AQUARISK 3.2
Probabilistic Ecological Risk Assessment
Probabilistic ERA, applied with the Precautionary Principle, is the most appropriate means to evaluate the risk posed by any environmental hazard to the organisms living within the receiving environment. The newly released Australian national water quality guidelines have been set using this approach and they recommend a similar method be taken when determining site-specific criteria. However, the guidelines are limited to aquatic environments and, also, do not describe what you should do with any data you derive for your site in terms of performing site-specific ERAs.
Quantitative, probabilistic ERAs use the data provided by any site-specific modelling or monitoring to evaluate the likelihood that the operations will:
a) exceed any regulatory criteria, or
b) exceed any threshold of unacceptable impact in the receiving environment,
as defined and agreed by the parties who are stakeholders in that environment. Obviously, this is beneficial for site-specific applications where species of particular concern are exposed to potential harm.
ERA works by converting measured or modelled concentrations of the contaminant in the environment (terrestrial, aquatic or atmospheric) into a distribution where each concentration has a different probability of occurring. This distribution can be further modified, using geochemical speciation modelling or other means that can evaluate bioavailability, to provide a probability function of the ecologically relevant concentrations. A similar distribution is subsequently derived for any dose-response information that you may have for the toxicant. The information can be obtained from the available scientific literature (or from databases such as that provided with the guidelines) that can be filtered to closely reflect the site in question, or can be obtained from bio monitoring and assessment of the site. Once the dose-response distribution is established, site-specific criteria can be obtained that reflect the agreed degree of impact that can be accepted within the environment. These values also reflect the degree of uncertainty in the data and should err on the side of protecting the environment, in accord with appropriate use of the Precautionary Principle.
Comparing the two probability distributions also allows you to predict the current or likely ecological ‘footprint’ of any effluent from the operation in the receiving ecosystem by a process of convolution. The uncertainties in these estimates can be used to decide what further information is required in order to adequately improve the predictions and protect the environment as well as the investment. That is, to come to an equitable balance between development and protection of biodiversity and other environmental values.
Whilst AQUARISK was developed with aquatic systems in mind, it can be applied to any environment. The program uses data provided by the assessor to perform all of the operations described above.