Sources and Control: Encouraging progress has been made on developing
on the factors governing the formation and control of soot and on the sources
of emissions of VOCs from engines. Professor Howard at MIT has developed
a new sectional model for calculating molecular which treats kinetics of
"molecules" with molecular weights covering eight order of magnitude
and thus able to follow the transition from gas phase species to particle
inception and growth. Data for testing such models has been obtained by
Prof. Beér at MIT, who by examining soot formation under widely
differing fuel/air ratios has provided a quantitative measure of the parallel
roles of acetylene and PAH reactions in soot growth. In parallel, a novel
method for minimizing soot as well as nitric oxide emissions by diesel
engines is being pursued by Professors Pfeffer and Shaw from NJIT by finding
the conditions which favor the soot reactions with nitric oxide over those
with oxygen. For purposes of developing for mitigation of VOC precursors
to tropospheric ozone Professors Heywood and Hochgreb from MIT have measured
engine deposits in-situ, using a new electrical inductance probe and have
shown that these deposits play a significant role in the escape of hydrocarbons
from engines as a result of adsorption and consequent re-emission by the
deposits. Kinetics of blends of oxygenates which pertain to the emissions
from engines is being pursued by Professor Bozelli of NJIT. His study of
the chemical kinetics of hydrocarbon/oxygenated fuel blends in complementary
experimental and theoretical studies has provided the data needed for engine
analysis with the surprising result that certain blends of methane and
methanol have burning velocities exceeding that of the pure fuel.
Transport and Transformation: One of the lesser understood photochemical
processes is that leading to the formation of organic aerosols. The yields
of aerosols from hydrocarbons have been obtained, by Professors Seinfeld
and Flagan in over 75 outdoor smog chamber experiments at Caltech, and
the results are being analyzed using mechanisms developed in a controlled
indoor smog chamber. These are being supported by the research of Professor
Bozelli at NJIT by the study of aromatics with hydroxyl radicals in the
presence of oxygen and nitrogen oxides. Detailed thermodynamic and kinetic
pathways for the reactions are being developed that show promising agreement
with experiments for the primary products of benzene photochemical reactions,
that is an important first step in the aerosol formation mechanism.
Monitoring and Source Apportionment: The problem of obtaining
analyses of the trace volatile organic compounds (VOCs) are being pursued
by Professors Kebbekus and Mitra of NJIT. They have used selective membrane
with canister sampling to concentrate the VOCs to multiples of the levels
in the ambient. This has been achieved by reducing water vapor transport
into the canister thus reducing a major constraint on the pressures that
can be used in sampling without condensation. The mapping of the temporal
and spatial distribution of the mutagenic activity in the LA basin has
been carried out by Prof. Cass of Caltech utilizing bacterial and human
cell mutations carried out at the MIT Center for Environmental Health Sciences.
He has shown that the mutagenic activity correlates better with primary
emissions from combustion products than with their photochemical transformation
products., since the activity is highest near the sources than downwind
and higher in winter than in summer. To complement the chemical signatures
developed at Caltech for the extractable organic portion of the particles,
Professors Vander Sande and Sarofim are generating quantitative measures
of the physical and chemical structures of soots using high resolution
electron microscopy. The methods show potential for use in both providing
insights on the mechanisms of formation and signatures for use in source
attribution studies.
Summer Symposia: The third annual Summer Symposium, scheduled
with the Science Advisory Committee, meeting was organized by Professors
John Heywood of MIT and Robert Sawyer of the University of California,
Berkeley (also a member of the SAC) on "Effective Technologies for
Reducing Vehicle Emissions." The Symposium brought together many of
the key researchers and policy-makers to discuss the status of the emerging
technologies for low emission vehicles. Like the first two symposia on
the ozone in the North East and the prioritization of hazardous air pollutants,
the 1995 Symposium provided opportunities for informal and sometimes spirited
discussions between the participants in informal surroundings. The symposium
planned for the summer of 1996 is on the next generation of air pollution
instrumentation and that for 1997 on the health effects of fine particles.