Does the addition of acid change alkalinity?
Calcium carbonate has a solubility of $\pu{13 mg/L}$ at room temperature. Adding acid to this solution will dissolve the calcium carbonate, by destroying the carbonate via the equilibria
$$\ce{CO3^2- &lt;=&gt;[+ H+][- H+] HCO3- &lt;=&gt;[+ H+][- H+] H2CO3 -&gt; H2O + CO2,}$$
with the carbon dioxide having a tendency to escape the solution.