Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 569, Issue -, Pages 416-422Publisher
ELSEVIER
DOI: 10.1016/j.scitotenv.2016.06.126
Keywords
Contamination; Leaching; Sediments; Oxyfluorfen; Terbuthylazine; Olive orchard
Categories
Funding
- PAIDI-Junta de Andalucia [P11-AGR-7400, AGR-264, P08-AGR-03925]
- FEDER funds
- RESEL (Spanish Ministry of Agriculture, Food and Environment)
- Recupera [Hito2.2.2.]
- [AGL2012-40128-C03-01]
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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, whereas 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. Accordingly, 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 suggest that herbicides with low solubility, as seen in the case oxyfluorfen, remain susceptible to offsite transport associated with sediments. (C) 2016 Elsevier B.V. All rights reserved.
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