Eugene Allwine

Isoprene fluxes measured by enclosure, relaxed eddy accumulation, surface layer gradient, mixed layer gradient, and mixed layer mass balance techniques

Isoprene fluxes were estimated using eight different measurement techniques at a forested site near Oak Ridge, Tennessee, during July and August 1992. Fluxes from individual leaves and entire branches were estimated with four enclosure systems, including one system that controls leaf temperature and light. Variations in isoprene emission with changes in light, temperature, and canopy depth were investigated with leaf enclosure measurements. Representative emission rates for the dominant vegetation in the region were determined with branch enclosure measurements. Species from six tree genera had negligible isoprene emissions, while significant emissions were observed for Quercus, Liquidambar, and Nyssa species. Above-canopy isoprene fluxes were estimated with surface layer gradients and relaxed eddy accumulation measurements from a 44-m tower. Midday net emission fluxes from the canopy were typically 3 to 5 mg C m−2 h−1, although net isoprene deposition fluxes of −0.2 to −2 mg C m−2 h−1 were occasionally observed in early morning and late afternoon. Above-canopy CO2 fluxes estimated by eddy correlation using either an open path sensor or a closed path sensor agreed within ±5%. Relaxed eddy accumulation estimates of CO2 fluxes were within 15% of the eddy correlation estimates. Daytime isoprene mixing ratios in the mixed layer were investigated with a tethered balloon sampling system and ranged from 0.2 to 5 ppbv, averaging 0.8 ppbv. The isoprene mixing ratios in the mixed layer above the forested landscape were used to estimate isoprene fluxes of 2 to 8 mg C m−2 h−1 with mixed layer gradient and mixed layer mass balance techniques. Total foliar density and dominant tree species composition for an approximately 8100 km2 region were estimated using high-resolution (30 m) satellite data with classifications supervised by ground measurements. A biogenic isoprene emission model used to compare flux measurements, ranging from leaf scale (10 cm2) to landscape scale (102 km2), indicated agreement to within ±25%, the uncertainty associated with these measurement techniques. Existing biogenic emission models use isoprene emission rate capacities that range from 14.7 to 70 μg C g−1 h−1 (leaf temperature of 30°C and photosynthetically active radiation of 1000 μmol m−2 s−1) for oak foliage. An isoprene emission rate capacity of 100 μg C g−1 h−1 for oaks in this region is more realistic and is recommended, based on these measurements.

Measurement of isoprene and its atmospheric oxidation products in a central Pennsylvania deciduous forest

Ambient concentrations of isoprene and several of its atmospheric oxidation productsmethacrolein, methylvinyl ketone, formaldehyde, formic acid, acetic acid, and pyruvic acid-were measured in a central Pennsylvania deciduous forest during the summer of 1988. Isoprene concentrations ranged from near zero at night to levels in excess of 30 ppbv during daylight hours. During fair weather periods, midday isoprene levels normally fell in the 5–10 ppbv range. Methacrolein and methylvinyl ketone levels ranged from less than 0.5 ppbv to greater than 3 ppbv with average midday concentrations in the 1 to 2 ppbv range. The diurnal behavior of formaldehyde paralleled that of isoprene with ambient concentrations lowest (∼1 ppbv) in the predawn hours and highest (>9.0 ppbv) during the afternoon. The organic acids peaked during the midday period with average ambient concentration of 2.5, 2.0, and 0.05 ppbv for formic, acetic, and pyruvic acid, respectively. These data indicate that oxygenated organics comprise a large fraction of the total volatile organic carbon containing species present in rural, forested regions of the eastern United States. Consequently, these compounds need to be included in photochemical models that attempt to simulate oxidant behavior and/or atmospheric acidity in these forested regions.

Landfill methane emissions measured by enclosure and atmospheric tracer methods

Methane (CH4) emissions were measured from the Nashua, New Hampshire municipal landfill using static enclosure and atmospheric tracer methods. The spatial variability of emissions was also examined using geostatistical methods. One hundred and thirty nine enclosure measurements were performed on a regular grid pattern over the emitting surface of the landfill resulting in an estimate of whole landfill emissions of 15,800 L CH4 min−1. Omnidirectional variograms displayed spatial correlation among CH4 fluxes below a separation distance of 7 m. Eleven tracer tests, using sulfur hexafluoride (SF6) as a tracer gas, resulted in a mean emissions estimate of 17,750 L CH4 min−1. The favorable agreement between the emission estimates was further refined using the observed relationship between atmospheric pressure and CH4 flux. This resulted in a pressure-corrected tracer flux estimate of whole landfill emissions of 16,740 L CH4 min−1.

The influence of atmospheric pressure on landfill methane emissions.

Landfills are the largest source of anthropogenic methane (CH4) emissions to the atmosphere in the United States. However, few measurements of whole landfill CH4 emissions have been reported. Here, we present the results of a multi-season study of whole landfill CH4 emissions using atmospheric tracer methods at the Nashua, New Hampshire Municipal landfill in the northeastern United States. The measurement data include 12 individual emission tests, each test consisting of 5-8 plume measurements. Measured emissions were negatively correlated with surface atmospheric pressure and ranged from 7.3 to 26.5 m3 CH4 min(-1). A simple regression model of our results was used to calculate an annual emission rate of 8.4 x 10(6) m3 CH4 year(-1). These data, along with CH4 oxidation estimates based on emitted landfill gas isotopic characteristics and gas collection data, were used to estimate annual CH4 generation at this landfill. A reported gas collection rate of 7.1 x 10(6) m3 CH4 year(-1) and an estimated annual rate of CH4 oxidation by cover soils of 1.2 x 10(6) m3 CH4 year(-1) resulted in a calculated annual CH4 generation rate of 16.7 x 10(6) m3 CH4 year(-1). These results underscore the necessity of understanding a landfills dynamic environment before assessing long-term emissions potential.

Development of atmospheric tracer methods to measure methane emissions from natural gas facilities and urban areas.

Environ. Sci. Techno/. 1995, 29, 1468-1 479 Introduction Tracer -Methods To Measure Downloaded by UNIV OF CALIFORNIA IRVINE on August 26, 2015 | http://pubs.acs.org Publication Date: June 1, 1995 | doi: 10.1021/es00006a007 Gas Faciliies and U h n Areas BRIAN K. LAMB,*,’ J. BARRY MCMANUS,* JOANNE H. SHORTER,* CHARLES E . KOLB,* BYARD MOSHER,

Monoterpene emission from ponderosa pine

R O B E R T C . HARRISS,§ EUGENE ALLWINE,’ DENISE BLAHA,

Evaluation of forest canopy models for estimating isoprene emissions

T O U C H E H O W A R D , ” A L E X GUENTHER,l ROBERT A. LOTT,A ROBERT SIVERSON,’ HAL WESTBERG,’ AND PAT ZIMMERMAN- Laboratory for Atmospheric Research, Department of Civil & Environmental Engineering, Washington State University, Pullman, WA 99164-2910, Center for Chemical and Environmental Physics, Aerodyne Research, Inc., Billerica, Massachusetts 01821, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, New Hampshire 03824, Indaco Air Quality Services, Inc., Pullman, Washington 99163, National Center for Atmospheric Research, Boulder, Colorado 80303, and Gas Research Institute, Chicago, Illinois 60631 -3562 A new, integrated methodologyto locate and measure methane emissions from natural gas systems has been developed. Atmospheric methane sources are identified by elevated ambient CH4 concentrations measured with a mobile laser-based methane analyzer. The total methane emission rate from a source is obtained by simulating the source with a sulfur hexafluoride (SFS) tracer gas release and by measuring methane and tracer concentrations along downwind sampling paths using mobile, real-time analyzers. Combustion sources of methane are dis- tinguished from noncombustion sources by concur- rent ambient carbon dioxide measurements. Three variations on the tracer ratio method are described for application to (1) small underground vaults, (2) above- ground natural gas facilities, and (3) diffuse methane emissions from an entire town. Results from controlled releases and from replicate tests demonstrate thatthe tracer ratio approach can yield total emission rates to within approximately &15%. The estimated accuracy of emission estimates for urban areas with a variety of diffuse emissions is &50%. Methane (CH4) has been a contributor to the increasing burden of greenhouse gases in the earth’s atmosphere for more than a century (1). Faced with significant risks identified in scenarios of increasing greenhouse gas con- centrations, many countries are developing plans to reduce emissions. However, uncertainties in specific source emission rates for CH4 and other non-COz greenhouse gases currently limit the quantitative risk-benefit analysis needed to answer key policy questions related to the socioeconomic impacts of large-scale mitigation actions (2, 3 ) . Initial attempts to estimate CH4 losses to the atmosphere from natural gas production and use assumed that emis- sions could be approximated by industry reports of “unac- counted for” gas (e.g., ref 4). Unaccounted for gas, defined as the difference between the amount of natural gas metered into a system and the amount of gas metered out of a system, does not account for gas losses from wells to the processing plant, gas used as fuel in facilities, theft of gas, meter inaccuracies, and differences in accounting procedures between companies (4,5). Thus, the unaccounted for gas estimates cannot unambiguously be considered an upper or lower bound on emissions (5). Extrapolation of engi- neering estimates or data obtained from component by component sniffing methods also leads to large uncertain- ties in estimated emissions. In the United Kingdom, the British Gas Company estimates CH4 emissions from gas distribution system components to be less than 1% of throughput, while others estimate losses as high as 11% of gas throughput (6). A recent estimate of CH4 leakage from the natural gas system in the former Soviet Union, which was characterized as “tentative and highly conditional” suggested a range of total losses from 3.3% to 7% of gas production ( 7 ) . The U.S. Environmental Protection Agency (EPA) and the Gas Research Institute (GRI) have recently sponsored an integrated field measurement and analysis program to better define methane emissions from the U.S. natural gas system. Drawing on initial measurements using some of the techniques reported here as weil as engineering estimates, GRI has developed a preliminary estimate of methane emissions from the gas industry that equals approximately 1.5 i 0.5% of annual throughput (8). In the case of CH4 emissions due to the use of natural gas, there is an added motivation for correctly prescribing the methane source strength. Since natural gas typically produces 32-45% less COz per unit of thermal output compared to coal and 30% less compared to fuel oil, switching from coal and fuel oil to natural gas has the potential to reduce carbon dioxide emissions and reduce global warming (5). However, CH4 is a more potent greenhouse gas than CO2 on a molecule for molecule basis (9- 1 I). As a result, increasing the usage of natural gas may * To whom correspondence should be addressed: e-mail address: blamb@wsu.edu. + Washington State University. Aerodyne Research, Inc. 5 University of New Hampshire. I’ Indaco Air Quality Services, Inc. National Center for Atmospheric Research. A Gas Research Institute. 1468 ENVIRONMENTAL SCIENCE &TECHNOLOGY / VOL. 29, NO. 6, 1995 0013-936)(/95/0929-1468

Hydrocarbon emissions from spruce species using environmental chamber and branch enclosure methods

09.00/0 @ 1995 American Chemical Society

The canopy horizontal array turbulence study

We explore the variability in monoterpene emissions from ponderosa pine beyond that which can be explained by temperature alone. Specifically, we examine the roles that photosynthesis and needle monoterpene concentrations play in controlling emissions. We measure monoterpene concentrations and emissions, photosynthesis, temperature, and light availability in the late spring and late summer in a ponderosa pine forest in central Oregon. We use a combination of measurements from cuvettes and Teflon bag enclosures to show that photosynthesis is not correlated with emissions in the short term. We also show that needle monoterpene concentrations are highly correlated with emissions for two compounds, α-pinene and β-pinene, but that Δ-carene concentrations are not correlated with emissions. We suggest that direct effects of light and photosynthesis do not need to be included in emission algorithms. Our results indicate that the role of needle concentration bears further investigation; our results for α-pinene and β-pinene are explainable by a Raoults law relationship, but we cannot yet explain the cause of our results with Δ-carene.

THE MEASUREMENT OF ROADWAY PM10 EMISSION RATES USING ATMOSPHERIC TRACER RATIO TECHNIQUES

During the summer 1992, environmental and biogenic hydrocarbon emissions data were collected in a mixed hardwood forest at scales ranging from leaf to canopy to the mixed layer for the purpose of investigating issues related to the scale-up of leaf or branch level emission measurements to regional emission inventories. Results from canopy measurements are compared to several different forest canopy emission models. These range in complexity from a no-canopy effects method to the PC-BEIS canopy profile method to a numerical forest canopy radiative transfer model. The investigation includes a model-to-model intercomparison of predicted canopy environmental parameters including photosynthetically active radiation (PAR) and leaf temperature. The work is seeking to evaluate relatively simple modeling approaches for use in regional emission inventories using field data and more sophisticated numerical models.