Collection, evaluation and characterization of biogeochemical background concentration data to inform metals assessments

BACKGROUND: The Ecological Assessment Division (EAD) of Environment Canada conducts ecological screening risk assessments of substances that met the categorization criteria set out in theCanadian Environmental Protection Act, 1999 (CEPA 1999) in order to determine whether these substances present or may present a risk to the environment. As part of the CMP, EAD is assessing the potential risk to the environment associated with the environmental exposure of over 1000 metal-containing substances, representing ~20 elements.A common characteristic of metals is their natural occurrence in the environment. The natural presence in the environment varies from one metal to another and between locations, according to a number of environmental and physico-chemical factors. To perform an ecological assessment, it may be important to discern relative contributions of the natural and anthropogenic metals. Metal concentration data and water quality parameters from a non-impacted area sharing similar characteristics to the identified site may also be collected to facilitate the assessment of the environmental fate of the anthropogenic releases.In fulfillment of the deliverables of this proposed contract, EAD will be provided with a comprehensive database of background data and a report that would provide a reliable statistical methodology to describe the natural background for all remaining metals to be assessed under the CMP. The natural background concentration is a contributor to the predicted environmental concentration, having a natural and an anthropogenic component. The knowledge of the natural fraction of the metal measured concentration in impacted sites may also inform potential risk management options.