Trophic magnification of legacy persistent organic pollutants in an urban terrestrial food web

Abstract

Legacy persistent organic pollutants (POPs), including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), persist for generations in the environment and often negatively impact endocrine functions in exposed wildlife. Protocols to assess the bioaccumulation potential of these chemicals within terrestrial systems are far less developed than for aquatic systems. Consequently, regulatory agencies in Canada, the United States, and the European Union rely primarily on aquatic information for the bioaccumulation assessment of chemicals. However, studies have shown that some chemicals that are not bioaccumulative in aquatic food webs can biomagnify in terrestrial food webs. Thus, to better understand the bioaccumulative behaviour of chemicals in terrestrial systems, we examined trophic magnification of hydrophobic POPs in an urban terrestrial food web that included an avian apex predator, the Cooper's hawk (Accipiter cooperii). Over 100 samples were collected from various trophic levels of the food web including hawk eggs, songbirds, invertebrates, and berries and analysed for concentrations of 38 PCB congeners, 20 OCPs, 20 PBDE congeners, and 7 other brominated flame retardants listed on the Government of Canada's Chemicals Management Plan. We determined trophic magnification factors (TMFs) for contaminants that had a 50% or greater detection frequency in all biota samples and compared these terrestrial TMFs to those observed in aquatic systems. TMFs in this terrestrial food web ranged between 1.2 (0.21 SE) and 15 (4.0 SE), indicating that the majority of these POPs are biomagnifying. TMFs of the legacy POPs investigated in this terrestrial food web increased in a statistically significant relationship with both the logarithm of the octanol-air (log KOA) and octanal-water partition (log KOW) coefficients of the POPs. POPs with a log KOA >6 or a log KOW >5 exhibited biomagnification potential in this terrestrial food web.