不同干燥方式对湖泊沉积物磷提取的影响

Effects of Different Drying Modes on Characteristics of Phosphorus Forms in Lake Sediment

以滇池5个典型区域表层沉积物为例,研究了自然风干、低温烘干和真空冻干等3种干燥方式对沉积物中磷的形态含量及其生物有效性测定的影响。结果表明:烘干、风干过程促进了沉积物有机磷的降解转化和微生物磷的释放,导致有机磷的含量偏低,总磷含量却比冻干高。各形态磷受不同干燥方式的影响程度不同,风干样品中BD-P较高,冻干样品中NaOH-rP含量最高,NH4Cl-P、HCl-P、残渣磷(Residual-P)由于含量较低或其化学性质比较稳定而差异不大。冻干样品中生物可利用磷分别比风干、烘干高26.7%、20.2%,表明冻干处理能较为真实地反映沉积物中磷的组成特征,是比较理想的样品干燥方式。各形态含量顺序为:藻类可利用磷(AAP)>NaHCO3可提取磷(Olsen-P)>水溶性磷(WSP)>易解吸磷(RDP)。沉积物中Olsen-P与NH4Cl-P、BD-P、NaOH-rP、活性磷及上覆水体总磷水平呈显著正相关,因此可作为评价滇池沉积物磷的生物有效性的重要指标。

Effects of three different drying modes,including air-drying,oven-drying,and vacuum freeze-drying modes,on the determination of phosphorus（P） forms and their bioavailabilities in five typical surface sediments from the Dianchi Lake were investigated.Results show that the content of organic P is underestimated due to its degradation and microbial biomass P release by oven-drying and air-drying,while total P is higher than that by freeze-drying.Effects of three drying modes on P forms appear to be different.BD-P is higher in air-dried sediments,NaOH-rP is the highest by freeze-drying,whereas NH4Cl-P,HCl-P and residual-P have little difference because of low contents and their stability.Contents of bioavailable P in freeze-dried sediments are 26.7% and 20.2% higher than those by oven-drying and air-drying,respectively,suggesting that freeze-drying could reflect the actual condition of lake sediments.Hence,this pretreatment seems to be the best drying mode.Content of different bioavailable P is followed by the order of AAP（alga available phosphorus）Olsen-P（NaHCO3 extractable phosphorus）WSP（water-soluble phosphorus）RDP（readily desorbed phosphorus）.Olsen-P is positively related with NH4Cl-P,BD-P,NaOH-rP,and labile P in sediment,as well as the P concentration in the overlying water,indicating the appropriate index for evaluating P bioavailability in sediments from Dianchi Lake.