PHOTOCHEMICAL OZONE FORMATION POTENTIAL OF AGRICULTURAL VOC EMISSIONS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: SPECIAL GRANT
• Reporting Frequency: Annual
• Accession No.: 0199550
• Grant No.: 2004-34484-14465
• Proposal No.: 2004-06138
• Project Start Date: Jul 1, 2004
• Project End Date: Jun 30, 2007
• Grant Year: 2004
• Program Code: [TM]- (N/A)

Recipient Organization
UNIVERSITY OF CALIFORNIA, DAVIS
410 MRAK HALL
DAVIS,CA 95616-8671

Performing Department
LAND, AIR AND WATER RESOURCES

Non Technical Summary
Ozone concentrations in The San Joaquin Valley exceed National Ambient Air Quality standards. This project seeks to improve current understanding of the emission of tropospheric ozone (tO3) precursors from animal feeding operations (AFO). Volatile organic compounds (VOC) from dairies are believed to be significant sources of tO3 formation. The importance of agricultural sources to tO3 formation depends on the accuracy of measurements of VOC emissions from those sources. Currently, a lack of knowledge of which specific VOC are emitted from dairies limits the relevance of VOC measurements. This project will determine if current measurement methods are capable of quantifying all VOC emissions important to tO3 formation. The experiments will compare the ozone actually formed from the gases emitted from a dairy operation to the ozone predicted when the VOC that can be quantified by current measurement methods are assumed to be the only ones present. Studies will be conducted to investigate the impact of these findings on tO3 measurements and forecasts for the San Joaquin Valley region of California.

Animal Health Component

50%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
133	0410	2000	100%

Knowledge Area
133 - Pollution Prevention and Mitigation;

Subject Of Investigation
0410 - Air;

Field Of Science
2000 - Chemistry;

Keywords

photochemistry

ozone

emissions

air quality

volatile substances

organic compounds

air

pollution control

air pollution

dairies

measurement

forecasting

animal metabolism

Goals / Objectives
The proposed research seeks to improve current understanding of the photochemical ozone formation potential in the unidentified fraction of volatile organic compounds (VOC) from agricultural sources. Projects currently underway in the proposing laboratories have identified a mass differential between measured concentrations of total non-methane, non-ethane, organic carbon (tNMNEOC) and total hydrocarbons (HC) upwind and downwind of commercial dairies. This project will investigate whether the apparent carbon mass not quantified by traditional HC analyses represents a significant pool of photochemically active ozone precursors. Thus, the importance of developing additional measurement techniques to quantify the missing mass can be determined. Experiments are also planned to determine how the basecase enhancement of O3 production due to livestock emissions is changed by the addition of HC and NOx. In simple terms, these experiments will determine if the O3 formation system is NOx or VOC limited so that the influence of the dairy emissions can be better understood in the regional airshed context. Modeling studies will be conducted to see if current ozone mechanisms are capable of reproducing the observed behavior of the experimental system. The results of this task will help establish confidence in ozone formation mechanisms used in regional air quality models applied to the San Joaquin Valley.

Project Methods
Concentrations of selected VOC suitable for ozone formation modeling, such as HC, will be measured in air streams impacted by a livestock operation. A (tNMNEOC) method that can estimate the total mass of the VOC, including the dark-reactive constituents, will be applied simultaneously. This will determine how much volatile carbon mass is missed in using the selected VOC method. The air stream will be directed into a 1 m3 Teflon bag where it will be exposed to a constant light and temperature regime that will be closely monitored. Ozone, NO, and NO2 concentrations will be measured during the photochemical experiment, which will be compared with a modeling prediction of ozone formation, based on the profile of select VOC. The difference between the assay results and the prediction would yield an estimate of the photoreactivity of the non-measured VOCs. A mass-based estimate of the photoreactivity of the non-measured VOC will be obtained from the difference of the measured and modeled photoreactivities and the difference of total mass and selected VOC mass. The wall-scavenging rate of each of the chemical species of interest will be determined through simple dark experiments that measure decay as a function of time. The kinetics of O3 formation in the Teflon bags will be tested with simple hydrocarbon + NOx mixtures that are irradiated for 4-8 hours. A kinetic model of O3 production such as SAPRC90, SAPRC99, or CACM will be applied to the measured starting conditions and results compared to ozone measurements in the bag to verify the performance of the system. A method for cleaning the bags between experiments will be developed and verified to avoid cross contamination artifacts. Side-by-side comparisons of lamp illumination and natural sun-light will be conducted to identify any bias in the ozone formation potentials achieved under artificial vs. natural light. Animal metabolism units will be used to supply relatively impacted and unimpacted gas streams. Samples from the chamber ventilation exhaust will be drawn into a bag that will then be sealed and irradiated. A parallel bag will be filled with ambient air from the chamber ventilation intake that will then be sealed and irradiated simultaneously. The discrepancy between measured and predicted ozone formation will be computed in the two samples. The relative difference in that discrepancy between incoming and exhaust gases will indicate the additional ozone formation potential, if any, caused by the animal units. Similar experiments will be carried out on a commercial dairy using air upwind and downwind of the dairy and/or intake and exhaust air from a particular process on the dairy (e.g. a covered lagoon).

Progress 07/01/04 to 06/30/07

Outputs
OUTPUTS: We have successfully developed field equipment and methodology to measure the actual ozone formation potential of whole emissions from an agricultural source, and have implemented this approach to the leading category of concern: dairy cows, their feed, and their fresh waste. We have completed field experiments on dairy cows emissions, quantified the VOC (gas) composition, and verified the ozone formation with laboratory studies on the leading VOC (ethanol), and with a photochemical model. Importantly, the standard photochemical model used for urban air pollution needed significant modification to account for the very different composition of air that is not dominated by industrial sources. However, the input from vehicle sources to the overall gas mixture (especially NOx) does play a central role in the amount of ozone produced. Finally, the amount of ozone produced is quite low, which is not entirely unexpected due to the low MIR (maximum incremental reactivity) of ethanol. In addition, we found that another source on dairies, VOC emissions from silage (corn or alfalfa which is fermented for feed) can produce significant amounts of ozone. Fortunately, this material is normally stored under tight coverage to minimize air exchange, so proper handling is appropriate. PARTICIPANTS: Dr. Peter G. Green Prof. Michael Kleeman Dr. Wenli Yang Dr. Anuj Kumar Cody Howard Doniche Derrick Collaborators Dr. Frank Mitloehner Irina Malkina Dr. Yongjing Zhao TARGET AUDIENCES: Our target audience includes local, regional, state and federal regulators involved in air quality. EPA region 9 has been very pleased to see our results. We received significant positive attention for our presentation last spring 2007-Apr, in Las Vegas, NV for the Western States Dairy Association, Air Quality Conference.

Impacts
These findings have contributed to an entirely new awareness of the potential impact on ozone that dairies might have. The focus should not be on the animals (nor their waste) but on peripheral silage storage and vehicles. Furthermore, in assessing other impacts on air or water quality, since diary cow VOCs are dominated by low reactivity molecules, mitigation of greenhouse gasses, ammonia, or other constituents of concern can take considerable priority.

Publications

• No publications reported this period

Progress 01/01/06 to 12/31/06

Outputs
This project uses a large (1 cubic meter) Teflon bag to sample in the field, and simulate in the lab air parcels enriched in Reactive Organic Gases (ROG) under various scenarios and compare measured to modeled production rates of ozone. Modeling has been conducted to estimate wall losses of ROG and NOx and appropriate levels of each component for experimental design have been computed. Concurrent work on other projects has indicated a need for improved sampling methods for the quantification of ROG concentrations, for which we have obtained a state-of-the-art INNOVA photo-acoustical IR monitor. We have moved on to use a Teflon bag photochemical chamber to assess the actual ozone production from sources, first using samples from dairy cow enclosures and metabolic chambers. Importantly, the ozone formation, even with the addition of relevant concentrations of NOx to represent the urban pockets of nearby affected population, is very low. Using photochemical model calculations, and scrutiny of widely used atmospheric chemical mechanisms, we have found an important weakness of past, urban-air oriented reaction classifications. This turns out to be especially important for dairy emissions, where the carbon-chain length of the dominant emissions (C2, ethanol) is markedly different from urban hydrocarbon mixtures (often C6 and larger).

Impacts
This project will investigate the ozone forming potential of Reactive Organic Gases from dairies in the San Joaquin Valley (SJV) in California. These data are critical to determining the source of tropospheric ozone in this district where national standards for ozone have not been attainable in the last decade. If dairies are found to be a significant source of ozone precursor organic gases, the results of this research will aid in identifying strategies to reduce ozone concentrations in the SJV.

Publications

• No publications reported this period

Progress 01/01/05 to 12/31/05

Outputs
This project uses a large (> 1 cubic meter) Teflon bag to simulate air parcels enriched in Reactive Organic Gases (ROG) under various scenarios and compare measured to modeled production rates of ozone. The first such bag has been designed and built in this reporting period and testing of filling and cleaning techniques, gas concentration monitors, and other practicalities have been successful. Modeling has been conducted to estimate wall losses of ROG and NOx and appropriate levels of each component for experimental design have been computed. Concurrent work on other projects has indicated a need for improved sampling methods for the quantification of ROG concentrations. Work is currently underway to develop ROG sampling and quantification techniques and to identify sources of the enriched air parcel for study. Field studies in the project are anticipated to begin in Spring 2006.

Impacts
This project will investigate the ozone forming potential of Reactive Organic Gases from dairies in the San Joaquin Valley (SJV) in California. These data are critical to determining the source of tropospheric ozone in this district where national standards for ozone have not been attainable in the last decade. If dairies are found to be a significant source of ozone precursor organic gases, the results of this research will aid in identifying strategies to reduce ozone concentrations in the SJV.

Publications

• No publications reported this period

Progress 01/01/04 to 12/31/04

Outputs
This project seeks to improve current understanding of the photochemical ozone formation potential in the unidentified fraction of Volatile Organic Compounds (VOC) from agricultural sources. Work on this project is proceeding on two fronts. Select VOC and Total Non-Methane Non-Ethane Organic Carbon (TNMNEOC) concentrations have been measured downwind of commercial dairies in the San Joaquin Valley (SJV) and in air vented from bovine metabolism units. These data will be assessed to determine what fraction of the total VOC, as represented by the TNMNEOC, is accounted for by various measurements of select VOC. A large bag (2 m3), a suitable vessel for conducting atmospheric chemistry experiments, has been obtained and the mechanics of conducting experiments to assess the ozone formation potential of that VOC are being explored. Functions such as providing photochemical energy to the system, cooling the light banks, housing the system, and filling the bag without influencing the chemical profile of the collected air will be standardized. A work plan has been developed through interaction with local IPM and DPR representatives, as well as members of the USDA Ag Task Force, to incorporate pesticide application as a source for study in this project. Consideration of current use rates in the SJV and ongoing research on other campuses led to identification of the most significant non-fumigant Active Ingredients (AI) by mass as chlorpyrifos and acrolein. In brief, that work plan includes development of headspace analytical methods and determination of volatility parameters for all formulation components of the pesticides of interest in the lab. The project will go on to field experiments using conventional flux chambers, open-top canopy chambers, and spray-drift quantification methods to measure emission rates for the volatile formulation components under bare ground and growing crop conditions. Photochemical ozone formation potential will be investigated for those components of the formulations that prove to be significantly emitted to the atmosphere under recommended application conditions.

Impacts
This project assess the importance of specific agricultural operations to the formation of tropospheric ozone in the San Joaquin Valley (SJV) in California. These data are critical to evaluating current precursor emission inventories with respect to determining the sources of ozone in this district where national standards for ozone have not been attainable in the last decade. If agricultural practices are found to be significant sources of ozone precursor organic gases, the results of this research will aid in identifying strategies to reduce ozone concentrations in the SJV.

Publications

• No publications reported this period