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2005 Progress Report: A Coupled Measurement-Modeling Approach to Improve Biogenic Emission Estimates: Application to Future Air Quality Assessments
EPA Grant Number: R831454Title: A Coupled Measurement-Modeling Approach to Improve Biogenic Emission Estimates: Application to Future Air Quality Assessments
Investigators: Mao, Huiting , Chen, Ming , Griffin, Robert J. , Sive, Barkley , Talbot, Robert , Varner, Ruth
Institution: University of New Hampshire - Main Campus
EPA Project Officer: Bloomer, Bryan
Project Period: January 1, 2004 through December 31, 2006
Project Period Covered by this Report: January 1, 2005 through December 31, 2006
Project Amount: $750,000
RFA: Consequences of Global Change for Air Quality: Spatial Patterns in Air Pollution Emissions (2003)
Research Category: Air Quality and Air Toxics , Global Climate Change
Description:
Objective:This investigation is focused on the northeastern United States. The specific objectives of this research project are to: (1) predict changes in regional climate that subsequently influence natural biogenic emissions and air quality; (2) quantify modifications in plant ecosystem composition as a result of changes in regional climate; (3) estimate regional biogenic emissions associated with a changing plant ecosystem; and (4) estimate aerosol loading, O3, NOx, hydrocarbons, and atmospheric oxidative capacity as a function of a changing regional climate and plant ecosystem. Our results will quantify changes in the level of critical atmospheric species under future climate scenarios for 2050-2100 and provide a basis to assess their potential societal impacts on human health and key economic factors.
Progress Summary:During Year 2 of the project, a 10 day field campaign was conducted at the Duke Forest, North Carolina, Forest-Atmosphere Carbon Transfer and Storage-I Research Facility (FACTS-I) during the period of June 1-12, 2005. We aim to investigate the: (1) impact of elevated CO2 on biogenic emissions of trace gases from midlatitude forests; and (2) source/sink strength of selected sulfur and halogen trace gases and the impact of the elevated CO2 on them. During this campaign, we measured the net exchange of a suite of volatile organic compounds (VOCs) under present day and elevated CO2 conditions using branch enclosure and soil flux chamber measurements. Preliminary results show that isoprene emissions were a factor of two to three higher in the elevated CO2 Plot, whereas both the α-pinene and β-pinene fluxes were reduced significantly. Moreover, higher CO2 levels seem to suppress CH3I emissions from trees, whereas its soil-to-atmosphere flux was increased. The latter is a significant finding because it uncovered a substantial terrestrial source of CH3I, which in the past has been used as a tracer for marine air masses.
Measurements of soil-atmosphere exchange also revealed that high levels of reactive hydrocarbons are released from the soil/litter at Duke Forest, but the CO2-enriched environment exhibited suppressed soil fluxes of these compounds. Analyses of observations from the September 2004 campaign suggest that compared to the ambient CO2 environment, on average in the CO2-enriched Plot: (1) isoprene mixing ratios were 8 percent higher; (2) α-pinene and β-pinene mixing ratios were 22-24 percent lower; and (3) O3 mixing ratios were increased by 6.5 ppbv. Box modeling results showed that the measured VOC species could account for 37 percent of the O3 increase in the elevated CO2 environment, implying the existence of unknown reactive VOCs. It appears that elevated CO2 levels can have opposing effects on biogenic emissions of reactive hydrocarbons, which in turn are linked closely to in situ O3 chemistry. Hence, our measurements suggest that it is a convoluted problem of how global warming accompanied by increased atmospheric CO2 may affect future O3 levels. More importantly, even with state-of-the-art instrumentation and modeling tools, it is likely that there is a large array of unknown but important highly reactive biogenic species. These need to be identified and their emissions and response to changes in ambient CO2 levels quantified. In the area of climate-air quality interaction we identified the relationship between the occurrence of high O3 levels across the Northeast and large-scale circulation patterns (or map types) during the 2000-2004 time period. Our reconstruction of the O3 trend as a function of frequency and intensity associated with the top five primary map types captured 46 percent of that observed, a significant improvement compared to traditional methods. The map typing technique used in this study has proven to be a powerful tool that can be applied in the evaluation of regional climate and air quality modeling results. The analysis of our climate model results alone resulted in a paper published in Geophysical Research Letters (October 2005). Here, we found that precipitation in the future should become more episodic and convectively driven than in present day conditions and with larger daily amounts. This implies an increased prevalence of drying and flooding conditions across the United States at the end of the 21st century. Furthermore, the present-day and future climate simulations coupled with a biographic model suggested that vegetation types would migrate systematically northward.
Preliminary results of the aerosol mass spectrometry measurements at Duke Forest suggest both anthropogenic and biogenic influences on secondary organic aerosol formation at the site. The Caltech Atmospheric Chemistry Mechanism (CACM) gas-phase chemistry model and The Model to Predict the Multiphase Partitioning of Organics (MPMPO) have been interfaced with Congestion Mitigation and Air Quality (CMAQ) to simulate O and particulate matter with a focus on secondary organic aerosols over the eastern United States during the period August 3-4, 2004. Unlike CMAQ with the built-in CB4/Secondary Organic Aerosol Model modules, CMAQ with CACM/MPMPO can provide more information about the mechanisms of secondary organic aerosol formation. Four-month long seasonal runs using CMAQ have been conducted for present-day and future climate scenarios. We have analyzed the model output and evaluated the present-day results against continuous ground-based and International Consortium for Atmospheric Research on Transport and Transformation field campaign measurements. The reasonable agreement with observations gives us confidence in conducting a future regional quality assessment.
Overall, we made significant progress in understanding the factors/processes shaping regional climate, biogenic emissions, and air quality to facilitate future climate and air quality assessments. Together, our findings have important implications for future air quality and considerations for developing emission control regulations and policies.
Future Activities:During Year 3 of the project our major objectives will focus on: (1) quantifying the apparent changes in the source/sink strengths of isoprene, monoterpenes, and selected sulfur and halogen compounds in the elevated CO2 Plot; (2) quantifying the impact of changes in the atmospheric abundance of these trace gases on air quality; (3) examining mesoscale processes for present day and future climate and assessing changes in them; and (4) conducting an assessment of present and future air quality in the Northeast because of climatically induced changes in vegetation and biogenic emissions. Specifically, our regional climate simulations will use a small domain with fine resolution to determine interannual variability in mesoscale processes. An associated ensemble of air quality episode simulations also will be conducted. Over the next few months, we will complete data processing and archiving from the Duke Forest Campaign of 2005. We also will aim to complete the ongoing in-depth analyses using the synthesized observational data sets from the ancillary 2004 and 2005 campaigns. Several key findings have been identified, and papers will be prepared on these topics. No changes are expected in the project schedule over the next reporting period.
Journal Articles:No journal articles submitted with this report: View all 28 publications for this project
Supplemental Keywords:vegetation type, organic particulate matter, NMHCs, chemical transport, O3 precursors, EPA Region 1, monitoring/modeling, aerosol formation, air sampling, biogenic ozone precursors, climate models, climate variability, climatic influence, ecological models,
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Ecosystem Protection/Environmental Exposure & Risk, Air, Scientific Discipline, RFA, Air Quality, Air Pollutants, climate change, Ecological Risk Assessment, Air Pollution Effects, Atmosphere, Atmospheric Sciences, particulate matter, Environmental Chemistry, Monitoring/Modeling, Environmental Monitoring, aerosols, meteorology, climate model, Global Climate Change, atmospheric models, airborne aerosols, BVOCs, ozone, atmospheric dispersion models, greenhouse gas, biogenic emission modeling, climatic influence, air quality models, climate models, aerosol formation, atmospheric chemistry, climate variability, environmental measurement, environmental stress, global change, atmospheric particulate matter, emissions monitoring, modeling, ambient air pollution, anthropogenic stress, atmospheric aerosol particles, ecological models, ambient aerosol, atmospheric transport, ecosystem models, greenhouse gases, air quality model
Progress and Final Reports:
2004 Progress Report
Original Abstract
2006 Progress Report
2007 Progress Report
Final Report