[Characteristics and bioavailability of organic phosphorus from different sources of sediments in Dianchi Lake].

The content and vertical distribution characteristics of organic phosphorus were studied by collecting core sediments of Dianchi Lake, characterizing the bioavailability of different organic phosphorus species of these sediments by enzymatic hydrolysis. The results indicated that, (1) The inorganic phosphorus represented primary portions of extractable phosphorus of sediments in Dianchi Lake, except for the H2O extractable organic phosphorus (H2O-P(o)). The rank of order of organic phosphorus fractionation in sediments was NaOH extractable organic phosphorus (NaOH-P(o)) > NaHCO3 extractable organic phosphorus (NaHCO3-P(o)) > H2O-P(o) > HCl extractable organic phosphorus (HCl-P(o)). The vertical distribution of NaOH-P(o), NaHCO3-P(o) and H2O-P(o) with relatively high mobility showed the trend of topper layer > middle layer > bottom layer. (2) Labile monoester P predominated in enzymatically hydrolysable phosphorus (EHP) of sediments in Dianchi Lake. The EHP content of NaOH-P0, NaHCO3-Po and H20-P0 in sediments of Dianchi Lake were 0.11-5.93, 0-45.32 and 0-107.11 mg x kg(-1), respectively. The EHP content of different organic phosphorus species followed the order: NaOH-P(o) > NaHCO3-P(o) > H2O-P(o), with the trend of vertical distribution of topper layer > middle layer > bottom layer. The bioavailability of organic phosphorus of different depth showed the order of topper layer > middle layer > bottom layer. (3) EHP was a considerable source of the bioavailable phosphorus of sediments in Dianchi Lake. The protection of water quality in Dianchi Lake should consider the effects of EHP in sediments. When the external phosphorus load was restricted gradually, the biogeochemical cycle of EHP in sediments might play an important role in maintaining the eutrophication of Dianchi Lake.