Twelve-Year Trends of PM₁₀ and Visibility in the Hefei Metropolitan Area of China

Figure 2

(a) Statistical box chart of long-term trends for the PM₁₀ concentration in Hefei during the period from 2001 to 2012. The range of the box represents the interquartile range of the data. (b) The worst 20% and 50% and best 20% region-average PM₁₀ concentration trends in Hefei during the period from 2001 to 2012. Dotted lines are the linear regression curves of the corresponding trend lines.

(a)

(b)