Spatial and Temporal Trends in PM2.5 Organic and Elemental Carbon across the United States
Figure 8
Long-term (1990–2010) trends (% ) in IMPROVE seasonal mean PM2.5 total carbon (TC = OC + EC) for (a) winter (DJF), (b) spring (MAM), (c) summer (JJA), and (d) fall (SON). White triangles correspond to IMPROVE sites. Upward pointing triangles correspond to increased concentrations and vice versa. Trends with significance levels (p) less than 0.10 were considered significant. (filled triangles). Unfilled triangles correspond to insignificant trends.
