This website is not perfect, but still, I think you will find it very interesting. The text is mostly about technical description, testing of the aircraft and comparison with other types, you can also find photographs, drawings, and profiles.
http://www.airwar.ru/enc/bww2/ar2.html
According to the text, VVS KA had 164 Ar-2 on 01/06/1941, including 147 (3 unserviceable) in operational units of the military districts. In 1941, 95 planes of this type were lost in combat.
Apparently 210 were built in 1940-1941 (but this should be checked as the source book is far from perfect), including 127 which were received in 1941 (this data being more reliable).
Hope that can help you.
Edit : I just found this (Ar-2 units, operational history,...) :
http://mig3.sovietwarplanes.com/ar-2/index.html