Seasonal Variation Of Organic Phosphorus Classes And Their Influence Factors In Water Of Taihu Lake

Phosphorus is one of the important nutritional factors which can lead to the Eutrophication of lakes. It is generally believed that orthophosphate can be most vulnerably used by phytoplankton. We always use it to measure the availability of phosphorus in water. But organic phosphorus as an important part of phosphorus, its stability and potential transformation ability can also affect the use of phosphorus in water. To further understand the bioavailability of phosphorus and its contribution to Lake Eutrophication. This paper takes a typical eutrophic lake, Taihu, as the research object, through the method of field sampling and indoor simulation, using 31 P nuclear magnetic resonance technology to analysis the seasonal variation of the composition of organic phosphorus in lake water, and also to explore the relationship between the composition of phosphorus and water environmental factors such as phytoplankton, temperature and dissolved oxygen. The main results of this paper are as follows:(1) The dissolved total phosphorus is composed of phosphonate, orthophosphate, phosphate monoester, phosphate diester and pyrophosphate in Taihu Lake. Phosphonate is mainly distributed in the heavy and moderate pollution zones with high stability, but its seasonal variation is not obvious. Orthophosphate, phosphate monoester and phosphate diester are the main part of dissolved phosphorus and their seasonal variation is obvious, and also the variation are not the same in different pollution zones. In heavy and moderate pollution zones, both the proportion and concentration of orthophosphate are the lowest in July. while they are the lowest in October in the light pollution zone, which is closely related with the species and growth periods of aquatic organisms In different pollution zones. But the change of phosphate monoester in the heavy and moderate pollution zones is opposite with orthophosphate, it is the highest in July. The proportion of phosphate diester is higher in the moderate and light pollution zones, which accounts for more than 60% in October in the light pollution zone. The concentration of phosphate monoester and phosphate diester are the highest in July, and the concentration of orthophosphate and phosphate monoester are the highest in heavy pollution zone.(2) The particulate total phosphorus is composed of orthophosphate, phosphate monoester, phosphate diester, pyrophosphate and polyphosphate in Taihu Lake. And orthophosphate and phosphate monoester are the main parts of the particulate phosphorus, their proportion account for more than 80%. In different pollution zones, the seasonal variations of the particulate phosphorus composition are the same. The concentration of orthophosphate and phosphate monoester is the highest in heavy pollution zone, and it is also the highest in July.(3) The transformation between particulate and dissolved phosphorus is dynamic. When the dissolved oxygen condition is same, the higher temperature can promote the transformation of organic phosphorus to dissolved reactive phosphorus. And when the temperature is same, the anaerobic condition is more conducive to the transformation of some organic phosphorus(phosphate monoester phosphate and diester) and the increase of the concentration of soluble reactive phosphorus than the aerobic condition. Among the different forms of organic phosphorus, DNA can be transformed more easily to soluble reactive phosphorus than AMP, and it can be completed in a short period of time, but CP can be difficultly translated.(4) The influence process of Microcystis Aeruginosa and different organic phosphorus is mutual. To a certain extent, Microcystis Aeruginosa is conducive to the transformation of DNA, AMP and CP, and it also can affect the mineralization of organic phosphorus by increasing the pH in water. The effect of different organic phosphorus on the growth of Microcystis Aeruginosa are different, DNA is more conducive to the long-term growth of Microcystis Aeruginosa than K2HPO4, and the coexistence of AMP, DNA and CP is also more conducive to the long-term growth than AMP, CP alone. And alkaline phosphatase plays an important role in the process of planktonic algae using organic phosphorus, its activity is related with soluble reactive phosphorus and different organic phosphorus.