Phosphorus and Nitrogen impacts
 

What kind of impacts can the elements Phosphorus and Nitrogen bring to a river or water body when dumped in them? How does that polluting process occur?

They will cause increased algea and water plant growth. (planets require a lot of nitrogen and phosphorus, in the right form, to grow). This pollution tends to occur from leaching of fertillizers from farmers fields into lakes, rivers, underground water tables etc.