Coal-fired power plants burning high-sulfur coal release significant amounts of sulfur dioxide (SO₂), a key contributor to acid deposition, which harms ecosystems and infrastructure. To comply with stricter Clean Air Act regulations, the plant needs an end-of-pipe technology that captures SO₂ from flue gas after combustion but before emission. A wet scrubber, also known as flue-gas desulfurization (FGD), is the most appropriate technology as it uses a liquid slurry, often containing lime or limestone, to chemically react with SO₂ in the exhaust stream. This reaction forms calcium sulfate (gypsum), effectively removing up to 95% of SO₂ and preventing its release into the atmosphere. Unlike electrostatic precipitators that target particulate matter like fly ash, or catalytic converters designed for vehicle exhaust, wet scrubbers are specifically engineered for large-scale SO₂ removal in industrial settings. Vapor recovery systems, on the other hand, are used for controlling volatile organic compounds during fuel handling, not for flue gas treatment. Thus, option C correctly identifies the wet scrubber as the technology that primarily targets SO₂ emissions.

Wet scrubbers target SO2, a primary acid-forming pollutant from coal, by removing it from emissions to reduce acid deposition under Clean Air Act. This approach is better than ESPs or catalytic converters for SO2. The best approach is the wet scrubber for SO2 removal. ESPs don't remove SO2; catalytic converters aren't for stacks or SO2. Scrubbers use chemical reactions for capture. They mitigate environmental damage from sulfur emissions.

Scrubbers primarily reduce SO2 from smokestacks by chemical absorption, matching technology to pollutant correctly in AP Environmental Science. Other pairings mismatch, like scrubbers for NOx or catalytic converters for SO2. The correct match is scrubbers for SO2 from smokestacks. Electrostatic precipitators target PM, not CO; catalytic converters are for vehicles. Understanding these roles aids in pollution reduction strategies. Scrubbers are key for industrial SO2 control under regulations.

CO and NOx from traffic are key pollutants under National Ambient Air Quality Standards. Requiring catalytic converters on vehicles uses catalysts to transform these into N2 and CO2 directly in exhaust. This approach aligns with Clean Air Act goals for urban areas. Scrubbers on tailpipes aren't feasible for cars. Electrostatic precipitators don't neutralize CO. Adding lime to gasoline isn't a standard method for NOx.

Installing a scrubber neutralizes SO2 from high-sulfur coal by reacting it with a base like limestone, forming collectible solids and reducing stack emissions. This directly addresses SO2, a key acid rain contributor, for Clean Air Act compliance. The correct change is the scrubber because it targets SO2 specifically at the source. ESPs remove particles, not gases; catalytic converters are for vehicles and NOx; increasing temperature might affect CO but not SO2. Scrubbers are effective post-combustion controls for sulfur-rich fuels. This approach helps mitigate environmental impacts like acidification of lakes and forests.

Diesel buses emit NOx and CO from incomplete combustion, and retrofits aim to reduce these for urban air quality under the Clean Air Act. A catalytic converter in the exhaust system promotes chemical reactions that oxidize CO to CO2 and reduce NOx to N2, but it has minimal effect on SO2, which comes from fuel sulfur. This matches the observed reductions in NOx and CO without changing SO2. An electrostatic precipitator on tailpipes isn't practical for vehicles and targets particulates. A wet scrubber is for industrial stacks, not mobile sources. Switching to higher-sulfur fuel would increase SO2, opposite of the goal.

Coal-fired power plants emit sulfur dioxide (SO2) from burning coal containing sulfur, which contributes to acid rain and violates Clean Air Act limits. An electrostatic precipitator removes particulate matter like ash by charging particles and collecting them on plates, but it does not affect gaseous SO2. A catalytic converter is designed for vehicle exhaust to reduce NOx, CO, and VOCs through catalytic reactions, not for industrial SO2 control. A wet scrubber, or flue-gas desulfurization system, sprays an alkaline slurry like limestone into the flue gas, where SO2 reacts chemically to form gypsum, effectively capturing and removing it before emission. This technology directly targets SO2 by dissolving and neutralizing the gas in a liquid medium, producing a manageable solid byproduct. Installing a wet scrubber would most directly reduce SO2 concentrations in the stack emissions. The thermal inversion layer is a meteorological phenomenon, not a control technology.

To reduce SO2 from coal, a scrubber sprays alkaline slurry that reacts with the gas to form solid salts like gypsum, capturing it effectively. This meets Clean Air Act limits by chemical neutralization. An electrostatic precipitator removes soot (PM), not SO2. A catalytic converter converts NOx, CO, VOCs. Increasing stack height disperses but doesn't reduce emissions.

Soot and metal oxide dust are forms of particulate matter, with mass loading regulated under Clean Air Act permits. An electrostatic precipitator is highly effective for such dry particulates, using electric charges to collect them. It directly meets the permit's focus on particulate control. A catalytic converter is for gaseous vehicle emissions. A scrubber is better for gases like SO2. CFC substitution relates to ozone depletion, not particulates.

Wet scrubbers are air pollution control devices designed to remove gaseous pollutants, particularly sulfur dioxide (SO2), from industrial flue gases by contacting them with a liquid absorbent. The mechanism typically involves spraying an alkaline solution, like lime or limestone slurry, into the gas stream, where SO2 dissolves and reacts to form solid byproducts that are collected. This process is effective for refineries and power plants burning sulfur-containing fuels to meet Clean Air Act standards. The correct technology is the wet scrubber because it is specifically engineered for SO2 removal from flue gases. Electrostatic precipitators target particulates, catalytic converters are for vehicle exhaust gases like NOx and CO, and diesel particulate filters capture soot from diesel engines. Using wet scrubbers reduces acid rain precursors and improves air quality in compliance with environmental regulations.