西辽河沉积物中不同粒径微团聚体磷的解吸特征

采用平衡解吸法研究了西辽河沉积物不同粒径微团聚体磷的解吸特征.结果表明,不同粒径团聚体磷的解吸比例为黏粒(0.20)<粉粒(0.28)<细砂(0.45)<粗砂(0.93);其原因为:细粒级微团聚体中腐殖质含量远远高于粗粒级;细粒级微团聚体中有机质是通过可溶有机质与黏土矿物相互结合形成复合体而富集,在其所形成的复合体团聚结构中引起的团聚体结构不可逆形变是导致磷的解吸比例降低,解吸迟滞性指数增大的根本原因;西辽河冲泻质泥沙黏粒和粉粒级微团聚体所携载的可解吸态磷(NAP)入海后可分别为上覆水提供磷(212.93±38.60)mg/kg,(159.45±31.44)mg/kg.沉积物黏粒级和粉粒级微团聚体所携载的NAP是磷素循环的重要组成部分.

Desorption characteristic of phosphorus from different grain sizes micro-aggregate of sediment in Western Liao River

Desorption characteristics of phosphorus from different grain sizes micro-aggregate of sediment in Western Liao River was investigated by batch experiments of equilibrium desorption. Results indicated that order of desorption ratio was: clay (0.20)< silt (0.28)< fine sand (0.45)< coarse sand (0.93). On the one hand, humus content of fine-grained size was higher than coarse-grained size aggregate. On the other hand, organic matter of fine-grained size aggregate was enriched by complexes, which were dissoluble organic matter combined with clay mineral, and irreversible transformation of aggregate structure was fundamental cause of desorption ratio lower and hysteresis index higher. Furthermore, releasing flux of adsorption state phosphorus carried by clay and silt were (212.93±38.60)mg/kg and (159.45±31.44)mg/kg when sediment was washed from Western Liao River to the sea. Consequently, adsorption state phosphorus from clay and silt was a vital part of phosphorus cycling.