Influence of carrier and bactericide on sorption coefficients of hydrophobic organic compounds for two lake sediments

Abstract

Sorption coefficients of a series of hydrophobic organic compounds were determined for two sediments, one with a high (RDD sediment) and one with a low organic carbon content (OVP sediment). The chemicals were administered to water using a generator column, or using one of the following carriers (0.5%, v/v): acetone, methanol or propanol. In addition to the influence of the mode of administration, the influence of the bactericide, sodium azide (NaN3), on the sorption coefficients was studied. For most compounds, higher sorption coefficients were found in RDD sediment than in OVP sediment. Only for the most hydrophobic compounds no large differences were found between the sorption coefficients in the two sediments. In RDD sediment, the use of the carriers showed lower sorption coefficients for almost all compounds, and in OVP sediment the use of the carrier showed only for some of the more hydrophobic compounds lower sorption coefficients, than the use of the generator column. The highest dry weight (DW) and total organic carbon (TOC) concentrations were found in the aqueous phase of the high organic carbon sediment (RDD). In addition, methanol and propanol resulted in significant increases in TOC concentrations. The influence of DW and TOC concentrations on the sorption coefficients could, however, not be quantified. Since carriers may have a significant effect on the experimental determination of sorption coefficients, we suggest to use the generator column for administering the compounds, in combination with a bactericide to prevent bacterial activity.