The coadsorption of flumequine (fluoroquinolone antibiotic) and copper(II) on a alkaline soil sample (collected from the Champagne-Ardenne region, France) was studied at macroscopic and molecular scales by means of batch experiments and X-ray absorption spectroscopy. The retained antibiotic amount onto the soil surface increases (from 2- to > 20-fold) with the copper concentration due to the formation of a Cu-II-flumequine ternary surface complex, which leads to the accumulation of flumequine into soils. Flumequine can be classified at environmentally relevant pH values as a slow-mobile compound in soils and a very slow-mobile compound in the presence of copper, even at relatively low concentrations. (C) 2011 Elsevier Inc. All rights reserved.