[Due to the increasing size of the archives, each topic page now contains only the prior 365 days of content. Access to older stories is now solely through the Monthly Archive pages or the site search function.]
EPA staff policy assessment recommends reduction in ozone standard from 75 ppb to 60-70 ppb
August 31, 2014
The staff of the US Environmental Protection Agency’s (EPA) Office of Air Quality Planning and Standards (OAQPS) has released the final version of the policy assessment (PA) for the review of the ozone (O3) National Ambient Air Quality Standards (NAAQS).
Among the staff recommendations are to further reduce the primary ozone standard from the current 75 ppb (parts per billion) to a revised level within the range of 70 ppb to 60 ppb—and preferably below 70 ppb.
Study finds external effects negate Hong Kong local efforts to reduce ozone pollution; multiregional policies needed
August 29, 2014
Researchers from Hong Kong Polytechnic University, Hong Kong’s Environmental Protection Department and UC Irvine present in a paper in the ACS journal Environmental Science & Technology direct evidence that increasing regional effects have negated local control efforts for O3 (ozone) pollution in Hong Kong over the past decade.
The researchers analyzed the daily maximum 8 h average O3 and Ox (=O3+NO2) concentrations observed during the high O3 season (September–November) at Air Quality Monitoring Stations. They found that the locally produced Ox showed a statistically significant decreasing trend over 2002–2013 in Hong Kong. Analysis by an observation-based model confirmed this decline in in situ Ox production, which the team attributed to a reduction in aromatic hydrocarbons.
Study: open trash burning worldwide significantly worsening air pollution; unaccounted for in emission inventories
August 28, 2014
Unregulated open trash burning around the globe is pumping far more pollution into the atmosphere than shown by official records. A new study led by the National Center for Atmospheric Research (NCAR) estimates that more than 40% of the world’s garbage is burned in such fires, emitting gases and particles that can substantially affect human health and climate change.
The new study provides the first rough estimates, on a country-by-country basis, of pollutants such as particulates, carbon monoxide, and mercury that are emitted by the fires. Such pollutants have been linked to serious medical issues. The researchers also estimated emissions of carbon dioxide, the most common greenhouse gas produced by human activity. Their paper is published in the ACS journal Environmental Science & Technology.
Black carbon linked to increased cardiovascular risk; exacerbated by co-exposure to motor vehicle emissions
August 26, 2014
Black carbon (BC) from incomplete biomass and fossil fuel combustion is the most strongly light-absorbing component of particulate matter (PM) air pollution and a major climate-forcing emission. A new international study led by McGill University (Canada) Professor Jill Baumgartner suggests that black carbon may also increase the risk of cardiovascular disease. The team’s findings are published in the Proceedings of the National Academy of Sciences of the United States (PNAS).
China’s particulate matter (PM) air pollution significantly exceeds health guidelines and is driven by industrial emissions, motor vehicles, and household use of biomass and coal fuels. Baumgartner and her colleagues measured the daily exposure to different types of air pollutants, including black carbon, in 280 women (mean age 51.9 y) in China’s rural Yunnan province, where biomass fuels are commonly used. They found that found that BC exposure from biomass smoke is more strongly associated with blood pressure—which directly impacts cardiovascular risk—than total PM mass, and that co-exposure to motor vehicle emissions may strengthen BC’s impact. Air pollution mitigation efforts focusing on reducing combustion pollution are likely to have major benefits for climate and human health.
MIT study finds air quality co-benefits of US carbon policies can significantly offset costs, depending upon the policy
August 25, 2014
The human health benefits associated with improvements in air quality related to the reduction in greenhouse gas emissions improvements can offset 26–1,050% of the cost of US carbon policies, depending upon the type of policy, according to a new study by a team from MIT. (Air quality co-benefits are additional to climate benefits realized from reduced CO2 emissions.)
In a paper published in the journal Nature Climate Science, the MIT researchers took a systems-level approach to analyzing how climate policies influence air quality, focusing on US emissions of O3 and PM2.5 precursors through 2030. They assessed the costs and air-quality-related benefits of three potential national-scale climate policies, examining the entire pathway linking climate policies, economic sector responses, emissions, regional air quality, human health and related economic impacts.
EPA report shows progress in reducing urban air toxics across US; 50% reduction from mobile sources since 1990
August 22, 2014
The US Environmental Protection Agency (EPA) released the Second Integrated Urban Air Toxics Report to Congress—the final of two reports required under the Clean Air Act (CAA) to inform Congress of progress in reducing public health risks from urban air toxics (also referred to as hazardous air pollutants or HAPs). HAPs are defined as those pollutants that cause or may cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental and ecological effects.
Using national emissions and air quality data, the Urban Air Toxics Report shows the substantial progress that has been made to reduce air toxics across the country since the Clean Air Act Amendments of 1990. Among the results highlighted is the removal of an estimated 1.5 million tons per year of HAPs from mobile sources, which represents a 50% reduction in mobile source HAP emissions. With additional fleet turnover, EPA expects these reductions to grow to 80% by the year 2030.
NIST study suggests severe corrosion in underground gasoline storage tanks may require component replacement sooner than expected; 500K USTs in US
July 30, 2014
|Optical micrographs of severe corrosion on steel alloy samples exposed to ethanol and acetic acid vapors—conditions typical of underground gasoline storage tanks—after 355 hours, 643 hours, and 932 hours. Source: NIST. Click to enlarge.|
In recent years, field inspectors in nine states have reported many rapidly corroding underground gasoline storage tank (UST) components such as sump pumps. These incidents are generally associated with use of gasoline-ethanol blends and the presence of bacteria, Acetobacter aceti, which convert ethanol to acetic acid, a component of vinegar. Corrosion can result in failures, leaks and contamination of groundwater, a source of drinking water.
Following up on the inspectors’ findings, a National Institute of Standards and Technology (NIST) laboratory study has demonstrated severe corrosion—rapidly eating through 1 millimeter of wall thickness per year—on steel alloy samples exposed to ethanol and acetic acid vapors. Based on this finding, NIST researchers suggest gasoline stations may need to replace submersible pump casings, typically made of steel or cast iron, sooner than expected.
Non-intrusive bio-monitoring system anticipates driver fatigue in the vehicle to prevent accidents
July 23, 2014
The Instituto de Biomecánica de Valencia (Biomechanics Institute - IBV) and its consortium partners in the European project HARKEN have developed a non-intrusive system integrated into smart materials which is capable of monitoring cardiac and respiratory rhythms in order to prevent drivers from falling asleep. The two-year project had its final meeting in June.
The system is based on three main components: the seat sensor, the seat belt sensor and the signal-processing unit (SPU), which processes the sensor data in real time. All are invisible to the user.
Critical review finds actual measurement data on segments of natural gas lifecycle sparse or lacking
July 08, 2014
After a critical review of the literature on the air impacts of increased natural gas acquisition, processing, and use, a team of US researchers has determined that that actual measurement data on various individual segments of the natural gas life cycle are sparse or critically lacking.
National and state regulators primarily use generic emission inventories to assess the climate, air quality, and health impacts of natural gas systems. These inventories rely on limited, incomplete, and sometimes outdated emission factors and activity data, based on few measurements, they found. In their paper, published in the ACS journal Environmental Science & Technology, they make a number of recommendations to maximize the benefits and minimize the negative impacts of the natural gas resource.
Pilot at BMW Munich plant evaluating use in vehicle assembly of custom orthotic devices produced by 3D printing
July 02, 2014
A pilot project in BMW’s Munich vehicle assembly plan is exploring the benefits of a new and innovative ergonomic tool—a flexible finger cot, which protects workers against excess strains on the thumb joints while carrying out certain assembly activities. The project is part of a dissertation in cooperation with the Department of Ergonomics at the Technical University of Munich.
Each of the flexible assembly aids is a unique piece, customized to the match the form and size of a worker’s hand. The BMW Group makes these orthotic devices in-house, using additive production procedures—i.e., “3D printing”.
China iCET releases 2014 Green Car China report ranking mainstream cars by green and health impacts
July 01, 2014
|Only hybrids performed very well on both the green rating and the smog index. Source: iCET. Click to enlarge.|
China’s Innovation Center for Energy and Transportation (iCET) recently released its 2014 Green Car China Annual Report, an evaluation of mainstream vehicles on sale in China by their lifecycle impacts and their health impacts.
Based on the lifecycle impact assessment, every vehicle obtains a green score (0-10). The higher the green score, the lower the environmental impact (i.e., the greener it is). After normalizing the health impacts of tailpipe emissions, every vehicle also obtains a smog index score (1-8). The lower the smog score, the more eco-friendly it is.
Researchers review risk to water resources from unconventional shale gas development in US
June 19, 2014
A team from Duke University, Stanford University, Dartmouth College and Ohio State University has published in the ACS journal Environmental Science & Technology an overview and synopsis of recent investigations (as of January 2014) into one set of possible environmental impacts from unconventional shale gas development: the potential risks to water resources.
They identified four potential modes of water resource degradation: (1) shallow aquifers contaminated by fugitive natural gas (i.e., stray gas contamination) from leaking shale gas and conventional oil and gas wells, potentially followed by water contamination from hydraulic fracturing fluids and/or formation waters from the deep formations; (2) surface water contamination from spills, leaks, and the disposal of inadequately treated wastewater or hydraulic fracturing fluids; (3) accumulation of toxic and radioactive elements in soil and the sediments of rivers and lakes exposed to wastewater or fluids used in hydraulic fracturing; and (4) the overuse of water resources, which can compete with other water uses such as agriculture in water-limited environments.
Study estimates global black carbon emissions up 72% from 1960-2007; BC emissions intensity down 52%
May 31, 2014
|Black carbon emissions and BC emissions intensity per year. Credit: ACS, Wang et al. Click to enlarge.|
A study led by a team from Peking University has estimated that global black carbon (BC) emissions increased from 5.3 teragrams/year in 1960 to 9.1 teragrams per year in 2007 (+72%). These estimates are 11-16% higher than produced by in previous inventories, the researchers noted in a paper published in the ACS journal Environmental Science & Technology.
Over the same period, BC emission intensity—the amount of BC emitted per unit of energy production—decreased by 52% for all the regions under assessment, especially China and India.
Study shows two-stroke scooters dominant source of air pollution in many cities; asymmetric polluters
May 23, 2014
A study by European researchers has found that two-stroke (2S) scooters, although constituting a small fraction of the fleet, can dominate urban vehicular pollution through organic aerosol and aromatic emission factors up to thousands of times higher than from other vehicle classes. The study by the team led by researchers from the Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Switzerland, appears in the journal Nature Communications.
The team calls 2S scooters “asymmetric polluters” as their emission factors (EFs) and evidence from air quality measurements before and after bans on scooters in Asian cities suggest they may dominate vehicular pollution despite their relatively small numbers.
OECD: rising air pollution-related deaths taking heavy toll on society; more should be done to reduce transport emissions
|Deaths from outdoor air pollution by region in 2005 and 2010. From 2005 to 2010, the death rate rose by 4% worldwide, by 5% in China and by 12% in India. OECD. Click to enlarge.|
Outdoor air pollution kills some 3.5 million people across the world every year, and causes health problems from asthma to heart disease for many more, according to data collected by the World Health Organization (WHO). (Earlier post.) This pollution is costing advanced economies plus China and India an estimated US$3.5 trillion a year in premature deaths and ill health; these costs will rise without government action to limit vehicle emissions, according to a new report published by the Organisation for Economic Co-operation and Development (OECD): “The Cost of Air Pollution: Health Impacts of Road Transport”.
In OECD countries, around half the cost is from road transport, according to the report, with diesel vehicles producing the most harmful emissions. Traffic exhaust is a growing threat in fast-expanding cities in China and India, as the steady increase in the number of cars and trucks on the road undermines efforts to curb vehicle emissions.
WHO data: global annual PM10 increased by 6% during recent 3-year period; based on data from 851 cities
May 08, 2014
Air quality in most cities worldwide that monitor outdoor (ambient) air pollution fails to meet World Health Organization (WHO) guidelines for safe levels, putting people at additional risk of respiratory disease and other health problems, according to WHO’s expanded ambient (outdoor) air pollution (AAP) in cities database 2014.
WHO’s 2014 AAP database consists mainly of urban air quality data—annual means for PM10 and/or PM2.5—and covers 1,600 cities across 91 countries. Only 12% of the people living in cities reporting on air quality reside in cities where this complies with WHO air quality guideline levels. About half of the urban population being monitored is exposed to air pollution that is at least 2.5 times higher than the levels WHO recommends—putting those people at additional risk of serious, long-term health problems, the UN organization said.
Study finds rising temperatures increase risk of unhealthy ozone levels absent sharp cuts in precursors
May 05, 2014
Ozone pollution across the continental United States will become far more difficult to keep in check as temperatures rise, according to new work led by the National Center for Atmospheric Research (NCAR). The study shows that Americans face the risk of a 70% increase in unhealthy summertime ozone levels by 2050, assuming continued greenhouse gas emissions with resultant significant warming (IPCC Scenario A2 and RCP (Representative Concentration Pathway) 8.5.)
However, the study also showed that a sharp reduction in the emissions of ozone precursors would lead to significantly decreased levels of ozone even as temperatures warm. Without those cuts, almost all of the continental United States will experience at least a few days with unhealthy air during warmer summers, the research shows. Heavily polluted locations in parts of the East, Midwest, and West Coast in which ozone already frequently exceeds recommended levels could face unhealthy air during most of the summer.
World Bank/ICCT report provides guidance to reducing black carbon emissions from diesels in developing countries
April 14, 2014
|Historical Trends in Black Carbon Emissions from Surface Transportation (teragrams of black carbon per year). Source: Minjares et al. Click to enlarge.|
The World Bank has published a report, undertaken by a team from the International Council on Clean Transportation (ICCT), intended to inform efforts to control black carbon emissions from diesel-based transportation in developing countries. The report proposes approaches for integrating black carbon emission reduction considerations in cost-benefit assessment and applies an analytic framework to four simulated projects to illustrate the associated opportunities and challenges at a project level.
The transportation sector accounted for approximately 19% of global black carbon emissions in the year 2000, according to the report. Road transportation accounted for 9% of global black carbon, with diesel engines responsible for nearly 99% of those emissions. In the near term, black carbon emissions from mobile engines are projected to decline as a consequence of policies implemented in the US, Canada, Europe, and Japan. However, black carbon emissions are projected to increase in the next decade as vehicle activity increases, particularly in East and South Asia.
LMU study finds 20% of gases from combustion of R1234yf MAC refrigerant consist of highly toxic carbonyl fluoride (correction and update)
April 11, 2014
Chemists at Ludwig Maximilians Universität München report that 20% of the gases produced by the combustion of R1234yf—the approved low global warming potential refrigerant for mobile air conditioning (MAC) systems, the adoption of which has met with resistance from German automakers (earlier post)—consist of the highly toxic chemical carbonyl fluoride.
Carbonyl fluoride is structurally related to phosgene (which contains chlorine in place of fluorine), which was used as a chemical weapon during the First World War. Kornath and his co-workers have just published the results of their investigation in the journal Zeitschrift für Naturforschung B.
WHO links 7 million premature deaths annually to air pollution; 12.5% of total global deaths
March 25, 2014
The World Health Organization now estimates that in 2012 around 7 million people died—one in eight (12.5%) of total global deaths—as a result of air pollution exposure. This new estimate more than doubles previous estimates and confirms that air pollution is now the world’s largest single environmental health risk, according to WHO, which is the directing and coordinating authority for health within the United Nations system.
WHO says that the new data reveal a stronger link between both indoor and outdoor air pollution exposure and cardiovascular diseases, such as strokes and ischemic heart disease (an insufficient supply of blood—and thus oxygen—to the heart), as well as between air pollution and cancer. This is in addition to air pollution’s role in the development of respiratory diseases, including acute respiratory infections and chronic obstructive pulmonary diseases.
Study finds engines emit exhaust nanoparticles even when not fueled during engine braking
January 19, 2014
A new study finds that as much as 20–30% of the number of vehicle engine exhaust particles larger than 3 nm may be formed during engine braking conditions—i.e., during decelerations and downhill driving while the engine is not fueled. However, the authors note, these particles have not been taken into account in emission regulations and in the assessment of associated health risks.
The study by researchers in Finland and Greece, published in the ACS journal Environmental Science & Technology, suggests that both the characteristics of these particles and the mechanism by which they form seem to differ significantly from those of soot and nucleation particles. The study also indicates that the particles were non-volatile, formed before the catalyst, and originating from engine oil. Results thus indicate that the emissions of engine braking particles can be reduced using exhaust particle filtration systems.
Researchers identify new nitrated PAH compounds from combustion that are hundreds of times more mutagenic than parent PAHs
January 06, 2014
A team led by researchers at Oregon State University has discovered novel nitrated polycyclic aromatic hydrocarbon (NPAH) compounds produced by combustion sources or formed in the atmosphere that are hundreds of times more mutagenic than their parent PAHs, which are known carcinogens. The findings were published in the ACS journal Environmental Science and Technology.
These new compounds were not previously known to exist, and raise additional concerns about the health impacts of heavily-polluted urban air or dietary exposure. It has not yet been determined in what level the new compounds might be present, and no health standards now exist for them.
Analysis finds air-quality justification for CNG vehicle conversion in developing cities, despite negative climate impact
December 03, 2013
|Impact pathway approach for modeling policy interventions in (a) air quality and (b) climate impacts. Credit: ACS, Zia and Tanzila. Click to enlarge.|
An analysis by a team in Bangladesh found large air quality and associated health benefits accruing to the residents of Dhaka (the capital of Bangladesh) as a result of the rapid conversion of the motor vehicle fleet to CNG. Around 2,045 avoided premature deaths in greater Dhaka can be attributed to air quality improvements from the CNG conversion policy in 2010, resulting in a saving of around US$400 million, they found.
However, CNG conversion was apparently detrimental from a climate change perspective, as CH4 emissions increased. (There is some uncertainty over the impact of ultrafine particulates.) As the greenhouse gas impacts (costs or benefits) are much smaller than the health benefits, the conversion of petroleum vehicles to CNG can be justified on the basis of local air pollution benefits alone, they concluded. Their paper is published in the ACS journal Environmental Science & Technology.
Study estimates 6% of lung cancer deaths in US and UK attributable to diesel exhaust
November 28, 2013
In 2012, the International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO), classified diesel engine exhaust (DEE) as carcinogenic to humans (Group 1). (Earlier post.)
Now, a study by researchers from the Netherlands, the US, and France estimates that approximately 6% of annual lung cancer deaths in the US and UK—combining both environmental and occupational exposures—may be due to DEE exposure. This translates to about 9,000 annual lung cancer deaths in the US and about 2,000 annual lung cancer deaths in the UK that may be attributable to DEE.
UC Berkeley study quantifies LD gasoline on-road emissions
November 27, 2013
Based on on-road measurements in their study, a team from the University of California Berkeley has estimated that, as of 2010, light-duty (LD) gasoline vehicles were responsible for 85% of CO; 18% of NOx; 18% of organic aerosol (OA); and 6% of black carbon (BC) emissions from on-road motor vehicles in the United States. Correspondingly, the study, reported in the ACS journal Environmental Science & Technology, also concluded that, as of 2010, diesel engines were the dominant on-road source of BC, OA, and NOx.
The researchers measured vehicle emissions of NOx, CO, fine particulate matter (PM2.5), OA and BC in bore 2 of the Caldecott tunnel in the San Francisco Bay Area. In bore 2, light-duty (LD) vehicles accounted for more than 99% of total traffic; heavy-duty trucks were not allowed.
Study finds biodiesel use in HD trucks in Canada will result in very minimal changes in air quality and health benefits
November 07, 2013
Results of a study by a team from Health Canada and Environment Canada suggest that the use of B5 and B20 biodiesel fuel blends (5% and 20% biodiesel, respectively) compared to ULSD in on-road heavy-duty diesels in Canada will result in very minimal changes in air quality and health benefits/costs across Canada, and that these were likely to diminish over time.
Health Canada is the Canadian Federal department responsible for helping Canadians maintain and improve their health; Environment Canada is the Federal agency tasked with, among other things, protecting the environment. An open-access paper on the study has been accepted for publication in the ACS journal Environmental Science & Technology.
ICCT report finds global implementation of advanced emissions and fuel-quality regs could cut early deaths from vehicle emissions by 75% in 2030
November 06, 2013
|Global trends in vehicle-kilometers traveled (VKT) and early deaths from vehicle-related fine particle exposure (2000–2030). Chambliss et al. Click to enlarge.|
Although many countries have adopted emission control regulations patterned on the European regulations, the significant majority of these have not implemented the latest and most stringent Euro 6/VI stage. A study by a team at the the International Council on Clean Transportation (ICCT) finds that if that lag persists and present trends in vehicle activity continue, early deaths from vehicle-related PM2.5 exposure in urban areas will increase 50% by 2030, compared to 2013.
Conversely, the report finds, if all countries were to follow an accelerated roadmap to Euro 6/VI-level regulations, in tandem with fuel-quality regulations limiting sulfur content to 10 to 15 parts per million (ppm), early deaths globally from road vehicle emissions would fall by 75% (200,000) in the year 2030, representing a cumulative savings of 25 million additional years of life.
UC Irvine study finds organic constituents of UFP play important role in heart disease; suggestions for more effective emission control
October 12, 2013
|Particle scale. Inset: 4 polydisperse modes of traffic-related ambient particulate matter span approximately 4 orders of magnitude from below 1 nm to above 10 μm. Source: Kleinman presentation. Click to enlarge.|
Results of a study funded and released by the California Air Resources Board (ARB) suggest that the organic constituents of ultrafine PM (UFP, particles ≤ 0.18 μm aerodynamic diameter) resulting from internal-combustion engine exhaust and from chemical reactions in the air play an important role in the progression of heart disease, the leading cause of death in the US. The findings thus suggest a direction for mor effective emission control measures—i.e., technology for the removal of the organic constituents as well as the reduction of the number of particles.
Led by Dr. Michael T. Kleinman of the University of California Irvine, the new study used a novel approach to determine whether or not the toxicity of UFP particles depends on the concentration and composition of semi-volatile and non-volatile fractions of the PM.
Study finds biodiesel blend reduces total particle mass in emissions but may have greater adverse health effect per mass than diesel
October 10, 2013
Findings from a study by researchers from the Department of Medicine and the School of Engineering at the University of Vermont suggest that the addition of biodiesel to diesel fuels will reduce the total particle mass of PM emissions—but that the biodiesel blend particles may contribute to greater biological effects per mass than B0, leading to potentially greater health risks.
As reported in a paper published in the ACS journal Environmental Science & Technology, the team first characterized exhaust particles produced by combustion of pure petrodiesel (B0) and B20 (20% soy biodiesel/ 80% B0) fuels using the same engine and running conditions, and then conducted experiments in two human cell lines representing bronchial epithelial cells and macrophages as well as in female mice. (Studies in cells alone do not necessarily reflect the integrated response of a whole animal, they noted.)
Italian study finds raised levels of PM10, even below current Euro limits, associated with increased acute cardiac events
October 09, 2013
Results of a study by a research team from Brescia and Parma, Italy, to be presented at the Acute Cardiac Care Congress 2013 by Dr. Savina Nodari from Spedali Civili Hospital of Brescia, support the hypothesis that raised levels of PM10—even below the current limits set by the European Environmental Protection Agency—are associated with increased admission rates for acute cardiac events, especially in males, older patients and those with previous cardiovascular hospitalizations.
The study evaluated the rate of hospitalizations for acute coronary syndrome (ACS); acute heart failure (AHF); malignant ventricular arrhythmias (MVA); and atrial fibrillation (AF) and the average daily concentrations of PM10 in Brescia over the period 2004-2007. The associations between average levels of PM10 and daily hospitalization for acute cardiovascular (CV) events were analyzed by a generalized linear model.
USC researchers find car ventilation setting critical to in-cabin exposure to particulate pollutants; new model for aiding exposure assessments
September 15, 2013
|In-vehicle-to-outside (I/O) ratios for four pollutants under different ventilation settings. Credit: ACS, Hudda and Fruin (2013). Click to enlarge.|
Researchers at USC have found that using recirculation rather than outside air ventilation in a car can effectively reduce in-cabin exposure to on-road particle pollution. In a study published in the ACS journal Environmental Science & Technology, they also report that in addition to the benefits of recirculation settings, exposures are lower in newer cars; at slower speeds; and on arterial roads, where pollutant concentrations are lower than on freeways.
Scott Fruin, assistant professor of preventive medicine, and Neelakshi Hudda, research associate in environmental health, both of the Keck School of Medicine of USC, performed a systematic study of in-vehicle exposure to include a full range of car types and operating conditions, as well as all types of particulate pollution. According to the researchers, concentrations of particle pollutants on freeways are often five to 10 times higher than elsewhere.
Researchers identify new pathways in low-temp oxidation of hydrocarbons; important to fuel combustion, atmospheric chemistry and biochemistry
September 05, 2013
|The diagram illustrates the newly-described reaction that transforms molecules of ketohydroperoxide into acids and carbonyl molecules, after going through intermediate stages. Credit: ACS, Jalan et al. Click to enlarge.|
Researchers at MIT, with colleagues at the University of Minnesota, have provided evidence and theoretical rate coefficients for new pathways in the low-temperature oxidation of hydrocarbons. Their paper is published in the Journal of the American Chemical Society.
The newly explained reaction—the basic outlines of which had been first hypothesized by Korcek and co-workers more than 30 years ago but the workings of which had never been understood in detail—is an important part of atmospheric reactions that lead to the formation of climate-affecting aerosols; biochemical reactions that may be important for human physiology; and combustion reactions in engines. The new study provides theoretical confirmation of Korcek’s hypothesis that ketohydroperoxide molecules (KHPs) are precursors to carboxylic acid formation.