sentences:  According to reports, a large area of water hyacinth has appeared in the lower reaches of the Han River in Wuhan for 20 consecutive days, posing a direct threat to the safe navigation of ships in the lower reaches of the Yangtze River.On the waters of the Yaojiang, Fenghua, and Minjiang rivers in Ningbo, Zhejiang, ships were also unable to sail because of the phoenix blue.Secondly, water hyacinth can absorb a large amount of harmful heavy metals and other substances.