Determination of iron speciation in lake and its effects through iron availability on algal blooming

采用1-亚硝基-2-萘酚（NN）在pH 8.1下的阴极溶出伏安法（CSV）测定淡水中总溶解铁的浓度及其化学形态。研究了霞浦湖及其入流河流中溶解铁及其化学形态的水平分布和时间变化。随着湖水从河流入口流向湖中心，溶解铁及其有机配体的浓度明显下降，表明它们起源于河流。在有机配合物中出现的铁的比例随着水流的增加而增加。溶解的铁大部分以有机配合物的形式存在（88.2%,99.9%）。以铜绿微囊藻（Microcystis aeruginosa）和agardhii浮游菌（plankton thrix agardhii） 2种蓝藻为研究对象，结合藻类生长势（AGP）测试和紫外辐照预处理DOM分解，研究了铁与DOM络合对富营养化Kasumigaura湖藻类生长的影响。铁限制了这两个物种，而氮和磷也限制了这两个物种。铁与DOM的络合作用抑制了两种植物的生长。研究了铜绿微囊藻（Microcystis aeruginosa）和agardhii浮游菌（plankton thrix agardhii）两种蓝藻在限铁连续培养条件下的生长特性。利用Monod和Droop方程确定了溶铁浓度、细胞铁配额与种群生长率之间的关系。根据本研究确定的生长特性，建立了铁限制下的动力学模型。模型模拟表明，微囊藻是铁限制条件下的优势竞争者。

Analytical methods were developed to determine the concentration of total dissolved iron and its chemical speciation in freshwater using cathodic stripping voltammetry (CSV) with 1-nitroso-2-naphthol (NN) at pH 8.1.The horizontal distribution and temporal variation of dissolved iron and its chemical speciation in Lake Kasumigaura and its inflowing rivers were investigated. Concentrations of dissolved iron and its organic ligands clearly decreased as lake water flowed from the river entry points toward the center of the lake, indicating their riverine origin. The fraction of iron occurring in organic complexes tended to increase with the water -flow. Most of the dissolved iron was present as organic complexes (882% 99.9%).Effects of iron complexation with DOM on algal growth in the eutrophic Lake Kasumigaura were assessed using 2 species of cyanobacteria, Microcystis aeruginosa and Planktothrix agardhii, by combining the algal growth potential (AGP) test and pretreatment of DOM decomposition by UV irradiation. Iron limited the 2 species, as did nitrogen and phosphorus in Lake Kasumigaura. Moreover, the growth of the 2 species was inhibited by iron complexation with DOM.The growth characteristics of two species of cyanobacteria, Microcystis aeruginosa and Planktothrix agardhii, in iron-limited continuous cultures were investigated. The relationships between dissolved iron concentration, cell quota of iron, and population growth rate were determined applying two equations, Monod's and Droop's equations. A kinetic model under iron limitation was developed based on the growth characteristics determined in this study. The model simulation suggested that Microcystis is a superior competitor under iron limitation.