Black Carbon Concentrations and Diesel Vehicle Emission Factors Derived from Coefficient of Haze Measurements in California: 1967-2003

We have derived ambient black carbon (BC) concentrations and estimated emission factors for on-road diesel vehicles from archived Coefficient of Haze (COH) data that was routinely collected beginning in 1967 at 11 locations in the San Francisco Bay Area. COH values are a measure of the attenuation of light by particles collected on a white filter, and available data indicate they are proportional to BC concentrations measured using the conventional aethalometer. Monthly averaged BC concentrations are up to five times greater in winter than summer, and, consequently, so is the population?s exposure to BC. The seasonal cycle in BC concentrations is similar for all Bay Area sites, most likely due to area-wide decreased pollutant dispersion during wintertime. A strong weekly cycle is also evident, with weekend concentrations significantly lower than weekday concentrations, consistent with decreased diesel traffic volume on weekends. The weekly cycle suggests that, in the Bay Area, diesel vehicle emissions are the dominant source of BC aerosol. Despite the continuous increase in diesel fuel consumption in California, annual Bay Area average BC concentrations decreased by a factor of ~;;3 from the late 1960s to the early 2000s. Based on estimated annual BC concentrations, on-road diesel fuel consumption, and recent measurements of on-road diesel vehicle BC emissions, diesel BC emission factors decreased by an order of magnitude over the study period. Reductions in the BC emission factor reflect improved engine technology, emission controls and changes in diesel fuel composition. A new BC monitoring network is needed to continue tracking ambient BC trends because the network of COH monitors has recently been retired

Emissions of Trace Gases and Particles From Savanna Fires in Southern Africa

Airborne measurements made on initial smoke from 10 savanna fires in southern Africa provide quantitative data on emissions of 50 gaseous and particulate species, including carbon dioxide, carbon monoxide, sulfur dioxide, nitrogen oxides, methane, ammonia, dimethyl sulfide, nonmethane organic compounds, halocarbons, gaseous organic acids, aerosol ionic components, carbonaceous aerosols, and condensation nuclei (CN). Measurements of several of the gaseous species by gas chromatography and Fourier transform infrared spectroscopy are compared. Emission ratios and emission factors are given for eight species that have not been reported previously for biomass burning of savanna in southern Africa (namely, dimethyl sulfide, methyl nitrate, five hydrocarbons, and particles with diameters from 0.1 to 3 μm). The emission factor that we measured for ammonia is lower by a factor of 4, and the emission factors for formaldehyde, hydrogen cyanide, and CN are greater by factors of about 3, 20, and 3–15, respectively, than previously reported values. The new emission factors are used to estimate annual emissions of these species from savanna fires in Africa and worldwide

A qualidade da informação financeira previsional como instrumento de avaliação do pressuposto da continuidade: o caso das empresas municipais

Mestrado em AuditoriaCom a crise e com os escândalos financeiros nos últimos anos, tem-se assistido à falência de várias empresas em todo o mundo, o que tem gerado grande insegurança nos mercados, afetando a tomada de decisões por parte dos diversos stakeholders, que têm por base as informações financeiras divulgadas pelas empresas. Consequentemente, o papel do auditor foi também bastante afetado com os escândalos que surgiram, o que gerou grande desconfiança por parte dos stakeholders, tendo as grandes organizações mundiais tomado medidas e criado mecanismos e controlos mais incisivos para colmatar esta desconfiança, por forma a aumentar a importância de um dos principais pressupostos da contabilidade: o princípio da continuidade. Neste contexto, “A qualidade da informação financeira previsional como instrumento de avaliação do pressuposto da continuidade: o caso das empresas municipais” vem mostrar a importância da divulgação da informação financeira previsional (IFP), como esta pode ser útil para a tomada de decisão e para o trabalho do auditor. O estudo centra-se em bibliografia emitida pelas grandes organizações internacionais e nacionais na área da auditoria e contabilidade, quer em sítios da Internet, como em publicações de artigos académicos e de outros autores especialistas na área, e num estudo baseado na informação financeira divulgada pelas empresas municipais, do qual deriva o fundamento empírico da dissertação. A metodologia baseia-se na análise documental, mais concretamente na comparação entre a informação financeira previsional e a informação financeira histórica recolhida dos vários sítios das empresas municipais. Embora não se consiga extrapolar uma conclusão que cubra todo o universo do estudo, concluiu-se, que na sua maioria, as previsões efetuadas não diferem muito da realidade, o que denota que esta é uma informação que pode ser bastante útil, permitindo assim antecipar cenários com maior precisão e dar um maior apoio à tomada de decisão dos diversos stakeholders.Due to crisis and financial scandals in recent years, several companies in the world have bankrupted. This situation has generated high uncertainty in the markets, affecting decision-making by the different stakeholders, which are based on the financial information disclosed by the companies. Consequently the auditor's role was also quite affected with those emerged scandals, which generated great distrust from stakeholders. Thus, major world organizations took action and created mechanisms and more incisive controls to overcome this distrust in order to increase importance of the key assumptions of accounting: Going Concern. In this context, "Prospective financial information quality as a basic tool for the evaluation of going concern: the case of municipal companies" is going to show the importance of disclosure of prospective financial information, as this can be useful for decision-making and for auditor. The study focuses on literature issued by major international and national organizations in the field of auditing and accounting, websites, academic articles and publications from other expert authors in this field, and in a study based on the financial information disclosed by municipal companies, which the empirical basis of the dissertation is from. The methodology is based on document analysis, specifically in real-provided comparison of financial information collected from different sites of the municipal companies. Although we can not extrapolate a conclusion that cover all universe of the study, it was concluded that the majority of the forecasts made do not differ much from reality, which indicates that this information can be very useful, allowing to anticipate scenarios with greater accuracy and increased support to the different decision-making stakeholders

Real-Time Black Carbon Emission Factor Measurements from Light Duty Vehicles

Eight light-duty gasoline low emission vehicles (LEV I) were tested on a Chassis dynamometer using the California Unified Cycle (UC) at the Haagen-Smit vehicle test facility at the California Air Resources Board in El Monte, CA during September 2011. The UC includes a cold start phase followed by a hot stabilized running phase. In addition, a light-duty gasoline LEV vehicle and ultralow emission vehicle (ULEV), and a light-duty diesel passenger vehicle and gasoline direct injection (GDI) vehicle were tested on a constant velocity driving cycle. A variety of instruments with response times ≥0.1 Hz were used to characterize how the emissions of the major particulate matter components varied for the LEVs during a typical driving cycle. This study focuses primarily on emissions of black carbon (BC). These measurements allowed for the determination of BC emission factors throughout the driving cycle, providing insights into the temporal variability of BC emission factors during different phases of a typical driving cycle

Trends in on-Road Vehicle Emissions of Ammonia

Motor vehicle emissions of ammonia have been measured at a California highway tunnel in the San Francisco Bay area. Between 1999 and 2006, light-duty vehicle ammonia emissions decreased by 38 {+-} 6%, from 640 {+-} 40 to 400 {+-} 20 mg kg{sup -1}. High time resolution measurements of ammonia made in summer 2001 at the same location indicate a minimum in ammonia emissions correlated with slower-speed driving conditions. Variations in ammonia emission rates track changes in carbon monoxide more closely than changes in nitrogen oxides, especially during later evening hours when traffic speeds are highest. Analysis of remote sensing data of Burgard et al. (Environ Sci. Technol. 2006, 40, 7018-7022) indicates relationships between ammonia and vehicle model year, nitrogen oxides, and carbon monoxide. Ammonia emission rates from diesel trucks were difficult to measure in the tunnel setting due to the large contribution to ammonia concentrations in a mixed-traffic bore that were assigned to light-duty vehicle emissions. Nevertheless, it is clear that heavy-duty diesel trucks are a minor source of ammonia emissions compared to light-duty gasoline vehicles

Optical and Physical Properties from Primary On-Road Vehicle ParticleEmissions And Their Implications for Climate Change

During the summers of 2004 and 2006, extinction and scattering coefficients of particle emissions inside a San Francisco Bay Area roadway tunnel were measured using a combined cavity ring-down and nephelometer instrument. Particle size distributions and humidification were also measured, as well as several gas phase species. Vehicles in the tunnel traveled up a 4% grade at a speed of approximately 60 km h{sup -1}. The traffic situation in the tunnel allows the apportionment of emission factors between light duty gasoline vehicles and diesel trucks. Cross-section emission factors for optical properties were determined for the apportioned vehicles to be consistent with gas phase and particulate matter emission factors. The absorption emission factor (the absorption cross-section per mass of fuel burned) for diesel trucks (4.4 {+-} 0.79 m{sup 2} kg{sup -1}) was 22 times larger than for light-duty gasoline vehicles (0.20 {+-} 0.05 m{sup 2} kg{sup -1}). The single scattering albedo of particles - which represents the fraction of incident light that is scattered as opposed to absorbed - was 0.2 for diesel trucks and 0.3 for light duty gasoline vehicles. These facts indicate that particulate matter from motor vehicles exerts a positive (i.e., warming) radiative climate forcing. Average particulate mass absorption efficiencies for diesel trucks and light duty gasoline vehicles were 3.14 {+-} 0.88 m{sup 2} g{sub PM}{sup -1} and 2.9 {+-} 1.07 m{sup 2} g{sub PM}{sup -1}, respectively. Particle size distributions and optical properties were insensitive to increases in relative humidity to values in excess of 90%, reinforcing previous findings that freshly emitted motor vehicle particulate matter is hydrophobic

Airborne Emissions from 1961 to 2004 of Benzo[a]pyrene from U.S. Vehicles per km of Travel Based on Tunnel Studies

We identified 13 historical measurements of polycyclic aromatic hydrocarbons (PAHs) in U.S. vehicular traffic tunnels that were either directly presented as tailpipe emission factors in μg per vehicle-kilometer or convertible to such a form. Tunnel measurements capture fleet cruise emissions. Emission factors for benzo[a]pyrene (BaP) for a tunnel fleet operating under cruise conditions were highest prior to the 1980s and fell from more than 30-μg per vehicle-km to approximately 2-μg/km in the 1990s, an approximately 15-fold decline. Total annual U.S. (cruise) emissions of BaP dropped by a lesser factor, because total annual km driven increased by a factor of 2.7 during the period. Other PAH compounds measured in tunnels over the 40-year period (e.g., benzo[ghi]perylene, coronene) showed comparable reduction factors in emissions. PAH declines were comparable to those measured in tunnels for carbon monoxide, volatile organic compounds, and particulate organic carbon. The historical PAH “source terms” determined from the data are relevant to quantifying the benefits of emissions control technology and can be used in epidemiological studies evaluating the health effects of exposure, such as those undertaken with breast cancer in New York State

Indoor, outdoor and regional profiles of PM2.5 sulfate, nitrateand carbon

Fine particle concentrations were measured simultaneously at three locations: a regional monitoring site in Fresno, California, a backyard of an unoccupied residence in Clovis, California located 6 km northeast of the regional site; and indoors at the same residence. Measurements included 10-min determination of PM{sub 2.5} nitrate, sulfate and carbon using an automated collection and vaporization system, and black carbon measured by light attenuation through a filter deposit. Specific outdoor PM{sub 2.5} constituents were compared to assess the appropriateness of using regional data to model indoor concentrations from outdoor sources. The outdoor data show that, in general, the regional results provide a good representation of the concentrations seen at the building exterior. The indoor concentrations showed considerable attenuation as well as a broadening and time-lag for the concentration peaks. The concentration reduction was the largest for PM{sub 2.5} nitrate, which appears to undergo phase changes in addition to indoor deposition and penetration losses