Long-Term Bioconcentration Kinetics of Hydrophobic Chemicals in Selenastrum Capricornutum and Microcystis Aeruginosa

Abstract

Abstract-The bioconcentration of two chlorobenzenes (CBs) and of seven polychlorobiphenyls (PCBs) to Selenastrum capricornutum and Microcystis aeruginosa was studied with accumulation experiments followed by gas purge elimination experiments. Henry's law constants at 10ЊC were needed to interpret the gas purge results and were measured in control experiments. For the M. aeruginosa culture, steady-state uptake was reached within days, whereas uptake by S. capricornutum took several weeks. The relationships between the log bioconcentration factors (BCF) and log octanol-water partition coefficients (K ow ) were nonlinear, with relatively low values for the more hydrophobic PCBs. Rate constants for the elimination of CBs and PCBs from the algal cells were shown to be larger than 1 per day when calculated with a one-compartment model. With such large rate constants, it is unlikely that the curvature observed for these species is caused by slow kinetics or that algal growth affects BCF by dilution of CB or PCB concentrations. The log BCF-log K ow relationships could be described by a simple three-phase model that accounted for the binding of CBs and PCBs to dissolved organic carbon (DOC). Modeling bioconcentration of hydrophobic chemicals in phytoplankton should account for the binding to DOC.

Trophic transfer and passive uptake of a polychlorinated biphenyl in experimental marine microbial communities

“…Recent studies [36,39] have shown a more rapid PCB uptake in phytoplankton than observed in this experiment. For example, Stange and Swackhamer [36] observed an initial 40% partitioning of high-chlorinated PCBs into the algal phase, whereas in this experiment, only 5% of the PCB initially partitioned into algae.…”

Particle-Dissolved Phase Partition of Polychlorinated Biphenyls in High Altitude Alpine Lakes

“…The weak relationship between K p and K ow could then be due to this substantial temporal variability in particulate organic matter content. Historically, PCBs uptake by phytoplankton was considered as a fast equilibrium process (from few minutes or hours), 65−67 but this got challenged by more recent results, [55][56][57]68 highlighting that the time required to approach equilibrium is much longer (several days or weeks) and that equilibrium was, most of the time, not even reached. Authors suggested that under intense phytoplankton growth, partitioning of PCBs between the algae and the dissolved phase occurred at much longer time scales than algal growth and that therefore nonequilibrium was observed.…”

Passive Partitioning of Polychlorinated Biphenyls between Seawater and Zooplankton, a Study Comparing Observed Field Distributions to Equilibrium Sorption Experiments

“…In the transfer of HOCs through aquatic food webs, the first and important concentration step from water to phytoplankton organic matter is considered to be a passive partitioning process driven by the fugacity gradient between the two phases (1). Sorption of PCBs to phytoplankton has been studied both in field (2)(3)(4) and in laboratory sorption experiments (2,5,6). A few studies in the previous decade suggested concentrations of PCBs in phytoplankton to be kinetically limited by high phytoplankton growth rates (2) or large cell sizes (3).…”

“…A few studies in the previous decade suggested concentrations of PCBs in phytoplankton to be kinetically limited by high phytoplankton growth rates (2) or large cell sizes (3). However, more recent studies, including larger field data sets covering different cell sizes and growth rates (4) or experimental sorption techniques avoiding known artifacts of PCBs sorbing to dissolved organic carbon (DOC) (5,6), have generated data consistent with phytoplankton being in near-equilibrium with surrounding water.…”