Shared starting conditionHuman-caused acidity enters soilNitrogen processes and historical air pollution supply strong acids.
CounterfactualNo agricultural lime
Acid consumes bicarbonate already present in soils and waterways.
Some bicarbonate carbon becomes CO₂ and can reach the atmosphere.
Accounting result: this release still occurs even though no new limestone was added.
Observed practiceAgricultural lime added
Limestone neutralizes acidity, producing an initial pulse of CO₂.
Calcium and bicarbonate are retained or carried through soil, groundwater and the river.
Modelled result: after the lag, cumulative atmospheric CO₂ is lower than in the no-lime case.
The clock matters: soil retention and groundwater transport stretch the comparison across decades. The claimed sink exists relative to the acidity-without-lime alternative, not as an instantaneous removal from air.