152
To summarize, mangroves and their sediments have an important ecological
value because they can act as natural sinks for heavy metals owing to the high
capacity to sequester such metals from tidal waters, estuaries, rivers and other
sources (Tam and Wong 1999).
Fig. 5.49 Porteresia coarctata bed in Indian Sundarbans: A potential sink of conservative
pollutants
Table 5.9 Monthly variations of heavy metals in P. coarctata collected from Canning during 2017
and 2018
Zn
Cu
Pb
Month
2017
2018
2017
2018
2017
2018
Jan
100.55
106.53
44.22
46.98
12.99
14.98
Feb
94.69
99.39
41.77
45.94
11.56
13.21
March
92.32
98.3
36.89
39.65
13.78
16.23
April
85.77
90.54
34.33
38.56
10.89
12.54
May
82.33
88.31
32.1
34.86
10.03
10.78
June
78.21
85.26
28.67
31.43
8.64
10.29
July
150.11
156.09
35.89
39.63
11.86
12.99
Aug
152.09
157.21
47.2
49.96
17.33
18.98
Sept
165.48
171.46
63.21
66.36
19.22
21.67
Oct
134.4
141.23
54.9
57.66
15.09
16.74
Nov
112.44
118.42
48.9
51.66
14.33
16.23
Dec
103.66
108.73
41.51
45.23
13.04
15.87
5 Mangroves: A Sink of Heavy Metals