The Basic model for aquatic ecosystem assessment using carbon and nitrogen stable isotopes

吉野河上游到中游的总氮浓度在0.19~0.55 mg/L之间，流域大部分为森林，下游随着人口和耕地的增加，总氮浓度从0.58 mg/L上升到1.19 mg/L，总氮的TN值在源头水为1.0%，中游为3.6-5.9%，下游为4.2-8.9%0。δ^&lt；15&gt；N&lt；Total-N&gt；与总氮浓度呈正相关(r=0.91p&lt；0.001)。随着流域内农田和人口的增加，δ、总氮和总氮浓度呈上升趋势，说明农业和生活排水对氮负荷的影响较大。10条主要入湖河流的δ、总氮、总氮与总氮浓度的关系与吉野铆钉的关系相似，最大值约为8%，δ为8%左右。稻田地区河流中总氮和总氮含量下降。在这样的河流中，氨浓度很高。结果表明，在厌氧环境中，由于硝化作用不充分，δ^&lt；15&gt；N_&lt；Total-N&gt；δ；15&gt；N的波动表明，δ^&lt；15&gt；N是反映人类活动对氮负荷影响的良好参数。通过对吉野河的调查，得到了δ^&lt；15&gt；N_&lt；(%o)=3.7x总-N浓度(mg/1)-0.30的δ^&N&gt；关系式。并成为未来考虑河流健全性的标准。在未来，这种关系表达将成为水域生态系统评估的标准。未来，这种关系表达将成为诊断水生生态系统健康状况的标准。

In the Yoshino River, The Total-N concentration were from 0.19 to 0.55mg/l in the top to middle reaches, which most in the catchment is a forest, in the lower reach, where population and farmland increased, the concentration rose from 0.58 to 1.19mg/l. δ^<15>N value of Total-N were 1.0% in the head water, 3.6-5.9%0 in the middle reach, and 4.2-8.9%0 in the lower reach. There was positive correlation (r=0.91, p<0.001) between the δ^<15>N_<Total-N> and Total-N concentration. The increase in the δ^<15>N_<Total-N> and Total-N concentration with the increase in the farmland and population in the catchment indicated that the effect of the nitrogen loading by agricultural and life drainage was large as a downstream.The relation between the δ^<15>N_<Total-N> and Total-N concentration in 10 main river flowed into Lake Biwa was similar to the relation got in the Yoshino Rivet However, about 8% was the maximal value, the δ^<15>N_<Total-N> decreased in the river in the paddy field region. In such river, the ammonia concentration was high. It was indicated that the δ^<15>N_<Total-N> decreased in the anaerobic environment because nitrification is not sufficiently carried out. The fluctuation of such δ^<15>N shows δ^<15>N is the good parameter to reflects the effect of nitrogen loading by the human activity. It is possible to make use of The δ^<15>N_<Total-N> for the diagnosis of the aquatic environment.From the investigation of the Yoshino River, the relation of δ^<15>N_<Total-N> (%o)=3.7×Total-N concentration(mg/1)-0.30 was obtained. and it becomes a standard in considering the soundness of the river in future. In the future, such relational expression will become a standard of the assessment of the waters ecosystem. In the future, such relational expression will become a standard to diagnose the health of the aquatic ecosystem.