Abstract
Understanding the patterns of chemical exposure among biota across a landscape is challenging due to the spatial heterogeneity and complexity of the sources, pathways, and fate of the different chemicals. While spatially-driven relationships between contaminant sources and biota body burdens of a single chemical are commonly modelled, there has been little effort on modelling chemical mixtures across multiple wildlife species in the Canadian Oil Sands region. In this study, we used spatial principal components analysis (sPCA) to assess spatial patterns of the body burdens of 22 metals and Potentially Toxic Elements (PTEs) in 492 individual wildlife, including fur-bearing mammals, colonial waterbirds, and amphibians collected from the Canadian Oil Sands region in Canada. Spatial analysis and mapping both indicate that some of the complex exposures in the studied biota are distributed randomly across a landscape, which suggests background or non-point source exposures. In contrast, the pattern of exposure for seven metals and PTEs, including mercury, vanadium, lead, rubidium, lithium, strontium, and barium, exhibited a clustered pattern to the east of the open-pit mining area and in regions downstream of oil sands development which indicates point-source input. This analysis demonstrated useful methods for integrating monitoring datasets and identifying sources and potential drivers of exposure to chemical mixtures in biota across a landscape. These results can be used to support an adaptive monitoring program by identifying regions needing additional monitoring, health impact assessments, and possible intervention strategies.
Highlights
Traditional risk assessments in ecotoxicology have focused on a chemical by chemical exposure approach [1]
We demonstrate the application of an spatial principal components analysis (sPCA) method and address current limitations of spatially assessing landscape-level complex exposures across different species and life stages
Results show that patterns observed in the sPCA were related to patterns of environmental exposures and not a difference in species-specific accumulation rates
Summary
Traditional risk assessments in ecotoxicology have focused on a chemical by chemical exposure approach [1]. While these simple models are easy to develop and interpret, they are not representative of the true nature of environmental chemical exposure in biota. As the biota in an ecosystem is often, if not always, exposed to environmental contaminant mixtures, better exposure models related to complex chemical mixtures are needed to reflect this ecological realism for valid risk assessments [2]. Complex exposures are true for biota living. Patterns of chemical exposure in the oil sands region of Canada to H.M. Chan; and the Canada-Alberta Joint Oil Sands Monitoring Program (JOSM) to B.D. Pauli
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