The environment around us 中的around的词性和在句中作为的成分

This is not a sentence, but only a phrase. The whole sentence is not very useful in understanding this phrase. The word around is followed by us in the objective case, therefore the word around is a preposition, not an adverb. Besides, English should never be understood as Chinese at all. English is to be understood as English, while Chinese is to be understood as Chinese.