高度城市化影响的胶州湾海-气界面CO2通量及主要控制机制

Jiaozhou Bay is a typical semi-enclosed shallow embayment which has already been affected by urbanization. We assume that the main mechanisms that control the air-sea CO2 flux in this area besides the annual fluctuation of temperature including: alternation and counteraction between intense respiration and biological uptake on a regional or seasonal scale, well-mixing throughout the water column all year long, and the sewage-aquaculture input induced benthic oxygen consumption which may also affect the carbon system equilibrium through the water column. The key scientific issue to unveil the controlling factors of the air-sea CO2 flux is the distribution and seasonal variation of net community production in Jiaozhou Bay. This proposal aims to improve the computational method of net community production in the open ocean and apply it in Jiaozhou Bay based on a comprehensive understanding of different biogeochemical processes mentioned above. Our study has its referential significance to other shallow coasts that also undergo pollution impact. Furthermore, our study can provide a foundation for the variation of carbon cycle and its controls during the urbanization process in the developing coastal cities in China, and the seeking of potential solutions to reduce the carbon source while enhance sink in those coastal cities.

胶州湾是一个典型的已经受城市化影响的半封闭浅海湾。我们假设在胶州湾除温度造成的pCO2正常波动外，影响胶州湾海-气界面CO2通量的主要机制还包括：好氧呼吸、浮游生物活动两个过程并存剧烈或交替剧烈(不同区域，不同季节)，常年的垂直混合作用使得水柱的生物、化学过程对海-气CO2交换产生深刻影响，而城市污水及海水养殖输入的大量海底有机沉积物耗氧呼吸过程及其产生的DIC，直接影响着水柱的碳酸盐体系平衡。而破解这一机制的关键科学问题是，明确不同污染状况区域净群落生产力NCP的分布水平及其季节演变。本申请书拟在充分考虑上述各过程的基础上，改进和补充在开阔海域使用的净群落生产力(NCP)评估方法，使之适于胶州湾。项目研究方法对于污染严重的其他浅海具有借鉴意义，研究结果将为揭示沿海地区城市化进程过程中碳循环变异及其调控因子奠定基础，为寻求减源增汇修复措施奠定基础。

胶州湾是一个典型的已经受城市化影响的半封闭浅海湾。除温度造成的pCO2正常波动外，好氧呼吸、浮游生物活动、处理后污水DIC的输入、以贝类养殖为主导致的碳酸钙沉降作用，以及这些过程的交替出现或叠加效应使得CO2分布的变化规律极其敏感和复杂。月际航次中，至少都是两个以上过程控制的局面。CO2源/汇控制的主要事例有：胶州湾东部好氧呼吸产生的CO2每天则可使pH降低0.023-0.042个单位，使pCO2升高68-166µatm。而西部海域的碳酸钙沉降则是pCO2的主要控制过程。冬季胶州湾浮游植物高峰期的存在规律，导致冬季始终是大气CO2的强汇。而基于构建的δ13CDIC、DIC及总碱度（TA）变化的三元DIC溯源模型评价，有机质降解和污水DIC直接输入是胶州湾东北海域DIC盈余和CO2强源的主要原因。污水DIC直接输入超过人为有机质降解产生的CO2。