Herbicide monitoring in soil, runoff waters and sediments in an olive orchard Maria Jesus Calderon a, ⁎, Elena De Luna b , Jose Alfonso Gomez c , M. Carmen Hermosin a a Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, Av. Reina Mercedes, 10, 41012 Sevilla, Spain b Area Producción Agraria, IFAPA, Av. Menéndez Pidal s/n, Campus Alameda del Obispo, 14004 Córdoba, Spain c Instituto de Agricultura Sostenible, CSIC, Av. Menéndez Pidal s/n, Campus Alameda del Obispo, Apartado 4084, 14080 Córdoba, Spain HIGHLIGHTS • We monitored two herbicides in olive orchard field under real rainfall condi- tions. • Terbuthylazine was less persistent in the first 2 cm of soil compared to oxyfluorfen. • Terbuthylazine concentration in runoff was low. • Oxyfluorfen recovered from sediments was 37.69% higher than terbuthylazine. • Oxyfluorfen on sediments favour long term water contamination. GRAPHICAL ABSTRACT abstract article info Article history: Received 27 April 2016 Received in revised form 16 June 2016 Accepted 16 June 2016 Available online xxxx Editor: J. Jay Gan Occurrences of surface water contamination by herbicides in areas where olive orchards are established reveal a need to understand soil processes affecting herbicide fate at field scale for this popular Mediterranean crop. A monitoring study with two herbicides (terbuthylazine and oxyfluorfen) in the first 2 cm of soil, runoff waters, and sediments, was carried out after under natural rainfall conditions following winter herbicide application. At the end of the 107 day field experiment, no residues of the soil applied terbuthylazine were recovered, where- as 42% of the oxyfluorfen applied remained in the top soil. Very low levels of both herbicides were measured in runoff waters; however, concentrations were slightly higher for terbuthylazine (0.53% of applied) than for oxyfluorfen (0.03% of applied), relating to their respective water solubilities. Congruent with soil residue data, 38.15% of the applied oxyfluorfen was found in runoff-sediment, compared to only 0.46% for terbuthylazine. Ac- cordingly, the herbicide soil distribution coefficients measured within runoff field tanks was much greater for oxyfluorfen (K d = 3098) than for terbuthylazine (K d = 1.57). The herbicide oxyfluorfen is co-transported with sediment in runoff, remaining trapped and/or adsorbed to soil particle aggregates, due in part to its low water solubility. In contrast, terbuthylazine soil dissipation may be associated more so with leaching processes, favored by its high water solubility, low sorption, and slow degradation. By comparing these two herbicides, our results reaffirm the importance of herbicide physico-chemical properties in dictating their behavior in soil and also Keywords: Contamination Leaching Sediments Oxyfluorfen Terbuthylazine Olive orchard Science of the Total Environment 569–570 (2016) 416–422 ⁎ Corresponding author. E-mail address: mjcalderon@irnase.csic.es (M.J. Calderon). http://dx.doi.org/10.1016/j.scitotenv.2016.06.126 0048-9697/© 2016 Published by Elsevier B.V. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv