Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control and Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET), School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing, 210044, China.
Nanjing Research Institute of Ecological and Environmental Sciences, Nanjing, 210013, China.
Environ Res. 2023 Dec 1;238(Pt 2):117247. doi: 10.1016/j.envres.2023.117247. Epub 2023 Sep 27.
Freshwater lakes undergo substantial alterations of the phosphorus (P) cycle in the water-sediment ecosystem due to thermal change. The impact process of seasonal fluctuation on P cycling in sediments has been scarcely investigated. P forms in sediments from a freshwater lake in China were analyzed using sequential extraction technique. The vertical distribution of soluble reactive P (SRP), Fe, and S in the interstitial water was measured using diffusion gradient technique (DGT). Fick's Law and DIFS model were used to obtain the diffusion fluxes of SRP and the kinetic parameters in the water-sediment system. The results showed that total P (TP) concentrations in the solid sediments varied from 207.5, 266.6 and 130.3 mg/kg to 614.7, 1053.1, and 687.6 mg/kg in winter, spring, and summer, respectively. The concentrations of individual P forms in spring were higher than those in other seasons, with Fe-bound P (Fe-P) concentration being the highest across all seasons. Notably, significant variations of SRP concentrations were found in the interstitial water between sedimentary depths of approximately 2 cm and 6 cm, particularly in the summer. Furthermore, higher diffusion fluxes of SRP through the interface were found in summer. A stable anaerobic environment failed to develop in spring with high water level, preventing the desorption of solid Fe-P and diffusion of Fe into the water due to the afflux and deposition of P-containing particulate into deeper sediment layers along with organic material. Under extreme high-temperature in summer, decreased rainfall and rising temperatures boosted the activity of aquatic organisms in the water, thereby reducing P fixation by sediments and leading to P release. This process increased the risk of P excess and potential eutrophication in the water. Generally, clarifying the resupplying processes of endogenous P in sediment systems experiencing seasonal variations is critical for eutrophication management of lakes.
淡水湖泊由于热变化而在水-沉积物生态系统中经历了大量的磷（P）循环改变。季节性波动对沉积物中 P 循环的影响过程尚未得到充分研究。本研究采用连续提取技术分析了中国淡水湖泊沉积物中的 P 形态。采用扩散梯度技术（DGT）测量了间隙水中可溶性反应性 P（SRP）、Fe 和 S 的垂直分布。采用菲克定律和 DIFS 模型获得了水-沉积物系统中 SRP 的扩散通量和动力学参数。结果表明，固相沉积物中的总磷（TP）浓度在冬季、春季和夏季分别为 207.5、266.6 和 130.3mg/kg 至 614.7、1053.1 和 687.6mg/kg。春季各季节个体 P 形态的浓度均高于其他季节，其中 Fe 结合态 P（Fe-P）浓度最高。值得注意的是，在夏季，在大约 2cm 和 6cm 沉积深度之间的间隙水中发现了 SRP 浓度的显著变化。此外，在夏季通过界面的 SRP 扩散通量更高。春季高水位导致稳定的厌氧环境无法形成，阻止了固相 Fe-P 的解吸和 Fe 向水中扩散，因为含 P 颗粒物质与有机物质一起沿着堆积和沉积到更深的沉积物层中。在夏季极端高温下，降雨量减少和气温升高，增加了水中水生生物的活动，从而减少了沉积物对 P 的固定，导致 P 释放。这一过程增加了水中 P 过剩和潜在富营养化的风险。一般来说，阐明经历季节性变化的沉积物系统中内源 P 的补给过程对于湖泊富营养化管理至关重要。
