Total amount of COD loaded to the Seto Inland Sea has continued to decrease since 1979 when the total amount control system was introduced on the basis of the Law Concerning Special Measures For Conservation Of The Environment Of The Seto Inland Sea.
The trend of yearly-averaged COD at the monitoring points for Environmental Standard, the trend of total amount of COD loaded, and the condition of COD concentration in 18 open seas in the Seto Inland Sea are shown in Figure 7-2, 7-3 and 7-4, respectively.
The total amount of phosphorus loaded tends to slowly decrease since 1974 when the guidance for reduction of load of phosphorus started. The trends of concentration of total phosphorus and total amount of phosphorus loaded are shown in Figure 7-5 and 7-6.
Total nitrogen concentration recently shows no improvement as shown in Figure 7-7, and its total amount loaded tends to increase since 1984 as shown in Figure 7-8. Accordingly, the guidance for reduction of total amount of nitrogen loaded has started in 1996.
Note: after the data by Environment Agency of Japan
Figure 7-2 The Trend of Yearly-Average COD at the Monitoring
Points
for Environmental Standard in the Seto Inland Sea
Note: after data by Environment Agency of Japan and the Association for the Environmental Conservation of the Seto Inland Sea
Figure 7-3 The Trend of Total Amount of COD Loaded in the Seto Inland Sea
Note: 1) yearly mean concentration in each open sea
2) after the data by Environmental Agency of Japan
Figure 7-4 Condition of COD Concentration in 18 Open Seas in the Seto Inland Sea
Note: 1) yearly mean concentration of 18 open seas in the Seto Inland Sea
2) after the data by Environmental Agency of Japan
Figure 7-5 The Trend of Concentration of Total Phosphorus in the Seto Inland Sea
Note: after the data by Environmental Agency of Japan
Figure 7-6 The Trend of Total Amount of Phosphorus Loaded in the Seto Inland Sea
Note: 1) yearly mean concentration of 18 open seas in the Seto Inland Sea
2) after the data by Environmental Agency of Japan
Figure 7-7 The Trend of Total Nitrogen Concentration in the Seto Inland Sea
Note: after the data by Environmental Agency of Japan
Figure 7-8 The Trend of Total Amount of Nitrogen Loaded in the Seto Inland Sea