Perhaps you should try some spelling variations:
"pollutant deposition reactive" » "pollutant depositions relative", "pollutant deposition rate", "pollutant decomposition reaction"
"pollutant emission reduction" » "pollutant emissions reduction", "pollutant dispersion reduction", "pollutant dimension reduction"

Try widening your search to All Fields.

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• If you are trying to use Boolean operators, they must be ALL CAPS: (("pollutant emission reduction") OR ("pollutant deposition reactive")).
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