By mercury, a toxic substance that exists naturally found in the air from industrial plants, but there are some soil and then spreads further into the River up to sea and ocean.
The Mercury is a toxic substance that is naturally found in the air from the plant, but there are some in the ground and then spread into the river until the seas and oceans.
Mercury is toxic by existing naturally found in the air from the factory, but some parts in the soil and later spread in the river continuously until the sea and ocean.