This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Amines are volatile organic compounds (VOCs) emitted to the atmosphere from a number of sources including intense emissions from animal feeding operations (AFOs). In the atmosphere, amines act as precursors for aerosols, but the fates of amines released incident to large-scale food production have not been studied in a quantitative manner to determine their importance in atmospheric gas and aerosol chemistry. This project will take an integrated laboratory/field approach to identify and quantify the impact of amines and the role they play in aerosol formation reactions. During the first year, development of methodology for analyzing amine-derivatives will be accomplished and environmental chamber studies of reaction rates of amines with atmospheric oxidants will begin. Year two of the research plan will continue chamber studies with a goal of identifying condensed-phase species that are present in the product aerosols. Also in year two, ambient aerosols and gases will be sampled in AFO-impacted air sheds in Utah and California, and the molecular speciation of amine and amine-derivative compounds will be determined.
The project has several broader impacts, including the education and training of two graduate students at Utah State University (USU) and one at the University of California, Riverside (UCR), to perform smog chamber studies of amine reactions. Undergraduate assistants at USU and UCR will assist with chemical analysis of aerosols and associated data analysis. The project also supports a sabbatical for a professor of chemistry at Claremont McKenna College (CMC) and two CMC undergraduate students to assist at USU with the analytical methodology development during year one and with ambient sampling work in Utah and California in year two. In addition to personnel support, the studies of aerosol formation reactions from amines yield new information on the atmospheric component of the biogeochemical cycle of nitrogen. Understanding the fundamental atmospheric chemistry of amines is critical for quantification of the fate of air pollutants associated with large-scale food production.
The chemical formation of particulate matter air pollution (also known as aerosols) is important to study for health and environmental reasons. Breathing in aerosols can cause an increase in respiratory illnesses, depending on the size, chemical composition, and concentration of the particles in the air. Aerosols of different chemical species can either absorb or reflect radiation as well, which has a direct impact on Earth’s energy balance and climate. Particles in the atmosphere can lead to reduced visibility in the atmosphere and often act as nuclei for water condensation to form clouds. Our research focused on how one type of gas phase pollutant (alkylamines, similar to ammonia but with organic groups attached to it in place of hydrogen atoms) can react to form particulate matter. These amines have many different gas phase sources to the environment, including automobile exhaust, sewage, incinerators, and agriculture. We chose to study animal feeding operations, dairies in particular, because they are believed a source of alkylamine emissions in the Central Valley of California and Northern Utah where amines have been detected in particulate matter. But not much is known about how these gas phase emissions react chemically in the atmosphere to form alkylamines in the particle form. We do know the amine gases are either oxidized, which form less volatile amines that can deposit on the particles, or they can react with an acid, such as nitric acid, to form a salt, which is also less volatile than the gas and will deposit on to a particle. We want to understand chemically how amines do this. Our research had a two pronged approach, the measurement of alkylamine particles at the source (a dairy in the Central Valley of California and the Cache Valley of Utah) and more theoretical studies to understand how the particles form in a controlled environmental chamber. At the dairy, we were the first groups to observe alkylamine salts in particles in real time. We measured small concentrations (ng m-3) of trimethylamine, dimethylamine, and ethylamine salts in particles that derived from gases emitted directly from the cattle. Now we knew that the alkylamines formed salt in the particles, but in the actual environment, it is difficult to understand what chemical mechanisms are taking place. It is impossible to control the weather conditions (humidity, light, and temperature all have impacts on particle formation) and there are a lot of different chemicals in the atmosphere that can react with the amines we are interested in. The second part of our study was to understand reaction mechanisms of alkylamines with oxidants in a controlled environment. In our environmental chamber, we are able to hold the humidity, light, and temperature constant, and we know what chemical species we are adding to the chamber as well. We performed a variety of experiments with different oxidants (ozone, NOx, and hydroxyl radicals) to simulate reactions that would happen during the day or night and with a variety of different humidities. We did these experiments on one amine at a time with three different alkylamines that are most commonly found in the atmosphere and have different chemical characteristics (butylamine, diethylamine, and trimethylamine). We used a variety of analytical tools to understand what chemical 2 species were forming in the chamber, such as mass spectrometry, ion chromatography, particle sizing and density measurements. We found that ozone did not really react with the amines gases to form particles to an appreciable amount, while NOx formed the most particles followed by the hydroxyl radical. When comparing how much aerosol derived from the alkyl amine gases, trimethylamine formed the highest yield of particles and butylamine the least. The salt fraction of the particles was the opposite though. Butylamine formed the highest fraction of salt in the aerosols, whereas trimethylamine formed the least. Increased humidity of the experiment usually led to higher salt fraction in the particles, which determines the hygroscopicity of the aerosol and directly affects cloud condensation nuclei. When thinking about the mechanism behind the formation of the particles, we actually observed polymeric formation of the amines, in addition to smaller molecules as well. Overall, we were able to learn more about how alkylamines react from the gas phase to form particles, both during studies in the field and more controlled environmental chamber experiments.
