Zhang Siqi, Yin Yongguang, Yang Peijie, Yao Cong, Tian Shanyi, Lei Pei, Jiang Tao, Wang Dingyong
Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, Department of Environmental Sciences and Engineering, College of Resources and Environment, Southwest University, Chongqing 400716, China.
Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Institute of Environment and Health, Jianghan University, Wuhan 430056, China.
Water Res. 2023 Apr 1;232:119644. doi: 10.1016/j.watres.2023.119644. Epub 2023 Jan 18.
Dissolved organic matter (DOM) is an essential component of environmental systems. It usually originates from two end-members, including allochthonous and autochthonous sources. Previously, links have been established between DOM origins/sources and its biogeochemical reactivities. However, the influence of changes in DOM characteristics driven by end-member mixing on DOM biogeochemical reactivities has not been clarified. In this study, we investigated variations of DOM reactivities responding to the dynamics of DOM characteristics induced by different mixing ratios of two DOM end-members derived from humic acid (HA) and algae, respectively. Four biogeochemical reactivities of DOM were evaluated, including biodegradation, ·OH production, photodegradation, and redox capacity. Results showed that the variations of DOM characteristics due to the two end-members mixing significantly impact its biogeochemical reactivities. However, not all spectral parameters and reactivities followed the conservative mixing behavior. In contrast to reactivities of ·OH production and redox capacity, mixed samples showed apparent deviations from conservative linear relationships in biodegradation and photodegradation due to the interaction between the two end-members. Regarding the role of DOM properties influencing reactivity changes, peak A and M were recognized as the most stable parameters. However, peak C and SUVA were identified as the most vital contributors for explaining DOM reactivity variations. These findings suggest that a general model for describing the dynamic relationship between DOM source and reactivity cannot be proposed. Thus, the dynamics of DOM reactivity in diverse ecosystems cannot be estimated simply by the "plus or minus" of the reactivity from individual end-member. The effect of end-member mixing should be evaluated in a given reactivity instead of generalization. This study provides important insights for further understanding the dynamics of DOM's environmental role in different ecosystems influenced by variations of source inputs. In future, more field investigations are needed to further verify our findings in this study, especially in the scenario of end-member mixing.
溶解有机物（DOM）是环境系统的重要组成部分。它通常源自两种端元，包括外源和内源。此前，已建立了DOM来源与其生物地球化学反应性之间的联系。然而，由端元混合驱动的DOM特性变化对DOM生物地球化学反应性的影响尚未阐明。在本研究中，我们调查了DOM反应性的变化，该变化响应于分别源自腐殖酸（HA）和藻类的两种DOM端元不同混合比所诱导的DOM特性动态变化。评估了DOM的四种生物地球化学反应性，包括生物降解、·OH生成、光降解和氧化还原能力。结果表明，由于两种端元混合导致的DOM特性变化显著影响其生物地球化学反应性。然而，并非所有光谱参数和反应性都遵循保守混合行为。与·OH生成和氧化还原能力的反应性不同，由于两种端元之间的相互作用，混合样品在生物降解和光降解方面表现出明显偏离保守线性关系的情况。关于DOM性质对反应性变化的作用，峰A和M被认为是最稳定的参数。然而，峰C和SUVA被确定为解释DOM反应性变化的最重要因素。这些发现表明，无法提出一个描述DOM来源与反应性之间动态关系的通用模型。因此，不同生态系统中DOM反应性的动态变化不能简单地通过单个端元反应性的“加或减”来估计。应在给定的反应性中评估端元混合的影响，而不是一概而论。本研究为进一步理解受源输入变化影响的不同生态系统中DOM环境作用的动态变化提供了重要见解。未来，需要更多的实地调查来进一步验证本研究中的发现，特别是在端元混合的情况下。
