It is true that Japan is a beautiful country, but its big cities are lately polluted.
日本的确是个美丽的国家，但最近日本的大都市已被污染。
The river has been polluted by waste products from the factory.
这条河已经受到工厂排放的废料的污染。
The tanker sank and the oil polluted the sea.
油轮沉没了，石油污染了海面。
