Fractions and distribution characteristics of organic phosphorus in the sediment of the water level fluctuation zone of Lake Nansi

Abstract

研究南四湖消落带底泥有机磷赋存形态及分布特征,有利于全面揭示湖区各形态磷迁移转化规律,对南四湖富营养化防控及南水北调东线调水水质保障具有重要的科学意义。以南四湖消落带底泥为研究对象,采用改进Hedley连续分级提取法测定底泥中各形态有机磷含量,通过紫外可见分光光谱与三维荧光光谱技术表征底泥有机分子结构特征及稳定性,反映消落带有机磷结构及稳定性差异,运用Pearson相关性分析及主成分分析解析底泥各形态磷与其他理化指标的相关性。研究结果表明,南四湖消落带底泥总磷含量均值为679.90 mg/kg,其中有机磷(OP)占比20.03%~45.69%。各赋存形态有机磷含量及相对比例大小依次为:残渣态有机磷(67.58%)＞钙结合态有机磷(16.61%)＞铁/铝结合态有机磷(7.62%)＞碳酸氢钠提取态有机磷(5.97%)＞水提取态有机磷(2.22%)。南四湖消落带底泥OP含量及形态主要受内源影响,主要来自内源性微生物代谢。南四湖消落带西岸底泥磷释放风险高于东岸和南岸消落带。相关性分析发现,消落带底泥pH与磷含量显著负相关,表明随着底泥碱性的增强可能导致底泥磷向水体中释放的风险更高;底泥有机质与OP显著正相关,表明有机质可能是OP的重要载体;主成分分析发现底泥各形态磷呈正相关性,表明消落带底泥各形态磷具有同源性。研究结果可为南四湖湖区内源磷释放控制及富营养化风险防控提供科学依据。;The study of the fractions and distribution characteristics of organic phosphorus in the sediment of the water level fluctuating zone of Lake Nansi is conducive to revealing the transformation of phosphorus in the lake, and has important scientific significance for controlling the eutrophication of Lake Nansi. Based on the sediment of the water level fluctuation zone of Lake Nansi, the improved Hedley continuous grading extraction, ultraviolet-visible spectroscopy and three-dimensional fluorescence spectroscopy were used to characterize the structural characteristics and stability of organic molecules in the sediment, and to reflect the differences in the structure and stability of organophosphates in the water level fluctuating zone; and the Pearson correlation analysis and principal component analysis were used to determine the correlation of various fractions of phosphorus and other physical and chemical indicators. The results showed that the average content of total phosphorus (TP) in the sediment of the water level fluctuation zone of Lake Nansi was 679.90 mg/kg, and the proportion of organic phosphorus (OP) was 20.03%-45.69%. The contents and relative proportions of organic phosphorus in each occurrence form were as follows: Residual organic phosphorus (Residual-Po, 67.58%) > calcium bound organic phosphorus (HCl-Po, 16.61%) > iron/aluminium bound organic phosphorus (NaOH-Po, 7.62%) > potentially active organic phosphorus (NaHCO₃-Po, 5.97%) > weakly adsorbed organic phosphorus (H₂O-Po, 2.22%). The content and fractions of OP in the sediment in the water level fluctuation zone of Lake Nansi were mainly influenced by endogenous sources, mainly from the metabolism of endogenous microorganisms. The risk of sediment phosphorus release in the fluctuating water level zone of the west bank of the lake was higher than that of the east and south banks. Correlation analysis showed that there was a significant negative correlation between sediment pH and phosphorus content in the fluctuating zone, indicating that the increase in sediment alkalinity may lead to a higher risk of phosphorus release to water. There was a significant positive correlation between organic matter and OP (R²=0.719, P<0.01), indicating that organic matter may be an important carrier of OP. Principal component analysis showed that all phosphorus fractions in the sediment were positively correlated, indicating that all phosphorus fractions in the water level fluctuation zone had homology. The results can provide a scientific basis for controlling the release of endogenous phosphorus and the risk of eutrophication in Lake Nansi.