An acid is a substance is that produces hydrogen ion in an aqueous solution. Increasing hydrogen ion contents depict increase in acidic contents.
An Alkaline is a substance that produces hydroxide ion in an aqueous solution. Increasing hydroxide ion depicts increase in alkalinity.
Using a pH scales to measure the acidity or alkalinity of a substance has a range value of 0 to 14 . Decreasing pH value depict increasing acidity contents . 0 to 2 is very acidic 3 to 5 is moderately acidic and so on . 7 pH scale means the substance is neutral . From 7 upward depict increasing alkalinity.
Since the pH of rainfall change from 4.22 to 4.40 that means the acidic content decrease. The most acidic rainfall is 4.22.
