fix altLabels and synonyms for aquatic POC, aquatic TOC, aquatic DOC, freshwater/oceanic TIC

[stevenchong]

Aquatic particulate organic carbon has the skos:altLabel (and exact synonym) POC. This is too broad and really it should be aquatic POC ( and probably 'POC in water' should be added ) -- there is such a thing as atmospheric POC.

Same situation for Aquatic total organic carbon concentration, with 'TOC' as an altLabel / synonym. There is atmospheric TOC too.

Aquatic dissolved organic carbon has an altLabel / synonym of 'DOC'. Again, too broad because soil DOC is a thing.

Both freshwater TIC and oceanic TIC have 'DIC' as an altLabel / synonym, which seems to be too broad to apply to them.

Side question: should each of these terms have 'concentration' in their labels or is it already implied?