Direct measurement of dissolved N sub(2) and denitrification along a subtropical river-estuary gradient, China

The spatial pattern and seasonal variation of denitrification were investigated during 2010-2011 in the Jiulong River Estuary (JRE) in southeast China. Dissolved N sub(2) was directly measured by changes in the N sub(2):Ar ratio. The results showed that excess dissolved N sub(2) ranged from -9.9 to...

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Bibliographic Details
Published in:Marine pollution bulletin 2013-01, Vol.66 (1-2), p.125-134
Main Authors: Wu, Jiezhong, Chen, Nengwang, Hong, Huasheng, Lu, Ting, Wang, Longjian, Chen, Zhuhong
Format: Article
Language:English
Subjects:
Brackish
Freshwater
Marine
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Summary:The spatial pattern and seasonal variation of denitrification were investigated during 2010-2011 in the Jiulong River Estuary (JRE) in southeast China. Dissolved N sub(2) was directly measured by changes in the N sub(2):Ar ratio. The results showed that excess dissolved N sub(2) ranged from -9.9 to 76.4 mu mol L super(-1). Tidal mixing leads to a seaward decline of dissolved gaseous concentrations and water-air fluxes along the river-estuary gradient. Denitrification at freshwater sites varied between seasons, associated with changes in N input and water temperature. The denitrification process was controlled by the nitrate level at freshwater sites, and the excess dissolved N sub(2) observed at the tidal zone largely originated from upstream water transport. Compared to other estuaries, JRE has a relative low gaseous removal efficiency (E sub(d)=12% of [DIN]; annual N removal=24% of DIN load), a fact ascribed to strong tidal mixing, coarse-textured sediment with shallow depth before bedrock and high riverine DIN input.
ISSN:0025-326X
DOI:10.1016/j.marpolbul.2012.10.020