Jd. Fuentes et Tf. Dann, GROUND-LEVEL OZONE IN EASTERN CANADA - SEASONAL-VARIATIONS, TRENDS, AND OCCURRENCES OF HIGH-CONCENTRATIONS, Journal of the Air & Waste Management Association [1995], 44(8), 1994, pp. 1019-1026
Over the past few years, concern has increased in Canada over the heal
th and environmental impacts of elevated concentrations of ground-leve
l ozone. During the summer the most populated regions of Canada freque
ntly record ozone concentrations that exceed the one-hour average maxi
mum acceptable air quality objective of 82 parts per billion (ppb). In
1988 the Canadian Council of Ministers of the Environment agreed to d
evelop a federal/provincial management plan to control nitrogen oxide
and volatile organic compound emissions to reduce ozone concentrations
in all affected regions of the country. In addition to the proposed i
nterim control measures, the plan recommended that studies be undertak
en to acquire the information necessary to develop sound control strat
egies. This report represents one of those studies and provides a summ
ary of ground-level ozone measurements for eastern Canada for the 1980
to 1991 period with an emphasis on seasonal variations, trends, and o
ccurrences of high concentrations.Southwestern Ontario experiences the
highest maximum hourly ozone concentrations and the greatest frequenc
y of hours greater than the 82 ppb acceptable objective. Urban sites h
ave the highest frequencies of ozone concentration measurements in the
< 10 ppb range, while rural and remote sites show peaks in frequency
distribution in the 20 to 30 ppb range. Trend analysis of summertime (
May to September) average daily maximum ozone concentration showed no
consistent pattern for eastern Canadian sites during 1980 to 1991. Sit
es in Montreal showed statistically insignificant downward trends whil
e sites in Toronto showed small but statistically significant upward t
rends. These ozone-increasing trends are associated with reductions in
nitric oxide concentrations. At all sites there was large year-to-yea
r variability in peak ozone levels and in the frequency of hours with
ozone concentrations above the maximum acceptable objective.