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Reducing NOx and SO2 emissions is the number one way to reduce acid rain. Crushed limestone, marble dust, eggshells (anything with calcium carbonate) can be added to soil or waters in order to neutralize pH
Any methods that reduce vehicle emissions like carpooling, electric cars, buses, biking/walking. Increased vehicle efficiency.
Methods that target sources of VOCs also help reduce smog. Less car use, less gasoline evaporation from gas stations. Fewer industrial petrochemical plants, dry-cleaning laundromats, etc.