Fate of beta blockers in aquatic-sediment systems: sorption and biotransformation

The fate of beta blockers (atenolol, acebutolol, bisoprolol, celiprolol, metoprolol, nadolol, pindolol, propranolol, and sotalol) was studied in surface water-sediment systems. A new analytical method was developed to determine the beta blockers in sediments by LC-ESI-tandem MS detection. The relative recoveries in sediments ranged from 89 +/- 7% (acebutolol) to 102 +/- 3% (nadolol) using deuterated surrogate standards. Beta blockers were present with concentrations up to 86 ng/g (bisoprolol) in the sediments of small German streams containing an elevated percentage of treated wastewater. Biotransformation studies and sorption isotherms of the beta blockers were performed with two natural river sediments ("Burgen", "Dausenau") differing in organic carbon content and particle size distribution. Biotransformation of beta blockers in the surface water-sediment systems exhibited a low to high persistence with 90% disappearance (DT(90)) ranging from 0.4-10 d (pindolol, atenolol) to >100 d (sotalol, propranolol or celiprolol). For sorption studies neither NaN(3) addition nor autoclavation led to a complete mass balance of the beta blockers, probably due to biotransformation. Isotherms at 6 h (apparent equilibrium, measuring aqueous and sediment phase) fitted by the Freundlich equation show that sorption of all beta blockers to the Burgen sediment were linear or close to it (i.e., n-values between 0.93 and 1.13), while in the Dausenau sediment the sorptions were slightly non linear (i.e., n-values 0.77-0.91). In river water the sorbed fraction is negligible in comparison to the dissolved fraction. Nevertheless, beta blockers can be detected with concentrations up to 86 ng/g (bisoprolol) in sediments of small streams containing more than 50% treated wastewater.