Tourists take a pleasure boat in the yellow haze hanging over Xuanwu Lake in Nanjing, the capital city of East China's Jiangsu province on June 10, 2012. The city was shrouded by the haze on June 10, 2012, turning the city yellow. Meteorological observatories in Jiangsu province issued visibility warnings. In several cities in Jiangsu province visibility was less than 3,000 meters, which will remain for the following days. [Photo/Asianewsphoto]

Boats docked in Nanjing's Xuanwu Lake shrouded by yellow haze on June 10, 2012. . Meteorological observatories in Jiangsu province issued visibility warnings. In several cities in Jiangsu province visibility was less than 3,000 meters, which will remain for the following days. [Photo/Asianewsphoto]