How is 1 pCi/L defined in terms of nuclear disintegration?

One picocurie per liter (1 pCi/L) is defined as a measure of radioactivity that corresponds to 2.22 nuclear disintegrations per minute. This measurement comes from the definition of a curie, which is a unit of radioactivity originally based on the decay rate of radium-226. A curie is equivalent to 37 billion disintegrations per second, which can be converted to disintegrations per minute. When you break that down, 1 picocurie is 1 trillionth of a curie, thus leading to the specific value of 2.22 disintegrations per minute for one picocurie.

This understanding is rooted in the broader context of radioactivity measurement, where the curie is a standard unit used to quantify the amount of radioactive material. Each option's value reflects a different interpretation of radioactivity, but only 2.22 disintegrations per minute aligns with the precise definition of 1 pCi/L.