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

应用序列提取方法和藻类生长潜力检测方法，对长加拉河流域和浅谷河流域江水和流域土壤中的悬浮物进行了研究。用顺序萃取法将颗粒态磷分离并定义为9种形态。研究结果表明：1)暴雨过程中，河水中可溶于盐基的无机磷、有机磷以及与铁、锰结合的氧化还原敏感型磷在河水颗粒态磷中占主导地位，占颗粒态磷的75%~90%。生物有效磷与颗粒态磷的比例在30%~40%之间。2)森林表层土壤中约50%的全磷是有机磷，稻田表层土壤中约40%是氧化还原敏感型磷与铁、锰结合。3)藻类生长潜力检测表明，颗粒态磷可供藻类生长。4)藻类生长潜力检测表明，森林表层土壤和稻田表层土壤中生物有效磷占总磷的比例分别为60%和90%左右。5)顺序提取法计算的生物有效磷与颗粒物的比值高于藻类生长潜力法的计算结果，说明顺序提取法可用于颗粒物中生物有效磷的定量测定。通过藻类生长潜力检测，进一步了解提取序列提取方法与生物利用度差异的原因，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.