Real-time measurements of SO2, H2CO, and CH4 emissions from in-use curbside passenger buses in New York City using a chase vehicle

The Aerodyne Mobile Laboratory "chased" in-use curbside passenger buses operated by various operators in New York City. With the cooperation of New York State's Metropolitan Transit Authority, the relationships between the emissions of the several gas-phase species and particulate loadings were investigated across several bus technologies, bus types, and fuels (diesel, ultralow sulfur diesel, and compressed natural gas, CNG). The CNG buses followed did not employ an oxidation catalyst. The buses characterized were not prescreened in any fashion and were measured while deployed on their normal in-service routes. This paper focuses on the fuel-based mass emissions of SO2, H2CO, and CH4, measured using tunable infrared laser differential absorption spectroscopy. Sulfur dioxide emissions from buses known to be burning ultralow sulfur diesel (<30 ppm(m) S) were 16 times lower than those from buses burning normal commercial diesel fuel, nominally less than 300 ppm(m) sulfur. Emissions of formaldehyde and methane from in-use CNG buses were approximately 15 times greater than those from diesel powered buses.     

Exhaust emissions from engines of the Detroit Diesel Corporation in transit buses: a decade of trends

In the U.S.A., exhaust emissions from city buses fueled by diesel are not characterized well because current emission standards require engine tests rather than tests of whole vehicles. Two transportable chassis dynamometer laboratories developed and operated by West Virginia University (WVU) have been used extensively to gather realistic emission data from heavy-duty vehicles, including buses, tested in simulated driving conditions. A subset of these data has been utilized for a comprehensive introspection into the trends of regulated emissions from transit buses over the last 7 years, which has been prompted by continuously tightening restrictions on one hand, along with remarkable technological progress, on the other hand. Two widely used models of diesel engines manufactured by the Detroit Diesel Corporation (DDC) have been selected as a case-study for such an overview, based on full-scale, on-site testing of actual city buses, driven in accordance with the SAE J1376 standard of a Commercial Business District (CBD) cycle. The results provide solid, quantitative evidence that most regulated emissions from engines produced by DDC have declined over the years, especially with the transition from the 6V-92TA to the Series 50 models. This improvement is remarkable mainly for the emissions of particulate matter (PM), that are lower by over 70%, on average, for the Series 50 engines, though the emissions of nitrogen oxides (NOx) exhibit a reversed trend, showing a degradation of about 6%, on average, with the transition from 6V-92TA to the Series 50 engines. The expected trend of decreasing emission levels with the model year of the engine is clear and consistent for particulate matter (PM), hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx), starting with the 1990 models, although it is not conclusive for carbon dioxide (CO2) emissions.     

Evaluation of response time of a portable system for in-use vehicle tailpipe emissions measurement

The objective of this paper is to quantify and evaluate the effects of response time of a portable emission measurement system (PEMS). The PEMS measures tailpipe emissions and vehicle dynamics on a second-by-second basis. Response times of the PEMS for exhaust concentrations were quantified on the basis of fixed periods of measurement of calibration gases for NO, hydrocarbons (HC), CO, and CO2. The time constant was quantified on the basis of the time to reach 63% of the maximum measured value when calibration gas was continuously administered for a period of typically 20 s or more. The time constant was found to be 6 s for NO and 3 s each for CO, HC, and CO2. Measurement errors associated with the response time of the PEMS were quantified. A first-order dynamic discrete model was developed to simulate the instrument measurements. Simulations showed that correction improves the measurement accuracy. Correction with smoothing better improves the measurement accuracy, especially when the noise is relatively large. On a trip level, the average error of the simulated measurements relative to the simulated signal before correction is -4%, which is deemed to be acceptable. For real-world data, smoothing and correction is recommended for major peaks to improve the measurement accuracy.     

Measurements of in-use emissions from modern vehicles using an on-board measurement system

Emissions from "low emitting" modern vehicles were measured on-road using a Fourier transform infrared (FTIR) on-board emissions measurement system. Twenty vehicles were tested on road and on a chassis dynamometer. A subset of four vehicles was tested on a test track as well as on the dynamometer. Comparison of on-board measurements with laboratory measurements while operating on the dynamometer showed agreement within measurement and test to test variability. Comparison of dynamometer measurements with test track measurements showed some larger differences attributable to track test conditions. On-road and dynamometer tests were conducted on the remaining 16 vehicles, with the on-road testing including freeway, arterial, and residential streets. The on-road testing showed that most of the low emitting vehicles under most operating conditions are operating below certification levels. Most vehicles reached a hot stabilized condition within 60 to 100 s. Hot running emissions were on average very low once the catalyst lights off. For NMHC, the majority of the "certification" emissions occur during the start-up, especially for PZEVs. NOx and CO also showed a high fraction of "certification" emissions during start-up, but also showed emission spikes under hot running conditions, especially during transients.     

Exposures to transit and other sources of noise among New York City residents

To evaluate the contributions of common noise sources to total annual noise exposures among urban residents and workers, we estimated exposures associated with five common sources (use of mass transit, occupational and nonoccupational activities, MP3 player and stereo use, and time at home and doing other miscellaneous activities) among a sample of over 4500 individuals in New York City (NYC). We then evaluated the contributions of each source to total noise exposure and also compared our estimated exposures to the recommended 70 dBA annual exposure limit. We found that one in ten transit users had noise exposures in excess of the recommended exposure limit from their transit use alone. When we estimated total annual exposures, 90% of NYC transit users and 87% of nonusers exceeded the recommended limit. MP3 player and stereo use, which represented a small fraction of the total annual hours for each subject on average, was the primary source of exposure among the majority of urban dwellers we evaluated. Our results suggest that the vast majority of urban mass transit riders may be at risk of permanent, irreversible noise-induced hearing loss and that, for many individuals, this risk is driven primarily by exposures other than occupational noise.     

A comparative investigation of ultrafine particle number and mass emissions from a fleet of on-road diesel and CNG buses

Particle number, particle mass, and CO2 concentrations were measured on the curb of a busy urban busway used entirely by a mix of diesel and CNG operated buses. With the passage of each bus, the ratio of particle number concentration and particle mass concentration to CO2 concentration in the diluted exhaust plume were used as measures of the particle number and mass emission factors, respectively. With all buses accelerating pastthe monitoring point, the results showed that the median particle mass emission from CNG buses was less than 9% of that from diesel buses. However, the median particle number emission from CNG buses was 6 times higher than the diesel buses, and the particles from the CNG buses were mainly in the nanoparticle size range. Using a thermodenuder to remove the volatile material from the sampled emissions showed that the majority of particles from the CNG buses, but not from the diesel buses, were volatile. Approximately, 82% of the particles from the CNG buses and 38% from the diesel buses were removed by heating the emissions to 300 degrees C.     

Investigation of NH3 emissions from new technology vehicles as a function of vehicle operating conditions

The objective of this study was to measure ammonia (NH3) emissions from modern technology vehicles since information is scarce aboutthis importantsource of particulate matter (PM) precursors. Test variables included the emission level to which the vehicle was certified, the vehicle operating conditions, and catalyst age. Eight vehicles with low-emission vehicle (LEV) to super-ultralow-emission vehicle (SULEV) certification levels were tested over the Federal Test Procedure (FTP75), a US06 cycle, a hot running 505, a New York City Cycle (NYCC), and a specially designed Modal Emissions Cycle (MEC01v7) using both as-received and bench-aged catalysts. NH3 emissions in the raw exhaust were measured by tunable diode laser (TDL) absorption spectroscopy. The results show that NH3 emissions depend on driving mode and are primarily generated during acceleration events. More specifically, high NH3 emissions were found for high vehicle specific power (VSP) events and rich operating conditions. For some vehicles, NH3 emissions formed immediately after catalyst light-off during a cold start.     

Emissions of nitrous oxide (N2O) from a tidal, freshwater river, the Hudson River, New York

Rivers receive a significant fraction of the anthropogenic nitrogen applied to the world's watersheds. Environmental conditions in rivers should be conducive to the formation of N2O, and recent models suggest that rivers could constitute up to 25% of the anthropogenic contribution of N2O to the atmosphere. Few direct measurements exist, however, of N2O flux between rivers, especially large rivers, and the overlying atmosphere. We measured the concentration of N2O over a 2-year period in a large, tidal, freshwater river. We coupled these measurements with a physical model of gas exchange based on inert gas tracer additions to this river and computed the flux of N2O to the atmosphere. The tidal, freshwater Hudson River is persistently supersaturated in N2O with respect to the atmosphere, with average partial pressure of N2O (pN2O) of 0.58 muatm or about 185% of atmospheric equilibrium. At all times during a 2-year cycle and at all locations sampled along a 200 km stretch of the river, the river was a net source of N2O to the atmosphere. We estimate that the tidal, freshwater Hudson River contributes 0.056 g of N2O-N m(-2) to the atmosphere annually. Despite relatively high concentrations of NO3 in the Hudson River, the tidal, freshwater river is a minor source of N2O in comparison to other rivers for which estimates exist and to components of its own watershed. The river itself accounts for only 1.3% of the total N2O contribution to the atmosphere that occurs in the Hudson watershed.     

Design and evaluation of a tobacco-prevention program targeting Chinese American youth in New York City.

In 1994 the Centers for Disease Control and Prevention recognized the importance of incorporating tobacco prevention programs into school curricula with the publication of guidelines for such programs. Included in these guidelines are recommendations to provide instruction about the consequences of tobacco use and to provide tobacco prevention programs to all students, with a particularly intensive curriculum in junior high school. Many school-based programs have been developed and tested; however, most have been delivered in English. This paper presents a culturally appropriate tobacco prevention curriculum developed for Chinese American 7th and 8th graders. The curriculum was delivered by a community organizer, in conjunction with lay health advocates, in one junior high school with a large proportion of Chinese immigrant students in New York City. This curriculum, delivered in English and Mandarin, began with 7th graders in four classrooms and consisted of seven sessions during the first year with a booster session the second year. Various presentation methods were used, including lectures, videos, demonstration, and group discussion. Valuable information about components that worked well and parts that need to be improved was gathered from school administrators, teachers, lay health advocates, and the community organizer who delivered the curriculum. This information should be incorporated into future tobacco prevention programs targeting the Chinese American community.     

Fluxes of polychlorinated biphenyls volatilizing from the Hudson River, New York measured using micrometeorological approaches

This study represents the first time that a micrometeorological technique, using turbulent transport measurements, has been used to determine the direction and magnitude of air-water exchange of polychlorinated biphenyls (PCBs). The study was conducted during July 2008 on the Hudson River estuary near the Tappan Zee Bridge, which is the site of some of the most serious PCB contamination in the world. Gas-phase ΣPCB concentrations measured at two heights above the water column averaged 1.1 ng m(-3), and concentrations were usually lower in the upper air sample, indicating net transport of PCBs from the water column to the air. Volatilization PCB fluxes were calculated using the modified Thornthwaite-Holzman equation. Values of friction velocity and atmospheric stability were calculated using the Aerodynamic Gradient and Eddy Correlation techniques. The PCB fluxes were corrected for changes in atmospheric stability using the atmospheric stability factor of water vapor (?(w)) calculated from empirical formulations which ranged from 1.0 to 3.2 (neutral to stable atmospheric boundary layer conditions). Vertical ΣPCB fluxes ranged from +0.5 μg m(-2) d (-1) to +13 μg m(-2) d (-1). Mono- through tri-homologues accounted for about half of ΣPCB fluxes, with tetra- through hexa-homologue accounting for the other half. This work demonstrates the utility of a micrometeorological approach to measuring the air-water exchange of organic contaminants.     

Apportionment of motor vehicle emissions from fast changes in number concentration and chemical composition of ultrafine particles near a roadway intersection

High frequency spikes in ultrafine number concentration near a roadway intersection arise from motor vehicles that accelerate after a red light turns green. The present work describes a method to determine the contribution of motor vehicles to the total ambient ultrafine particle mass by correlating these number concentration spikes with fast changes in ultrafine particle chemical composition measured with the nano aerosol mass spectrometer, NAMS. Measurements were performed at an urban air quality monitoring site in Wilmington, Delaware during the summer and winter of 2009. Motor vehicles were found to contribute 48% of the ultrafine particle mass in the winter measurement period, but only 16% of the ultrafine particle mass in the summer period. Chemical composition profiles and contributions to the ultrafine particle mass of spark vs diesel vehicles were estimated by correlating still camera images, chemical composition and spike contribution at each time interval.. The spark and diesel contributions were roughly equal, but the uncertainty in the split was large. The distribution of emissions from individual vehicles was determined by correlating camera images with the spike contribution to particle number concentration at each time interval. A small percentage of motor vehicles were found to emit a disproportionally large concentration of ultrafine particles, and these high emitters included both spark ignition and diesel vehicles.     

Short communication: Evaluation of milk urea nitrogen as a management tool to reduce ammonia emissions from dairy farms

The purpose of this study was to compile and evaluate relationships between feed nitrogen (N) intake, milk urea N (MUN), urinary urea N (UUN), and ammonia (NH₃) emissions from dairy farms to aid policy development. Regression relationships between MUN, UUN, and NH₃ emissions were compiled from studies conducted in Wisconsin, California, and the Netherlands. Relative reductions in NH₃ emissions were calculated as percentage decreases in NH₃ emissions associated with a baseline MUN level of 14 mg/dL (prevailing industry average). For 3 studies with cows in stanchion barns, relative NH₃ emission reductions of 10.3 to 28.2% were obtained when MUN declined from 14 to 10 mg/dL. Similarly, analyses of 2 freestall studies provided relative NH₃ emission reductions of 10.5 to 33.7% when MUN levels declined from 14 to 10 mg/dL. The relative reductions in NH₃ emissions from both stanchion and freestall barns can be associated directly with reductions in UUN excretion, which can be determined using MUN. The results of this study may help create new awareness, and perhaps eventual industry-based incentives, for management practices that enhance feed N use efficiency and reduce MUN, UUN, and NH₃ emissions from dairy farms.     

Measurements of methane emissions from landfills using a time correlation tracer method based on FTIR absorption spectroscopy

Methane is an important climate gas contributing significantly to global warming. A large part of the anthropogenic emissions of methane comes from landfills. Due to the biogenic origin of these emissions and the inhomogeneous characteristics of landfills and their soil cover, these emissions show large spatial variation. Thus, development of reliable and cost-effective methods for measurements of these emissions is an important task and a challenge to the scientific community. Traditionally, field chamber methods have been used but also different area integrating methods based on downwind plume measurements. These measurements have been supported by meteorological data either directly from local measurements or by controlled release of tracer gas from the landfill providing the dispersion characteristics of the plume. In this paperwe describe a method,the Time Correlation Tracer method, combining controlled tracer gas release from the landfill with time-resolved concentration measurements downwind the landfill using FTIR absorption spectroscopy. The method has been tested and used on measurements at a landfill in southern Sweden over the past 1.5 years. The method has proven to be a usable method for measurements of total methane emission from landfills, and under favorable meteorological conditions we estimate an achievable accuracy of 15-30%. The real time analysis capability of the FTIR makes it possible to judge the success of the measurement already on site and to decide whether more measurements are necessary. The measurement strategy is relatively simple and straightforward, and one person can make a measurement from a medium sized landfill (1-4 ha) within a few days to a week depending on the meteorological situation.     

Estimation of genetic parameters for measures of calf survival in a population of Holstein heifer calves from a heifer-raising facility in New York State

The objectives of this study were to estimate the genetic parameters of survival to weaning and survival to exit for a population of Holstein calves from New York State, as well as to associate the estimated breeding values determined in the current study with traits from ongoing genetic evaluations used in Canada and the United States. Data were recorded for 7,372 heifer calves at a commercial rearing facility in New York State from arrival at 1 to 7 d of age for the duration of stay at the facility (on average, heifers departed the facility 1 mo before calving). Performance and disease up to weaning and mortality before and after weaning were recorded. Analyzed data were limited to daughters of sires with at least 10 calves originating from farms that had sent a minimum of 5 calves to be raised at the facility. As such, calves from 264 sires and 36 herds were studied using 2 statistical methods. The first method, calf survival, used a Weibull proportional hazards model, with survival defined as age at culling, death, or censoring. The second method, a 2-trait sire model, included survival from arrival to weaning (SUV1) and survival from weaning to exit (SUV2). Both models included fixed effects of arrival weight, serum total protein, weaning weight, season and year of birth, and calving ease score. Herd and sire were included as random effects. Significant associations among all fixed effects and calf survival were observed. In general, very light or heavy weight at arrival, low total protein, low weaning weight, and difficult birth increased risk of mortality for calves. The heritability of survival from the first method was 0.063. The heritabilities from the linear model were 0.001 for SUV1 and 0.036 for SUV2. The genetic correlation between SUV1 and SUV2 was 0.58. Genetic variance was close to zero for survival of calves to weaning, but was greater for survival after weaning through the growing period. Breeding values were estimated for SUV1 and SUV2 and correlated with routinely evaluated traits from Canadian and US genetic evaluations. Significant associations between genetic evaluations for survival traits and routinely evaluated traits in Canada and the United States were found, in particular with conformation body traits, somatic cell score, fertility, and longevity.     

Pesticide measurements from the first national environmental health survey of child care centers using a multi-residue GC/MS analysis method

The U.S. Department of Housing and Urban Development, in collaboration with the U.S. Consumer Product Safety Commission and the U.S. Environmental Protection Agency, characterized the environments of young children (<6 years) by measuring lead, allergens, and pesticides in a randomly selected nationally representative sample of licensed institutional child care centers. Multi-stage sampling with clustering was used to select 168 child care centers in 30 primary sampling units in the United States. Centers were recruited into the study by telephone interviewers. Samples for pesticides, lead, and allergens were collected at multiple locations in each center by field technicians. Field sampling was conducted from July through October 2001. Wipe samples from indoor surfaces (floors, tabletops, desks) and soil samples were collected at the centers and analyzed using a multi-residue GC/MS analysis method. Based on the questionnaire responses, pyrethroids were the most commonly used pesticides among centers applying pesticides. Among the 63% of centers reporting pesticide applications, the number of pesticides used in each center ranged from 1 to 10 and the frequency of use ranged from 1 to 107 times annually. Numerous organophosphate and pyrethroid pesticides were detected in the indoor floor wipe samples. Chlorpyrifos (0.004-28 ng/cm2), diazinon (0.002-18 ng/cm2), cis-permethrin (0.004-3 ng/cm2), and     

Testing for bias between the Kjeldahl and Dumas methods for the determination of nitrogen in meat mixtures, by using data from a designed interlaboratory experiment

Bias between the Dumas and the Kjeldahl methods for the determination of protein nitrogen in food was studied by conducting an interlaboratory study involving 40 laboratories and 20 different test materials. Biases were found to be small and statistically significant only for the chicken test materials, where a bias of 0.020 ± 0.004% m/m was detected.