Characteristics of Organic Phosphorus Fractions in the Sediments of the Black Water Aggregation in Lake Taihu

Abstract

Potential release of phosphorus in lake sediments depends largely on the fractions and distribution of organic phosphorus. MaoDu was chosen as the research area in the west of Lake Taihu. The chemical forms of the surface sediments were investigated by the Ivannoff extraction methods. The results showed that the main organic phosphorus form of sediments at different sampling places was humic acid-OP. It accounted for 35% of the total organic phosphorus. Horizontal distribution: Total organic phosphorus content from the shore to the middle of total showed a trend of rising after decline; vertical distribution: Total organic phosphorus content was the lowest in 2-6 cm and the highest in 4-8 cm. Various phosphorus content followed the order of humic acid-OP > residual-OP > HCl-OP > fulvic acid-OP; the relative content of NaHCO3-OP in the total organic phosphorus content showed a trend of rising followed by reduction and then rising again from the shore to the middle, cyanobacteria residue deposition increased the content of NaHCO3-OP in sediment. Contents of NaHCO3-OP and humic acid-OP both first reduced, then increased and finally reduced in the vertical distribution, the content of NaHCO3-OP was the lowest in 4-6 cm and humic acid-OP was the highest in 4-8 cm. HCl-OP and fulvic-OP decreased with increasing depth in the vertical distribution. The content of residual-OP showed stable tendency in the vertical direction and was about 45 μg·g-1. Labile OP and pH, DO, the depth of water were significantly negatively correlated, OM and NaOH-Pi were significantly correlated with total organic phosphorus, labile OP, moderately labile OP and nonlabile OP. Three components of organic phosphorus had bio-availability and played an important role in lake eutrophication. The increase of the content of labile OP might promote the black water aggregation (BWA) in cyanobacteria accumulation.