Aerial photo taken on Oct. 15, 2020 shows workers producing salt amid salt ponds in Luannan County, north China's Hebei Province. (Xinhua/Mu Yu)

A worker produces salt at a salt pond in Luannan County, north China's Hebei Province, Oct. 15, 2020. (Xinhua/Mu Yu)

Aerial photo taken on Oct. 15, 2020 shows workers producing salt amid salt ponds in Luannan County, north China's Hebei Province. (Xinhua/Mu Yu)

Aerial photo taken on Oct. 15, 2020 shows workers producing salt amid salt ponds in Luannan County, north China's Hebei Province. (Xinhua/Mu Yu)

Aerial photo taken on Oct. 15, 2020 shows workers producing salt amid salt ponds in Luannan County, north China's Hebei Province. (Xinhua/Mu Yu)

Aerial photo taken on Oct. 15, 2020 shows workers producing salt amid salt ponds in Luannan County, north China's Hebei Province. (Xinhua/Mu Yu)

Aerial photo taken on Oct. 15, 2020 shows a vehicle driving through salt ponds in Luannan County, north China's Hebei Province. (Xinhua/Mu Yu)