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In this study we extend from the visible to the UV a traditional method for studying the radiative properties of black carbon. We apply this measuring possibility to a practical study carried out in the Southern Iberian Peninsula during summer 2004. Using an optical technique based on the integrating sphere method, absorption coefficients, sigma(a), were determined in the visible and in the ultraviolet regions of spectrum. The obtained values are representative of remote areas including during desert episodes that reach this area. To analyse the spectral shape of sigma(a) we derived a parameter (alpha(a)) which is the slope of the linear fit of the log-log plot of sigma(a) versus lambda. This parameter is similar to the Angstrom exponent used for extinction. The reported alpha(a) values for the UV appear as very original data in the literature.