Publications Published in Environmental Science & Technology

1. Accurate Estimation of Forest Carbon Stocks by 3-D Remote Sensing of Individual Trees. Omasa, Kenji; Qui, Guo Yu; Watanuki, Kenichi; Yoshimi, Kenji; Akiyama, Yukihide.
   Environmental Science & Technology: 2003
   Notes
   Forests are one of the most important carbon sinks on Earth. However, owing to the complex structure, variable geography, and large area of forests, accurate estimation of forest carbon stocks is still a challenge for both site surveying and remote sensing. For these reasons, the Kyoto Protocol requires the establishment of methodologies for estimating the carbon stocks of forests (Kyoto Protocol, Article 5). A possible solution to this challenge is to remotely measure the carbon stocks of every tree in an entire forest. Here, we present a methodology for estimating carbon stocks of a Japanese cedar forest by using a high-resolution, helicopter-borne 3-dimensional (3-D) scanning lidar system that measures the 3-D canopy structure of every tree in a forest. Results show that a digital image (10-cm mesh) of woody canopy can be acquired. The treetop can be detected automatically with a reasonable accuracy. The absolute error ranges for tree height measurements are within 42 cm. Allometric relationships of height to carbon stocks then permit estimation of total carbon storage by measurement of carbon stocks of every tree. Thus, we suggest that our methodology can be used to accurately estimate the carbon stocks of Japanese cedar forests at a stand scale. Periodic measurements will reveal changes in forest carbon stocks.
   
   
   
2. Anaerobic methane oxidation in a landfill-leachate plume. Grossman, E. L.; Cifuentes, L. A.; Cozzarelli, I. M..
   Environmental Science & Technology: 2002
   Notes
   The alluvial aquifer adjacent to Norman Landfill, OK, provides an excellent natural laboratory for the study of anaerobic processes impacting landfill-leachate contaminated aquifers. We collected groundwaters from a transect of seven multilevel wells ranging in depth from 1.3 to 11 m that were oriented parallel to the flow path. The center of the leachate plume was characterized by (1) high alkalinity and elevated concentrations of total dissolved organic carbon, reduced iron, and methane, and (2) negligible oxygen, nitrate, and sulfate concentrations. Methane concentrations and stable carbon isotope (delta(13)C) values suggest anaerobic methane oxidation was occurring within the plume and at its margins. Methane delta(13)C values increased from about -54parts per thousand near the source to > -10parts per thousand downgradient and at the plume margins. The isotopic fractionation associated with this methane oxidation was -13.6 +/- 1.0parts per thousand.
   
   
   
3. Characterization of the Single Particle Mixing State of Individual Ship Plume Events Measured at the Port of Los Angeles. Andrew P. Ault, Cassandra J. Gaston, Ying Wang, Gerardominguez, Mark H. Thiermes, Kimberly A. Prather.
   Environmental Science & Technology: 2010
   DOI: 10.1021/es902985h
   Notes
   Ship emissions contribute significantly to gaseous and particulate pollution worldwide. To better understand the impact of ship emissions on air quality, measurements of the sizeresolved chemistry of individual particles in ship emissions were made at the Port of Los Angeles using real-time, singleparticle mass spectrometry. Ship plumes were identified through a combination of ship position information and measurements of gases and aerosol particles at a site 500 m from the center of the main shipping channel at the Port of Los Angeles. Single particles containing mixtures of organic carbon, vanadium, and sulfate (OC-V-sulfate) resulted from residual fuel combustion (i.e., bunker fuel),whereashigh quantities of fresh soot particles (when OC-V-sulfate particles were not present) represented distinct markers for plumes from distillate fuel combustion (i.e., diesel fuel) from ships as well as trucks in the port area. OC-V-sulfate particles from residual fuel combustion contained significantly higher levels of s lfate and sulfuric acid than plume particles containing no vanadium. These associations may be due to vanadium (or other metals such as iron) in the fuel catalyzing the oxidation of SO2 to produce sulfate and sulfuric acid on these particles. Enhanced sulfate production on OC-V-sulfate ship emission particles would help explain some of the higher than expected sulfate levels measured in California compared to models based on emissions inventories and typical sulfate production pathways. Understanding the overall impact of ships emissions is critical for controlling regional air quality in the many populated coastal regions of the world.
   
   
   
4. Comparative oxidation and net emissions of methane and selected non-methane organic compounds in landfill cover soils. Schueta, Charlotte; Bogner, Jean; Chanton, Jeffrey; Blake, Donald; Morchet, Muriel; Kjeldsen, Peter.
   Environmental Science & Technology: 2003
   Notes
   The surface emissions of methane (CH4) and non-methane organic compounds (NMOCs) were determined at two different areas at a French landfill: a permanently covered and fully vegetated area (40 cm coarse sand + 80 cm of loam) and a temporarily covered area (40 cm of coarse sand). The 37 NMOCs quantified in the landfill gas samples included alkanes (C1-C10), alkenes (C1-C4), halogenated hydrocarbons (including (H)CFCs), and aromatic hydrocarbons. Both positive and negative CH4 fluxes ranging from -0.01 to 0.008 gm-2 d-1 were measured from the permanently covered cell. However, high spatial variation was observed, and a hot spot with a high flux (10 g m-2 d-1) was identified. A higher CH4 emission occurred from the temporarily covered cell (CH4 flux of 49.9 g m-2 d-1) as compared to the permanently covered cell. The NMOC fluxes from the permanently covered zone were all very small with both positive and negative fluxes in the order of 10-7 to 10-5 g m-2 d-1. Higher and mainly positive NMOC fluxes in the order of 0-5 to 10-4 g m-2 d-1 were obtained from the temporarily covered zone. The lower emission from the permanently covered and fully vegetated cell was attributable to the thicker soil layer, which functions as microbial habitat for methanotrophic bacteria. The NMOC oxidation capacity was investigated in soil microcosms incubated with CH4. Maximal oxidation rates for the halogenated aliphatic compounds varied between 0.06 and 8.56 íg (g of soil)-1 d-1. Fully substituted hydrocarbons (tetrachloromethane, perchloroethylene, CFC-11, CFC-12, and CFC-113) were not degraded in the presence of CH4 and O2. Benzene and toluene were rapidly degraded, giving very high maximal oxidation rates (28 and 39 íg (g of soil)-1 d-1). On the basis of the emission measurements and the batch experiments conducted, a general pattern was observed between emissions and biodegradability of various NMOCs. The emissions mainly consisted of compounds that were not degradable or slowly degradable, while an uptake of easily degradable compounds was registered. As an example, perchloroethylene, trichloromethane, CFC- 11, and CFC-12 were emitted, while atmospheric consumption of aromatic hydrocarbons and lower chlorinated hydrocarbons such as vinyl chloride, dichloromethane, and chloromethane was observed. This study demonstrates that landfill soil covers show a significant potential for CH4 oxidation and co-oxidation of NMOCs. Under certain conditions, landfills may even function as sinks for CH4 and selected NMOCs, like aromatic hydrocarbons and lower chlorinated compounds.
   
   
   
5. Comparative oxidation and net emissions of methane and selected non-methane organic compounds in landfill cover soils. Scheutz, C.; Bogner, J.; Chanton, J.P.; Blake, D. R.; Morcet, M.; Kjeldsen, P..
   Environmental Science & Technology: 2003
   DOI: 10.1021/es034016b
   Notes
   The surface emissions of methane (CH4) and non-methane organic compounds (NMOCs) were determined at two different areas at a French landfill: a permanently covered and fully vegetated area (40 cm coarse sand + 80 cm of loam) and a temporarily covered area (40 cm of coarse sand). The 37 NMOCs quantified in the landfill gas samples included alkanes (C1-C10), alkenes (C1-C4), halogenated hydrocarbons (including (H)CFCs), and aromatic hydrocarbons. Both positive and negative CH4 fluxes ranging from -0.01 to 0.008 gm-2 d-1 were measured from the permanently covered cell. However, high spatial variation was observed, and a hot spot with a high flux (10 g m-2 d-1) was identified. A higher CH4 emission occurred from the temporarily covered cell (CH4 flux of 49.9 g m-2 d-1) as compared to the permanently covered cell. The NMOC fluxes from the permanently covered zone were all very small with both positive and negative fluxes in the order of 10-7 to 10-5 g m-2 d-1. Higher and mainly positive NMOC fluxes in the order of 0-5 to 10-4 g m-2 d-1 were obtained from the temporarily covered zone. The lower emission from the permanently covered and fully vegetated cell was attributable to the thicker soil layer, which functions as microbial habitat for methanotrophic bacteria. The NMOC oxidation capacity was investigated in soil microcosms incubated with CH4. Maximal oxidation rates for the halogenated aliphatic compounds varied between 0.06 and 8.56 íg (g of soil)-1 d-1. Fully substituted hydrocarbons (tetrachloromethane, perchloroethylene, CFC-11, CFC-12, and CFC-113) were not degraded in the presence of CH4 and O2. Benzene and toluene were rapidly degraded, giving very high maximal oxidation rates (28 and 39 íg (g of soil)-1 d-1). On the basis of the emission measurements and the batch experiments conducted, a general pattern was observed between emissions and biodegradability of various NMOCs. The emissions mainly consisted of compounds that were not degradable or slowly degradable, while an uptake of easily degradable compound was registered. As an example, perchloroethylene, trichloromethane, CFC- 11, and CFC-12 were emitted, while atmospheric consumption of aromatic hydrocarbons and lower chlorinated hydrocarbons such as vinyl chloride, dichloromethane, and chloromethane was observed. This study demonstrates that landfill soil covers show a significant potential for CH4 oxidation and co-oxidation of NMOCs. Under certain conditions, landfills may even function as sinks for CH4 and selected NMOCs, like aromatic hydrocarbons and lower chlorinated compounds.
   
   
   
6. Decadal and shorter period variability of surf zone water quality at Huntington Beach, California. Boehm, A. B.; Grant, S. B.; Kim, J. H.; Mowbray, S. L.; McGee, C. D.; Clark, C. D.; Foley, D. M.; Wellman, D. E..
   Environmental Science & Technology: 2002
   Notes
   The concentration of fecal indicator bacteria in the surf zone at Huntington Beach, CA, varies over time scales that span at least 7 orders of magnitude, from minutes to decades. Sources of this variability include historical changes in the treatment and disposal of wastewater and dry weather runoff, El Nino events, seasonal variations in rainfall, spring-neap tidal cycles, sunlight-induced mortality of bacteria, and nearshore mixing. On average, total coliform concentrations have decreased over the past 43 years, although point sources of shoreline contamination (storm drains, river outlets, and submarine outfalls) continue to cause transiently poor water quality. These transient point sources typically persist for 5-8 yr and are modulated by the phase of the moon, reflecting the influence of tides on the sourcing and transport of pollutants in the coastal ocean, Indicator bacteria are very sensitive to sunlight; therefore, the time of day when samples are collected can influence the outcome of water quality testing. These results demonstrate that coastal water quality is forced by a complex combination of local and external processes and raise questions about the efficacy of existing marine bathing water monitoring and reporting programs.
   
   
   
7. Development of atmospheric tracer methods to measure methane emissions from natural gas facilities and urban areas. Lamb, Brian K; McManus, J Barry; Shorter, Joanne H; Kolb, Charles E; Mosher, Byard; Harriss, Robert C; Allwine, Eugene; Blaha, Denise; Howard, Touche; Guenther, Alex; Lott, Robert A; Siverson, Robert; Westberg, Hal; Zimmerman, Pat.
   Environmental Science & Technology: 1995
   Notes
   Describes an integrated methodology to locate and measure methane emissions from natural gas systems. Comparison of the tracer ratio approach to existing emission measurement techniques; Applicability of the tracer ratio method in large and small natural gas facilities.
   
   
   
8. Effects of meteorological conditions on aerosol composition and mixing state in Bakersfield, CA. Whiteaker, J. R.; Suess, D. T.; Prather, K. A..
   Environmental Science & Technology: 2002
   Notes
   Particle and meteorological instrumentation were used to characterize ambient atmospheric conditions, aerosol size distributions, aerosol mass concentrations, and single particle size and chemical composition in Bakersfield, CA for the period January 9, 1999 through January 28, 1999. The sampling period included four distinct meteorological periods of stagnation, clearing, haze, and rain. Particle number and mass concentrations were the highest during the stagnation episode when a heavy and extensive fog developed. Mass and number concentrations also approached these high levels during the haze period. Single particle size and composition data from an aerosol time-of-flight mass spectrometer (ATOFMS) are used to provide unique continuous information on the diversity in types of particles present, the effects of meteorology on particle size and composition, and the distribution of important chemical species within individual particles. Aerosol composition and mixing state are found to vary with meteorological conditions. Single particle data show that carbonaceous aerosol with secondary ammonium, nitrate, and sulfate dominate the aerosol concentration during a stagnation period with a dramatic composition shift occurring to sodium type particles during the haze period. The aerosol is internally mixed with respect to carbon, nitrate, sulfate, and ammonium during the stagnation period. The mixing state changes significantly over the haze period when much greater diversity in the associations of chemical species within individual particles occurs.
   
   
   
9. Emissions from waterborne commerce vessels in United States continental and inland waterways. Corbett, J. J.; Fischbeck, P. S..
   Environmental Science & Technology: 2000
   Notes
   We present an inventory of emissions from marine vessels engaged in waterborne commerce (i.e., cargo transport) on the U.S. navigable waters. Emissions are estimated for 1997 for various U.S regions and types of traffic, including oceangoing (international), coastwise (domestic), inland-river system, and Great Lakes. Nearly all emissions in U.S. waters occur in shipping channels outside of port regions, either on rivers or within 200 miles of shore. NO, emissions from commercial marine engines considered in this study account for about half of the U.S. EPA baseline inventory of similar to 1000 tons per year for all marine vessels ( I). This equals 4% of all U.S. transportation emissions, more than double previous nationwide inventories of vessel emissions (2). Waterborne commerce emissions are not negligible when compared to other sources.
   
   
   
10. Estimating methane emissions from dairy cattle housed in a barn and feedlot using an atmospheric tracer. Kaharabata, S. K.; Schuepp, P. H..
    Environmental Science & Technology: 2000
    Notes
    Methane emissions from a barn and feedlot/paddock housing dairy cattle were estimated using a tracer gas (SF6) to simulate the dispersion of CH4. The tracer gas was released from 16 point sources distributed within the barn or feedlot to simulate the CH4 sources (cows). Using a two-dimensional (y, z) sampling grid, the observed downwind SF6/CH4 crosswind concentration field was integrated to give the portion of the SF6/CH4 plume that was captured by the sampling grid. Assuming that both SF6 and CH4 underwent similar turbulent atmospheric transport, the ratio of the respective captured plumes was then used to estimate the emission strength of methane from the known release rate of SF6. The predicted source strength of CH4 from the barn was within 6% of the estimate made using a different technique whereby the entire barn was used as an enclosed chamber. The methane emissions predicted in the barn and feedlot experiments were 542 (+/- 30%) L CH4 d(-1) cow(-1) and 631 (± 30%) L CH4 d-1 cow-1, respectively. Using census data on the population of dairy cattle in Canada, a national estimate of 0.245 (± 50%) Tg CH4 yr-1 was made.