[1] Univ Complutense, Fac Quim, Dept Quim Fis, E-28040 Madrid, Spain
[2] Univ Politecn Madrid, ETS Ingn Montes, Dept Quim & Bioquim, E-28040 Madrid, Spain
[3] Univ Pablo Olavide, Dept Ciencias Ambientales, Seville, Spain
[4] CSIC, Inst Matemat Aplicadas & Fis Fundamental, E-28006 Madrid, Spain