D ≤ 10

10 < D ≤ 20

20 < D ≤ 30

30 < D ≤ 40

40 < D ≤ 50

50 > D

监测站数量

62

141

141

60

19

7

百分比

14.4%

32.8%

32.8%

14.0%

4.4%

1.6%