Comparing laboratory and field measured bioaccumulation endpoints.

An approach for comparing laboratory and field measures of bioaccumulation is presented to facilitate the interpretation of different sources of bioaccumulation data. Differences in numerical scales and units are eliminated by converting the data to dimensionless fugacity (or concentration-normalized) ratios. The approach expresses bioaccumulation metrics in terms of the equilibrium status of the chemical, with respect to a reference phase. When the fugacity ratios of the bioaccumulation metrics are plotted, the degree of variability within and across metrics is easily visualized for a given chemical because their numerical scales are the same for all endpoints. Fugacity ratios greater than 1 indicate an increase in chemical thermodynamic activity in organisms with respect to a reference phase (e.g., biomagnification). Fugacity ratios less than 1 indicate a decrease in chemical thermodynamic activity in organisms with respect to a reference phase (e.g., biodilution). This method provides a holistic, weight-of-evidence approach for assessing the biomagnification potential of individual chemicals because bioconcentration factors, bioaccumulation factors, biota-sediment accumulation factors, biomagnification factors, biota-suspended solids accumulation factors, and trophic magnification factors can be included in the evaluation. The approach is illustrated using a total 2393 measured data points from 171 reports, for 15 nonionic organic chemicals that were selected based on data availability, a range of physicochemical partitioning properties, and biotransformation rates. Laboratory and field fugacity ratios derived from the various bioaccumulation metrics were generally consistent in categorizing substances with respect to either an increased or decreased thermodynamic status in biota, i.e., biomagnification or biodilution, respectively. The proposed comparative bioaccumulation endpoint assessment method could therefore be considered for decision making in a chemicals management context.

Development of a preliminary relative risk model for evaluating regional ecological conditions in the Delaware River Estuary, USA.

Effective environmental management and restoration of urbanized systems such as the Delaware River Estuary requires a holistic understanding of the relative importance of various stressor-related impacts throughout the watershed, both historical and ongoing. To that end, it is important to involve as many stakeholders as possible in the management process and to develop a system for sharing of scientific data and information, as well as effective technical tools for evaluating and disseminating the data needed to make management decisions. In this study, we describe a preliminary assessment that was undertaken to evaluate the relative risks for the variety of stressors currently operating within the Delaware Estuary using a relative risk model (RRM) framework. This model was constructed using existing data and information on the ecological conditions and stressors in the main-stem Delaware River below the head of tide at Trenton, New Jersey, USA. A large database was developed with pertinent data from a variety of library, scientific, and regulatory sources. Data were compiled, reviewed, and characterized before development of the Estuary-specific RRM. Our primary goals and objectives in developing this preliminary RRM for the Estuary were to 1) determine if the RRM framework can be adapted to a large complex estuarine system such as the Delaware River, 2) identify the issues associated with adapting the model framework to the various management issues and regional areas/habitats of the River, 3) help identify data needs and potential refinements that might be needed to more specifically quantify relative stressor risks in various areas and habitats of the Estuary to better inform future management goals/actions by Stakeholders. The key conclusions of our preliminary assessment are 1) a diverse suite of stressors is likely affecting the ecological conditions of the Delaware Estuary, 2) chemical (toxicants/contaminants) and physical (sedimentation, habitat loss) stressors were found to be on par with regards to their ranking, and 3) the RRM, in its current form, made it difficult to effectively balance the inequality in the sizes of the study subareas considered in the assessment. Management objectives and related research activities should focus on collecting the necessary data and information to further refine the RRM and assess the relative impacts of these stressors at various scales in the Estuary. By having such a framework and tool available, we believe that stakeholders within the Delaware River watershed will be able to make more informed and risk-based management decisions regarding restoration options for the Estuary.