Fig. 5.

Contents of heavy metals in the air pollution control residues. NCWG and CWG denote samples from incinerator without and with clinical waste input, respectively. Median, 25th, and 75th percentiles are plotted as horizontal solid lines of the boxes. The six-pointed stars represent mean values. The upper and lower whiskers extend to data no more than 1.5-times of the interquartile range from the upper and lower edge of the box, respectively. The black dots represent outliers. The results obtained using different co-incineration ratios were compared (P values were computed using Student's t-test, *** denotes P < 0.001, i.e., difference in the mean value is statistically significant).