More than 77 percent of Chinese coastal city sewer outlets discharged excessive amounts of pollutants into the sea in the first six months, State Oceanic Administration revealed on Friday.

According to an oceanic monitoring report issued by the administration, the total amount of discharged pollutant from more than 500 coastal city sewers exceeded that of the same period last year by 18.2 percent.

Most of the sewer outlets were improperly arranged, with 43 percent constructed in aquiculture, tourism and reserved areas and 33 percent located in harbor and shipping areas, the report said.

Only 8.4 percent of the sewer outlets were located in designated discharge areas, it said.

Organic compounds, suspended matter, phosphates and ammoniacal nitrogen were the major pollutants.

The report said 82.8 percent of the sewer outlets along east China's Yellow Sea discharged excessive pollutants.

Li Chunxian, spokesperson with the administration, said the average daily pollutant discharge from the outlets in the first half was 9,230 tons, 6.7 percent more than the same period last year.

However, Li said the average daily sewage discharged into the sea dropped to 60.65 million tons, a decline of 16.3 percent.

The decline was mainly due to less runoff during dry periods, Li said.

The administration would intensify monitoring of sewer outlets in coastal areas and tighten controls over sewage disposal of high resource-consuming enterprises in coastal areas and the amounts of major pollutants discharged, Li said.