A wage is sometimes paid in shorter increments than a salary. For example, we talk about an annual salary, but a weekly wage. However, to all intents and purposes they represent the same thing - money that you are paid (payment) for working for someone.
Circumstance and situation are synonyms. Your environment is the things that are around you - for example your "work environment," is the things that are around you at work. Under certain circumstances this word can mean a similar thing to situation... consider the following examples:
1) "There is a toxic (poisonous) situation at work," = there is a specific problem that is causing everyone problems at work.
2) "There is a toxic circumstance at work" = very similar
3) "There Is a toxic work environment" = there isn't just one specific problem but the whole atmosphere at work is toxic.
4) "His work circumstances are toxic" = the same as the above (but we would not use situation for this).
Note: in all of the above examples, we are not speaking literally - nobody is actually being poisoned - we mean that the atmosphere is very unpleasant.
We also tend to use the word "environment," to describe our physical surroundings too - for example "his work environment is always cluttered." (cluttered means that he has lots of things around or on his desk). We would not use "situation," or "circumstance," in this context.