Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, College of Urban and Environmental Sciences, Northwest University, Xi'an, 710127, China; State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710061, China.
Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, College of Urban and Environmental Sciences, Northwest University, Xi'an, 710127, China.
J Environ Manage. 2023 Aug 15;340:117984. doi: 10.1016/j.jenvman.2023.117984. Epub 2023 Apr 20.
River ecosystems interact strongly with adjacent terrestrial environments and receive dissolved organic matter (DOM) from a variety of sources, all of which are vulnerable to human activities and natural processes. However, it is unclear how and to what extent human and natural factors drive DOM quantity and quality changes in river ecosystems. Here, three fluorescence components were identified via optical techniques, including two humic-like substances and one protein-like component. The protein-like DOM was mainly accumulated in anthropogenically impacted regions, while humic-like components exhibit the opposite trend. Furthermore, the driving mechanisms of both natural and anthropogenic factors on the variations in DOM composition were investigated using partial least squares structural equation modelling (PLS-SEM). Human activities, especially agriculture, positively influence the protein-like DOM directly by enhancing anthropogenic discharge with protein signals and also indirectly by affecting water quality. Water quality directly influences the DOM composition by stimulating in-situ production through a high nutrient load from anthropogenic discharge and inhibiting the microbial humification processes of DOM due to higher salinity levels. The microbial humification processes can also be restricted directly by a shorter water residence time during the DOM transport processes. Furthermore, protein-like DOM was more sensitive to direct anthropogenic discharge than indirect in-situ production (0.34 vs. 0.25), especially from non-point source input (39.1%), implying that agricultural industry optimization may be an efficient way to improve water quality and reduce protein-like DOM accumulation.
河流生态系统与相邻的陆地环境相互作用强烈，并从多种来源接收溶解有机物质 (DOM)，所有这些来源都容易受到人类活动和自然过程的影响。然而，尚不清楚人类和自然因素如何以及在何种程度上影响河流生态系统中 DOM 的数量和质量变化。在这里，通过光学技术鉴定了三种荧光成分，包括两种腐殖质样物质和一种蛋白质样成分。蛋白质样 DOM 主要在人为影响的地区积累，而腐殖质样成分则呈现相反的趋势。此外，还使用偏最小二乘结构方程建模 (PLS-SEM) 研究了自然和人为因素对 DOM 组成变化的驱动机制。人类活动，特别是农业，通过增强具有蛋白质信号的人为排放，直接对蛋白质样 DOM 产生积极影响，也通过影响水质间接产生影响。水质通过从人为排放中获得高养分负荷来刺激原位生产，从而直接影响 DOM 组成，并由于盐度水平升高而抑制 DOM 的微生物腐殖化过程。微生物腐殖化过程也可以通过 DOM 运输过程中的较短水停留时间直接受到限制。此外，蛋白质样 DOM 对直接人为排放比间接原位生产更敏感 (0.34 对 0.25)，特别是来自非点源输入 (39.1%)，这意味着农业产业优化可能是改善水质和减少蛋白质样 DOM 积累的有效途径。
