Development of determination method of bioavailable phosphorus using algal growth potential and sequence extraction and evaluation its runoff loading

序列提取方法和藻类生长潜力的检查被施加到河水和流域土壤中的悬浮固体的长良河流域和Asutani河流域。采用顺序萃取法将颗粒态磷分离为9种形态。研究结果表明：1）暴雨期间，河水中颗粒态磷主要以碱溶性无机磷、有机磷和Fe、Mn结合的氧化还原敏感性磷为主，占颗粒态磷的75%~ 90%;生物有效磷占颗粒态磷的比例在30%~ 40%之间。2）森林表层土壤有机磷占全磷的50%左右，稻田表层土壤中约有40%的磷是氧化还原敏感的铁锰结合态磷。3）藻类生长潜力测定表明，颗粒态磷对藻类生长是有效的。藻类生长势测定结果表明，森林表层土壤和稻田表层土壤生物有效磷占全磷的比例分别约为60%和90%，（5）序列提取法计算的生物有效磷与颗粒物的比值高于藻类生长势法结果表明，顺序萃取法可用于颗粒物中生物有效磷的定量测定。通过藻类生长势的测定，了解提取序列提取方法与生物有效性之间差异的原因还需进一步研究。

The sequence extraction method and algal growth potential examinations were applied to suspended solids in river water and watershed soil of the Nagara River watershed and the Asutani River watershed. Particulate Phosphorus were separated and defined as 9 forms by the sequence extraction method. Only particulate phosphorus in suspended solids from the river water or the soil of the watersheds used in the algal growth potential examinations.The results of this study are the following :1)During storm events, the inorganic phosphorus compounds soluble in bases, organic phosphorus, and redox-sensitive phosphorus bound to Fe and Mn were dominated among the particulate phosphorus forms of the river water, and the content of these phosphorus forms in particulate phosphorus ranged from 75% to 90%. The ratio of bioavailable phosphorus to particulate phosphorus was between 30% and 40%.2)About 50% of total phosphorus in forest surface soil was organic, and about 40% in the paddy field surface soil was redox-sensitive phosphorus bound to Fe and Mn.3)The algal growth potential examination indicated that the particulate form of phosphorus could be available for algal growth.4)The algal growth potential examinations showed that the ratio of bioavailable phosphorus to total in forest surface soil and in paddy field surface soil were about 60% and 90%, respectively.5)The ratio of bioavailable phosphorus to particulate solids calculated by the sequence extraction method was higher than that by the algal growth potential examination.These results suggested that sequence extraction method is useful for the quantitative determination of bioavailable phosphorus in particulates. Further studies are necessary to know the reason of the difference between extracted sequence extraction method and bioavailability by algal growth potential examination.