Summer-time denitrification and nitrous oxide exchange in the intertidal zone of the Yangtze Estuary

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• 作者：Dongqi Wang ; Zhenlou Chen ; Jun Wang ; Shiyuan Xu ; Hongxia Yang ; Hua Chen ; Longyuan Yang ; Lingzhen Hu
• 关键词：Yangtze Estuary ; intertidal zone ; denitrification ; N₂O ; nitrous oxide exchange
• 刊名：Estuarine, Coastal and Shelf Science
• 出版年：2007
• 出版时间：June 2007
• 年：2007
• 卷：73
• 期：1-2
• 页码：43-53
• 全文大小：700 K

文摘

Sediment denitrification rates and nitrous oxide (N₂O) exchange fluxes in the Yangtze estuary intertidal zone (mudflats and salt marshes) were measured in summer-time using an acetylene inhibition technique and an in situ static closed chamber method. N₂O natural production rates ranged between 0.10 μmol N m⁻² h⁻¹ and 8.50 μmol N m⁻² h⁻¹, and the denitrification rates ranged from 18.71 μmol N m⁻² h⁻¹ to 35.87 μmol N m⁻² h⁻¹. The N₂O natural production rates in overlying water were low, with intertidal sediment being the source of overlying water N₂O during the submerged period. Data analysis indicated that most sediment N₂O was not derived from denitrification, but from several other nitrogen-cycling processes. During the low tide, the middle tidal marsh was the source of atmosphere N₂O (exchange fluxes changed between −11.03 μmol N m⁻² h⁻¹ and 13.17 μmol N m⁻² h⁻¹). 5 cm and 10 cm depth ground temperatures were significant factors controlling the emission flux. At the low tidal flat, N₂O emission flux rates ranged from −5.75 μmol N m⁻² h⁻¹ to 0.49 μmol N m⁻² h⁻¹ at the sediment-atmosphere interface. Overall, the middle tidal marsh was the source of atmospheric N₂O, while the low tidal flat was a sink for atmospheric N₂O. Plants of the intertidal zone (Scirpus mariqueter and benthic algae) were significant factors controlling N₂O exchange flux. Photosynthesis of intertidal zone plants inhibited the emission of N₂O and induced consumption, while plant respiration may enhance N₂O emission from the intertidal zone. N₂O emission and consumption at the intertidal zone-atmosphere interface correlated positively with the emission and consumption of CO₂.