Would it be possible to identify the source of pollution and the effect (and order) that each anti-pollution improvement is applied.
Not directly from the city-screen as such.
But the pollution-model in CivIII is fairly simple. There are only two potential causes of pollution from towns: specific buildings (only Industrial- and Modern-era buildings, in the epic game), and large populations.
The more pollution-points that any given town produces
in total (illustrated by the pollution-icons at the bottom left of the city-screen), the greater the probability (+1% per pollution point?) that a tile in that town's Fat Cross may be randomly
contaminated each turn (i.e. requiring Worker-cleanup before the tile is usable again).
The longer that a tile is left contaminated, the greater the probability that it will
degrade per the terrain-settings in the Editor (in the epic-game, the sequence used is broadly "Jungle/ Marsh/ Tundra —> Grassland —> Plains —> Desert"; Forests degrade to their respective base-terrain, Tundra or Grass or Plains).
(Contamination produced by nuclear weapons — and possibly also nuclear meltdowns? — causes instant tile-degradation)
The greater the total number of pollution-points produced by all towns on the map (yours
and the AI's), the greater the probability that Global Warming will cause a random tile(s) to degrade,
somewhere in the world, even without prior contamination.
The pollution-point total from any given town can
only only be mitigated by erecting additional buildings in that town.
Building-generated pollution:
Pollution-effects of buildings are set in the Editor, and should (ideally) be detailed in the 'Pedia-entry for each building (at the very least, the entry should note that it produces pollution!). Any building can be set to add any given number of pollution-points (e.g. the epic-game Factory produces +2 pollution-points) to that town; these pollution-point values are simply totalled up, so the more polluting buildings you install in a town, the greater the number of pollution-points (=icons) produced by that town. After an "Anti-building-pollution" building is added (= Recycling Center in the epic-game), building-pollution is capped at +1 pollution-point
in total, regardless of how many polluting buildings exist in that town
Population-generated pollution:
Each population-point above the Size-2 cap (i.e. Pop12 in the epic-game, before a Hospital is built; I do not know what the town-size caps are in RARR) is
hardcoded to add +1 pollution-point to that town (i.e. a Pop20 Metropolis in the epic-game would produce 20 – 12 = 8 population-pollution points/icons). After an "Anti-population-pollution" building is added (= Mass Transit in the epic-game), population-pollution is capped at +1 pollution-point
in total, regardless of city-size
Basically, you only need one of each pollution-mitigating building-type; their effects are cumulative with each other, so once both building-types have been installed, the town will produce no more than 2 pollution-points (+1 from excess population, +1 from buildings).