Research Overview
Research approach
Research that addresses the interconnected issues of environmental pollution, climate change, energy use and global development demands a crosscutting approach. Our research is highly cross-disciplinary, with activities spanning a variety of fields including engineering, atmospheric sciences, policy analysis and public health. However, we are primarily engineers and experimentalists – we use measurement, in controlled laboratory experiments or in real-life settings, to help build understanding. Experiments and data are important, but answering the big questions almost always require some kind of modeling, and so thinking about how experiments can inform models and vice-versa is important!
What we study:
Ambient air pollution, especially atmospheric aerosol or particulate matter (PM), and household air pollution (HAP) are associated with millions of premature deaths each year. Air pollution impacts people across all boundaries: social, national, personal, etc. Further, aerosols have significant climate impacts and are currently the largest source of uncertainty in our accounting of the planet’s radiative energy balance. Organic compounds contribute a substantial fraction of the total atmospheric aerosol, but the sources and effects of the organic aerosol are poorly understood.
We aim to do work that advances the basic understanding of the sources, behavior and impacts of air pollutants, but also provides results or insights that can be used in a very immediate way to address these impacts. Finding this ‘sweet spot’ requires an understanding of the broader context and an intense focus on the details.
Some examples of past and present research projects:
How clean is a ‘clean cookstove’?
Inefficient use of solid fuel for indoor cooking is associated with approximately 2 million premature deaths each year in less-developed countries (LDCs), mostly in the women and children who are heavily exposed. This issue has received increased attention over the past few decades, with several large-scale national programs (China, India) having differing levels of impact. In the past few years, the issue has gotten more attention due to the formation of the Global Alliance for Clean Cookstoves. The end goal is to provide cooking and heating for people is as clean, efficient and easy as what we in wealthy, industrialized nations have. ‘Improved’ cookstoves use fuel more efficiently and should reduce pollutant emissions and cooks' exposure. How ‘improved’ is enough? I’ve done some modeling analyses exploring this question. We have completed or on-going field measurements of in-use stove performance and air pollution exposure in Karnataka and Himachal Pradesh in India and in Rwanda and Malawi, in southern Africa.
Understanding organic aerosols’ atmospheric transformations
Measurements of the volatility of diesel engine primary organic aerosol (POA) emissions and the in-plume aging of biomass-burning emissions resulted in parameterizations that have been applied in atmospheric chemistry models. This work helped form a new view of POA to replace that of it as a non-volatile and non-reactive atmospheric species. In the new model, OA undergoes dramatic evolution within hours of emission, with aging of aerosol from diverse sources producing chemically-similar OA. This latter fact complicates the establishment of robust source-receptor relationships but also provides the potential to simplify measurements and atmospheric model representations of OA. Characterizing emissions, finding efficient ways to represent their behavior in the atmosphere and helping develop better ways to make these measurements are all topics of interest.
Characterizing combustion sources
Testing auto-rickshaws in India: detailed laboratory vehicle emission measurements in New Delhi, India involved over 40 separate dynamometer tests. The goal of this study was to characterize emissions of air pollutants and climate-active substances (e.g., CO2, CH4 and black carbon aerosols) from in-use autorickshaws (3-wheeled taxis) with different engine-fuel combinations. The study measured emission rates and is providing detailed characterization of PM emissions, including volatility distributions, organic marker source ‘fingerprints’ and individual particle morphology. We also developed an instantaneous emissions model, based on our test data, to model changes in fleet and activity on bulk emissions and local exposures. Results will aid development of air pollution mitigation policies and give valuable insight into the effectiveness of implemented air quality management policies (e.g., the mandated use of compressed natural gas as a transport fuel). Scientifically interesting and policy-relevant measurements of emission sources are of central interest to the group.
