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Staggering reductions in atmospheric nitrogen dioxide across Canada in response to legislated transportation emissions reductions

Reid, Holly ; Aherne, Julian

Atmospheric Environment, December 2016, Vol.146, pp.252-260 [Periódico revisado por pares]

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  • Título:
    Staggering reductions in atmospheric nitrogen dioxide across Canada in response to legislated transportation emissions reductions
  • Autor: Reid, Holly ; Aherne, Julian
  • Assuntos: Mann-Kendall ; Changepoint Analysis ; National Air Pollution Surveillance Program (Naps) ; Emission Regulations ; Nitrogen Dioxide ; Engineering ; Environmental Sciences
  • É parte de: Atmospheric Environment, December 2016, Vol.146, pp.252-260
  • Descrição: It is well established that atmospheric nitrogen dioxide (NO ), associated mainly with emissions from transportation and industry, can have adverse effects on both human and ecosystem health. Specifically, atmospheric NO plays a role in the formation of ozone, and in acidic and nutrient deposition. As such, international agreements and national legislation, such as the , and the have been put into place to regulate and limit oxidized nitrogen emissions. The objective of this study was to assess the response of ambient air concentrations of NO across Canada to emissions regulations. Current NO levels across Canada were examined at 137 monitoring sites, and long-term annual and quarterly trends were evaluated for 63 continuous monitoring stations that had at least 10 years of data during the period 1988–2013. A non-parametric Mann-Kendall test (Z values) and Sen's slope estimate were used to determine monotonic trends; further changepoint analysis was used to determine periods with significant changes in NO air concentration and emissions time-series data. Current annual average NO levels in Canada range between 1.16 and 14.96 ppb, with the national average being 8.43 ppb. Provincially, average NO ranges between 3.77 and 9.25 ppb, with Ontario and British Columbia having the highest ambient levels of NO . Long-term tend analysis indicated that the annual average NO air concentration decreased significantly at 87% of the stations (55 of 63), and decreased non-significantly at 10% (5 of 63) during the period 1998–2013. Concentrations increased (non-significantly) at only 3% (2 of 63) of the sites. Quarterly long-term trends showed similar results; significant decreases occurred at 84% (January–March), 88% (April–June), 83% (July–September), and 81% (October–December) of the sites. Declines in transportation emissions had the most influence on NO air concentrations, and changepoint analysis identified three significant changepoints for the air concentration of NO and transportation emissions data. The air concentration changepoints occurred immediately following changepoints in transportation emissions. The introduction of emissions limiting legislation, primarily from transportation sources, has lead to dramatic decreases of 32% in NO emissions (42% from transportation sources [road, rail, air, marine]) and 47% in ambient NO concentrations across Canada. With respect to human health, legislated changes in transportation emissions have the greatest impact on ambient concentration in urban areas.
  • Idioma: Inglês

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