Study On Mechanisms Of In-situ Organic Phosphorus Control By Zeolite In Shallow Lake Sediments

The internal contamination has played a significant role in eutrophication afterexternal contamination was effectively controlled. The lake sediments in-situ controltechnology has made a good progress in the past years. However, the theory ofphosphorus release and precipitation can’t fully explain the whole life process ofnutrition,the control effect of eutrophication is not satisfactory. Combined with thehigh output features of natural zeolite, zeolite capping is selected to explore the releaseand transformation mechanisms of organic phosphorus control.Phosphorus, an essential element for the growth of aquatic organisms such as algeis a key factor of the internal nutrition loading when existing in the lake sediments. Inthis study the shallow lake sediments is in-situ covered by the nature zeolite, thus anenvironmental system consisted by water body, zeolite, sediments and aquaticorganisms is created. This paper mainly disscussed the release and transformationmechanisms of moderately labile organic phosphorus (MLOP) and moderately resistantorganic phosphorus (MROP) and the effect on these from zeolite and aquaticorganisms.The sediment extracted from Yunying Lake, located in Changsha University ofScience and Technology, is taken as the research object. The experiment was run underdifferent simulated laboratory conditions (pH value, temperature, particle sizes, lightand dissolved oxygen). The release mechanisms of MLOP and MROP was studied aswell as the mechanisms of their transformation to inorgainc phosphorus. Further theorganic phosphorus absorption by zeolite and aquatic organisms was also investigated.The results showed that: the release of MLOP under weak acidic environment andMROP under weak alkaline environment are more readily achieved compared with thatunder neutral environments. Low temperature and light both promotes the release ofMLOP and MROP. Particle sizes has no apparent effect. The release of MLOP isprohibitted by high dissolved oxygen (DO) concentration, while DO concentration hasno effect on MROP. The content of aluminum phosphate (AP) and iron phosphate (IP)have relevance with that of MLOP with a correlation coefficient of0.9177at25℃,light conditions, when the particle size is20mesh. However no such relevance wasobserved between AP, IP and MROP. The phosphorus released from sediments isreadily absorbed by zeolite in the weak acidic or weak alkaline water body, high temperature and DO concentration. The growth of diatom could also consumephosphorus.