BEIJING — China launched a sweeping on-spot check campaign in four coastal cities on June 24 for pollution emission into the Bohai Sea.

The weeklong on-spot checks will cover the coastline of about 1,700 km in Tangshan, Tianjin, Dalian and Yantai, according to the Ministry of Ecology and Environment.

A total of 260 work teams involving 780 people were sent to the four cities to screen for potential outfalls including culverts, ditches and pipelines by means of satellite remote sensing, unmanned aerial vehicles and on-spot checks.

The ministry will conduct on-spot checks for nine other cities later this year to prepare for future monitoring, source tracing and treatment.

The Bohai Sea is China’s only semi-closed inland sea, which faces grim ecological pressure despite efforts in local environmental protection.