Figure 4.4: Percentage of measured one-hour and 24-hour average SO2 concentrations within air quality categories in Hornby and Opawa, Christchurch
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There are four charts measuring SO2 concentrations in Christchurch. The first two charts show one-hour and 24-hour concentrations at Opawa from 1995 to 1999. 24-hour concentrations were comparatively poor in 1995 (over 10% of readings just “Acceptable”, and only 20% were “Excellent”), improved considerably in 1996 (over 80% of measurements were “Excellent”), but declined through the rest of the period until in 1999 just over 40% of measurements were “Excellent”.
The second two charts show 24-hour and one-hour concentrations at Hornby from 1995 to 2001. While the majority of measurements were Excellent or Good, 24-hour concentrations increased slightly from 1998 to 2002.
