Nanjing Institute of Geography and Limnology, State Key Laboratory of Lake Science and Environment, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Molecular Eco-Geochemistry (MEG) Laboratory, Department of Geological Sciences, The University of Alabama, 201-7th Ave, Tuscaloosa, AL 35485, USA.
J Hazard Mater. 2022 Jul 5;433:128791. doi: 10.1016/j.jhazmat.2022.128791. Epub 2022 Mar 26.
Humic acid (HA) and phosphate interactions play a vital role in the biogeochemical cycle of carbon and nutrients and thus the trophic state of a lake. The adsorption behavior of HAs to sediments in the absence and presence of phosphate was investigated in this study. Three types of HAs were used, AHA from algae-dominated lake sediments, MHA from macrophyte-dominated lake sediments, and a reference HA (RHA) with terrestrial sources. The adsorption capacity of lake sediments was highest for AHA, which can be explained by that AHA contained more carboxyl-containing molecules, proteinaceous compounds and polysaccharides that were preferentially adsorbed by minerals. Phosphate showed a stronger inhibitory effect on MHA adsorption than on AHA adsorption, suggesting that AHA can more effectively replace phosphate adsorbed to sediments. Our findings show that the functional groups of organic compounds control not only their fractionation and burial but also their ability to replace phosphate in sediments. We propose a novel mechanism to explain the legacy effect of lake eutrophication. That is, as lakes shift from a macrophyte-dominated state to more eutrophic, algae-dominated state, increasing algae-derived organic compounds can promote the release of phosphate from sediments, forming a positive feedback loop that sustains internal phosphorus loading and hence lake eutrophication.
腐殖酸（HA）与磷酸盐的相互作用对碳和养分的生物地球化学循环以及湖泊的营养状态起着至关重要的作用。本研究考察了在不存在和存在磷酸盐的情况下，HA 对沉积物的吸附行为。使用了三种类型的 HA，藻类占优势的湖泊沉积物中的 AHA、大型植物占优势的湖泊沉积物中的 MHA 和具有陆地来源的参考 HA（RHA）。AHA 对湖泊沉积物的吸附能力最高，这可以解释为 AHA 含有更多的含羧基分子、蛋白质化合物和多糖，这些物质优先被矿物质吸附。磷酸盐对 MHA 吸附的抑制作用强于对 AHA 吸附的抑制作用，这表明 AHA 可以更有效地替代吸附在沉积物上的磷酸盐。我们的研究结果表明，有机化合物的官能团不仅控制着它们的分馏和埋藏，还控制着它们在沉积物中替代磷酸盐的能力。我们提出了一种新的机制来解释湖泊富营养化的遗留效应。也就是说，随着湖泊从大型植物占优势的状态向富营养化的藻类占优势的状态转变，藻类衍生的有机化合物的增加可以促进从沉积物中释放磷酸盐，形成一个正反馈循环，维持内部磷负荷，从而维持湖泊富营养化。
