长江中下游与云南高原湖泊沉积物磷形态及内源磷负荷

为揭示长江中下游与云南高原湖泊沉积物磷形态及沉积物-水界面磷负荷特征,探讨其区域差异性及主要影响因素,分析了区域内9个湖泊100个沉积物样品总磷(TP)及不同形态磷含量,比较了不同湖泊沉积物-水界面磷负荷.结果表明,云南高原湖泊沉积物ω(TP)为(1256±621)mg/kg,高于长江中下游湖泊(601±76)mg/kg];前者沉积物磷形态以钙结合态磷(HCl-P)为主,主要受水土流失等影响,湖泊较高的矿化度易于磷埋藏,且沉积物有机质含量较高,减缓了磷的移动能力,其沉积物-水界面磷负荷为0.17~1.07mg/(m2·d),对湖泊富营养的贡献较小;而长江中下游湖区湖泊沉积物磷形态以可还原态磷(BD-P)等形态为主,主要由面源及浮游植物生长调控,其中可移动磷(Mobile-P,除残渣态磷(Res-P)和HCl-P以外的所有形态磷之和)相对含量占ω(TP)的60.60%,约为云南高原湖泊的2倍,其沉积物-水界面磷负荷为0.002~1.32mg/(m2·d),对湖泊富营养化贡献较大.由此可见,长江中下游湖区湖泊应该加强流域面源污染等外源治理,修复退化水生植被,而在云南高原湖泊则应重点加强流域水土流失治理,施行农田最佳施肥等措施.

Sediments phosphorus forms and loading in the lakes of the mid-lower reaches of the Yangtze River and Yunnan Plateau,China

Differences of phosphorus forms in lake sediments and its flux across the sediment-water interface (SWI Pflux) between lakes located in the Middle and Lower Yangtze River drainage basin (MLYR) and those in the Yunnan Plateau (YN) were determined. The average ω(TP) in YN was (1256±621) mg/kg, which was higher than that in MLYR (601±76)mg/kg]. Soil erosion resulted in the higher content of calcium bound phosphorus (HCl-P) in the sediments of YN, and the high salinity of their lake water were conductive to phosphorus burial. High organic matter content in sediments also inhibited the migration of phosphorus in lakes of YN, and the SWI Pflux was 0.17~1.07mg/(m2·d). However, in MLYR phosphorus forms were closely related to non-point source nutrient pollution and phytoplankton bloom, and redox sensitive phosphorus (BD-P) accounted for the majority of TP. The potential mobile phosphorus (the sum of loosely adsorbed P, BD-P, NaOH bound P) accounted for 60.60% of TP, which was around 2 times of that in YN, and its SWI Pflux was 0.002~1.32mg/(m2·d). Thus, measures including reducing agricultural nonpoint source pollution, maintaining and recovering macrophytes in lakes should be taken to improve water quality in MLYR. However, preventing the soil erosion, and implementing the best nutrient management practices are more important in the watershed of YN.