State Key Laboratory of Green Pesticide; Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Center for R&D of Fine Chemicals of Guizhou University, Guiyang, 550025, China.
Environmental and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China.
Environ Geochem Health. 2024 Jul 29;46(9):350. doi: 10.1007/s10653-024-02131-y.
Dissolved organic matter (DOM), a pivotal component in the global carbon cycle, plays a crucial role in maintaining the productivity and functionality of aquatic ecosystems. However, the driving factors of variations in the properties of riverine DOM in tropical islands still remain unclear. In this study, the spatiotemporal response of the optical characteristics of riverine DOM to seasonality and land use on Hainan Island in southern China was investigated. Our results revealed that DOM in the rivers of Hainan Island exhibited a relatively high proportion of fulvic acid and demonstrated strong terrestrial sources. The optical properties of DOM exhibited significant variations both seasonally and spatially. Land use exerted a dominant influence on riverine DOM. Specifically, during the wet season, riverine DOM exhibited larger molecular weight, increased chromophoric DOM (CDOM) abundance, and higher Fmax compared to the dry season. Furthermore, riverine DOM influenced by grassland and farmland showed higher CDOM abundance, Fmax, and humification degree in contrast to those impacted by forest and urban. Random forest and correlation analysis results indicated that grassland and farmland enhanced the Fmax of DOM by increasing levels of TP, NO-N, Chl a, and NH-N in the dry season. However, during the wet season, the increased Fmax of DOM induced by grassland and farmland relied on the increments of Chl a and TP concentrations. This study improves our understanding of the spatiotemporal fluctuations of DOM in the rivers of Hainan Island, highlighting the effects of season and land use on DOM. It offers valuable support for improving water quality and contributes to enhancing human comprehension of the global carbon cycle.
溶解有机质（DOM）是全球碳循环的关键组成部分，对维持水生生态系统的生产力和功能起着至关重要的作用。然而，热带岛屿河流水体 DOM 性质变化的驱动因素仍不清楚。本研究调查了中国南部海南岛河流水体 DOM 的光学特性对季节性和土地利用的时空响应。结果表明，海南岛河流 DOM 中富里酸的比例相对较高，具有强烈的陆源特征。DOM 的光学性质在季节性和空间上均发生显著变化。土地利用对河流水体 DOM 具有主导影响。具体而言，在雨季，河流水体 DOM 的分子量较大，色生源 DOM（CDOM）丰度增加，Fmax 值较高，与旱季相比。此外，受草地和农田影响的河流水体 DOM 的 CDOM 丰度、Fmax 和腐殖化程度高于受森林和城市影响的河流水体 DOM。随机森林和相关分析结果表明，在旱季，草地和农田通过增加 TP、NO-N、Chl a 和 NH-N 水平来增强 DOM 的 Fmax。然而，在雨季，草地和农田对 DOM 的 Fmax 的增加依赖于 Chl a 和 TP 浓度的增加。本研究提高了我们对海南岛河流 DOM 时空波动的认识，强调了季节和土地利用对 DOM 的影响。它为改善水质提供了有价值的支持，并有助于提高人类对全球碳循环的理解。
