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

自1995年以来，稻川桥湖的pH值缓慢上升。到目前为止，这一现象的原因尚不清楚。虽然浮游植物<20μm的初级生产力在总量中占主导地位，但到2003年为止一直在减少，目前尚不清楚这是由于溶解无机碳的减少还是由于光子的限制。在这项研究中，我们试图确定限制因素和分析水质的水响应模型。2004年表层碳氮比为1±2，5m层碳磷比为330±110。2005年表层分别为8.5±1.0和354±82，5m层分别为8.7±1.1和324±51。由于这两年的C/P比都很高，磷是限制稻川桥湖的因素。此外，尽管该湖为酸性湖泊，但由于PCO_2水平较低，无机碳也是其限制因素。因此，由于无机碳和磷的缺乏，初级生产力处于较低水平。由于CO_2在无机碳中的垂直分布没有从表层到深层的变化，因此大气CO_2的补给量与河流无机碳的补给量相比并不重要。

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.