1. Department of Hydrogeology and Analytical Chemistry, University of Almería, La Cañada de San Urbano, 04071 Almería, Spain, Department of Statistics and Applied Mathematics, University of Almería, La Cañada de San Urbano, 04071 Almería, Spain, and Laboratory of Pesticide Residue CUAM, El Ejido, 04700 Almería, Spain