PARENT SESSION

1H c (1) - Pharmaceuticals
Hall 6
1:45 PM - 3:30 PM, Wednesday, 30 April 2003
Chair: Tolls, J.¹, ¹
Co-chair: Kümmerer, K.², ²

(WE6/11) The influence of pH and ionic strength to the sorption of Veterinary Pharmaceuticals to soil.

ter Laak, Thomas¹, Gebbink, Wouter¹, Tolls, Johannes², ¹ Institute of Risk Assessment Sciences, Utrecht, The Netherlands, The Netherlands² Henkel KGaA, Düsseldorf, Germany, Germany

ABSTRACT- Tetracyclins, macrolids and sulfonamids account for more than 75% of the veterinary antibiotics used in the Netherlands. These compounds reach the soil environment, since the excreta of the treated animals are applied as fertilizer. Influences of pH and ionic strength on the sorption of three compounds, Oxytetracycline (OTC), Tylosin (TYL) and Sulfachloropyridazine (SCP) have been investigated in two pH-neutral agricultural soils. The sorption coefficient (Kp) of OTC is high (1814 ± 67 for the clay loam soil and 655 ± 36 for the loamy sand soil), while TYL sorbs less (85.4 ± 6.6 for clay loam and 6.83 ± 0.22) for loamy sand), and SCP is even more mobile (2.04 ± 0.07 for clay loam and 1.06 ± 0.02 for loamy sand). Remarkable changes in Kp-values due to pH and ionic strength have been observed. The pH changes sorption-coefficients of OTC a factor 10, TYL a factor 5, and SCP a factor 15. Ionic strength varying from 0.001 to 0.1M CaCl2 or NaCl has a similar effect on the Kp of OTC and TYL, but the Kp of SCP was did not change. The effect of pH and ionic strength on the free concentration in the soil solution is discussed regarding speciation and complexation of these antibiotics.

Key words: soil sorption, veterinary pharmaceuticals, pH, ionic strength