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PW14 Probabilistic Ecological Risk Assessment
(PW236) Comparison of probabilistic and deterministic risk assessment results for terrestrial ecological receptors in a city park.
Aplin, M1, Odland, P1, Roy, M1, 1 URS Corporation, Austin, TX, USA
ABSTRACT- Typically ecological risk assessments are completed in a deterministic manner, due to both technical and regulatory constraints. Although probabilistic risk assessment techniques are available and have been examined by numerous regulatory bodies, including extensive review and discussion by the USEPA, their use and acceptance has been sporadic. Results of deterministic risk assessment methods are often adequate for making risk management decisions, but due to the use of multiple conservative inputs, they may unrealistically overestimate risks. Identifying and characterizing the uncertainty and variability that go into estimates of exposure and risk using probabilistic techniques allows a more realistic and focused risk assessment to be completed. By comparing the results of a deterministic risk assessment with the results of a probabilistic risk assessment, we will demonstrate the key input variables that impact the final risk calculations. Specifically, this evaluation will focus on ecological risk to urban tolerant terrestrial receptors that are potentially impacted by contaminants in a city park. The park is located above a former municipal landfill, and has been contaminated particularly by lead and illegal disposal of organochlorine pesticides. The probabilistic risk assessment will be well defined, with the methods and assumptions clearly documented. The sensitivity of parameters will be examined, correlations and dependencies will be identified, and detailed information on each input, and output distribution will be provided. This information will allow a transparent and detailed comparison to the deterministic risk evaluation. Ultimately, the ability to compare the probabilistic results with the deterministic results will allow a more dynamic and interactive decision making process between the risk assessor and risk manager, as well as with other interested parties.
Key words: monte carlo, probabilistic risk assessment, uncertainty, variability
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