Polycyclic aromatic hydrocarbon sorption kinetics in three iron oxide-coated aquifer sands

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1995.Includes bibliographical references.by Britt A. Holmén.Ph.D

Environmental Traffic Assignment: Developing Emission-based Models

ABSTRACT Vehicle tailpipe emissions are major sources of air pollution and greenhouse gases. In addition to the ongoing efforts on emissions reduction, we believe there is a need to explore an innovating approach in which drivers routing decisions are influenced to minimize emissions and fuel consumption. In order to evaluate such transportation systems, we develop environmental traffic assignment models (E-TA) based on user equilibrium (UE) and system optimal (SO) behavioral principles. Extending the traditional travel time based UE and SO principles to E-TA is not straightforward because, unlike travel time, vehicle emissions increase with the increase in vehicle speed beyond a certain point. The results of various TA models show a network-wide traffic control strategy in which vehicles are routed according to SO based E-TA, can reduce system wide emissions. However, a system in which drivers make routing decisions to minimize their own emissions, (E-UE system) results in increased individual as well as systemwide emissions. KEY WORDS: Traffic Assignment, vehicle emissions, link cost function 3 Patil, Aultman-Hall, and Holme

Instantaneous Hybridization Factor (IHF) Development for HEV Energy-Emissions Analyses Using Real-World, On-Board Data

Past research has shown on-road emissions patterns unique to HEVs, indicating the need to account for them in emissions models. The main objective of this work is to outline a framework for development of new HEV emissions models based on current knowledge of CV emissions. The premise is that accurate knowledge of the instantaneous (1 Hz) power split between the HEV combustion and electric propulsion sources can be used to modify existing CV emission models for HEV emission predictions that are currently lacking in regulatory models. The HEV power split metric, instantaneous hybridization factor (IHF), was developed and quantified with on-road data collected from a 2010 Toyota Camry HEV operating on a fixed route in hilly Vermont over all seasons. IHF is the second-by-second ratio of electric system power to total system power and accounts for energy storage in the high voltage battery. IHF ranges from -1 to +1 and varies widely with vehicle speed and VSP. Different road types on the driving route were associated with different proportions of binned IHF activity, which represent the three key HEV operating states defined in this study: electric-drive only (EDO), power recovery and electric-drive assist. A more detailed analysis of IHF relationships to tailpipe emissions and road grade is found in a recently published article (Ref 1).View the NCST Project Webpag

Comparison of particle mass and number emissions from a diesel transit bus across temporal and spatial scales

This study analyzes particle number and mass emission rates measured from the exhaust of a 2002 diesel transit bus in real-world driving conditions. The dynamics of the particle number and mass emission rates are examined at resolved temporal and spatial scales across an urban arterial, a rural arterial and a divided freeway. Time-based particle number and mass emission rates were highest on the freeway, but the distance-based particle emission rates of emission/km at “hot-spots” for exposure assessment for selected 50-m road segments occurred at intersections when the bus accelerated from a stop or traveled up high grades. Comparisons of particle mass and number emission rates between idling and acceleration indicate that unless the bus is extending idling for several minutes, public exposure to bus particle emissions near bus stops can be mainly attributed to accelerations. Generally, particle number and mass emissions rates are highly correlated both temporally and spatially. Some deviations occur because particle mass emissions are highly elevated during sustained fueling events such as traveling on high grades and during sustained accelerations, while particle number emissions are more sensitive to fuel and engine speed fluctuation