A man walks on a beach covered by a layer of an unknown black substance in Qingdao city, East China's Shandong province, September 4, 2011. The black layer forced a lot of people to stop swimming and leave the water, fearing the substance was oil from Bohai Bay, an area where an oil leak occurred at an oilfield jointly owned by ConocoPhillips China and China National Offshore Oil Corp. A sample of the black substance was taken to be tested by relevant departments. [Photo/CFP]

A woman shows two moon cakes she made on her own at a shop in Shenyang, Northeast China's Liaoning province, September 4, 2011. People can make their own moon cakes, which Chinese people eat as a tradition during Mid-Autumn Festival, in this shop. The Mid-Autumn Festival, a time for Chinese people to get together with their families and enjoy the full moon, falls on the fifteenth day of the eighth month according to Chinese lunar calendar and this year is on September 12. [Photo/CFP]