Duncan Boyd

A Decision Making Framework for Sediment Assessment Developed for the Great Lakes

A rule-based, weight-of-evidence approach for assessing contaminated sediment on a site-by-site basis in the Laurentian Great Lakes is described. Information from four lines of evidence—surficial sediment chemistry, laboratory toxicity, invertebrate community structure and invertebrate tissue biomagnification—is integrated within each line to produce a pass (‘−’) or fail (‘+’) conclusion, then combined across lines resulting in one of 16 outcome scenarios. For each scenario, the current status of the site, interpretation, and management recommendations are given. Management recommendation(s) can range from no action to risk management required (9 of the 16 scenarios). Within each line of evidence, the strength of each response can also be ranked (e.g., score of 1 to 4), providing managers with more information to aid decision options. Other issues that influence scientific management recommendations include site stability, subsurface contamination and spatial extent of effects. The decision framework is intended to be transparent, comprehensive (incorporating exposure, effect, weight-of-evidence, and risk), and minimally uncertain.

Limitations on the Development of Quantitative Monitoring Plans to Track the Progress of Beneficial Use Impairment Restoration at Great Lakes Areas of Concern

The implementation of Annex 2 (Remedial Action Plans and Lakewide Management Plans) of the Great Lakes Water Quality Agreement (GLWQA) in 1987 has resulted in many significant efforts to restore, protect, and conserve environmental conditions at Areas of Concern (AOCs). Within the Canadian portion of the Great Lakes, accomplishments such as “delisting” the Collingwood and Severn Sound AOCs, and the recognition of the Spanish Harbour AOC as an “area in recovery,” are direct results of multi-stakeholder actions directed by the GLWQA. A review of Stage 2 Remedial Action Plan (RAP) updates and progress reports reveal that there have been numerous successful projects implemented at various AOCs with the expectation of improved environmental conditions. However, despite this progress, there are 15 Canadian sites that remain designated as AOCs, and in many cases RAP partners can only provide qualitative descriptions as to how close they are to restoring the Beneficial Use Impairments (BUIs) responsible for their AOC designation. “Continuous improvement” may be an admirable guiding principle for environmental management when water quality and wildlife habitat is severely degraded. However, as environmental conditions improve, RAP partners must start thinking more quantitatively about what remains to be accomplished before BUIs can be reported as restored. In this context, continuous improvement is no longer sufficient; it describes the journey, but fails to es-

SEDS: setting environmental decisions for sediment, a decision making tool for sediment management

Abstract The need for guidance on the management of contaminated sediment has been articulated by the International Joint Commission, scientists and resource managers in many jurisdictions. There is a growing convergence on what constitutes a valid comprehensive sediment assessment but active debate on how to synthesize multiple pieces of information on sediment chemistry, biological information from field monitoring and laboratory sediment bioassessment. Recognizing the current state of knowledge, we provide a recommended approach to bioassessment sediment management strategies. The intent is to facilitate the formulation of data interpretation tools needed for a decision making process that is flexible to enable site-specific determination regarding the need to take action beyond the control of sources of contamination. While the concepts contained herein have been employed implicitly in Canada and Ontario, the details on data collection, evaluation, and reaching a management decision are explicitly lai...

Estimating sediment quality thresholds to prevent restrictions on fish consumption: Application to polychlorinated biphenyls and dioxins–furans in the Canadian Great Lakes

Sediment quality thresholds (SQTs) are used by a variety of agencies to assess the potential for adverse impact of sediment-associated contaminants on aquatic biota, typically benthic invertebrates. However, sedimentary contaminants can also result in elevated fish contaminant levels, triggering consumption advisories that are protective of humans. As such, SQTs that would result in fish concentrations below consumption advisory levels should also be considered. To illustrate how this can be addressed, we first calculate biota sediment accumulation factors (BSAFs) for polychlorinated biphenyls (total PCB) and polychlorinated dioxins-furans (PCDD/Fs) in the Canadian Great Lakes using measured lake sediment and fish tissue concentrations in 4 fish species, namely, lake trout, whitefish, rainbow trout, and channel catfish. Using these BSAFs and tissue residue values for fish consumption advisories employed by the Ontario Ministry of the Environment (OMOE, Canada), we derive fish consumption advisory-based SQTs (fca-SQTs) that are likely to result in fish tissue residues that are safe to eat without restriction. The PCDD/Fs fca-SQTs ranged from 6 to 128 pg toxic equivalents (TEQ)/g dry weight (dw) and were above the Canadian Council of the Ministers of the Environment (CCME) threshold effect level (TEL) of 0.85 pg TEQ/g dw. In contrast, the total PCB fca-SQTs ranged from 1 to 60 ng/g dw and were generally below the CCMEs TEL of 34.1 ng/g and OMOEs lowest effect level (LEL) of 70 ng/g; however, they were consistent with the OMOEs no effect level (NEL) of 10 ng/g. The fca-SQTs derived using the BSAF as well as food chain multiplier (FCM) approach for a smaller scale system (Hamilton Harbour in Lake Ontario) corresponded well with average lakewide Lake Ontario fca-SQTs. This analysis provides approximate sediment concentrations necessary for reducing fish consumption advisories for each of the Canadian Great Lakes and emphasizes the impacts of historical lake sediment contamination on fish advisories. We believe that this approach merits consideration in sediment guideline development.

Hamilton Harbour over the last 25 years: Insights from a long-term comprehensive water quality monitoring program

Hamilton Harbour was identified by the International Joint Commission as a problem area in 1978 and later identified as an Area of Concern in 1985. In response to its Remedial Action Plan, the harbour has been systematically monitored since 1987. In this study, we present the long-term water quality record (1987 to 2012) of Hamilton Harbour, focusing on the parameters and seasonal intervals of particular importance to the Remedial Action Plan beneficial use impairments. The long-term summer records showed that total phosphorus concentrations decreased in the first decade and have remained relatively unchanged since 1998, while an increasing trend in Secchi disc depth was observed until 2005 only to be reversed since then. No significant changes in chlorophyll a concentrations have been observed since 1987 despite significant changes in total phosphorus. Hypoxia in the hypolimnion of Hamilton Harbour remains a common occurrence and despite long-term trend improvements there has been little change over the last decade. Spring conditions have also changed, and higher conductivity values and chlorophyll a concentrations have been measured in recent years. A strong correlation between spring hypolimnetic dissolved organic carbon concentrations and dissolved oxygen depletion rates was found suggesting the organic material load to the harbour is an important controlling factor for hypoxia. Finally, the data suggest that the hypolimnetic accumulation rate of soluble reactive phosphorus in the summer has increased since 1987, most notably since the early 2000s. However, it is only since 2008 that this translated into an increasing trend in hypolimnetic soluble reactive phosphorus concentrations. These data suggest that conditions have recently changed in Hamilton Harbour and that sediment phosphorus release may delay water quality improvements for many years following reductions in total phosphorus loadings. Further research is needed to understand the implications to the Remedial Action Plan water quality goals.

Modelling phosphorus dynamics in Cootes Paradise marsh: Uncertainty assessment and implications for eutrophication management

Cootes Paradise marsh, a hypereutrophic wetland draining into the western end of Hamilton Harbour, Ontario, has historically been considered an important regulatory factor of the severity of local eutrophication phenomena. In this study, we present a modelling exercise that aims to draw inference on the relative contribution of various external and internal flux rates to the phosphorus budget of Cootes Paradise. We first examined the capacity of a phosphorus mass-balance model, accounting for the interplay among water column, sediments and macrophytes, to reproduce the observed total phosphorus dynamics over a 17-year period (1996–2012). Water level fluctuations were one of the key challenges for balancing the phosphorus budget during model calibration. Our analysis shows that the model satisfactorily reproduced the average seasonal patterns, as well as the year-to-year total phosphorus variability (coefficient of determination = 0.20, relative error = 26.8%, root mean square error = 62.2 μg P l−1, model efficiency = 0.15). However, our model failed to capture two years of the study period (1997 and 2007), when ambient TP levels significantly deviated from the typically prevailing conditions. Model sensitivity analysis identified the sedimentation of particulate material and diffusive reflux from sediments as two critical processes to characterize the phosphorus cycle in the wetland. Based on the current parameter specification, our model postulates that the sediments still act as a net sink, whereas macrophyte processes (respiration rates, nutrient uptake from interstitial water) appear to play a minor role. We conclude by discussing the various sources of uncertainty and additional remedial actions required in Cootes Paradise marsh to realize a shift from the current turbid-phytoplankton dominated state to its former clear-macrophyte dominated state.

Monitoring water quality on the central Toronto waterfront: Perspectives on addressing spatiotemporal variability

Toronto Harbour, adjacent to a large urban centre on Lake Ontario, receives inputs from storm sewers, combined sewer overflows, and urban runoff that lead to contrasting water quality over the waterfront. Toronto’s Inner and Outer Harbours, mesotrophic and meso-oligotrophic, respectively, were investigated in 2008 to assess how water quality conditions were affected by loading gradients, weather and lake circulation. Spatially-intensive measurements of UV fluorescence, turbidity, conductivity, and chlorophyll a, together with lab-based analysis of chemistry at discrete sites, were used to depict patterns and contrasts in water quality in the harbour. Spatially-integrated field sensor data were also employed to examine the efficacy of using discrete water quality sampling to represent average conditions. Nitrogen, total phosphorus, dissolved organic carbon, major ions and E. coli gradients were a recurrent feature among surveys with concentrations decreasing away from the Don River mouth. The limited point-sample data reasonably depicted average conditions among areas of the harbour on the days of survey as did the results interpolated for a long-term monitoring station in the Inner Harbour. The strong variability seen within the Inner Harbour indicates that the most affected water quality conditions are likely under represented by area-wide conditions. Temporal variability in water quality, correlated with the discharge from the Don River, was strong yet under represented by the field-based sampling. Empirical prediction of total phosphorus concentrations in the Inner Harbour, and correlated with Don River discharge, were used to demonstrate both the critical need to address temporal variability in monitoring design and the possibility of using empirical predictive approaches drawing upon field sensor data to fill this gap.