Ozone Comparison*
Ozone (O3) is a major component of summer-time
smog. Volatile organic compounds and oxides of nitrogen combine in the presence of sunlight to form O3. Ozone
is also transported to the ground from the "ozone rich" upper atmosphere by natural weather processes. The majority of
O3 in the atmosphere comes from natural processes. There is a Canada-wide Standard for ozone concentrations.
The Standard states that an eight-hour ozone concentration measurement should not exceed 65 ppb (parts per billion).
The five-year average (1998 to 2003) showed that Edmonton exceeded the CWS an average of 2 days a year while Calgary
averaged zero days a year. Edmonton and Calgary were among the cities with the lowest number of exceedances. Toronto,
Hamilton and Windsor averaged the most days that exceeded the Standard. Over the five-year period, Windsor
averaged 27 days a year. The 2003 averages showed very similar results. Edmonton did not see any days where ozone
concentrations exceeded the Standard, while Calgary saw 2 days. These again were among the lowest number of days with
exceedances for Canadian cities. As before Hamilton, Windsor, and Toronto all had the highest number of days that
exceeded the Standard.
There is also an Alberta Objective for ozone concentrations. This Objective
for O3 is based on the prevention of adverse effects on human health and vegetation. The Objective states that
a 1-hour average concentration should not exceed 82 ppb. The five-year average showed that Edmonton and Calgary had very
few exceedances of the Alberta Objective. Edmonton averaged 1 exceedance a year while Calgary averaged zero. These were
also the same number of exceedances as Edmonton and Calgary saw in 2003. These were among the lowest number of exceedances
for Canadian cities. Windsor, Toronto and Hamilton all had significantly more exceedances for both the five-year average
and in 2003 than any other city in Canada. Windsor had the most exceedances averaging 67 per year from 1998 to 2003.
Windsor also had the most exceedances in 2003 with 64. The cities that had the most exceedances of the Canada-wide
Standard also had the most exceedances of the Alberta Objective. Although not obvious just looking at the five-year
averages, examining the exceedances by year revealed that in 2000 there was an across Canada drop in the number of
ozone exceedances. Looking deeper into this revealed that this was mainly due to it being a particularly cold and wet
summer. This abnormal summer weather (particularly in Eastern Canada) resulted in lower ozone concentrations, which
limited the number of exceedances.
|
Number of Exceedances of the CWS for Ozone (8-hour > 65 ppb)
|
|
City
|
5 Year Average (1998-2003)
|
2003
|
|
St. John's
|
0
|
0
|
|
Halifax
|
2
|
0
|
|
Saint John
|
2
|
0
|
|
Montreal
|
9
|
10
|
|
Quebec
|
5
|
5
|
|
Ottawa
|
5
|
9
|
|
Windsor
|
27
|
23
|
|
Toronto
|
19
|
16
|
|
Hamilton
|
22
|
20
|
|
Winnipeg
|
0
|
1
|
|
Regina
|
0
|
4
|
|
Saskatoon
|
0
|
0
|
|
Edmonton
|
2
|
0
|
|
Calgary
|
0
|
2
|
|
Fort Saskatchewan
|
2
|
1
|
|
Fort McMurray
|
0
|
1
|
|
Greater Vancouver
|
0
|
0
|
|
Victoria
|
0
|
0
|
*The cities were compared by looking at the differences in their annual averages over a five-year period (1998-2003) and their most recent annual averages (2003). The city averages were calculated by finding the average of the annual average values for each station within a city. Each city did not necessarily have the same number of stations and it is important to note that this may affect exactly how representative an average is for a given city. Also, some stations may not have been operational for a majority of the time of the comparison, and therefore only stations that had data for at least four out of the five years were used. These same stations were also used in calculating the 2003 averages. The table below shows the number of stations that satisfied the criteria and were thus used for calculating the city averages.
|
Number of Exceedances of the Alberta Objective for Ozone (1-hour > 82 ppb)
|
|
City
|
Five Year Average (1998-2003)
|
2003
|
|
St. John's
|
0
|
0
|
|
Halifax
|
1
|
0
|
|
Saint John
|
2
|
0
|
|
Montreal
|
11
|
9
|
|
Quebec
|
2
|
1
|
|
Ottawa
|
4
|
7
|
|
Windsor
|
67
|
64
|
|
Toronto
|
40
|
45
|
|
Hamilton
|
39
|
52
|
|
Winnipeg
|
0
|
0
|
|
Regina
|
0
|
6
|
|
Saskatoon
|
0
|
0
|
|
Edmonton
|
1
|
1
|
|
Calgary
|
0
|
0
|
|
Fort Saskatchewan
|
2
|
1
|
|
Fort McMurray
|
0
|
0
|
|
Greater Vancouver
|
0
|
0
|
|
Victoria
|
0
|
0
|
|
City
|
# of Stations Used in Analysis
|
|
St. John's
|
1
|
|
Halifax
|
1
|
|
Saint John
|
3
|
|
Montreal
|
11
|
|
Quebec
|
2
|
|
Ottawa
|
2
|
|
Windsor
|
2
|
|
Toronto
|
5
|
|
Hamilton
|
2
|
|
Winnipeg
|
2
|
|
Regina
|
1
|
|
Saskatoon
|
1
|
|
Edmonton
|
3
|
|
Calgary
|
3
|
|
Fort Saskatchewan
|
1
|
|
Fort McMurray
|
1
|
|
Greater Vancouver
|
12
|
|
Victoria
|
1
|
|
