POWERCHINA Chengdu Engineering Corporation Limited, Chengdu, 611130, China.
Sichuan Municipal Water Environment Treatment Engineering Technology Research Center, Chengdu, 611130, China.
Bull Environ Contam Toxicol. 2023 Jun 7;110(6):103. doi: 10.1007/s00128-023-03744-2.
Hydrophyte debris decomposition may contribute to phosphorus (P) release from the sediments in riverine systems, but the transport and transformation of organic phosphorus during this process has not been studied well. Here, a ubiquitous hydrophyte in southern China (Alternanthera philoxeroides, A. philoxeroides) was selected to identify the processes and mechanisms of sedimentary P release in late autumn or early spring by laboratory incubation. The results showed that the physio-chemical interactions changed quickly during the beginning of the incubation, where the redox potential and dissolved oxygen at the water-sediment interface decreased rapidly, reaching reducing (299 mV) and anoxic (0.23 mg∙L) conditions, respectively. Soluble reactive P, dissolved total P and total P concentrations in overlying water all increased with time from 0.011, 0.025 and 0.169 mg∙L to 0.100, 0.100 and 0.342 mg∙L on average, respectively. Furthermore, the decomposition of A. philoxeroides induced sedimentary organic P release to overlying water, including phosphate monoester (Mono-P), and orthophosphate diesters (Diesters-P). The proportions of Mono-P and Diesters-P were higher at 3 to 9 days than at 11 to 34 days, being 29.4% and 23.3 for Mono-P, 6.3% and 5.7% for Diesters-P, respectively. Orthophosphate (Ortho-P) increased from 63.6 to 69.7% during these timeframes, which indicated the transformations of both Mono-P and Diester-P to bio-available orthophosphate (Ortho-P), causing the rising P concentration in the overlying water. Our results revealed that hydrophyte debris decomposition in river systems might lead to autochthonous P contribution even without external P import from the watershed, accelerating the trophic state of receiving waterbodies.
水生植物碎屑分解可能导致河流系统沉积物中磷（P）的释放，但在此过程中有机磷的迁移和转化尚未得到很好的研究。本研究选用中国南方常见的水生植物（空心莲子草），通过实验室培养来鉴定深秋或早春期间沉积物中磷释放的过程和机制。结果表明，在培养开始时，理化相互作用迅速发生变化，水-沉积物界面的氧化还原电位和溶解氧迅速下降，分别达到还原（299 mV）和缺氧（0.23 mg·L）条件。上层水中的可溶解性反应磷、溶解总磷和总磷浓度均随时间增加，分别从 0.011、0.025 和 0.169 mg·L 增加到 0.100、0.100 和 0.342 mg·L。此外，空心莲子草的分解导致沉积物中有机磷向水体释放，包括磷酸单酯（Mono-P）和正磷酸盐二酯（Diesters-P）。Mono-P 和 Diesters-P 的比例在 3 至 9 天内高于 11 至 34 天，分别为 29.4%和 23.3%的 Mono-P、6.3%和 5.7%的 Diesters-P。正磷酸盐（Ortho-P）在此期间从 63.6%增加到 69.7%，这表明 Mono-P 和 Diester-P 都转化为生物可利用的正磷酸盐（Ortho-P），导致上层水中磷浓度上升。本研究结果表明，即使没有流域外部磷输入，河流系统中的水生植物碎屑分解也可能导致本地磷的贡献，从而加速受纳水体的富营养化状态。
