Trace metal Month Snail shell Sediment tissue/ sediment ratio (BF)
V August 8.56 ± 2.12 1.08 ± 0.28 7.93
  September 6.25 ± 1.72 3.12 ± 1.32 2.00
  October 7.68 ± 2.32 2.18 ± 0.21 3.52
Mn August 148.14 ± 10.22 25.20 ± 2.14 5.88
  September 126.32 ± 6.76 34.34 ± 5.62 3.68
  October 142.33 ± 14.18 44.43 ± 12.21 3.20
Fe August 6337.12 ± 113.12 888.25 ± 15.62 7.13
  September 5219.32 ± 104.12 1249.60 ± 15.23 4.18
  October 4012.01 ± 88.39 1192.21 ± 19.78 3.37
Co August 8.52 ± 2.15 2.23 ± 1.02 3.82
  September 9.23 ± 2.14 2.12 ± 1.19 4.35
  October 5.63 ± 1.29 2.91 ± 0.40 1.93
Ni August 12.61 ± 3.20 3.23 ± 1.20 3.90
  September 27.02 ± 5.11 6.12 ± 2.12 4.42
  October 16.82 ± 3.23 4.21 ± 1.76 4.00
Cu August 132.89 ± 9.71 20.62 ± 8.22 6.44
  September 80.21 ± 12.31 21.43 ± 6.82 3.74
  October 96.12 ± 7.34 25.40 ± 6.12 3.78
Zn August 24.10 ± 3.32 4.21 ± 0.54 5.72
  September 65.21 ± 9.24 15.06 ± 4.24 4.33
  October 86.64 ± 5.78 16.02 ± 5.23 5.41
As August 4.33 ± 0.75 1.11 ± 0.68 3.90
  September 3.35 ± 1.09 1.05 ± 0.96 3.19
  October 2.97 ± 0.37 0.98 ± 0.12 3.03
Se August 19.10 ± 3.97 5.62 ± 1.82 3.40
  September 23.10 ± 4.83 5.98 ± 1.42 3.86
  October 16.40 ± 3.27 5.13 ± 2.11 3.20
Mo August 4.32 ± 0.90 0.97 ± 0.32 4.45
  September 3.99 ± 1.21 1.99 ± 0.45 2.01
  October 3.09 ± 0.74 1.93 ± 0.12 1.60
Ag August 6.88 ± 2.17 1.95 ± 0.84 3.53
  September 4.89 ± 1.31 1.56 ± 0.43 3.13
  October 2.79 ± 0.25 1.37 ± 0.82 2.03
Cd August 13.73 ± 2.37 3.02 ± 0.78 4.55
  September 13.28 ± 5.24 3.98 ± 1.10 3.34
  October 12.23 ± 3.98 3.46 ± 0.99 3.53
Pb August 24.30 ± 4.21 4.33 ± 1.86 5.61
  September 21.65 ± 6.42 5.02 ± 2.89 4.31
  October 14.34 ± 3.88 4.01 ± 1.03 3.58
Table 2: The mean trace metal content of Melanoides tuberculata and sediment samples downstream of the effluent outfall in Alaro stream (parts per million, ppm)