In Chambers County, in addition to any and all other taxes heretofore levied, the county commission is hereby authorized to levy and impose an additional ad valorem tax in the amount of two mills on each dollar of taxable property. The tax shall be earmarked to the county general fund to be used for general county purposes. The additional ad valorem tax imposed by this section shall be collected at the same time and in the same manner as existing ad valorem taxes are collected.