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Exploring the environmental covariates of E. coli and total coliforms in Ontario’s groundwater Bache, Tenny Risette

Abstract

Microbial contamination of drinking water poses a danger to human health, and although the risk of exposure to waterborne microbes is highest in developing nations, outbreaks continue to affect populations in developed countries. Complacency toward groundwater protection can have tragic consequences - an example of which is the May 2000 outbreak of waterborne disease in Walkerton, Ontario, where seven people died and over 2100 became ill. In a response to such incidents, our research investigates the potential mechanisms of microbial contamination of Ontario’s groundwater sources, which supply over 25% of the Province’s twelve million residents with drinking water. In this project, we identify environmental risk factors for private well contamination by coliform bacteria, specifically Escherichia coli (E. coli), in Southern Ontario. Inspired by concepts of landscape epidemiology, multiple methodologies were employed to assess the impact of local environmental characteristics on groundwater quality. A Geographic Information System (GIs) was used to integrate and analyze several datasets, including: land use, agricultural animal densities and farming practices, private well locations and corresponding water quality, human population densities, and geology. Through spatial and statistical analyses, we found that areas of agricultural land, low infiltration rate soil and surficial geology, and carbonate bedrock are significantly more prevalent near contaminated wells; whereas areas of developed land, soils with high infiltration rates, and non-carbonate bedrock are more prevalent near clean wells. The outcomes and methodologies identified in this project help further our understanding of the potential processes responsible for effective transfer of microbes from the environment and animals to humans. Microbial contamination of drinking water poses a danger to human health, and although the risk of exposure to waterborne microbes is highest in developing nations, outbreaks continue to affect populations in developed countries. Complacency toward groundwater protection can have tragic consequences - an example of which is the May 2000 outbreak of waterborne disease in Walkerton, Ontario, where seven people died and over 21 00 became ill. In a response to such incidents, our research investigates the potential mechanisms of microbial contamination of Ontario’s groundwater sources, which supply over 25% of the Province’s twelve million residents with drinking water. In this project, we identify environmental risk factors for private well contamination by coliform bacteria, specifically Escherichia coli (E. coli), in Southern Ontario. Inspired by concepts of landscape epidemiology, multiple methodologies were employed to assess the impact of local environmental characteristics on groundwater quality. A Geographic Information System (GIs) was used to integrate and analyze several datasets, including: land use, agricultural animal densities and farming practices, private well locations and corresponding water quality, human population densities, and geology. Through spatial and statistical analyses, we found that areas of agricultural land, low infiltration rate soil and surficial geology, and carbonate bedrock are significantly more prevalent near contaminated wells; whereas areas of developed land, soils with high infiltration rates, and non-carbonate bedrock are more prevalent near clean wells. The outcomes and methodologies identified in this project help further our understanding of the potential processes responsible for effective transfer of microbes from the environment and animals to humans.

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