|The Center has, in its first five years, made substantial progress
on its goals of providing:
The Center is a good example of the viability of the information superhighway in bringing together expertise which is distributed at three locations. Frequent exchanges between the Center's directors, principal investigators, the EPA project officer, and the Science Advisory Committee (SAC) take place via electronic mail and a remarkable degree of coordination has been made possible by the Internet.
The Center has been fortunate in having a very able and active Science Advisory Committee (SAC) which has worked hard to make sure the Center achieves the environmental goals for which it was established. The members of the SAC have been subdivided into the three principal program focus areas and have prepared statements on the short and long term objectives of each focus area which have been folded into the request for proposals for the Center. The SAC has been particularly active in seeking opportunities for collaboration between the projects within the Center and in the development of the agenda for the summer symposia sponsored by the Center.
Eleven projects were originally supported by the Center. Partly as a result of the guidance provided by the SAC, a number of redirections of the activities within the projects have taken place to take advantage of the resources available elsewhere within the Center. Center projects lead to synergies that cross institutional and disciplinary lines. Examples are the redirection of the studies of the estimation of rate constants and chemical analysis of polar compounds at NJIT to focus on the chemicals of importance in the smog chamber studies at Caltech, the use by a doctoral student at Caltech of the facilities for bacterial and human cell mutagenicity assays at MIT, and the provision to MIT researchers working on source attribution of some of the well documented source samples from Caltech. At the recommendation of the SAC the projects are funded for two year periods, so that half of the projects are terminated every year and replaced with new ones or, where justified, continued but usually with a new orientation.
The students and the principal investigators have an opportunity for direct contact once a year at the summer symposia held in an informal setting near Boston. Poster and oral presentations on the different projects are included in the summer symposia and associated SAC meeting. This provides the Center's investigators with opportunities to learn about each other's activities and to obtain useful suggestions on their research from other participants within the Center, the SAC, and other symposium attendees. At the suggestion of the SAC the meetings are organized so as to separate the functions of outreach to the specialized community addressed by the summer symposia and workshops bringing together the students and faculty in the Center.
This past summerÔs symposium continued the CenterÔs record of successful gatherings of representatives from industry, EPA and other government agencies, public interest groups, and acadame, to address an important scientifically-intensive environmental issue with major public policy implications. The focus was fine particles in the atmosphere, with special interest in the new PM2.5 standard for atmospheric aerosols proposed for implementation by the US EPA. Highlights of the symposium are presented in a recent report, which in also available in its entirety on the CenterÔs web site:
As elaborated below, the past year has also witnessed significant progress in fulfilling major research goals of our Center. One example is the development of new modeling tools for assessing environmental impacts. Thus, we have simplified for practical applications a model to predict soot and PAH concentrations in flames (Prof. Howard). We have also assembled a comprehensive database on the role of biogenic hydrocarbons in generating atmospheric aerosols (Profs. Seinfeld and Flagan). Further, we have established a detailed elementary reaction model to describe atmospheric reactions of toluene, a prototypical light aromatic hydrocarbon pollutant (Prof. Bozelli). However, Center research also demonstrates (Prof. McRae) that the predictive capability of airshed models can be diminished by uncertainties in critical input parameters. This work shows the importance of the Center and other research programs to overcome these uncertainties. We have also expanded our understanding of how pollutants form or transform within primary sources. A particular focus has been combustion-generated pollutants in automobile engines. Thus Prof. Bozzeli has examined chemical processes involved in burning oxygenated fuels. Prof. Hochgreb has studied various processes by which hydrocarbon fuels contribute to pollution from spark-ignition engines. Examples are post-flame transport and chemical reactions, and the accumulation of deposits on the combustion chamber (the latter in collaboration with Prof. Heywood).
We have also advanced current experimental capabilities to characterize atmospheric organic pollutants. We are developing apparatus to shed light on processes by which aerosols and other contaminants form and change chemical composition, as well as equipment to reliably sample pollutants at their source or in the atmosphere. Thus Prof. Hochgreb and Dr. Lafleur have improved our understanding of how operating parameters effect the performance of a dilution tunnel for sampling particulate emissions from a spark-ignition engine. They have applied this understanding to relate particulate emissions to the operating conditions of a 4-stroke spark-ignition engine. Prof. Molina has set up and tested specialized instrumentation (a reaction flow tube sampled by a chemical ionization mass spectrometer) to study complex chemical reactions important in the generation and survival of atmospheric pollutants. He has used this equipment to study a transient aromatic species important to urban air pollution, i.e., a toluene-OH radical adduct. Profs. Carr and Farmer have made further advances in fabricating key components and testing their specialized mass spectrometer apparatus for in-situ analysis of atmospheric organic pollutants.
We have also made headway in field characterization of pollutants and in identifying methodologies to reduce adverse emissions. Thus Dean Vander Sande has employed advanced solids characterization instrumentation to distinguish soot emissions from two separate diesel test engines and to fingerprint the extent of oxidation of these soots. Prof. Cass has measured changes in the chemical composition of atmospheric aerosols passing over the Los Angeles urban airshed. Profs. Shaw and Pfeffer have shown that it may be possible to lower NOx emissions from diesel-powered vehicles by promoting chemical reactions between the NOx and carbon monoxide emitted by the engine.