The figure above illustrates the slowing
down process for Fairfield County, Connecticut. Note the rapid
decrease in the early years and then a "flattening"
of the curve in the later years. The
year-by-year figure below illustrates the changes in the 4th
highest daily maximum concentration. A rapid decrease in the
early years occurred, but less of a decline occurred in the later
years. For this monitoring site, a weaker statistically significant
downward trend was observed for the 1994-2008 period than for
the 1980-2008 period (-1.07 %/year versus -1.82 %/year, respectively)
(Lefohn et al., 2010).
Reference
Lefohn, A.S., Shadwick,
D., Oltmans, S.J. (2010). Characterizing Changes of Surface Ozone
Levels in Metropolitan and Rural Areas in the United States for
1980-2008 and 1994-2008. Atmospheric Environment. 44:5199-5210.
