有色可溶性有机物来源与组成多方法联合识别及对流域水交换过程的响应

Dissolved organic matter (DOM) in natural waters is the largest carbon pool on earth. Chromophoric DOM (CDOM) is an important fraction of DOM that could strongly absorb light at the UV and blue region and its translocation and transformation directly impact the global carbon cycling and climate change. Urbanization and industrialization usually take place in large fluvial plains and coastal lake watersheds, and lakes in these ecosystems receive sewage derived from intensive residential areas and are often eutrophic and contain high concentrations of CDOM, and thereby are hot spots of inland carbon cycling. The elevation of the Lake Taihu watershed is mostly lower than 5 meters, and numerous rivers and man-made channels are connected to the lake. Water flow directions of the channels connecting to Lake Taihu are largely controlled by anthropogenic disturbance (e.g. hundreds of floodgates), typhoon passages, and tidal exchange, and are broadly similar to that of lagoon systems. The sources, composition, and biodegradability of CDOM in Lake Taihu and the connecting channels will be unraveled using a combination of CDOM absorption, fluorescence, stable isotopes, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and laboratory bio-incubation experiment. Finally, combined with net inflow runoff to the lake from different sub-watersheds, this project aimed to unravel how water exchange between different lake regions and the connecting channels, including inflow runoff to the lake and backflow runoff to the connecting channels, may quantitatively control the sources and composition of CDOM in Lake Taihu watershed. This project will help revealing the inland carbon cycling and the driving mechanisms, and water environment protection for lake waters.

天然水体中溶解性有机物是全球最大的有机碳库，作为其重要成分的有色可溶性有机物的迁移转化过程直接影响全球碳循环及气候变化。大型冲积平原区湖泊承接流域范围内营养物质输入，水体中有色可溶性有机物浓度较高，是内陆碳循环的重要枢纽。太湖流域地势低平，河流、渠道及港汊闸坝等密集，受人类活动(筑坝)、台风过境及潮汐等因素影响，太湖与周边连通河道之间水交换过程频繁，连通河道水流方向往复不定。本项目以太湖及周边河道为研究对象，基于光谱吸收、三维荧光、稳定性同位素及傅里叶变换离子回旋高分辨率质谱等方法及室内生物培养实验，揭示太湖有色可溶性有机物来源、组成及生物可利用性的时空分布格局。在此基础上结合各湖区净入湖径流量，定量揭示不同湖区有色可溶性有机物来源与组成对相应子流域湖泊与河道之间水交换过程(入湖及倒灌径流量)的响应机制，为准确把握内陆水体碳循环及其驱动机制以及湖泊水环境管理提供科学依据。

溶解性有机物（DOM）是天然有机质最重要的赋存形态及活跃成分，有色DOM（CDOM）是DOM中能够强烈吸收紫外辐射的部分。CDOM来源于陆地土壤淋溶和人类生产生活产生的有机质、藻类新陈代谢或降解释放物质，由复杂的有机分子组成。河口三角洲区域湖泊水流在特定的人类活动、气候和潮汐作用下流向往复不定，河-湖系统间水交换尤其是子流域净来水量（Qnet）如何影响各湖区DOM归趋的相关报道较为鲜见。针对科学问题冲积平原区大型浅水湖泊DOM来源与组成多方法联合识别及DOM来源组成对流域水交换过程的响应，本项目开展包括历史数据的收集、野外样品采集及原位与室内模拟实验三个部分。获取了太湖各子流域长时间序列逐月净来水量。基于2018-2021年太湖及周边连通51条河流野外观测数据及历史监测数据，获得了太湖及周边入出湖河流DOM光谱特征、稳定性同位素δ13C-DOC（溶解性有机碳）和δ15N-TDN（溶解性总氮）及傅里叶变换离子回旋超高分辨率质谱（FT-ICR MS）所揭示DOM分子组成信息。开展了室内生物培养实验，揭示出太湖及周边入出湖河道DOC的生物可利用性水平。在此基础上厘清了太湖及周边河流不同水文季节不同湖区DOM来源组成及生物可利用性的时空分异格局及对各子流域水交换过程尤其是各湖区DOM组成对子流域净来水量（Qnet）的响应机制，为准确把握平原区大型浅水湖泊碳循环及其驱动机制以及湖泊水环境管理提供科学依据。项目执行期间发表基金标注的研究论文34 篇，其中SCI论文20篇且均为二区以上，包括TopSCI论文19篇，EI或CSCD论文14篇，授权发明专利3项，软件著作权2项，编写论著1本，参编论著1部。获得2021年度生态环境部环境保护科学技术奖二等奖一项（排名第7）。项目资助联合培养硕士生3名，超额完成了计划书中的预期目标。