Nitrous oxide in the Changjiang (Yangtze River) Estuary and its adjacent marine area: Riverine input, sediment release and atmospheric fluxes

• Main Authors: G.-L. Zhang, J. Zhang, S.-M. Liu, J.-L. Ren, Y.-C. Zhao
• Format: Article
• Language: English
• Published: Copernicus Publications 2010-11-01
• Series: Biogeosciences
• Online Access: http://www.biogeosciences.net/7/3505/2010/bg-7-3505-2010.pdf

Dissolved nitrous oxide (N<sub>2</sub>O) was measured in the waters of the Changjiang (Yangtze River) Estuary and its adjacent marine area during five surveys covering the period of 2002–2006. Dissolved N<sub>2</sub>O concentrations ranged from 6.04 to 21.3 nM, and indicate great temporal and spatial variations. Distribution of N<sub>2</sub>O in the Changjiang Estuary was influenced by multiple factors and the key factor varied between cruises. Dissolved riverine N<sub>2</sub>O was observed monthly at station Xuliujing of the Changjiang, and ranged from 12.4 to 33.3 nM with an average of 19.4 ± 7.3 nM. N<sub>2</sub>O concentrations in the river waters showed obvious seasonal variations with higher values occurring in both summer and winter. Annual input of N<sub>2</sub>O from the Changjiang to the estuary was estimated to be 15.0 × 10<sup>6</sup> mol/yr. N<sub>2</sub>O emission rates from the sediments of the Changjiang Estuary in spring ranged from −1.88 to 2.02 μmol m<sup>−2</sup> d<sup>−1</sup>, which suggests that sediment can act as either a source or a sink of N<sub>2</sub>O in the Changjiang Estuary. Average annual sea-to-air N<sub>2</sub>O fluxes from the studied area were estimated to be 7.7 ± 5.5, 15.1 ± 10.8 and 17.0 ± 12.6 μmol m<sup>−2</sup>d<sup>−1</sup> using LM86, W92 and RC01 relationships, respectively. Hence the Changjiang Estuary and its adjacent marine area are a net source of atmospheric N<sub>2</sub>O.