Details

Autor(en) / Beteiligte

• Davis, J A
• Stubbins, A
• Helms, J
• Dias, R F
• Mopper, K

Titel

Using 18O as a Tracer of Oxygen in the Photochemical Alteration of Dissolved Organic Matter

Ist Teil von

• Eos (Washington, D.C.), 2006-12, Vol.87 (52)

Erscheinungsjahr

2006

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• The biogeochemical cycling of dissolved organic matter (DOM) in natural waters is affected by numerous processes, including photochemical alteration. Photochemical processes result in the net oxidation and mineralization of DOM concomitant with dissolved oxygen consumption and production of dissolved inorganic carbon (DIC; principally CO2). The photochemical oxygen budget is not well constrained i? while DIC production accounts for nearly all the dissolved oxygen consumed, conflicting data suggests that more than half of the oxygen consumed is required to account for observed DOM oxidation and hydrogen peroxide production. An alternate source of oxygen is required to balance this budget; water itself may provide the answer. In order to determine the source of oxygen, a number of time series irradiations were performed using Great Dismal Swamp water (southeast Virginia) with 18O enrichments as either dissolved oxygen or water. Early results, upon irradiation in a UV solar simulator, show significant incorporation of 18O-enriched oxygen into high molecular weight (HMW) DOM from both sources. While the majority of the incorporated oxygen originated from the dissolved oxygen, at least 5 percent originated from water. Data will be presented showing the rate and degree of incorporation of 18O-enriched oxygen from both sources as well as the production of 18O-enriched carbon dioxide. The movement of 18O label will be discussed in relation to shifts in spectral qualities, including photobleaching and spectral slope, of the irradiated samples and selective incorporation as detailed by FT- ICRMS.