| 摘要: |
| 分别于2014年10月和2015年6月对南海北部陆坡区进行了调查，研究了其溶存氧化亚氮（N2O）的分布、产生并估算了其海-气交换通量。结果表明：秋季南海北部表层海水中溶解N2O浓度为（8.19±0.79）nmol/L，饱和度为132.5%±13.4%；夏季表层海水中溶解N2O浓度为（7.72±0.56）nmol/L，饱和度为135.5%±9.7%。夏季由于受到珠江冲淡水的影响，表层N2O浓度随盐度升高呈降低趋势，秋季调查区域东北部受到穿过吕宋海峡的黑潮分支表层水的影响，N2O浓度较低。结合文献资料，南海北部陆坡区表层N2O浓度季节变化特征为春末>秋季>夏季，同一季节，南海陆坡区的N2O浓度高于其他区域。温度是影响N2O分布的重要因素，ΔN2O与表观耗氧量（apparent oxygen utilization，AOU）和N3O-的显著相关说明硝化作用是南海水体中N2O产生的主要机制，由此估算硝化作用的N2O产率分别为秋季0.033%，夏季0.035%。利用N2000和W2014公式分别估算了该区域秋季和夏季N2O的海-气交换通量：秋季为1.81-23.81（11.11±6.52，平均值±SD，下同）（N2000）和1.73-24.38（11.30±6.81）（W2014），夏季为1.01-21.57（7.04±6.10）（N2000）和0.75-22.69（6.94±6.49）（W2014），单位均为μmol/（m2·d）。初步估算出南海北部陆坡N2O释放量为0.055Tg/a，约占全球海洋总释放量的0.39%，远高于其面积比，说明南海北部陆坡是N2O释放的活跃海域，是大气N2O的重要源。 |
| 关键词: 南海 N2O 分布 产生 海-气交换通量 |
| DOI：10.11693/hyhz20160600137 |
| 分类号: |
| 基金项目:国家重点基础研究发展规划（973）项目，2014CB441502号；国家自然科学基金项目，41376088号；国家自然科学创新研究群体基金项目，41521064号；国家重点研发计划项目，2016YFA0601302号，2016YFA0601301号。 |
|
| DISTRIBUTION, FORMATION AND AIR-SEA FLUX OF DISSOLVED NITROUS OXIDE IN NORTHERN CONTINENTAL SLOPE OF SOUTH CHINA SEA IN SUMMER AND AUTUMN |
|
REN Yan-Yan, ZHENG Wen-Jing, YE Wang-Wang, ZHANG Yun-Yan, ZHANG Gui-Ling
|
|
Key Laboratory of Marine Chemistry Theory and Technology(OUC), Ministry of Education Ocean University of China, Qingdao 266100, China
|
| Abstract: |
| Distributions, production and air-sea fluxes of dissolved N2O in the continental slope of the South China Sea (SCS) were investigated during two cruises in October 2014 and June 2015. The dissolved N2O concentration in surface waters ranged 6.82-9.95nmol/L in average of (8.19±0.79)nmol/L (132.5%±13.4% saturation) in autumn, and ranged (6.85-9.07)nmol/L in average of (7.72±0.56)nmol/L (135.5%±9.7% saturation) in summer. The surface N2O concentrations decreased with the increase of salinity in summer due to the influence of Zhujiang (Pearl) River Diluted Water. In autumn, however, N2O concentrations were low in the northeastern part of the sampling area due to the intrusion of Kuroshio. Our data and previously published data show that, the maximum surface N2O concentrations occurred in late spring, followed by autumn and summer. N2O emission from continental slope was higher than other parts of the SCS. Temperature was a major factor affecting distribution of dissolved N2O concentrations. Notably positive correlations were found between ΔN2O and apparent oxygen utilization (AOU), and ΔN2O and nitrate, indicating that nitrification might be the major mechanism of N2O formation in the SCS. In addition, the N2O yield from nitrification we calculated was 0.033% in autumn and 0.035% in summer; the air-sea fluxes of N2O varied 1.81-23.81 (11.11±6.52)μmol/(m2·d) (in N2000 method) and 1.73-24.38 (11.30±6.81)μmol/(m2·d) (in W2014 method) in autumn and 1.01-21.57 (7.04±6.10)μmol/(m2·d) (N2000) and 0.75-22.69 (6.94±6.49)μmol/(m2·d) (W2014) in summer; N2O emission from the continental slope of the northern SCS was 0.055Tg/a, accounting for 0.39% of global oceanic N2O emission, suggesting that this area was a hotspot to produce N2O and a net source of atmospheric N2O. |
| Key words: South China Sea N2O distribution generation air-sea flux |
