I propose an experiment whereby we spray Calcium Hydroxide over the clouds in Acid Rain-heavy states.
This will not only titrate the acidic gases in the air, it will be a form of cloud seeding, increasing rain.
The states which I propose to titrate most heavily are Ohio and Pennsylvania. Downwind
impact states will be New York, New Jersey, Rhode Island, Connecticut, Massachusetts, West Virginia, Virginia, Maryland, Delaware, and DC.
Acid rain is caused by Sulfur, Nitrogen-Oxygen Compounds, and CO2. CO2 forms very weak acids, but acids nonetheless.
By spraying the air with Calcium Hydroxide, The Sulfur Compounds will become gypsum, the nitrate will form calcium nitrate, and CO2 will form calcium carbonate.
As long as the sprayings are done in moderation, any rain that falls will be less acidic, but not basic.
Because lime is capable of cloud seeding, a refund program for water losses will have to be formed to reimburse the downwind states. Additional flood control protections will have to be added in Pennsylvania (it needs them anyway), and such flood management systems can redirect the water to a thirsty New York City, DC, and other areas expected to loose rainfall.
Water treatment will not be adverserly effected, as Lime is an additive in water treament already.
Fuel for the planes will be an initial drawback, but in this case, solar power might provide at least some of the energy.
Any lime produced on the ground will need to have the involved carbon sequestered or this will basically be a wash, but that should have gone without saying.
There will much engineering required to optimize the calcium hydroxide sprays. I currently envision a wet delivery system(because lime dust is bad), where the plane sprays a calcium hydroxide in solution with water at a pH of 13 at high altitudes. However, optimizing the sprayed droplets to encourage reactions with acidic gases, and form safe rain(no hail or floods), might be a challenge.