OPTIMAL EMPs
5.4. RESULTS AND DISCUSSION
5.4.1. LEACHING OF SOIL AND SEDIMENT
5.3.7. ANALYSIS OF IONIC CONCENTRATION OF LEACHATE SAMPLES The digested soil samples and the leachate samples were analysed for Na, K, Ca and trace metals (Fe, Mn, Ni, Pb and Cd) by following the procedure as described in 4.4.1.
Table 5.2: Summary of the results of leaching study for the collected samples
pH(L)
EC(L) (µ S/cm)
Na (L) (µ gm/g m)
K (L) (µ gm/g m)
Ca (L) (µ gm/gm )
Pb (L) (µ gm/g m)
Ni (L) (µ gm/g m)
Fe (L) (µ gm/g m)
Mn (L) (µ gm/g m) Average 7.41 74.17 44.26 53.07 166.05 2.01 1.31 61.57 17.42 Standard
deviation 0.60 88.89 99.05 88.26 200.80 1.02 0.74 74.11 23.50 Range 6.1-8.2 9.6-432
BDL-
571 1-394 1.2-687 0.2-3.4
0.08- 2.36
BDL- 188
0.06- 64.5
The variation of pH in all the samples was almost consistent (Figure 5.2), significant variation was observed for EC values (Figure 5.3), indicating the variability in the ionic concentrations through all the samples.
Figure 5.2: pH values in the leachate samples 0
1 2 3 4 5 6 7 8 9
S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18 S19 S20 S21 S22 S23 S24 S25 S26 S27 S28 B1 B2 B3 B4
Sample code
Figure 5.3: EC values in the leachate samples
In Figure 5.4, the variation of Na, K and Ca in the leachate samples are shown.
The leaching of Na, K, Ca is higher for the soil samples from the urban areas representing comparatively polluted sites (sample code S1-S11)and also for river bed sediments (sample code B1-B4) than the samples that are from the hilly watershed areas (sample code S12- S28) ,i.e. in Games village watershed and experimental watershed. The leaching of Pb and Ni were more in the soil samples from the urban areas (sample code S12-S16) compared to the samples from the hilly watershed areas (Figure 5.5), except for one samples from the experimental watershed of IIT Guwahati site. The leaching of Fe and Mn was much higher for the soil samples of experimental watershed of IIT Guwahati site (sample code S17- S28) than the other sites (sample code S1-S16) (Figure 5.6), except the Fe leachate for bed sediment of Basistha river (sample code B2).
Figure 5.4: Na, K and Ca concentrations in the leachate samples 0
50 100 150 200 250 300 350 400 450 500
S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18 S19 S20 S21 S22 S23 S24 S25 S26 S27 S28 B1 B2 B3 B4
µS/cm
Sample code
0 100 200 300 400 500 600 700 800
S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18 S19 S20 S21 S22 S23 S24 S25 S26 S27 S28 B1 B2 B3 B4
µgm/gm
Samples code
Na (L) K (L) Ca (L)
Figure 5.5: Pb and Ni concentrations in the leachate samples
Figure 5.6: Fe and Mn concentrations in the leachate samples
Relation of leachate concentrations with initial concentrations of elements in the soil The correlation matrix (Table 5.3) of the leachate quantities and their initial concentrations in the soil samples indicated:
(i) The soil pH has moderate positive correlation (0.72) with the pH of the soil leachate.
(ii) The soil EC has moderate positive correlation (0.69) with the EC of the soil leachate.
(iii) The initial concentration of Na in soil has moderate positive correlation (0.69) with initial concentration of Pb in soil.
0 0.5 1 1.5 2 2.5 3 3.5 4
S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18 S19 S20 S21 S22 S23 S24 S25 S26 S27 S28 B1 B2 B3 B4
µgm/gm
Sample code
Pb (L) Ni (L)
0 20 40 60 80 100 120 140 160 180 200
S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18 S19 S20 S21 S22 S23 S24 S25 S26 S27 S28 B1 B2 B3 B4
µgm/gm
Sample code Fe (L) Mn (L)
(iv) The initial concentration of Na in soil has moderate positive correlation (0.78) with K of the soil leachate.
(v) The initial concentration of Na in soil has very good positive correlation (0.97) with Na of the soil leachate.
(vi) The initial concentration of K in soil has moderate positive correlation (0.77) with initial concentration of Ca in soil.
(vii) The initial concentration of K in soil has moderate positive correlation (0.67) with initial concentration of Fe in soil.
(viii) The initial concentration of Ca in soil has moderate positive correlation (0.72) with initial concentration of Pb and Fe in soil.
(ix) The initial concentration of Ca in soil has good positive correlation (0.81) with the pH of the soil leachate.
(x) The initial concentration of Ca in soil has moderate positive correlation (0.77) with the Pb leaching.
(xi) The initial concentration of Ca in soil has good positive correlation (0.84) with the Ni leaching.
(xii) The initial concentration of Ca in soil has moderate negative correlation (-0.72) with the Fe leaching.
(xiii) The initial concentration of Ca in soil has moderate negative correlation (-0.71) with the Mn leaching.
(xiv) The initial concentration of Pb in soil has moderate positive correlation (0.74) with the Na leaching.
(xv) The initial concentration of Pb in soil has moderate positive correlation (0.78) with the K leaching.
(xvi) The initial concentration of Ni in soil has moderate positive correlation (0.76) with the initial concentration of Fe in soil.
(xvii)The initial concentration of Ni in soil has moderate positive correlation (0.71) with the Ni leaching.
(xviii) The initial concentration of Fe in soil has moderate positive correlation (0.75) with the Pb leaching.
(xix) The initial concentration of Fe in soil has moderate positive correlation (0.74) with the Ni leaching.
(xx) The pH of the leachate has good positive correlation (0.84) with the Pb leaching.
(xxi) The pH of the leachate has good positive correlation (0.83) with the Ni leaching.
(xxii)The pH of the leachate has moderate negative correlation (-0.73) with the Fe leaching.
(xxiii) The pH of the leachate has moderate negative moderate correlation (-0.79) with the Mn leaching.
(xxiv) The Na leaching has moderate positive correlation (0.76) with the K leaching.
(xxv)The Pb leaching has good positive correlation (0.83) with the Ni leaching.
(xxvi) The Ni leaching has moderate negative correlation (-0.72) with the Mn leaching.
(xxvii)The Fe leaching has good positive correlation (0.83) with the Mn leaching.
115
Table 5.3: Correlation coefficient of all soil and leachate samples
pH (S) EC(S) Na (S) K (S) Ca (S) Pb (S) Ni (S) Fe (S) Mn (S) pH(L) EC(L) Na (L) K (L) Ca (L) Pb (L) Ni (L) Fe (L) Mn (L) pH (S) 1.00
EC(S) 0.42 1.00 Na (S) 0.12 0.02 1.00 K (S) 0.34 0.06 0.13 1.00
Ca (S) 0.57 0.24 0.28 0.77 1.00 Pb (S) 0.37 0.16 0.69 0.46 0.72 1.00 Ni (S) 0.23 0.33 -0.01 0.57 0.66 0.48 1.00 Fe (S) 0.25 0.28 -0.03 0.67 0.72 0.40 0.76 1.00
Mn (S) -0.11 0.03 0.09 0.31 0.24 0.30 0.49 0.63 1.00 pH(L) 0.72 0.35 0.14 0.64 0.81 0.51 0.50 0.65 0.16 1.00 EC(L) 0.31 0.69 -0.06 0.02 0.12 0.16 0.48 0.17 0.12 0.17 1.00
Na (L) 0.20 0.06 0.97 0.23 0.41 0.74 0.06 0.04 0.08 0.26 -0.08 1.00 K (L) 0.40 0.06 0.78 0.25 0.38 0.64 0.19 0.07 0.07 0.37 0.14 0.76 1.00
Ca (L) 0.49 0.26 0.49 0.40 0.68 0.78 0.59 0.28 0.01 0.57 0.32 0.54 0.69 1.00 Pb (L) 0.52 0.27 0.03 0.61 0.77 0.43 0.58 0.75 0.33 0.84 0.12 0.14 0.18 0.41 1.00 Ni (L) 0.62 0.37 0.12 0.62 0.84 0.51 0.71 0.74 0.22 0.83 0.33 0.20 0.37 0.63 0.83 1.00 Fe (L) -0.55 -0.35 -0.10 -0.60 -0.72 -0.46 -0.64 -0.65 -0.25 -0.73 -0.26 -0.18 -0.31 -0.54 -0.64 -0.67 1.00
Mn (L) -0.63 -0.35 -0.09 -0.62 -0.71 -0.40 -0.52 -0.59 0.02 -0.79 -0.23 -0.18 -0.31 -0.50 -0.63 -0.72 0.83 1.00
The two sets of samples from the experimental watershed and the Games village watershed were studied separately to see the behaviour of leaching within them.
5.3.3. LEACHING BEHAVIOUR OF SOIL OF EXPERIMENTAL WATERSHED