The persistence of the antibacterial agents oxytetracycline chloride (
OTC), oxolinic acid (OA), flumequine (FLU),sarafloxacin (SAR), florfen
icol (FLO), sulfadiazine (SDZ) and trimethoprim (TRM) were compared in
marine sediments. Polyethylene boxes were filled with sediment, the a
ntibacterial compounds added and placed on the sea bed at approximatel
y 15 m depth for a period of 180-230 days, Sediment cores were collect
ed by a diver and analyzed for residues of the antibacterials in four
depth intervals from 1 to 7 cm. OTC and the quinolones OA, F and SAR w
ere found to be very persistent in the sediment. In the deeper layer o
f the sediment the initial concentrations of these compounds were pres
ent after 180 days, whereas the residues in the top layer of the sedim
ent depurated more rapidly. The depuration of these substances from th
e sediment is most probably due to leaching and redistribution rather
than degradation. The quinolones were found to adsorb to sediment. SDZ
and TRM were less persistent than the quinolones; however, the estima
ted half-life in the deepest layer (6-7 cm) was approximately 90 days
for both substances. The concentration of FLO decreased rapidly in the
sediment with a calculated half-life of 4.5 days, and a metabolite, f
lorfenicol amine, was identified in the sediment.