滇池沉积物磷的释放以及不同形态磷的贡献

Release of Phosphorus from Sediment sand Contributions of Different P Forms in Dianchi Lake

在实验室控制条件下,以滇池表层新鲜沉积物为材料,研究了水体溶解氧、pH值对沉积物磷释放的影响以及沉积物不同形态磷对释放的贡献。结果表明,随着水体pH值的升高,沉积物的释磷量明显增加,湖水碱性条件下的释放量是中性条件的几百倍。与好氧条件相比,厌氧状态促进沉积物中磷的释放。可还原态磷是厌氧条件下磷释放的主要形态,碱性条件下金属氧化物结合态磷对沉积物磷释放的贡献很大。滇池北部沉积物磷以金属氧化物结合态磷、有机磷形式为主,钙结合态磷次之,可还原态和弱吸附态磷含量很少。不同形态磷在沉积物剖面总的变化规律为表层含量大于底层。

E ut rophication became more and more serious in the last 20years,and alg a blooms occurred frequently from April to November every year in Dianchi Lake.It has b een recognized that external P load is important for water quality,but internal load also should be taken into account,especially for high eutrophication.In the present study,fresh surface sedime nts were used in laboratory to study the effects of dissolved oxy gen and pH value in lake water on phosp horus(P)rele ase from sediments and the contr ibution of different P forms in sediment to rel e ase in Dianchi Lake.The results show ed that P released amount enhanced wi th the increasing pH value in lake water,and the amount wa s several hundred time s higher in alk aline condition than that in neutral condition.Compared with ae robic condition,P release am ount was much higher under anoxic con dition.In t his paper,sediment P was divided into loosely adsorbed P (NH 4 Cl-P ),redox-sensitive P(BD-P ),metal oxides bound P (NaOH-P ),calcium bound P (HCl-P )and or-ganic P(Org-P ).NH 4 Cl-P represents the loosely adsorbed P,this fraction may contain porewa t er P,released from CaCO 3-associated phosphorus or leached P f rom decaying cells of bacterial biom ass in deposited phytodetrital aggregates.BD-P represents the redox-sensiti ve P forms,mainly bound to Fe-hydroxides and Mn compou nds.The NaOH-P repr esents P bound to metal oxide,mainly of Al and Fe,which is exchangeable again with OH-and inorganic P compound soluble in bases.The HCl-P represents P f orms sensitive to low p H,assumed to consist mainly of apatite P,P bound to ca rbonates and traces of hydrolysable organic P.The results of release showed tha t BD-P was the main release forms under anoxic condition and the con tribution of NaOH-P to release was significant in alkaline condition.NaOH-P and Org-P were the main P forms in sediments fr om the northern Dianchi Lake,HCl-P follow ed,and the concentrations of BD-P an d NH 4 Cl-P were low.Vertical profile of se diment showed an increasing total P concent rations towards the sediment surfac e.