Additionally, there is also no Environment International and Environmental Pollution in there. So do I need to learn the "styles code" and construct them by myself?
That would be the easiest. See here
http://www.zotero.org/support/dev/citation_styles#editing_csl_10_styles
for some helpful links.
You can also request a style
http://www.zotero.org/support/requesting_styles
but there are no guarantees how quickly someone (usually me) will find the time to code it - can easily take a month or two.
The three journals are all from Elsevier & a cursory look suggests that http://www.zotero.org/styles/elsevier-harvard/dev?install=1 may fit your needs. Check it & let us know: dependent styles can be made so that others can find this more easily or it can be adapted to fit your needs.
For Chemosphere and Environment International, the author instructions for references are identical to the documentation used for the style I linked to. What changes do you think need to be made?
Upgrade Storage
http://www.zotero.org/support/dev/citation_styles#editing_csl_10_styles
for some helpful links.
You can also request a style
http://www.zotero.org/support/requesting_styles
but there are no guarantees how quickly someone (usually me) will find the time to code it - can easily take a month or two.