  Aerosols from natural and antropogenic sources are one of the atmospheric
components that have the largest spacial-temporal variability, depending on the
type (land or ocean) surface, human activity and climatic conditions (mainly
temperature and wind). Since Cherenkov photons generated by the incidence of a
primary ultraenergetic cosmic gamma photon have a spectral intensity
distribution concentrated in the UV and visible ranges [Hillas AM. Space
Science Reviews, 75, 17-30, 1996], it is important to know the aerosol
concentration and its contribution to atmospheric radiative transfer. We
present results of this concentration measured in typical rather calm (not
windy) days at San Antonio de los Cobres (SAC) and El Leoncito/CASLEO proposed
Argentinean Andes range sites for the placement of the Cherenkov Telescope
Array (CTA). In both places, the aerosol concentration has a peak in the
2.5-5.0$\mu$m range of the mean aerosol diameter and a very low mean total
concentration of 0.097$\mu$g/m$^3$ (0.365$\mu$g/m$^3$) for SAC(CASLEO). The
data were collected the days 15/Dec/2012 (27-28/Dec/2012) for the first
(second) place with a GRIMM aerosol spectrometer, who determines the aerosol
concentration at a given diameter (0.22-32 $\mu$m range) with a laser
technique. We also present AOD values for each CTA proposed place, derived with
the improved Deep Blue algorithm, from data measured by SEAWiFS instrument on
board of SeaStar/NASA satellite. They have very low mean values, determined for
the 1998-2010 period, AOD$_{550nm, SAC}$ = 0.026 $\pm$ 0.011 and AOD$_{550nm,
CASLEO}$ = 0.030 $\pm$ 0.014. Also, we introduce the spectral (380 nm) solar
irradiance as a test in these sites of the tropospheric UV atmospheric
transmittance.
