Spatial Distribution of Methane in Surface Water from Terrestrial Sources to Coastal Regions Kaitlyn J. Steele Research and Discover 2009 Faculty Advisor: Dr. Ruth K. Varner, EOS

Greenhouse gases Carbon dioxide concentration in the atmosphere has increased from 280 ppm before the Industrial Revolution to 370 ppm in 2000 Carbon dioxide concentration in the atmosphere has increased from 280 ppm before the Industrial Revolution to 370 ppm in 2000 Methane has increased from 700 ppb to 1,745 ppb Methane has increased from 700 ppb to 1,745 ppb Methane has a global warming potential 23 times greater than CO 2 Methane has a global warming potential 23 times greater than CO 2 MEA 2005

Role of Oceans The coastal marine ecosystem is attributed with producing 75% of CH 4 emitted by the world’s oceans (Bange et al. 1994) The coastal marine ecosystem is attributed with producing 75% of CH 4 emitted by the world’s oceans (Bange et al. 1994) Ebullition and molecular diffusion are responsible for transport of methane out of sediments (Chanton et al. 1989) Ebullition and molecular diffusion are responsible for transport of methane out of sediments (Chanton et al. 1989) In coastal ecosystems the major pathway for bacterial methane formation is CO 2 reduction by hydrogen In coastal ecosystems the major pathway for bacterial methane formation is CO 2 reduction by hydrogen CO H 2 → CH H 2 O 4 H 2 + HCO 3- + H + → CH H 2 O Methane also produced by acetate fermentation but is limited by sulfate reduction Methane also produced by acetate fermentation but is limited by sulfate reduction CH 3 COOH → CH 4 + CO 2 Whiticar et al Hemond and Fechner-Levy 2000

Objectives Determine the flux of methane produced by anoxic coastal sediments Determine the flux of methane produced by anoxic coastal sediments -Incubation of sediment from tidal flats -Sample surface water of Great Bay estuary Examine the spatial distribution of methane from freshwater to coastal ecosystems Examine the spatial distribution of methane from freshwater to coastal ecosystems -Sample surface of rivers flowing into estuary -Use GIS to identify sources of methane and evaluate transport to coastal regions Methanogenesis: Acetate fermentation Wetlands, WWTP, etc Oxidation, Diffusive Flux, Advective Transport Estuary, saltmarsh Methanogenesis: CO 2 Reduction Oxidation, Air-Sea Exchange

Methods Incubations Sediment core taken in Great Bay Estuary at tidal flats Sediment core taken in Great Bay Estuary at tidal flats g of sediment from 0-5, 5-10, and cm incubated under anaerobic conditions g of sediment from 0-5, 5-10, and cm incubated under anaerobic conditions 10 mL of headspace sampled daily and analyzed for CH 4 concentration using GC-FID 10 mL of headspace sampled daily and analyzed for CH 4 concentration using GC-FID Water Sampling Surface water collected in container and syringe used to sample 30 mL of water Surface water collected in container and syringe used to sample 30 mL of water 30 mL of ambient air drawn in and syringe shaken to flush dissolved methane into the headspace 30 mL of ambient air drawn in and syringe shaken to flush dissolved methane into the headspace Headspace injected into GC-FID to obtain CH 4 concentration Headspace injected into GC-FID to obtain CH 4 concentration

Methane Concentration in Surface Water

Methane Concentration in Rivers Examples of Sources: Sallie’s Fen 4805 ppmv Durham Wastewater Treatment Plant 44 ppmv

Difference in CH 4 Concentration from 2008 to 2009

Methane Flux from Rivers to Atmosphere

Soil Incubations Depth (cm) Moisture Content (%) Organic Matter (%) Average Flux (mg CH 4 /g sed*day) ± ± ± ± ± ± ± ± ± ± ± ± 13.05

Future Work Methane produced through CO 2 reduction is isotopically light with δ 13 C values between -110 and -60‰ Methane produced through CO 2 reduction is isotopically light with δ 13 C values between -110 and -60‰ CH 4 produced by acetate fermentation has δ 13 C values between -65 and -50‰ CH 4 produced by acetate fermentation has δ 13 C values between -65 and -50‰ Methane oxidation converts some of the methane produced at depth to carbon dioxide as it rises to a level where oxygen is present Methane oxidation converts some of the methane produced at depth to carbon dioxide as it rises to a level where oxygen is present Since the 13 C/ 12 C ratios of dissolved CO 2 are affected by the equilibria of many kinetic isotope effects it is necessary to calculate the carbon isotopic fractionation between methane and carbon dioxide Since the 13 C/ 12 C ratios of dissolved CO 2 are affected by the equilibria of many kinetic isotope effects it is necessary to calculate the carbon isotopic fractionation between methane and carbon dioxide Whiticar et al. 1986

NASA Relevance Evaluating sources of methane can aid in determining processes that produce atmospheric methane Evaluating sources of methane can aid in determining processes that produce atmospheric methane TDL spectroscopy from aircraft TDL spectroscopy from aircraft Remote sensing using AIRS instrument on AQUA satellite Remote sensing using AIRS instrument on AQUA satellite AIRS CH 4 at 300hPa

Acknowledgements Dr. Ruth Varner Dr. George Hurtt Olivia DeMeo Jordan Goodrich NASA/UNH R&D

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