Figure 12.  Aerosol Mass Concentrations in TSP Samples Collected during November 1997 - June 1999 Figure 13.  Aerosol Mass Concentrations in Aerosol Samples Collected during November 1997 - June 1999 The top and bottom of each box are the 25th and 75th percentiles, respectively. The line within each box is the median, and the external upper lines and lower lines are the 10th and 90th percentiles, respectively. Individual circles are values outside the 10th and 90th percentiles.