Spatial and temporal variability of PCBs in Detroit River water assessed using a long term biomonitoring program

An assessment of polychlorinated biphenyls (PCBs) in water of the Detroit River, North America, was performed using mussel biomonitoring data generated between 1996 and 2010. The study included a temporal monitoring program at six locations and an enhanced spatial survey performed during 2002. Mussels were transplanted at biomonitoring stations and collected after 21-226 d. A toxicokinetic model was used to perform steady state and control corrections followed by an equilibrium partitioning model to estimate bioavailable water concentrations of PCBs. Bioavailable water concentrations of PCBs were similar in magnitude and trends to dissolved water concentrations reported in previous studies using direct sampling approaches. PCB concentrations exhibited complex temporal patterns at the six biomonitoring stations with multi-year declines in PCB trajectories between 1996 and 2002 and less consistent trends occurring across stations in later years. Spatial patterns of PCBs during 2002 revealed significantly higher water contamination on the US side of the river (seasonal average mean ± standard error (SE) sum PCB concentration of 0.63 ± 0.11 ng L(-1)) compared to the Canadian side (mean ± SE sum PCB concentration of 0.09 ± 0.01 ng L(-1)). Spatial/temporal variability of bioavailable PCB concentrations was greatest between countries, followed by moderate variation across years and by river reach (upstream, midstream and downstream sections within a country) and lowest when comparing intra-seasonal variation.