Determinants of the short-term dynamics of PCB uptake by plankton

Abstract

Many studies relate the ecological fate of a contaminant to its chemical structure, but few combine quantitative structure-activity relationships with environmental properties that may modulate those effects, so the modulating role of such properties remains unquantified. This study determines the effects of variations in suspended biomass, dissolved and colloidal organic carbon, and pH on the time course of 2, 2[prime], 4, 4[prime], 5, 5[prime]-hexachlorobiphenyl uptake by laboratory cultures of Selenastrum capricornutum Printz. Variations in pH had no effect, but uptake increased with biomass and decreased at higher levels of organic carbon, measured as absorbance at 440 nm (Abs, per meter). Coefficients for these effects combined with existing relations based on simple first-order molecular connectivity ([chi]) or capacity ratio (K[prime]) yielded semi-empirical equations to predict the instantaneous rate of uptake and bioconcentration factor (BCF) of organic contaminants: log rate = [minus]3.30 + 0.32[chi] + 1.1 log biomass [minus] 0.42 log Abs; log BCF = 4.11 + 0.86 log K[prime] [minus] 0.87 log biomass [minus] 0.22 log Abs. These equations, entirely based on pure laboratory cultures, were assessed by comparing predicted uptake with the time courses of polychlorinated biphenyl (PCB) uptake by plankton in water from 11 Quebec lakes and proved tomore » be more effective than predictions based on contaminant properties alone.« less