洱海沉积物中不同形态磷的时空分布特征

为揭示洱海沉积物磷形态变化的影响因素及其内源磷负荷状况,研究了洱海沉积物中不同形态磷的空间分布和季节性变化特征. 结果表明,洱海表层沉积物中w(TP)为418.71～1108.34mg/kg,空间分布总体呈中部湖区＞南部湖区＞北部湖区；w(IP)为302.35～871.00mg/kg,分布趋势与w(TP)相同；w(Fe/Al-P)为36.22～406.40mg/kg,与w(IP)分布趋势相同；w(Ca-P)为172.34～420.38mg/kg,北部最高；Fe/Al-P和Ca-P是IP的主要形态. 夏季(7月)w(TP)、w(IP)和w(Fe/Al-P)升高,w(labile-P)(labile-P为弱吸附态磷)和w(Fe/Al-P)季节性差异显著. 沉积物柱状样w(TP)、w(OP)、w(labile-P)和w(RSP)(RSP为可还原态磷)随着沉积物深度的增加呈下降趋势,表层富集明显；w(IP)、w(Fe/Al-P)和w(Ca-P)随深度的增加呈上升趋势. 洱海沉积物磷时空分布主要受外源磷输入影响,随水深增加沉积物中w(TP)呈升高趋势,不同形态磷分布受水生生物活动影响较大. 与长江中下游湖泊相比,洱海沉积物中w(TP)高,其中w(IP)及其所占w(TP)的比例较小,磷内源可释放量较低,Fe/Al-P和RSP等生物可利用磷的质量分数及其占w(TP)的比例较大,释放风险较高. 

Characteristics of Temporal and Spatial Distribution of Different Forms of Phosphorus in the Sediments of Erhai Lake

The factors affecting phosphorus morphological changes and the situation of endogenous phosphorus loading were investigated through study of the spatial and temporal variations of different forms of phosphorus in the surface sediments of Erhai Lake. The results showed that in the surface sediments the contents of TP were between 418.71and 1108.34mg/kg and the overall trends of spatial distribution were from high to low in the central, southern and northern. The contents of IP were ranged from 302.35and 871.00mg/kg,and its spatial distribution trends were same as that of TP. The contents of Fe/Al-P were ranged from 36.22to 406.40mg/kg, which were same as that of IP. The contents of Ca-P were ranged from 172.34to 420.38mg/kg, with the highest in the north, and Fe/Al-P and Ca-P were the main forms of IP. The contents of TP, IP and Fe/Al-P had increased in July. The contents of labile-P and Fe/Al-P significantly varied with the season change. The contents of TP, OP, labile-P and RSP of the core samples collected from the sediments showed a decreasing trend with the depth increase and were rich in the surface. Meawhile, the contents of IP, Fe/Al-P and Ca-P reversely showed a increasing trend. Temporal and spatial distributions of phosphorus in the sediments of Erhai Lake were mainly affected by the phosphorus input phosphorus from the external source. With the water depth increasing, the contents of phosphorus in sediment increased, and the activities of aquatic organisms had a great impact on the distribution of different forms of phosphorus. Compared with lakes in the middle and lower reaches of the Yangtze River, the contents of TP in the sediment of Erhai Lake were higher, but the content of IP and its proportion in the TP were relatively low. The content of endogenous releasing phosphorus was low, and the surface enrichment of TP was significant. The contents of phosphorus and its proportion in the TP that could be used by aquatic organisms such as Fe/Al-P and RSP, and its releasing risk were higher.