Investigation of Hydrophobic Organic Carbon (HOC) Partitioning to 1 kDa Fractionated Municipal Wastewater Colloids

Natural organic matter from the aquatic environment passing a 1 kDa filter has been hypothesized to not contribute appreciably to hydrophobic organic compound (HOC) partitioning; however, to our knowledge this limit has not been verified experimentally for any sorbate/sorbent system. Presently, colloidal organic carbon (COC) < 1 kDa approached 70% of the total COC (<1.5 μm) mass in primary effluent (PE) from a municipal wastewater treatment plant. Partitioning of HOCs 1,2,4,5-tetrachlorobenzene, pentachlorobenzene, and hexachlorobenzene to COC for both 1.5 μm and 1 kDa filtrates of PE was investigated using the gas-stripping technique. Contrary to the hypothesis, significant HOC–COC partitioning to the 1 kDa filtrate was observed with organic carbon-normalized partitioning coefficients (log<i>K</i>_COC) of 4.30, 4.36, and 3.74 for 1,2,4,5-TeCB, PeCB, and HCB, respectively. Further, partitioning to COC < 1 kDa dominated the overall partitioning of the three chlorobenzenes in the 1.5 μm filtrate, and the partitioning behavior did not follow the trend based on hydrophobicity (<i>K</i>_OW). The results show that significant partitioning of HOC may occur to OC < 1 kDa and highlights the need for further experiments with other HOCs and COC characterization to better understand and explain the observed partitioning

Calibration of the Gastrointestinal Magnification Model to Predict Maximum Biomagnification Potentials of Polychlorinated Biphenyls in a Bird and Fish

The gastrointestinal magnification (GI-magnification) model was calibrated in ring doves and Japanese koi using matched data on dietary assimilation and fecal depuration of polychlorinated biphenyls (PCBs). Mass transport parameters describing PCB flux from gut contents to organism (<i>D</i>_go^′; mol d^–1 Pa^–1) and organism to gut contents (<i>D</i>_og; mol d^–1 Pa^–1) were quantified to test the hypothesis that the ratio of these two terms approached unity. For birds, <i>D</i>_go^′/<i>D</i>_og ranged from 2.9 to 6.3 and for fish the ratios ranged from 0.7 to 3.1. In both species, the ratio commonly exceeded 1. The GI-magnification model was used to predict maximum PCB biomagnification factors (BMF_max) for each species which ranged from 18.5 to 33.8 for ring doves and 7.9 to 14.8 for Japanese koi. Chemical losses via respiration reduced steady state biomagnification factor (BMF_ss) estimates by a negligible amount in birds, whereas for fish, predicted BMF_ss decreased to values from 0.5 to 7.2. This study demonstrated that chemical transfer efficiency during assimilation exceeds organism/feces transfer which contributes to elevated PCB biomagnification potentials in birds and fish. Combined with reduced losses of chemical across respiratory surfaces, higher <i>D</i>_go^′/<i>D</i>_og ratios of birds contribute to elevated biomagnification in birds over fish

Calibration of the Gastrointestinal Magnification Model to Predict Maximum Biomagnification Potentials of Polychlorinated Biphenyls in a Bird and Fish

The gastrointestinal magnification (GI-magnification) model was calibrated in ring doves and Japanese koi using matched data on dietary assimilation and fecal depuration of polychlorinated biphenyls (PCBs). Mass transport parameters describing PCB flux from gut contents to organism (<i>D</i>_go^′; mol d^–1 Pa^–1) and organism to gut contents (<i>D</i>_og; mol d^–1 Pa^–1) were quantified to test the hypothesis that the ratio of these two terms approached unity. For birds, <i>D</i>_go^′/<i>D</i>_og ranged from 2.9 to 6.3 and for fish the ratios ranged from 0.7 to 3.1. In both species, the ratio commonly exceeded 1. The GI-magnification model was used to predict maximum PCB biomagnification factors (BMF_max) for each species which ranged from 18.5 to 33.8 for ring doves and 7.9 to 14.8 for Japanese koi. Chemical losses via respiration reduced steady state biomagnification factor (BMF_ss) estimates by a negligible amount in birds, whereas for fish, predicted BMF_ss decreased to values from 0.5 to 7.2. This study demonstrated that chemical transfer efficiency during assimilation exceeds organism/feces transfer which contributes to elevated PCB biomagnification potentials in birds and fish. Combined with reduced losses of chemical across respiratory surfaces, higher <i>D</i>_go^′/<i>D</i>_og ratios of birds contribute to elevated biomagnification in birds over fish

Bioamplification and the Selective Depletion of Persistent Organic Pollutants in Chinook Salmon Larvae

The maternal provisioning of yolk to eggs transfers significant quantities of persistent organic pollutants (POPs). As yolk utilization progresses via metabolic activity, there is a potential to realize further increases in POP concentrations if yolk lipids are depleted at a faster rate than POPs, a condition referred to as bioamplification. This study investigated the bioamplification of POPs in Chinook salmon (Oncorhynchus tshawytscha) eggs and larvae. Chinook eggs were sampled from the Credit River, ON, Canada, and brought to an aquaculture facility where they were fertilized, incubated, and maintained posthatch until maternally derived lipid reserves became depleted (approximately 168 days). The loss of chemicals having an octanol–water partition coefficient (log <i>K</i>_OW) greater than 5.8 was slow to negligible from days 0–135. However, during the increase in water temperatures in early spring, <i>K</i>_OW-dependent elimination of POPs was observed. Bioamplification was maximized for the highest log <i>K</i>_OW POPs, with an approximate 5-fold increase in lipid equivalents concentrations in 168 day old larvae as compared to newly fertilized eggs. This study demonstrates that later yolk-sac Chinook larvae (before exogenous feeding) are exposed to higher lipid equivalents POP concentrations than predicted by maternal deposition, which could lead to underestimates in the toxicity of critical life stages

Assessing fish consumption Beneficial Use Impairment at Great Lakes Areas of Concern: Toronto case study

<p>Beneficial use of fish consumption was designated impaired in the 1980s in many Areas of Concern across the North American Great Lakes. Remedial Action Plans have guided the restoration of beneficial use impairments with the goal of delisting the Areas of Concern. Here we present generic re-designation criteria and a three-tier Assessment Framework to assess the status of the fish consumption beneficial use impairments using the Toronto and Region Area of Concern as a case study. Tier 1 assessment identified that consumption advisories for many resident fish on the Toronto waterfront are non-restrictive (8+ meals month⁻¹). Advisory assessments in Tier 1 found that most migratory fish species, Carp and White Sucker are still restrictive in some cases preventing a ‘not impaired’ re-designation. Tier 2 Comparison with Reference Sites found that the advisories for most local fish are either non-restrictive or similar to reference locations in Lake Ontario, but some advisories due to elevated levels of polychlorinated biphenyl are still more restrictive for the Toronto waterfront and do not favour a ‘not impaired’ re-designation. An evaluation of multiple lines of evidence in Tier 3 including fish contaminant trend analyses, time to reach target fish levels, sediment concentrations and fish consumption patterns resulted in outcomes ranging from <i>neutral</i> (not conclusive) to <i>not impaired</i>. As a precautionary approach, the impaired status of the beneficial use impairment should be maintained to ensure continued polychlorinated biphenyl declines in fish. It is recommended that the Remedial Action Plan team update the fish consumption survey, investigate where additional feasible actions can be taken including examining potential polychlorinated biphenyl sources on the Humber and Don Rivers, and collect new data to undertake a future assessment.</p

Evaluation and Interconversion of Various Indicator PCB Schemes for ∑PCB and Dioxin-Like PCB Toxic Equivalent Levels in Fish

Polychlorinated biphenyls (PCBs) remain chemicals of concern more than three decades after the ban on their production. Technical mixture-based total PCB measurements are unreliable due to weathering and degradation, while detailed full congener specific measurements can be time-consuming and costly for large studies. Measurements using a subset of indicator PCBs (iPCBs) have been considered appropriate; however, inclusion of different PCB congeners in various iPCB schemes makes it challenging to readily compare data. Here, using an extensive data set, we examine the performance of existing iPCB3 (PCB 138, 153, and 180), iPCB6 (iPCB3 plus 28, 52, and 101) and iPCB7 (iPCB6 plus 118) schemes, and new iPCB schemes in estimating total of PCB congeners (∑PCB) and dioxin-like PCB toxic equivalent (dlPCB-TEQ) concentrations in sport fish fillets and the whole body of juvenile fish. The coefficients of determination (<i>R</i>²) for regressions conducted using logarithmically transformed data suggest that inclusion of an increased number of PCBs in an iPCB improves relationship with ∑PCB but not dlPCB-TEQs. Overall, novel iPCB3 (PCB 95, 118, and 153), iPCB4 (iPCB3 plus 138) and iPCB5 (iPCB4 plus 110) presented in this study and existing iPCB6 and iPCB7 are the most optimal indicators, while the current iPCB3 should be avoided. Measurement of ∑PCB based on a more detailed analysis (50+ congeners) is also overall a good approach for assessing PCB contamination and to track PCB origin in fish. Relationships among the existing and new iPCB schemes have been presented to facilitate their interconversion. The iPCB6 equiv levels for the 6.5 and 10 pg/g benchmarks of dlPCB-TEQ₀₅ are about 50 and 120 ng/g ww, respectively, which are lower than the corresponding iPCB6 limits of 125 and 300 ng/g ww set by the European Union