Answer:
1. Many people don't know the danger of soil pollution. (dangerous)
-Danger
2. the river is seriously (contaminate) contaminated by the factory's waste.
-Contaminated
3. High blood (press) Pressure can be brought about by noise pollution.
-Pressure
4. the water color can show us how (pollute) polluted the river is
-Polluted
5. A lot of (die) dead fish are floating on the surface of the lake.
-dead