| Title |
Investigators | Department | Objectives | Approach Keywords | Progress Reports | Impact Statements | Publications | |
Project * COL00699 | |
| Title | Development and Application of Continuous Measurement Methods for Assessing Air Quality Impacts of Confined Animal Feeding Operations |
| Investigator(s) | Collett, JL; |
| Department | Atmospheric Science |
| Objectives | The general objective of this project is to provide new, improved tools for quantifying agricultural emissions of ammonia and their impact on local and regional air quality. Specific objectives of the project include the following: 1. Existing instrumentation for semi-continuous measurement of atmospheric fine particle composition will be modified to add capabilities for determining gaseous ammonia concentrations. The combined system will be capable of deployment on a mobile platform for measuring CAFO emissions of gaseous ammonia (NH3(g))and subsequent formation of particulate ammonium (NH4+(p)), at a time resolution of 15 minutes. 2. The new semi-continuous measurement approach will be validated by comparison with conventional annular denuder/filter-pack ammonia/ammonium measurement techniques. 3. The new NH3(g)/NH4+(p) measurement system will be used to determine spatial and temporal (15 min resolution) variability in CAFO ammonia emissions and their impact on downwind concentrations and compositions of atmospheric fine particles and to examine how emissions change as a function of environmental conditions (e.g., temperature and wind speed). 4. Study findings will be disseminated to promote knowledge transfer of the newly developed measurement approaches and to better inform stakeholder communities of air quality impacts associated with CAFOs. |
| Approach | The major efforts planned as part of the proposed work are the development, validation, and deployment of a new system for making semi-continuous measurements of ammonia and atmospheric particle composition. An existing, state-of-the-art, Particle-Into-Liquid Sampler (PILS) will be modified to permit simultaneous measurement of gaseous ammonia, fine particle ammonium, and other key aerosol species (sulfate and nitrate) at a time resolution of 15 minutes. The PILS operates by capturing fine particles in a stream of flowing water that is automatically fed into a pair of ion chromatographs for on-line measurement of anions and cations. By modifying the PILS particle collection system we will extend these capabilities to include gaseous ammonia as well as fine particle ammonium and other fine particle ions (NO3-, SO42-, K+, Na+, and Cl-). The new semi-continuous measurement system will be validated through side-by-side comparison with traditional ammonia and ammonium measurement systems made using annular denuders and filter packs produced commercially. Comparisons will be made in both clean and heavily impacted environments to test performance of the semi-continuous measurement system over a broad concentration range. The validated system will be deployed in a mobile air quality laboratory to measure concentrations of gaseous ammonia and fine particle ammonium up- and downwind of Colorado CAFOs. Initial work is planned in conjunction with USDA-funded CAFO emissions research already underway at CSU. Adding the mobile, high time resolution ammonia/ammonium measurements as part of this project will greatly enhance the ability of the combined project to characterize temporal variability in CAFO emissions and resulting air quality impacts. It will also permit better spatial mapping of the ammonia-rich CAFO plume than is possible by the fixed-site measurements planned for the USDA project Results of this project will be analyzed, presented, and published in a timely fashion in order to disseminate information about the new measurement technology and its application to characterizing CAFO emissions to stakeholder communities. |
| Keywords | ammonia, nitrate, ammonium, confined animal feeding operations, air quality, aerosols, emissions, measurement methods |
| Progress Reports | |
| 2005 | The goal of this project is to develop improved approaches for high time resolution measurement of ammonia concentrations emitted by confined animal feeding operations. Measurements of this type are critical to improving understanding of how CAFO emissions of ammonia interact with other atmospheric pollutants and impact downwind concentrations of airborne fine particles. Although ammonia itself is not a regulated ambient air pollutant, the fine particles that form from reaction of ammonia with nitric acid and sulfates are regulated due to their adverse effects on human health and visibility. Efforts during the first 6 months of the project focused on development and testing of a system for high time resolution measurement of both airborne particle composition and concentrations of gaseous ammonia. An existing, state-of-the-art, Particle-Into-Liquid Sampler (PILS) was modified to permit simultaneous measurement of gaseous ammonia, fine particle ammonium, and other key aerosol species at a time resolution of 15 minutes. The PILS operates by capturing fine particles in a stream of flowing water that is automatically fed into a pair of ion chromatographs for on-line measurement of anions and cations. By modifying a second PILS particle collection system, we extended these capabilities to include gaseous ammonia as well as fine particle ammonium and other fine particle ions (NO3-, SO42-, K+, Na+, and Cl-). The system was also modified to permit measurement of gaseous nitric acid and sulfur dioxide. The new measurement system was tested during side-by-side comparison with a traditional air pollution sampler using commercially available annular denuders and filter packs. Initial comparisons were made over several days in November 2005 at an active dairy operation in northern Colorado. Results of this testing yielded several important findings: 1. Concentrations of ammonia at this dairy site were very high and quite variable, with concentration spikes reaching 300 micrograms of NH3 per cubic meter. The average ammonia concentration increased from approximately 20 micrograms per cubic meter upwind of the dairy to approximately 90 micrograms per cubic meter downwind during a period where paired upwind/downwind samplers were operated. 2. The high ammonia concentrations present at the site pose a challenge for conventional, denuder-based ammonia sampling systems. The capacity of the denuder to collect gaseous ammonia was typically exhausted in a period of 4-6 hours. Future experiments will need to either limit denuder exposure to shorter time periods, switch denuders frequently, or make use of denuders with greater collection capacities. 3. Gaseous ammonia concentrations determined using the PILS sampling system were considerably lower than those measured using the conventional, denuder sampler due to apparent loss of a fraction of the sampled ammonia to wet walls inside the PILS instrument. This is a consequence of the instrument's original design for particle-only sampling. Plans are currently being made to modify the gas sampling system to a steam sampler design that collects and analyzes all gases and particles. |
| 2006 | The goal of this project is to develop improved approaches for high time resolution measurement of ammonia concentrations emitted by confined animal feeding operations. Measurements of this type are critical to improving understanding of how CAFO emissions of ammonia interact with other atmospheric pollutants and impact downwind concentrations of airborne fine particles. Although ammonia itself is not a regulated ambient air pollutant, the fine particles that form from reaction of ammonia with nitric acid and sulfates are regulated due to their adverse effects on human health and visibility. Efforts during the initial months of the project focused on development and testing of a system for high time resolution measurement of both airborne particle composition and concentrations of gaseous ammonia. An existing, state-of-the-art, Particle-Into-Liquid Sampler (PILS) was modified to permit simultaneous measurement of gaseous ammonia, fine particle ammonium, and other key aerosol species at a time resolution of 15 minutes. Testing of the PILS measurement system was conducted at a local dairy field site in conjunction with a separate USDA NRI funded ammonia emissions project. Gaseous ammonia concentrations determined using the PILS sampling system were considerably lower (by ~50%) than those measured using a conventional, denuder sampler due to apparent loss of a fraction of the sampled ammonia to wet walls inside the PILS instrument. This is a consequence of the instrument's original design for particle-only sampling. The loss of ammonia in the modified PILS system led us to select a new sampling approach for the high time resolution measurements. This new approach makes use of a steam jet sampler, in which particles and gases are simultaneously collected into aqueous solution by mixing them with high temperature steam. The condensed water is collected and analyzed by ion chromatography. As with the PILS, the steam sampler is capable of measuring not only ammonia, but also other key air pollutants including sulfates and nitrates. The steam sampler approach is not new, but to our knowledge has not previously been used in a high ammonia environment such as a dairy farm. pH increases from water capture of large ammonia quantities could raise solution pH high enough to decrease the efficiency of ammonia scavenging from the gas phase (a pH dependent process). If this becomes problematic, the steam pH might need to be lowered by acid injection. A steam sampler was constructed and tested in our lab. The sampler was then deployed to the dairy site for a number of intercomparison measurement periods in Fall 2006. Samples collected with the steam sampler have been analyzed in our laboratory and are currently being compared with conventional denuder measurements to evaluate the system's field performance. |
| Impact | |
| 2005 | Development of semi-continuous measurement systems for key particle and trace gas species concentrations will greatly enhance the ability of air quality researchers to document impacts of CAFO and other ammonia emission sources on downwind air quality. By deploying these systems on mobile measurement platforms, they can be positioned downwind of different emissions sources, even within a given operation, to look at both ammonia emissions fluxes and how emitted ammonia impacts formation of new particles downwind. Information gained from measurements of this type will aid emissions researchers and CAFO operators evaluate dominant ammonia emissions sources and test approaches to emissions reduction. Findings from applying this new measurement approach will also help air quality researchers and regulators to better understand the impact of agricultural ammonia emissions sources on regional concentrations of fine particles. |
| 2006 | Development of semi-continuous measurement systems for key particle and trace gas species concentrations will greatly enhance the ability of air quality researchers to document impacts of CAFO and other ammonia emission sources on downwind air quality. By deploying these systems on mobile measurement platforms, they can be positioned downwind of different emissions sources, even within a given operation, to look at both ammonia emissions fluxes and how emitted ammonia impacts formation of new particles downwind. Information gained from measurements of this type will aid emissions researchers and CAFO operators evaluate dominant ammonia emissions sources and test approaches to emissions reduction. Findings from applying this new measurement approach will also help air quality researchers and regulators to better understand the impact of agricultural ammonia emissions sources on regional concentrations of fine particles. |
| Publications | |
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