Oil Toxicity Field Guide for Aquatic Habitats
The Oil Toxicity Field Guide for Aquatic Habitats is a proof-of-concept project developed by the Coastal Response Research Center (CRRC) - a joint partnership between the National Oceanic and Atmospheric Administration's Office of Response and Restoration (NOAA OR&R) and the University of New Hampshire. The field guide and its companion data CD [hereafter referred to as "field guide"] are designed to display selected oil toxicity information in a consistent and searchable format that is easy to read and interpret during an oil spill. The initial development of the field guide is linked directly with an outcome of the 2006 CRRC PAH Toxicity Summit. At the summit, participants concluded there was a strong need to synthesize toxicity research and make raw toxicity and oil properties data more available to oil spill responders in the field. Several recent projects funded by CRRC resulted in oil toxicity datasets that have been incorporated into the field guide (McGrath and DiToro 2007).
The field guide is a proof-of-concept project and thus unable to be released or published in its current form. The project development team is currently working to meet the applicable requirements for agency publication and/or determine a path forward for public release of the guide. Currently, the field guide contains information in two key topic areas: (1) median lethal effecfinalt concentrations (LC50) for individual polycyclic aromatic hydrocarbons (PAHs); and (2) composition of PAHs in selected unweathered source oils. A third topic area, model-predicted PAH weathering patterns using standard environmental conditions, is currently being addressed by the project team. Resource constraints limited the number of source oils in this version of the field guide, but the three chosen are common in spills in North America (Alaskan North Slope crude, South Louisiana sweet crude, and diesel).
The field guide was developed in two phases. First, an oil toxicity database for PAHs was compiled, so that toxicity data could be standardized for use in tables and graphs. Second, background and interpretive information about selected source oils and species used in the guide was collected to assist responders with their evaluation of the potential effects of discharged oil on aquatic species. A key outcome of the initial phase of the project is a set of 40 standardized toxicity graphs for freshwater and saltwater conditions, graphed by individual PAH and species. See Figure 1 (Example Graph for the toxicity of the PAH Acenaphthene to Fish in Freshwater). Another key outcome is PAH composition charts and tables for selected source oils (see Figure 2 and Table 1 for Alaskan North Slope Crude Oil).
The field guide integrates several fields of research and may be useful in the following situations:
- Communication of synthesized toxicity information to a variety of stakeholders in the response community;
- Training oil spill responders, modelers, scientists, and natural resource damage specialists on the acute effects of PAHs to aquatic species;
- Informing stakeholders about the need to collect or analyze water samples or other field data in a timely manner; and
- Rapid evaluation of toxicity thresholds in freshwater and saltwater for individual species or species groups.
As a final note, the field guide already has been used by NOAA staff to inform decision-making about the potential toxicity of oil to aquatic species during spills. Additionally, two recent large spills involving heavy fuel oil (e.g., IFO 380, #6 Fuel Oil) prompted the developers to include a PAH compositional chart and table for that oil type. The project development team will continue to take advantage of opportunities to "beta-test" the current version of the guide over the coming months as other project-related issues are addressed more fully.
|Figure 1. A graph indicating the median lethal concentration (LC50) of Acenaphthene to four fish species in freshwater at 24, 48, 72, and 96 hours. All concentrations are presented in µg/L, or parts per billion (ppb). The approximate solubility of the polycyclic aromatic hydrocarbons (PAH), Acenaphthene, is also indicated on the graph.|
This graph is an example of a type of figure that is presented in the field guide for freshwater and saltwater environments. Thirty-nine other graphs indicating the toxicity of PAHs to selected individual species and species groups also are in the field guide. The data used to generate this graph and others in the field guide were classified as measured (i.e., concentrations of PAHs in the laboratory were measured during an experiment). Toxicity data classified as nominal or unknown were not used to generate graphs in the field guide but are contained in the companion CD to the field guide. All measured and nominal toxicity data compiled during the project are contained in the companion CD. Six different PAHs were selected for the field guide based on resource constraints and initial data availability: Acenaphthene, Anthracene, Fluoranthene, Naphthalene, Phenanthrene, and Pyrene. Additional toxicity data for PAHs and monoaromatic hydrocarbons (MAHs) (e.g., Benzene) may be added to the field guide in the future.
Figure 2. A histogram indicating average composition of polycyclic aromatic hydrocarbons (PAHs) for unweathered Alaskan North Slope Crude Oil in the current version of the field guide. Data were provided to the project development team by the Louisiana State University Response & Chemical Assessment Team. Ten replicate samples of unweathered oil were analyzed for PAHs so that a profile of average PAH composition could be constructed. All PAH concentrations are presented in µg/L, or parts per billion (ppb).
In addition to Alaskan North Slope Crude oil, the two other oil types selected for the current version of the field guide were South Louisiana Sweet Crude and Diesel. As development of the field guide progresses, additional oil types may be added. Ahistogram of PAH composition may be used graphically determine which PAHs in an oil may be important to consider in decision-making during the first 96 hours of a spill (typically a time period when incident-specific data and models are not available). Site-specific samples of weathered oil also may be compared to unweathered oil profiles in this field guide to facilitate analysis of oil degradation patterns. Histograms are derived from average PAH concentrations in unweathered source oils (e.g., Table 1).
Note: Concentrations of PAH's were reported from LSU RCAT as ng/g (ppb). The following information was converted to µg/L (ppb) for consistent presentation in this guide.
Table 1. Average composition of polycyclic aromatic hydrocarbons (PAHs) for unweathered Alaskan North Slope Crude Oil in the current version of the field guide. Data were provided to the project development team by the Louisiana State University Response & Chemical Assessment Team. Ten replicate samples of unweathered oil were analyzed for PAHs so that a profile of average PAH composition could be constructed. All PAH concentrations are presented in µg/L, or parts per billion (ppb).
In addition to Alaskan North Slope Crude oil, the two other oil types selected for the current version of the field guide were South Louisiana Sweet Crude and Diesel. As development of the field guide progresses, additional oil types may be added. Concentrations of PAHs in unweathered source oils are useful in the prediction of oil fate and transport following spills and inform responders and assessment specialists about which PAHs in oil may be important to consider in decision-making during the first 96 hours of a spill (typically a time period when incident-specific data and models are not available). Tables of PAH concentrations in unweathered source oils are used to create corresponding histograms (e.g., Figure 2).