Fig.4

Principal component analysis (PCA) based on the heavy metals of sediments: (a) site #1, (b) site #2, (c) site #3, (d) site #4, (e) site #5, (f) site #6, (g) site #7, (h) site #8, (i) site #9, (j) site #10. No. 1 = 0–20 cm; No.2 = 20–40 cm; No.3 = 40–60 cm; No.4 = 60–80 cm; No.5 = 80–100 cm; No.6 = 100–120 cm; No.7 = 120–140 cm; No.8 = 140–160 cm; No.9 = 160–180 cm; No.10 = 180–200 cm. (variables with weaker impact located at lower left corner)