Meteorological influences on the spatial and temporal variability of NO2 in Toronto and Hamilton

The spatial and temporal variability of nitrogen dioxide (NO₂) concentrations and their relationships with meteorology was evaluated in the Toronto–Hamilton urban airshed. NO₂ concentrations were highest in the early morning and late evening. Mean concentrations were highest in winter, although individual one-hour NO₂ concentrations were found to be highest in summer. Wind direction was the strongest control on hourly NO₂ concentration, and temperature and wind speed also had an effect. Our analysis of NO₂ concentration variation by wind direction showed that areas downwind of major highways, urban centres and industry were exposed to higher pollutant concentrations. Seasonal patterns of NO₂ concentration displayed significant spatial heterogeneity, in particular, in Toronto. Onshore winds sheltered coastal inhabitants from the full extent of NO₂ exposure they would otherwise experience. Seasonal variations in meteorology and emissions mean that the degree of spatial variability in NO₂ concentrations changes from season to season. This study will help to improve existing land-use regression-based NO₂ prediction models by incorporating meteorological controls on NO₂ distributions for health effect studies.     

Anthropogenic pressures on coastal dunes, southwestern Newfoundland

Sand‐dominated coastlines backed by transverse foredunes, dome dunes, and parabolic dunes occur at several sites along the coastline of southwest Newfoundland, extending from Sandbanks Provincial Park (Burgeo) to Grand Bay West (Channel‐Port‐aux‐Basques) and north to J.T. Cheeseman Provincial Park. The coastal dunes developed during the mid‐Holocene in response to enhanced sediment availability and flux, coupled with effective sediment retention. Under present environmental conditions, development of aeolian dunes is hindered. Recent changes in the geomorphology of these coastlines provide evidence of the impact of anthropogenic activity. Differing time scales of both weather/climate events and landform response complicate interpretation. Anthropogenic modification, both intentional and accidental, represents a locally dominant geomorphic influence, and these dunes have evolved rapidly in response to anthropogenic pressure coupled with storm events. Changes in the southwest Newfoundland economy have led to increased interest in tourism, and consequent pressure on the sandy coastlines and backing dunes. Increased anthropogenic utilization of the coast for recreational purposes, both by residents and tourists, and limited offshore winter ice and onshore snow cover have resulted in accelerated erosion and degradation of the dunes and coastlines. The influx of sand from the beaches is insufficient to replace that removed through natural and anthropogenic causes. Consequently, the coastal dunes of southwest Newfoundland are essentially relict and will not regenerate following anthropogenic disturbance. On trouve à plusieurs endroits le long des côtes sud‐ouest de Terre‐Neuve, du parc provincial Sandbanks (Burgeo) à Grand Bay Ouest (Channel‐Port‐aux‐Basques) et vers le nord jusqu'au parc provincial J.T. Cheeseman, des littoraux à prédominance de dunes où se sont formées des avant‐dunes transversales, des dunes en forme de dôme et des dunes paraboliques. Les dunes maritimes sont apparues vers le milieu de l'ère holocène en réaction à la disponibilité accrue de sédiments et à leur flux alliés à leur rétention efficace. Ainsi, les conditions environnementales actuelles entravent la formation de dunes éoliennes. Des changements récents à la géomorphologie de ces littoraux fournissent la preuve que l'activité anthropique a des conséquences. Les événements météorologiques et climatiques ainsi que la réaction topographique étant reliés à des échelles de temps différentes, compliquent l'interprétation. Une modification anthropique, qu'elle soit intentionnelle ou accidentelle, constitue une influence géomorphologique locale dominante. Ces dunes ont évolué rapidement en raison de ces pressions anthropiques alliées à des événements pluvio‐hydrologiques. Des changements dans l'économie du sud‐ouest de Terre‐Neuve ont suscité un regain d'intérêt pour le tourisme, ce qui a eu pour effet de créer des pressions sur les littoraux sablonneux et les dunes. L'accroissement de l'utilisation du littoral à des fins récréatives, tant par les résidents que les touristes, et l'accumulation limitée de glace en mer et de neige sur les côtes ont accéléré l'érosion et la détérioration des dunes et des littoraux. L'afflux de sable des plages est insuffisant pour remplacer celui qui disparaît pour des raisons naturelles ou anthropiques. En conséquence, les dunes maritimes du sud‐ouest de Terre‐Neuve sont essentiellement des reliques et ne se régénéreront pas si elles sont perturbées par des causes anthropiques.