洱海沉积物中磷的赋存形态

利用磷连续提取方法浸提洱海沉积物弱吸附态磷、Fe P、Al P、Ca P和残渣磷，采用石灰性土壤无机磷形态分级法对Ca P进行了分级〔Ca2 P、Ca8 P和惰性钙磷(主要为Ca10 P)〕. 结果表明，洱海沉积物中w(TP)(710.30~1 961.23 mg/kg)较高，以无机磷(占64.44%~82.04%)为主，其中较易释放到上覆水中的弱吸附态磷含量〔占w(TP) 1%以下〕、w(Ca2 P)(14.63~29.66 mg/kg)和w(Ca8 P)(14.62~31.24 mg/kg)均较低，并且洱海目前环境条件不利于其沉积物中Al P和Fe P的释放. 沉积物中w(Ca P)及w(残渣磷)均较高，Ca P中惰性钙磷所占比例(＞85%)也较高，导致洱海沉积物磷不易被释放到上覆水中. 沉积物无机磷赋存形态是洱海目前水质较好的原因之一. 如果污染进一步加剧引起洱海水体pH增加和ρ(DO)降低等变化，其沉积物中Al P、Fe P的释放风险将可能增加. 近30年来，洱海沉积物w(Ca2 P)和w(Ca8 P)变化较小，但w(惰性钙磷)变化较大，Ca P各组分之间存在相互转化机制，这与洱海沉水植物的生长以及其对Ca P的吸收、转化有关. 

Fractions of Phosphorus in Sediments of Lake Erhai

A sequential phosphorus extraction method was used to extract the loosely-bound reactive phosphorus,Fe-P,Al-P,calcium phosphorus(Ca-P),and the refractory-bound reactive phosphorus from the sediments of Lake Erhai.The extraction method of Ca-P forms in calcareous soil was also used to study Ca2-P,Ca8-P and refractory calcium phosphorus(mainly Ca10-P) in the sediments.The results showed that the content of TP in the sediments of Lake Erhai was very high(710.30-1961.23 mg/kg),and was mainly in the form of inorganic phosphorus(64.44%-82.04%).The contents of the loosely-bound reactive P,which is easily released into the overlying water,Ca2-P(14.63-29.66 mg/kg) and Ca8-P(14.62-31.24 mg/kg) were all low.The current environmental condition of Lake Erhai is not suitable for Al-P and Fe-P release from the sediments.The high contents of Ca-P and residual refractory bound reactive phosphorus in the sediments,and the high proportion(>85%) of the inert calcium phosphorus in Ca-P,prevent the release of phosphorous from the sediments to the overlaying water in Lake Erhai.The characteristic of the fractions of inorganic phosphorus forms in the sediments of Lake Erhai is one of the major factors maintaining the good quality of the water.If the pollution of Lake Erhai becomes worse and causes the increase in pH and decrease of DO concentration in the overlying water,then the risk of Al-P and Fe-P release from its sediments will be significantly increased.The contents of Ca2-P and Ca8-P in the sediments of Lake Erhai changed little during the last 30 years,while the content of the refractory calcium phosphorus(Ca10-P) changed greatly,and there was transformation among different forms of calcium phosphorus.These changes may be related to the aquatic plant growth,as well as the uptake and transformation of Ca-P across different ages in Lake Erhai.