Howard,K.W.F. and Maier,H.(2007): Road de-icing salt as a potential constraint on urban growth in the Greater Toronto Area, Canada. Journal of contaminant Hydrology, 91, 146-170.

『カナダの大トロント地域における都市発展に対する潜在的制約としての道路凍結防止用塩』


Abstract
 North America's fifth most populated municipality - the Great Toronto Area (GTA) - is undergoing rapid urban development with serious questions being raised regarding the long-term impacts of urban growth on the quality and quantity of ground and surface water. Degradation of groundwater quality by NaCl de-icing salt is the primary concern since there are no cost effective alternatives to NaCl de-icing salt and there is little evidence that salt loadings to the subsurface can be significantly reduced. In 2001, the issue acquired a new sense of urgency when de-icing chemicals containing inorganic chloride salts (with or without ferrocyanide de-caking agents) were designated as toxic under the Canadian Environmental Protection Act.
 To heighten concerns, future growth in the GTA will inevitably take place in areas where groundwater is regularly used for potable supply. Studies using groundwater flow and transport models show that significant deterioration of groundwater quality can be expected in shallow aquifers as a result of urban development with chloride concentrations approaching the drinking water quality standard of 250 mg/l. Results demonstrate that urban planning needs a fresh approach that explicitly includes groundwater protection and aquifer management in the decision-making process, clearly defines acceptable environmental performance standards and makes greater use of groundwater models to evaluate alternative urban designs.

Keywords: Urban groundwater; Road salt; Models; Urban planning』

1. Introduction
 1.1. Documented impacts of de-icing salt on GTA groundwater
 1.2. The challenge
 1.3. A new sense of urgency
 1.4. The goal
2. The Seaton lands study area
 2.1. Geology and hydrogeology of the study area
 2.2. Background water quality
 2.3. Proposed environmental protection measures for the Seaton lands
3. Model predictions of urban impact
 3.1. Methodology and experimental design
 3.2. Pre-development simulations
 3.3. Post-development predictions
 3.4. Model results
4. Discussion - implications for the planning process
5. Conclusion
Acknowledgments
References


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