Background

'Air quality' refers to the combination of the physical-chemical-biological constituents of air masses in the lower atmosphere with which humans, animals, plants, lands, and water bodies of the earth interact. These constituents may take the form of solids (such as suspended particulates), gases (such as oxygen and nitrogen), and liquids (such as water droplets or vapor). We use the term 'air quality' to refer to the state of air with reference to its ability to maintain a high level of human health as the first priority with secondary priorities associated with animal and environmental health. Air quality affects and is affected by human, plant, and animal activities, including life functions. The sweep of winds and the exchange of gases, liquids, and solids between air masses and land and water surfaces affect air quality.

Air quality has both local and global contexts. Odors emitted by a localized source, for example, may be readily detectable by humans within a relatively short distance as the compounds that are identified by the nose become dispersed. On the other hand, particulates of very small size may enter intercontinental air streams and travel around the globe, sometimes for years, as is exemplified by colorful sunsets that follow periods of intense volcanic activity.

Agriculture is a necessary human activity that interacts with air; it benefits from good quality air, and it contributes air pollutants. Agriculture needs air that is free of excessive amounts of such constituents as ozone, dust, suspended pesticides, and odors. But agriculture may also contribute these substances to the air in quantities that are offensive or even threatening to human and environmental health in downwind areas.

The Agricultural Research Service (ARS) has developed an Air Quality National Program because it believes that many problems associated with air quality degradation by agriculture can be reduced or eliminated through research to understand polluting processes and application of that understanding to develop solutions. Similarly, it believes that air pollution impacts on agriculture can be resolved through research and development.

Program Components

Particulate Emissions. This component addresses particulates regulated under the NAAQS, including fugitive dust in the PM-10 and PM-2.5 categories (10 micrometer and 2.5 micrometer, respectively). Dust emissions result from wind erosion, on-farm operations, agricultural industry, and smoke from agricultural burning. The research seeks to elucidate the biological, physical, and chemical mechanisms by which particulates are generated, how they are transported and suspended in the air and their patterns of movement and deposition. The research goal is to support development of technology to reduce or prevent agricultural particulate emissions.

Ammonia and Ammonium Emissions. The central regulatory issue is agriculturally-emitted ammonia as a major source of secondary, PM-2.5 particulates as a result of its interactions with other atmospheric compounds. The focus of this component is on understanding ammonia emissions and their role in forming secondary particulates, developing methods to measure emissions, establishing emission factors for various agricultural activities, and suppressing ammonia and ammonium emissions beyond farm boundaries.

Malodorous Compounds. Although not regulated, offensive odors from animal production operations are a major nuisance and may have health impacts. Basic and applied research will be done to identify odor-producing agents and to understand the biological and chemical processes that produce odors, emit them to the atmosphere, and govern their distribution and movement off-farm. This will permit the development of mitigating measures for application at the emitting source.

Ozone Impacts. High concentrations of ozone in the lower atmosphere result in reduction of crop yields by up to 20%. Carbon dioxide may have a mitigating effect on these losses. ARS research assesses the effects of ozone and the interaction of ozone and carbon dioxide upon crop production and searches for the basis for developing ozone-tolerant crop varieties.

Pesticides and Other Synthetic Organic Compounds. Volatilized pesticides are a complex of very fine liquid particulates and gaseous phase compounds, or may be attached to particulates from other agricultural or non-agricultural sources. The research objectives are to understand the biological, physical, and chemical mechanisms that influence pesticide volatilization and transport, to understand transport processes, to understand the impacts of deposition, and develop means to reduce emissions.

Agricultural enterprises throughout the Nation free from air quality concerns

Mission

Through research, to understand the processes of air pollution emissions from agricultural enterprises and the effects of air quality upon agriculture, to develop and test control measures, and to provide decision aids that will be useful in minimizing and reducing agricultural air pollution emissions and predicting and mitigating the impacts of air quality upon agriculture.

In January 2000, ARS met with representatives of its customers and stakeholders in Sacramento, California, to explore problems associated with agriculture and air quality. This meeting was the first step in developing a list of high-priority research needs and a research program to address those needs. An important source of input to the meeting was the Agricultural Air Quality Task Force (the Task Force), which had previously provided a list of research needs to the Secretary of Agriculture. The U.S. Environmental Protection Agency (EPA) has been actively seeking ARS research in several agricultural air quality topic areas so that it might base its regulations on scientifically sound data.

After the meeting, ARS research personnel met to begin the process of developing the research program, using all of the available inputs. This document is the first result. It discusses issues from the California meeting, Task Force recommendations, and contacts with EPA. Using this document, ARS will continue to develop and implement a research program in agricultural air quality on the highest priority problems. This research plan and any modifications will be available on the Internet.

Based on customer issues raised at the workshop, ARS research in agricultural air quality has been organized into five categories, which will be called 'components' of the ARS Air Quality National Program:

• Particulate Emissions
• Ammonia and Ammonium Emissions
• Malodorous Compounds
• Ozone Impacts
• Pesticides and Other Synthetic Organic Chemicals

All components except Ozone Impacts focus on understanding and reducing emissions by agriculture. Ozone research will focus on protecting agricultural productivity from excessive ozone.

Air quality is intimately associated with most aspects of agricultural operations and is therefore also associated with other ARS national programs. Odors are most commonly agricultural issues in the context of animal production. The Malodorous Compounds component of this national program is closely related to a similar component of the Manure and Byproducts Utilization National Program.

The division between the Air Quality National Program components is not always clear. Ammonia, near the source of emission, may be an odor issue, among others. It also often interacts with other pollutants to form particulates. The Particulate Emissions component of the Air Quality National Program was delineated because of agricultural contributions of what is calledA fugitive dust@ by agricultural operations or by wind erosion to air masses that sometimes cause air quality to fall below EPA= s National Ambient Air Quality Standards. However, odors also may be associated with particulates. Ammonia, as stated, is a precursor for particulates, and pesticides may be emitted as particulates or they may be precursors of particulates. Thus, an interested reader needs to peruse most components of this national program for a complete view of the particulates issue.

The following sections discuss each of the Air Quality National Program components. Component issues are stated briefly; the state of knowledge is discussed; and research goals are defined. ARS resources do not permit addressing all of the goals listed. Those that will be addressed will be of the highest priority and will appear in the research plans developed for the ensuing five years. Others must await additional funding, resolution of the problems that will be addressed during the next five years, or resolution by other agencies or institutions.

Table 1 lists the ARS locations across the U.S. that are presently contributing to research in the Air Quality National Program. ARS scientists strive to take advantage of this geographical, disciplinary, and issue-oriented diversity by collaborating across locations.

Program Components
State	Locations	Particulate Emissions	Ammonia & Ammonium Emissions	Malodorous Compounds	Ozone Impacts	Pesticides & Other Synthetic Organic Compounds
AR	Fayetteville		X	X
CA	Albany				X
CA	Riverside	X				X
CO	Akron	X
GA	Athens	X		X
GA	Tifton			X
GA	Watkinsville		X
IA	Ames	X	X	X		X
KS	Manhattan	X
MD	Beltsville	X	X	X	X	X
MN	St. Paul					X
NC	Raleigh				X
ND	Mandan	X
NE	Clay Center		X	X
NE	Lincoln	X	X	X
NM	Mesilla Park	X
SC	Florence			X
TX	Bushland	X		X
TX	College Station		X			X
TX	Lubbock	X
WA	Pullman	X