Critical Issues in Aviation and the Environment 2014 consists of 12 individually authored sections, representing the authoring experts opinions on issues that address the major environmental components affected by aviation activities, sustainable solutions that have evolved and continue to be developed to minimize environmental impacts, and the key processes that link aviation and the environment. As in past versions, the focus of this e-circular is on the state of science, rather than policy, and on identification of priority research with potential to yield benefits during the next several years to several decades. This e-circular focuses on research conducted in the United States, although international activities are discussed where public or private entities in this country are closely involved. A wide range of published and unpublished material, public information, and individual contributions was collected to prepare these papers, as noted in the additional resources at the end of each section. Due to scope constraints, the critical issues portions of each section do not necessarily address all potentially critical issues in a given field.

关键词：大气；空气污染；环境保护

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Workplace exposure to respirable crystalline silica can cause silicosis, a progressive lung disease marked by scarring and thickening of the lung tissue. Quartz is the most common form of crystalline silica. Crystalline silica is found in several construction materials, such as brick, block, mortar and concrete. Construction tasks that cut, break, grind, abrade, or drill those materials have been associated with overexposure to dust containing respirable crystalline silica. Fiber-cement products can contain as much as 50% crystalline silica, and cutting this material has been shown to cause excessive exposures to respirable crystalline silica. NIOSH scientists are conducting a study to develop engineering control recommendations for respirable crystalline silica from cutting fiber-cement siding. This site visit was part of that study.

关键词：大气；空气污染；环境保护

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This project was motivated by the continuing need to improve ambient air quality. As of December 2012, more than 74 million Americans live in areas that violate the National Ambient Air Quality Standard for fine particulate matter (or PM2.5). Organic aerosol often contributes between 30 and 60% of ambient fine particulate matter. However, the sources of ambient organic aerosols are not well understood and state-of-the-art chemical transport models often underpredict the measured organic aerosol concentrations by a factor of 2 or more. Better understanding of the sources of organic aerosols may be needed for the development of effective control strategies. This report describes results from a three-phase test program that characterized the emissions from on-road gasoline vehicles, on-road diesel vehicles, and small off-road engines. The overarching goal of the project was to investigate the atmospheric transformations of mobile source emissions to better quantify their contribution to ambient PM levels in other words to link tailpipe to ambient. This was done by characterizing the tailpipe emissions from in-use sources and by investigating the atmospheric evolution of the emissions using dilution tunnels and smog chambers.

关键词：大气；空气污染；燃料控制

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On May 22, 2013, the National Institute for Occupational Safety and Health (NIOSH) received a request for technical assistance from the shelter manager at a large homeless shelter in Dallas, Texas, linked to an ongoing tuberculosis outbreak. The request asked NIOSH to assess the heating, ventilation, and air-conditioning (HVAC) systems and make recommendations to improve overall environmental controls at the shelter. During an on-site evaluation of the homeless shelter in June 2013, we collected physical and ventilation measurements in all key areas of the facility. We focused on areas where shelter guests typically congregate or spend significant amounts of time. We recorded the make and model number of all air-handling units (AHUs) providing air to the facility, and visually inspected the units. When possible, we measured the air flow rate through supply diffusers and return grilles. The AHUs in place were state-of-the-art and were controlled by a modern building automation system. The ventilation systems were well maintained and functional during our visit, and all AHUs were equipped with proper filter configurations. Despite their excellent condition and maintenance, certain aspects of the ventilation systems' operation could potentially contribute to airborne disease transmission among shelter guests. During our visit, it appeared the AHUs were not providing adequate outdoor air to the occupied spaces under certain occupancy and environmental conditions, as is required by the Dallas Mechanical Code and ASHRAE standards. In addition to alleviating odors and maintaining occupant comfort, outdoor air serves to dilute infectious aerosols, such as Mycobacterium tuberculosis droplet nuclei that are responsible for TB transmission. Since the TB outbreak began, the shelter has taken numerous steps to improve administrative controls, particularly when it comes to identifying guests showing signs and symptoms of TB. We recommend additional improvements to the administrative and environmental controls at the shelter. From a ventilation standpoint, we suggest that all occupied spaces at the shelter complex be supplied adequate amounts of outdoor air, as prescribed by the Dallas Mechanical Code and ASHRAE standards.

关键词：大气；健康危害；大气污染

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The Health Hazard Evaluation Program received a request from employees at a medical office building. They were concerned about indoor environmental quality and exposure to sewer gas, specifically hydrogen sulfide. The medical office building was a four-story, concrete masonry office building constructed in the 1960s that had been renovated twice; the three main floors were converted into offices and exam rooms. The building was surrounded by manholes that had been identified as sources of odors. The building was within 30 feet of a 24-inch trunk line that carried sewage from approximately 60% of the surrounding area toward the wastewater treatment facility. Most of the building's current plumbing was the original cast iron waste and vent piping, which can become brittle and crack with age. We visited the facility in April 2013 and measured hydrogen sulfide, carbon dioxide, temperature, and humidity levels throughout the building. We also inspected the building's heating, ventilation, and air-conditioning system. We did not detect hydrogen sulfide in the building. We found that carbon dioxide concentrations generally increased when moving further away from the supply air discharge point on each floor; outdoor air supplied to each floor was not uniformly distributed. Temperature and humidity were within ANSI/ASHRAE recommended levels. We found problems with duct dampers, heat pumps, and the computerized control system, and determined that air flowed from the restrooms into the hallways. We found odor sources within and near the building such as dry drain traps and manholes.

关键词：大气；空气污染；室内环境

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Two kinds of welding methods,including SMAW and GTAW,were employed to connect 16MnR steel and 2205 steel.OM and TEM was used to observe the microstructure.EDX line scan was used to analyze elements in special areas of the joint.The results show that the degree of carbon migration in the side of 16MnRofthe seam welded by GTAW is larger than that by SMAW.Particle and chain-island are two maiin form of Fe3C in micro-area of carbon migration.The grain size of seam material in GTAW section is larger than that of SMAW and the content of austenitic of seam material in GTAW section is more than that of SMAW.The tongues in the side of 16MnR appear in both two seams welded by SMAW and GTAW and they are parts from base metal.

关键词：异种钢；焊接方法；热输入；微观结构

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In August 2010, Midwest Roadside Safety Facility (MwRSF) developed and crash tested a low-cost, energy-absorbing bridge rail for the Manual for Assessing Safety Hardware (MASH) TL-3 applications. This low-cost bridge rail was designed to be compatible with the Midwest Guardrail System (MGS) such that an approach transition would not be required between the two barriers. It was desired that the system minimize bridge deck and rail costs. As part of this project, several concepts for an energy-absorbing bridge post were developed and tested. These concepts included strong-post systems designed with plastic hinges and weak-post systems designed to bend near the attachment to the bridge deck. The final post concept incorporated S3 OE 5.7 steel sections designed to yield at their bases. These posts were located on 6 ft-3 inches on center. A W-beam section was used as the rail element and was attached to the posts with a bolt designed to break during and impact event. Two full-scale crash tests were performed according to the TL-2 impact conditions provided in MASH. The new bridge rail system successfully met all the safety performance criteria for MASH TL-2. The Texas Type T631 Bridge Rail was developed as a low-cost, energy absorbing bridge rail system for TL-2 applications. Many of the features used for the system tested at Midwest Roadside Safety Facility for TL-3 were incorporated into the design developed for this project for MASH TL-2 application. The TxDOT Type T631 Bridge Rail designed and developed for this project was evaluated under MASH TL-2.

关键词：大桥护栏；碰撞测试；钢铁

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Illinois, like many other large states, has several microclimates where temperature and rainfall can vary. These variations can affect the corrosion rates of sign and signal structures, light poles, and other highway structures. Each atmospheric zone, whether they are rural, semirural, suburban, industrial, or marine areas, may be subjected to salt fall or salt spray, which can affect metals or coatings after prolonged exposure. These highway structures are typically fabricated from weathering steel, galvanized steel, painted steel, or aluminum. Each of these metals and their coatings bear a fabrication cost and have distinct ranges of durability in different atmospheres. Rural and semi-rural atmospheres cause the least corrosion damage to metal and coated surfaces. Suburban environments generally have moderate effects, compared to industrial and saline areas, which have the most corrosive atmospheres. Weathering steels have greater durability in moderate and many industrial atmospheres compared to carbon steels, such as ASTM A36 or SAE 1020. The cost differences between ASTM A36 and ASTM A588 vs. the ASTM A710 Grade 50 steel described in this report are small. Based on data obtained from WorldSteelPrices.com, as of July 2013, the price of ASTM A36 was about $0.295 per lb compared to $0.340 per lb for ASTM A588. Because A710 has slightly higher nickel and copper contents than A588, its cost is estimated to be about $0.36 per lb, based on a metric tonne.

关键词：涂料；耐腐蚀；损害；钢铁

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The Health Hazard Evaluation Program received a request from the manager of a federal government office complex. Employees were concerned about health problems including cancer, gallbladder problems, and chronic obstructive pulmonary disease. Some employees believed their health problems were associated with contamination of the buildings, soil, and groundwater from an adjoining weapons component manufacturing agency. The entire complex consisted of 13 buildings with the largest structure at the site containing over 1 million square feet across three floors. This structure contained two main areas: (1) Buildings 1 and 2 (office and warehouse space where most of the complex's employees worked) and (2) the weapons component agency. A floor-to-ceiling fire wall physically separated Buildings 1 and 2 from the weapons component agency. We reviewed environmental sampling records, did a visual inspection of Building 1 and 2 ventilation systems, spoke with employees about their health. We also tested former and current employees with sarcoidosis (an inflammatory disease that is nearly identical to chronic beryllium disease) for sensitization to beryllium, which was used for weapons manufacturing. Our evaluation found (1) no reports of employee overexposures to volatile organic compounds, polychlorinated biphenyls, beryllium or other metals, solvents, formaldehyde, or radon; (2) no evidence of beryllium sensitization among 22 persons tested; and (3) no cancer excess or abnormal pattern of disease. We noted that (1) Buildings 1 and 2 have separate ventilation systems from the weapons component agency and (2) potentially contaminated exhaust air from the weapons component agency was unlikely to enter the outdoor air intake(s) for Building 1 and 2. We recommended the employer encourage employees to learn about their personal cancer risk factors and educate employees on what they can do to reduce their risk for cancer. We also advised the employer to stop all investigations of cancer incidence and routine air and surface wipe sampling for chemicals.

关键词：大气；空气污染；健康

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关键词：汽车；交叉研究；交通安全

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