SORPTION COEFFICIENTS OF POLYCYCLIC AROMATIC-HYDROCARBONS FOR 2 LAKE-SEDIMENTS - INFLUENCE OF THE BACTERICIDE SODIUM-AZIDE

Sorption coefficients (K(p)s) of a series of polycyclic aromatic hydro carbons (PAHs) were determined in two Dutch freshwater lake sediments to improve the insight into sorption in the aquatic environment. The i nfluence of experimental factors, such as compound concentration, equi libration time, and influence of a bactericide on K-p, was studied. No significant influence of compound concentration on K-p was found. A c ontact time of 48 h was sufficient to reach equilibrium between PAHs i n the sediment and water phase. In the absence of the bactericide, sod ium azide, incomplete mass balances, and high K-p of low molecular wei ght PAHs were found that were not caused by volatilization from, photo degradation in, or sorption by the test system. In the presence of sod ium azide, however, high mass balances and lower K-p were found for th ese compounds. This suggested that significant biodegradation of these compounds occurred in the water phase in the absence of sodium azide. The organic carbon-normalized sorption coefficients (K-oc) of the PAH s in Lake Oostvaardersplassen were two to three times higher than thos e in Lake Ketelmeer sediment. Although K-oc of the PAHs differed for t he two sediments, a clear relationship was found between K-oc and the octanol/water partition coefficient for both sediments and between the K-oc of both sediments. In conclusion, the methodology to determine K -p of biodegradable compounds should include the prevention of bacteri al activity, e.g., by addition of sodium azide. Sorption of PAHs in th e Dutch lake sediments is determined by the hydrophobicity of the PAH, the organic carbon content of the sediment, and one or more unspecifi ed sediment-specific characteristics.