Relationship between formation process of water quality and natural pH recovery, and response estimation model for water quality on acid lake

稻川湖的pH值自1995年以来呈缓慢上升趋势。到目前为止，这种现象的原因还不清楚。虽然以20 μm以下的纳米浮游植物为主，但到2003年仍呈下降趋势，不清楚这是由于溶解无机碳的减少还是由于光子的限制。在本研究中，我们试图确定稻川湖水质的限制因子，并分析水质的水响应模型。2004年表层碳氮比（C/P）和5 m层碳磷比（C/P）分别为1±2和330±110。2005年，表层温度分别为8.5±1.0和354±82,5m温度分别为8.7±1.1和324±51。由于这两个年份的碳磷比都很高，磷是稻田湖的限制因素。此外，由于该湖为酸性湖泊，但pCO_2水平较低，无机碳也是制约因素。由于缺乏无机碳和无机磷，初级生产水平较低。由于含CO_2的无机碳从表层到深层的垂直分布没有变化，因此大气对CO_2的补给与河流对无机碳的补给相比并不重要。

Slow rise of pH value was observed in Lake Inawashiro since 1995. Until now, the cause of this phenomenon is not made clearly. Although mass of primary production with nanophytoplankton smaller than 20 μm dominated to the total amount, it was decreasing until 2003, and it is unclear that this is due to decreasing dissolved inorganic carbon or due to limiting of photon. In this study, we attempted to determine limiting factor and analysis water response model of quality in Lake Inawashiro. Ratio of carbon to nitrogen (C/P) and carbon to phosphorus (C/P) were 1±2 and 330±110 in surface layer and 5 m layer, respectively in 2004. Those in 2005 were, 8.5±1.0 and 354±82 in surface layer, and 8.7±1.1 and 324±51 in 5 m layer. As C/P ratio was so higher in both years, phosphorus is limiting factor in Lake Inawashiro. In addition, inorganic carbon was also limiting factor as pCO_2 was in low level although this lake was acid lake. Therefore, primary production was in low level as inorganic carbon and phosphorus lacking. As vertical distribution in inorganic carbon including CO_2 was did not change from surface to deep layer, supply of CO_2 from atmosphere is not important as compared with supply with inorganic carbon loading from inflowing river.