太湖梅梁湾水华生消对沉积物磷迁移转化的影响

Effect of outbreak and extinction of algal bloom on the migration and transformation of phosphorus in sediment of Meiliang Bay,Lake Taihu

湖泊水华通常会影响沉积物中磷的迁移转化,但该现象的背后机制目前尚不明晰.本研究在太湖梅梁湾开展了一周年的月度采样,依据湖水叶绿素a(Chl a)浓度的月度变化,判定6-9月为水华期,其他月为非水华期.通过对比研究发现,水华生消对沉积物中磷迁移转化有重要影响:水华期沉积物总磷含量显著增加,其中,沉积物铁结合态磷(Fe-P)平均含量减少了11.98%,而沉积物中铝结合态磷、有机磷和弱吸附态磷平均含量却分别增加了12.63%、15.05%和45.83%,沉积物钙结合态磷和残渣磷含量无明显变化;水华期沉积物间隙水中溶解态活性磷(SRP)平均浓度(0.73 mg·L^(-1))和平均扩散通量(2.16 mg·m^(-2)·d^(-1))均显著增加,分别达到非水华期的3.06倍和6.75倍.结构方程模型结果显示,水华可能通过降低沉积物中DO浓度和增加沉积物中溶解性有机质含量,促使沉积物中Fe-P溶解释放磷,从而增加沉积物中SRP浓度和释放通量.本研究深化了人们对富营养化湖泊沉积物中磷迁移转化的认识.

Algal blooms usually affect the migration and transformation of phosphorus in sediment,but the underlying mechanism of this phenomenon is currently unclear.We conducted a one-year monthly sampling in Meiliang Bay,Lake Taihu.Based on the monthly variation of Chl a concentration in lake water,we classified the months of June-September as algal blooms stage,and the other months are as non-algal blooms stage.By the comparison analysis,it was found that the outbreak and extinction of algal blooms had an important impact on the migration and transformation of phosphorus in sediments:during the algal blooms,the content of total phosphorus in sediment significantly increased,with the average content of iron bound phosphorus(Fe-P)in sediment decreasing by 11.98%,the average content of aluminum bound phosphorus,organic phosphorus,and loosely adsorbed phosphorus in sediment increasing by 12.63%,15.05%and 45.83%,respectively.There was no significant change in the content of calcium bound phosphorus and residual phosphorus in sediment.The average concentration(0.73 mg·L^(-1))and release flux(2.16 mg·m^(-2)·d^(-1))of soluble reactive phosphorus(SRP)in pore water of sediment during the algal blooms significantly increased,which were 3.06 and 6.75 times of those during non-algal blooms,respectively.The results of the structural equation model indicate that algal blooms should promote the dissolution of Fe-P in sediment by reducing DO concentration and increasing dissolved organic matter content,thereby increasing the concentration and release flux of SRP in sediment.This study contributes to the deepening of understanding on the migration and transformation of phosphorus in sediments of eutrophic lakes.