Aerial photo shows the Changlu Hangu salt field, one of China's oldest coastal salt fields, in north China's Tianjin. Autumn harvest has recently started at the salt field and is expected to last until late October. [Photo/tj.people.com.cn]

A photo shows Changlu Hangu salt field, one of China's oldest coastal salt fields, in north China's Tianjin. [Photo/tj.people.com.cn]

Aerial photo shows machines working at the Changlu Hangu salt field, one of China's oldest coastal salt fields, in north China's Tianjin. Autumn harvest has recently started at the salt field and is expected to last until late October. [Photo/tj.people.com.cn]