of the chemical associations of these metals could give us valuable clues as to the origin of the particles and their subsequent processing."
Mass spectrometry results were available on the spot, while additional informative data came from later laboratory analyses, including proton-induced x-ray emission and computer-controlled scanning electron microscopy directed by Alexander Laskin at the W. R. Wiley Environmental Molecular Sciences Laboratory at DOE's Pacific Northwest National Laboratory in Washington State, the STXM studies by Mary Gilles at Berkeley Lab's ALS, and other researchers using additional techniques.
Narrowing the suspects
By comparing the mixing of lead, zinc, and chloride in the T0 particles to previous studies characterizing the sources of metal-containing aerosols, clues to the source of the Mexico City particles quickly emerged. Both nonferrous (non-iron) smelters and municipal waste incinerators emit particles that contain lead and zinc, and both have similar compositions - except that smelter particles do not contain phosphorus and chlorine, while incinerator particles do.
The particles that contained lead and zinc in the T0 aerosols did contain phosphorus and chlorine, and had other species in common with incinerator samples, including soot. Particles from smelting typically have more iron; moreover, smelter emissions do not have large amounts of chlorine but do have high concentrations of sulfates, which were missing in the T0 samples.
ALS beamline 11.0.2 helped further zero in on the chemical makeup of particles containing zinc. Incinerators produce metal chlorides, which in the atmosphere can react with acidic gases and become other species like nitrates: many of the zinc-containing particles from T0 were zinc nitrates, suggesting their origin in incinerator emissions. Zinc oxides were also among the particles collected at T0; nitrates, chlorides, and sulfates are partitioned on zinc oxide surfaces, and all are found in the lead and zinc-rich aerosols from T0.
The occurrence of lead and zinc particles at different times of day - and even different days of the month - added more evidence for incineration as the principal source of the airborne metals. On most days, metal-rich particles at the T0 site peaked early in the morning, as early morning air masses from the northeastern part of the city carried them to other neighborhoods. The lag time of metal nitrates behind metal chlorides matched the time needed for reactions with nitric acid in the air. Perhaps most telling, during the month-long collection, the lowest concentration of metal-rich particles occurred on a holiday weekend when most industrial processes were shut down.
The lead-bearing aerosol particles found in Mexico City are small, many of them needle-shaped, making them easy to inhale and likely to stay in the lungs. As time passes, the initial metal chlorides are converted to lead nitrates, which are soluble and readily enter the blood stream.
Can garbage incineration be unequivocally identified as the source of the worst pollution in the Mexico City Metropolitan Area? Not quite yet, says Moffet.
"At present the government is not keeping track of emissions from incinerators, and incineration is not even listed in the emissions inventory for the metropolitan area," he says, "although we saw garbage incinerators in the northern part of Mexico City. But even short of absolute proof of bad health effects, incineration - especially of discarded electronics, which are loaded with heavy metals and chlorine - is a dangerous process and a growing problem in developing countries."
"Characterization of aerosols containing Zn, Pb, and Cl from an industrial region of Mexico City," by Ryan Moffet, Yuri Desyaterik, Rebecca Hopkins, Alexei Tivanski, Mary Gilles, Vaithiyalingam Shutthanandan, Luisa Molina, R. Gonzalez Abraham, Kenneth Johnson, Violeta Mugica, Mario Molina, Alexander Laskin, and Kimberly Prather, appears in Environmental Science & Technology and is available to subscribers at http://dx.doi.org/10.1021/es7030483
Lawrence Berkeley National Laboratory
Air Pollution Current Events and Air Pollution News RSSResearch reveals exactly how coughing is triggered by environmental irritants
Scientists have revealed how environmental irritants such as air pollution and cigarette smoke cause people to cough, in research published today in the American Journal of Respiratory and Critical Care Medicine.
Exposures to metals and diesel emissions in air linked to respiratory symptoms in children
Exposure shortly after birth to ambient metals from residential heating oil combustion and particles from diesel emissions are associated with respiratory symptoms in young inner city children.
Hidden threat: Elevated pollution levels near regional airports
Scientists are reporting evidence that air pollution - a well-recognized problem at major airports - may pose an important but largely overlooked health concern for people living near smaller regional airports.
Consumption of certain fish during pregnancy associated with poorer cognitive performance
Children who eat fish more than 3 times per week show a worse performance in the general cognitive, executive and perceptual-manipulative areas.
Nitrogen loss threatens desert plant life, study shows
As the climate gets warmer, arid soils lose nitrogen as gas, reports a new Cornell study. That could lead to deserts with even less plant life than they sustain today, say the researchers.
Air pollution increases infants' risk of bronchiolitis
Infants who are exposed to higher levels of air pollution are at increased risk for bronchiolitis, according to a new study.
USC study finds big air pollution impacts on local communities
Heavy traffic corridors in the cities of Long Beach and Riverside are responsible for a significant proportion of preventable childhood asthma, and the true impact of air pollution and ship emissions on the disease has likely been underestimated, according to researchers at the University of Southern California (USC).
Researchers discover links between city walkability and air pollution exposure
A new study compares neighborhoods' walkability (degree of ease for walking) with local levels of air pollution and finds that some neighborhoods might be good for walking, but have poor air quality.
Shifting the world to 100 percent clean, renewable energy as early as 2030 -- here are the numbers
Most of the technology needed to shift the world from fossil fuel to clean, renewable energy already exists. Implementing that technology requires overcoming obstacles in planning and politics, but doing so could result in a 30 percent decrease in global power demand.
Report examines hidden costs of energy production and use
A new report from the National Research Council examines and, when possible, estimates "hidden" costs of energy production and use -- such as the damage air pollution imposes on human health -- that are not reflected in market prices of coal, oil, other energy sources, or the electricity and gasoline produced from them.
More Air Pollution Current Events and Air Pollution News Articles
 |
Fundamentals of Air Pollution, Fourth Edition by Daniel Vallero Dr. Vallero holds a Ph.D. in engineering from Duke University a Masters in Environmental Health Sciences from the University of Kansas a Masters in City and Regional Planning from Southern Illinois University and a Bachelors in the Earth Sciences and Psychology from SIU. (Author) Fundamentals of Air Pollution is an important and widely used textbook in the environmental science and engineering community. Written shortly after the passage of the seminal Clean Air Act Amendments of 1990, the third edition was quite timely. Surprisingly, the text has remained relevant for university professors, engineers, scientists, policy makers and students up to recent years. However, in light of the transition in the last five years from predominantly technology-based standards (maximum achievable control technologies or MACTs) to risk-based regulations and air quality standards, the text must be updated significantly. The fourth edition will be updated to include numerous MACTs which were not foreseen during the writing of the third edition, such as secondary lead (Pb)... |
 |
Air Pollution: Its Origin and Control (3rd Edition) by Kenneth Wark (Author), Cecil F. Warner (Author), Wayne T. Davis (Author) A well-respected air pollution text, this book is suitable for a variety of engineers and scientists who wish to gain an introduction to the field of air pollution. Known for its detailed development and application of equations, the text emphasizes an understanding of the relationship between sources and control of air pollution, rather than being a simple "handbook" on the subject. The book presents information on four broad areas of interest in the air pollution field: the effects of pollutants on health and welfare; the laws and regulations that have been passed in efforts to improve air quality; the modeling of atmospheric dispersion of pollutants; the approaches to the control of emissions (from both stationary and mobile sources). The third edition of... |
 |
Air Pollution (True Books: Environment) by Rhonda Lucas Donald (Author) Ideal for today's young investigative reader, each A True Book includes lively sidebars, a glossary and index, plus a comprehensive "To Find Out More" section listing books, organizations, and Internet sites. A staple of library collections since the 1950s, the new A True Book series is the definitive nonfiction series for elementary school readers. |
 |
Air Pollution Control (3rd Edition) by C. David Cooper (Author), F. C. Alley (Author) Since the First Edition appeared, Air Pollution Control: A Design Approach has become the leading air pollution control text on the strengths of good writing, comprehensive coverage, an emphasis on design, and excellent real-world examples. The Third Edition continues this tradition of excellence, incorporating new and updated information throughout the text while retaining the topical organization and features that have made it an invaluable learning tool for instructors and students alike. The Third Edition successfully achieves two main objectives. First, it presents detailed information about air pollution and its control. Causes, sources, effects, and regulation of air pollution are discussed, as well as the economic analysis necessary for efficient and effective control of air... |
 |
Air Pollution: Problems and Solutions (Science and Society) by J. S. Kidd (Author), Renee A. Kidd (Author) The impact society has on the progress and acceptance of new science - and vice versa - is greater than most people think. For instance, over the past five years, events indicate that citizens' views have helped change the focus of the research and development carried out by both the U.S. Department of Agriculture and by the Environmental Protection Agency. Likewise, citizen actions have influenced the direction of the activities of organizations such as the World Bank in their efforts to improve agriculture and living conditions in the developing nations of the world. The new "Science and Society" set not only highlights the "what" of science, but also the "why," the "how," and the "who." Each volume provides an accessible, authoritative view of the history and current state of a... |
 |
Atmospheric Pollution by Mark Z. Jacobson (Author) This book provides a comprehensive introduction to the history and science of major air pollution issues. It begins with an introduction to the basic atmospheric chemistry and the history of discovery of chemicals in the atmosphere, and then moves on to a discussion of the evolution of the earth's atmosphere, and the structure and composition of the present-day atmosphere. It also offers a comprehensive and accessible discussion of the five major atmospheric pollution topics: urban outdoor air pollution, indoor air pollution, acid deposition, stratospheric ozone reduction, and global climate change. |
 |
Air Pollution, Smog, and Acid Rain DVD Starring: Artist Not Provided The thin layer of air that envelops the earth is essential to life. Unfortunately, modern living produces chemical by-products that threaten not only the quality of life, but also the number of living creatures and organisms that can survive in such conditions. |
|
Nsca Pollution Handbook by Natl Soc for Clean Air The National Society for Clean Air and Environmental Protection publishes this annual guide to legislation in the UK for pollution control. | |
 |
Air Pollution Engineering Manual by Air & Waste Management Association (Author), Wayne R. Davis (Editor) The definitive resource for information on air pollution emission sources and the technology available to control them. The Air Pollution Engineering Manual has long been recognized as an important source of information on air pollution control issues for industries affected by the Clean Air Act and regulations in other countries. Thoroughly updated to reflect the latest emission factors and control measures for reducing air pollutants, this new edition provides industry and government professionals with the fundamental, technological, and regulatory information they need for compliance with the most recent air pollution standards. Contributing experts from diverse fields discuss the different processes that generate air pollution, equipment used with all types of gases and... |
 |
Chasing Clean Air by Donna Barnett Join tens of thousands of clean air seekers who read Chasing Clean Air; a leading online blog devoted to clean air destinations, resources, and the latest health impact of air pollution studies and practical solutions. Chasing Clean Air documents one woman's search for clean air. With over 900 informative articles and 1000s of photographs, Chasing Clean Air aspires to inspire tens of millions of Americans living in the world's growing smog belt to reach out and breathe clean air.Let Donna entertain, educate, and inspire you with stories from the clean air road! Clean air travel, adventures, and getaways are emphasized, along with toxic pollution when found along the way. If you've ever said, Enough smog and traffic already! join Chasing Clean Air readers who aspire to breathe better... |
| © 2009 BrightSurf.com |