Guangzhou, Dec. 18 - Three days after receiving the Asian Games flag, Guangzhou mayor Zhang Guangning knows improving the city's environment is his next mission.

Speaking at a press conference before a group of nation-wide web journalist, Zhang put environment as his second biggest task after economic growth in a city which will hold the 2010 Asian Games.

In this July, Zhang, together with provincial governor Huang Huahua and 4,600 citizens backed to the Zhujiang River and swam across the improved water to demonstrate achievements the city has made in environment improvement.

"Swimming across the Zhujiang River is a tradition of the city that we continued this after a 30-year stop due to deteriorating water quality," Zhang said, but he admitted that the river is only suitable for swimmers sometime at some spells.

Now 72% sewage of downtown Guangzhou is treated before charged in the Zhujiang River, according to a news release from the press. By the year of 2010, the percentage will be improved to 90.

The mayor also said more than 300 quarries in the city have been closed or moved in past three years.

"We expect the environment will see improvement every year and a big change in ten years," a resolute Zhang said, making it the target of the government's environmental units.