Sorption and mobility of metronidazole, olaquindox, oxytetracycline and tylosin in soil

Laboratory studies were conducted to characterise four different antibiotic compounds with regard to sorption and mobility in various soil types. Dist ribution coefficients (K-d values) determined by a batch equilibrium method varied between 0.5 and 0.7 for metronidazole, 0.7 and 1.7 for olaquindox a nd 8 and 128 for tylosin. Tylosin sorption seems to correlate positively wi th the soil clay content. No other significant interactions between soil ch aracteristics and sorption were observed. Oxytetracycline was particularly strongly sorbed in all soils investigated, with K-d values between 417 in s and soil and 1026 in sandy loam, and no significant desorption was observed . Soil column leaching experiments indicated large differences in the mobil ity of the four antibiotic substances, corresponding to their respective so rption capabilities. For the weakly adsorbed substances metronidazole and o laquindox the total amounts added were recovered in the leachate of both sa ndy loam and sand soils. For the strongly adsorbed oxytetracycline and tylo sin nothing was detected in the leachate of any of the soil types, indicati ng a much lower mobility. Results from defractionation and extraction of th e columns (30 cm length) showed that 60-80% of the tylosin added had been l eached to a depth of 5 cm in the sandy loam soil and 25 cm in the sand soil . (C) 2000 Elsevier Science Ltd. All rights reserved.