The Study Of Regularity And Mechanism Of Different Valence Iron On Algal Blooms

Algal bloom, the direct result of eutrophication, is an abnormal ecological phenomena with the algae fulminant value-added result from the change of water environment. It not only destroies the balance of water ecological, but also severely pollution raw water quality which results in increasing cost, lowering quality of finished water, lowering reliability of water supply, threaten human health. As iron is one of the necessary trace elements and plays a huge role in algae growth. The regularity study of different valence iron(Fe2+、Fe3+) on algae growth that is a focus of object and is the key point in probing the cause of algal bloom.Preliminary water quality investigation shows that every sampling lake in Guangzhou Higher Education Mega Center(HEMC) suffers from different degrees of total nitrogen(TN) and total phosphorus(TP) pollution. And the concentration of TN changes between3.541mg/L and48.117mg/L, TP changes between0.02mg/L and3.341mg/L. TN changes gentlly within a year, TP changes severe and irregular. Iron has the largest concentration of investigated trace elements and is influenced by antagonism of iron and manganese. pH and Eh, microbe. Iron concentration ranged from0.2mg/L to1.4mg/L. More than60%of it is Fe2+which dominates.Considering the result of investigations to design the single factor experiment that inspects the influence of different valence iron(Fe2、Fe3+) towards natural algal groups and pure algal groups. The results show that:The effect of different valence iron is significant under the same free concentration. Compared to Fe3+, Fe2+has larger peak value and is more bioavailability which displays a faster promoting aging and a bigger average growth rate; The valence of iron has some influence in algae population structure, and it has guiding effect which Fe2+is more favorable to form the dominant algal groups.There is an optimum iron environment for algae growth, the optimum growth concentration of Fe2+varies from algae species:the optimum concentration of natural algae group is about0.3mg/L; Scenedesmus quadricauda tends to absorb the lower initial iron concentration, its optimum growth concentration is0.4mg/L; Anubaena flos-aquae adapt to a larger range of concentration, it shows a greater promoting effect under the concentration interval between0.2～1.0mg/L and the optimum growth concentration is in the vicinity of 0.6mg/L. In the case of adequate nutrition (N.P,Fe2+), the growth curve of the pure algae meet the following type:the simulated curve of Scenedesmus quadricauda is y=Aln(x)+B, and the simulated curve of Anabaena flos-aquae is y=-Ax3+Bx2-Cx+D, A. B. C, D are all positive constant.Tlirough the further research on microcosmic mechanism of iron, it was found that the absorption mechanism of iron includes interchange and protein transport which is the main ways for the absorption and utilization of Fe2+. After revising Shakde’s absorption model of iron, protein transport can be divided into two parts such as Fe2+reduction and Fe2+transport. Iron and phosphorus play a very important cooperative role in algae growth. Iron with different valences may affect the bioavailability of phosphorus for algae, and Fe2+is more conducive to absorb and utilize P compare with Fe3+for algae. Besides the valence of iron, the initial iron concentration, water environmental conditions and so on are all the important factors.