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See all EPA publications for John Walker, Jr. Include records from any date Include records from any EPA source

Records 1 to 25 of 37 records from [ORD-NRMRL] published between 07/16/2013 and 07/16/2018 from author John Walker, Jr.

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2018

Chen, X., X. Mingjie, M. Hays, E. Edgerton, D. Schwede, AND Johnt Walker. Characterization of organic nitrogen in aerosols at a forest site in the southern Appalachian Mountains. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, Germany, 18(9):6829-6846, (2018). https://doi.org/10.5194/acp-18-6829-2018

Beaulieu, J., A. Balz, M. Birchfield, J. Harrison, C. Nietch, M. Platz, W. C. SQUIER, S. Waldo, Johnt Walker, K. White, AND J. Young. Effects of an experimental water-level drawdown on methane emissions from a eutrophic reservoir. ECOSYSTEMS. Springer, New York, NY, 21(4):657-674, (2018).

Waldo, S., J. Beaulieu, W. Barnett, AND Johnt Walker. Methane Emissions from a Eutrophic Reservoir: Using Non-Linear Models to Gap Fill and Assess Biophysical Drivers. American Meteorological Society Fourth Conference on Biogeosciences, Boise,ID, May 13 - 18, 2018.

Oishi, C., C. Miniat, K. Novick, S. Brantley, J. Vose, AND Johnt Walker. Warmer Temperatures Reduce Net Carbon Uptake, but Do Not Affect Water Use, in a Mature Southern Appalachian Forest. AGRICULTURAL AND FOREST METEOROLOGY. Elsevier Science Ltd, New York, NY, 252:269-282, (2018).

2017

Chen, X., Johnt Walker, AND Chris Geron. Chromatography related performance of the Monitor for Aerosols and Gases in Ambient Air (MARGA): laboratory and field based evaluation. Atmospheric Measurement Techniques. Copernicus Publications, Katlenburg-Lindau, Germany, 10:3893-3908, (2017). https://doi.org/10.5194/amt-10-3893-2017

Wu, Z., Johnt Walker, AND L. Zhang. Development, evaluation and application of a modified micrometeorological gradient method for long-term estimation of gaseous dry deposition over forest canopies. Presented at Ozone Dry Deposition: Constraints from multiplatform observations and multi-scale modeling, Palisades, CA, October 05 - 06, 2017.

Wu, Z., D. Tomer, Johnt Walker, X. Chen, C. Oishi, D. Schwede, AND J. Iiames. Estimation of in-canopy flux distributions of reactive nitrogen and sulfur within a mixed hardwood forest in southern Appalachia. American Geophysical Union, New Orleans, LA, December 11 - 15, 2017.

Waldo, S., J. Beaulieu, AND Johnt Walker. Improving our process understanding of methane emissions from a mid-latitude reservoir by combining eddy covariance monitoring with spatial surveys. AGU Fall Meeting, New Orleans, LA, December 11 - 15, 2017.

Chen, X. AND Johnt Walker. Laboratory and field based evaluation of chromatography related performance of the Monitor for AeRosols and Gases in ambient Air (MARGA). 2017 AAAR, Raleigh, North Carolina, October 16 - 20, 2017.

Chen, X. AND Johnt Walker. Laboratory and field based evaluations of chromatography related performance of the Monitor for AeRosols and GAses in ambient Air (MARGA). AAAR 2017, Raleigh, NC, October 16 - 20, 2017.

Walker, Johnt, X. Chen, M. Xie, M. Hays, E. Edgerton, AND D. Schwede. Organic nitrogen in aerosols at a forest site in southern Appalachia. National Atmospheric Deposition Program Fall Meeting, San Diego, CA, October 30 - November 03, 2017.

2016

Beaulieu, J., B. Deemer, J. Harrison, C. Nietch, S. Waldo, AND Johnt Walker. Accounting For Greenhouse Gas Emissions From Flooded Lands. Presented at AGU Fall Meeting, San Francisco, CA, December 12 - 16, 2016.

Rumsey, I. C. AND J. T. WALKER. Application of an online ion chromatography-based instrument for gradient flux measurements of speciated nitrogen and sulfur. Atmospheric Measurement Techniques. Copernicus Publications, Katlenburg-Lindau, Germany, 9(6):2581-2592, (2016).

Duman, T., Johnt Walker, J. Bash, K. Gannam, C. Huang, K. Andrey, AND G. Katul. Estimating sources, sinks and fluxes of reactive atmospheric compounds within a forest canopy. 2015 American Geophysical Union, San Francisco, CA, December 14 - 18, 2015.

Waldo, S., J. Beaulieu, AND Johnt Walker. Investigating physical controls on methane and carbon dioxide fluxes over reservoirs using the eddy covariance method. Presented at American Geophysical Union Fall Meeting, San Francisco, CA, December 12 - 16, 2016.

Waldo, S., J. Beaulieu, AND Johnt Walker. Investigating physical controls on methane and carbon dioxide fluxes over reservoirs using the eddy covariance method-abstract. AGU Fall Meeting, San Francisco, CA, December 12 - 16, 2016.

Walker, Johnt, X. Chen, D. Schwede, R. Daly, A. Djurkovic, D. Kirchgessner, C. Oishi, AND M. Puchalski. Investigation of ammonia air-surface exchange processes in a deciduous montane forest in the southeastern U.S. Presented at National Atmospheric Deposition Program Fall Meeting, Santa Fe, New Mexico, October 31 - November 04, 2016.

Chen, X., Johnt Walker, AND Chris Geron. Laboratory and field based evaluation of chromatography related performance of the Monitor for Aerosols and Gases in Ambient Air (MARGA). Presented at National Atmospheric Deposition Program Fall Meeting, Santa Fe, New Mexico, October 31 - November 04, 2016.

Beaulieu, J., C. Nietch, S. Waldo, AND Johnt Walker. Methane emissions from reservoirs. To be Presented at Ohio River Basin Water Quality Workshop, Cincinnati, Ohio, December 06 - 08, 2016.

Li, Y., B. Schichtel, Johnt Walker, D. Schwede, X. Chen, C. Lehmann, M. Puchalski, D. Gay, AND J. Collett, Jr. The Increasing Importance of Deposition of Reduced Nitrogen in the United States. PNAS (PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES). National Academy of Sciences, WASHINGTON, DC, 113(21):5874-5879, (2016).

Walker, Johnt. The Measurement and modeling of the contribution of ammonia to total nitrogen deposition from canopy to regional scale. Presented at Invited Seminar - College of Charleston, Charleston, SC, March 03, 2016.

Walker, Johnt AND A. Leytem. USDA-EPA Collaborative Ammonia Research. Presented at USDA Agricultural Air Quality Task Force, Arlington, VA, April 07, 2016.

Sullivan, R., P. Crippa, A. Hallar, L. Clarisse, S. Whitburn, M. Van Damme, W. Leaitch, Johnt Walker, A. Khlystov, AND S. Pryor. Using satellite-based measurements to explore spatiotemporal scales and variability of drivers of new particle formation. JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES. American Geophysical Union, Washington, DC, 121(20):12217-12235, (2016).

George, I., R. Black, Johnt Walker, Chris Geron, J. Aurell, M. Hays, W. Preston, AND B. Gullett. Volatile and semivolatile organic compounds in laboratory peat fire emissions. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 132:163-170, (2016).

2015

Oishi, C., C. Miniat, K. Novick, S. Brantley, J. Vose, AND Johnt Walker. Climate and Vegetation Effects on Temperate Mountain Forest Evapotranspiration. Presented at 2015 American Geophysical Union Annual Meeting, San Francisco, CA, December 14 - 18, 2015.