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BEHAVIOUR OF HEAVY METALS IN
SEWAGE-SLUDGE AMENDED SOIL
Sourav Bhattacharyya
and
Prof. P. K. Mani
DEPARTMENT OF AGRICULTUR...
Essential heavy metal Non essential heavy
metal
Fe, Zn, Cu, Mn, Mo, Ni Pb, Hg, Cd, Cr, Se
Heavy metals :
 Atomic no. > 20...
Sewage : Sewage is water-carried waste, in
solution or suspension, that is intended to
be removed from a community.*
Sludg...
Table 1. Agricultural use of sewage sludge in different
countries:
Country Year Sludge
production
(t/yr)
Agriculture
(t/yr...
Table 2: The content of heavy metals in agricultural soils (mg/kg)
Country Cr Cu Pb Zn Ni Cd Hg Reference
Spain 63.48 107....
Samples Standards Fe Zn Cu Pb Cd Mn Cr
Water
(mg L-1)
Indian Standard (Awashthi,
2000)
NA 5.0 0.05 0.10 0.01 0.1 0.05
WHO/...
Behaviour of heavy metals in sewage sludge-
amended soils and their impact on food composition
 The concentrations of hea...
Heavy metal availability
in sewage sludge
amended soils
‘Available’ heavy metals - fraction of the total concentration
of heavy metals in the soil, which is present in the soil
s...
Factors affecting heavy metal availability to plant
A)Soil properties
B)Plant factors
C)Soil-plant transfer coefficient
Soil properties
a) pH
 Availability of cationic
heavy metals decreases with
increase in pH
pH
(Alloway and Jackson, 1991)...
b) Organic matter
 Application of organic matter reduces the mobility of metals in soil
and thus lowers their availabilit...
C) Clays and hydrous oxides
Clays and hydrous oxides determine metal availability by -
2) Non-specific adsorption (exchang...
d) Redox potential-
Flooded condition-
SO4
2- → SO3 - → S2-
S2- + M2+ → MS
 H2S precipitates with Cd in the form of CdS, ...
 With high P contents, at neutral to alkaline pH, a
precipitation of Cd3(PO4)2 takes place.
 Increase in the Ca2+ concen...
f) CaCO3 content-
 At high pH and high pCO2 (partial pressure
of CO2) values, calcite (CaCO3) sorbs Cd as
CdCO3 and dimin...
Movement of metals within the profiles of sludged soil
 Cd, Cr, Cu, Mo, Ni, Pb and Zn all moved from the surface to withi...
Table 5. Average heavy metal concentration at different
depths in a sewage irrigated soil(mg kg-1)
Depth
(cm)
Cd Cr Ni Cu ...
g) Other factors-
Soil moisture
Soil temperature
Soil aeration
Table 5. Total heavy metals content (mg kg−1) in waste
water irrigated soils of peri-urban Kolkata(0-20cm)
Parameters Zn C...
Parameters Unamended soil 6 kg m-2 SSA 9 kg m-2 SSA 12 kg m-2 SSA
pH (1:5) 8.18 8.06 8.09 7.85
EC (mScm-1) 0.24 0.29 0.32 ...
Heavy metal accumulation
in soils and plants
Plant factors
a) Plant species
Metal High accumulations Low accumulations
Cd Spinach, Lettuce, Celery,
Cabbage
Potato, Mai...
Table 8. Accumulation of heavy metals (mg kg−1) in crops
grown in sewage-irrigated soils
Crops Zn Cu Pb Cd Ni
Sesame (n=10...
Other plant factors:
b) Cultivars
15 cultivars of potato varied widely in Cd
concentrations on the same soil with ranges
...
Soil-Plant Transfer Coefficient
Transfer Coefficient (TC)= ----------------
[M]plant
[M]soil
[M]plant- concentration of an...
Table 9. Transfer coefficient (TC) of metals from soil to
plants in waste water-irrigated soils of peri-urban
Kolkata
Meta...
Effect of sewage sludge amendment on
microorganisms activity
 A 50% reduction in nitrogen fixation is obesrved in a soil
...
Changes in the availability of heavy metals to
crops during the residual period
Any changes which are observed in the bioa...
Changes in the availability of heavy metals to crops during the residual period
(contd.)
 The metals remained available f...
Table 10. Concentration of heavy metals (mg kg-1) in leaves
of Chinese cabbage grown in soil amended with
various content ...
Table 11. Concentrations of heavy metals in
vegetable edible parts (mg kg-1)
Vegetable
Type
Vegetable
Species
Pb (mg kg-
1...
Cumulative accumulation of heavy metals (Cd, Cr, Ni) in edible parts of
vegetables (mg kg−1 dry weight) grown in treated s...
Table 12. Yield parameters of mung bean plants grown at
different Sewage Sludge amended rates(SSA)
Treatment No. of pods/p...
Way outs
A) Prevention of heavy
metal contamination
B) Management of
contaminated soil
Prevention of heavy metal contamination
i) Reducing heavy metal content of sewage
sludge-
Acid thermal hydrolysis
Alkaline...
Table14. Concentration (mg kg-1 dry solid) of heavy
metals in the sludge cake after subjected to hydrolysis
Heavy metals U...
Management of contaminated soil
Increasing the soil pH to 6.5 or higher
Draining wet soils
Applying phosphate
Careful sele...
Conclusions
Heavy metal content of both sewage sludge and soil
should be considered during making decisions regarding
sew...
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BEHAVIOUR OF HEAVY METALS IN SEWAGE-SLUDGE AMENDED SOIL

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BEHAVIOUR OF HEAVY METALS IN SEWAGE-SLUDGE AMENDED SOIL

  1. 1. BEHAVIOUR OF HEAVY METALS IN SEWAGE-SLUDGE AMENDED SOIL Sourav Bhattacharyya and Prof. P. K. Mani DEPARTMENT OF AGRICULTURAL CHEMISTRY AND SOIL SCIENCE FACULTY OF AGRICULTURE BIDHAN CHANDRA KRISHI VISWAVIDYALAYA Mohanpur, Nadia, 741252, India pabitramani@gmail.com
  2. 2. Essential heavy metal Non essential heavy metal Fe, Zn, Cu, Mn, Mo, Ni Pb, Hg, Cd, Cr, Se Heavy metals :  Atomic no. > 20  Specific gravity > 5 Brady N.C. (2002)
  3. 3. Sewage : Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community.* Sludge: A mixture of solid and water, produced during the treatment of waste water or sewage.* *Central Pollution Control Board(1993)
  4. 4. Table 1. Agricultural use of sewage sludge in different countries: Country Year Sludge production (t/yr) Agriculture (t/yr) % of total Germany* 2007 2056486 1439540 70 Spain* 2006 1064972 692231 65 Sweden* 2006 210000 30000 14 UK* 2006 1544919 1050544 68 Austria* 2006 252800 38400 16 Italy* 2006 1070080 189554 18 USAa 1998 6900000 2800000 41 *United Nations Human Settlement Program (2008)  In India production of sewage sludge is estimated to be around 1000-1300 tonnes/day. Deshbhratar et al. (2001)
  5. 5. Table 2: The content of heavy metals in agricultural soils (mg/kg) Country Cr Cu Pb Zn Ni Cd Hg Reference Spain 63.48 107.65 213.93 427.80 34.75 1.42 - Zimakowska- Gnoinska et al., 2000 America - 95.00 23.00 - 57.00 0.78 - Han et al., 2002 Korea - 2.98 5.25 4.78 - 0.12 0.05 Kim and Kim, 1999 Slovakia - 65.00 139.00 140.00 29.00 - - Wilcke, 2005 USA 48.5 48 55 88.5 29 13.5 - Jean-Philippe et al., 2012 India 1.23 2.62 2.82 4.65 0.14 0.05 Prajapati and Meravi, 2014 Iran 10.36 9.62 5.17 11.56 11.28 0.34 - Sayyed and Sayadi, 2011 Zojaji et al., 2014
  6. 6. Samples Standards Fe Zn Cu Pb Cd Mn Cr Water (mg L-1) Indian Standard (Awashthi, 2000) NA 5.0 0.05 0.10 0.01 0.1 0.05 WHO/FAO (2007) NA 2.0 0.20 5.0 0.01 0.2 0.10 European Union Standards (EU2002) - - - - - - - USEPA (2010) NA 2.00 1.00 .015 .005 .05 0.10 Kabata-Pendias(2010) 0.80 NA NA NA NA NA NA Soil (mg kg-1) Indian Standard (Awashthi 2000) NA 300-600 135-270 250-500 3-6 NA NA WHO/FAO (2007) - - - - - - European Union Standards(EU2002) NA 300 140 300 3.0 NA 150 USEPA (2010) NA 200 50 300 3.0 80 NA Kabata-Pendias (2010) 1000 NA NA NA NA NA NA Plant (mg kg-1) Indian Standard (Awashthi, 2000) NA 50.0 30.0 2.5 1.5 NA NA WHO/FAO (2007) 450 60.0 40.0 5.0 0.2 500 5.0 European Union Standards (EU2002) NA 60 40 0.30 0.20 NA NA USEPA (2010) - - - - - - - Table 3. Guidelines for safe limits of some heavy metals in water, soil & plants
  7. 7. Behaviour of heavy metals in sewage sludge- amended soils and their impact on food composition  The concentrations of heavy metals in sludge-amended soils.  The bioavailability of these heavy metals to crops.  Effects of soil properties on the bioavailability of heavy metals.  Changes in bioavailability during the residual period.  Differences between crop species and cultivars in the uptake and accumulation of heavy metals in edible organs.  Movement of heavy metals in the soil profile and the potential risk of groundwater pollution.
  8. 8. Heavy metal availability in sewage sludge amended soils
  9. 9. ‘Available’ heavy metals - fraction of the total concentration of heavy metals in the soil, which is present in the soil solution or easily exchangeable from the soil exchange surfaces. Total heavy metal (M) M in soil solution Exchangeable M bound to carbonates M bound to Fe & Al oxides M bound to organic matter Residual fraction Readily available Naoum et al. (2001) = + + + + +
  10. 10. Factors affecting heavy metal availability to plant A)Soil properties B)Plant factors C)Soil-plant transfer coefficient
  11. 11. Soil properties a) pH  Availability of cationic heavy metals decreases with increase in pH pH (Alloway and Jackson, 1991)  Whereas, availability of Mo and elements with anionic species increases with increasing soil pH pH (Smith, 1996)
  12. 12. b) Organic matter  Application of organic matter reduces the mobility of metals in soil and thus lowers their availability to plants. Environmental Protection Capacity (EPC) factor = DxH2K Dx - thickness of the soil layer (cm) H - soil humus content K - constant depending on the humus quality. Sludge + O.M Soil humus EPC Heavy metal availability Hargitai (1989)  Humic acids bind metals and reduce their availability to plants and thus, metal retention by the soil increases when sewage sludge is applied. Piccolo (1989)
  13. 13. C) Clays and hydrous oxides Clays and hydrous oxides determine metal availability by - 2) Non-specific adsorption (exchange) 1) Specific adsorption to surface hydroxyl groups (Miller et al., 1987) 3) Co-precipitation (Martinez and McBride, 1998) 4) Precipitation as the discrete metal oxide or hydroxide (Martinez and McBride, 1998). (Basta and Tabatabai, 1992)
  14. 14. d) Redox potential- Flooded condition- SO4 2- → SO3 - → S2- S2- + M2+ → MS  H2S precipitates with Cd in the form of CdS, which is an insoluble compound. Evans (1989)  Metals expected to precipitate as sulphides include Ag+, Ni2+, Zn2+, Hg2+ and Fe3+.
  15. 15.  With high P contents, at neutral to alkaline pH, a precipitation of Cd3(PO4)2 takes place.  Increase in the Ca2+ concentration in the solution from 10-3 to 10-2 M, Cd concentration decreases by 67%.  Sulfur, inhibits the transport of Pb in the plants from roots to shoots and it was found that S-deficiency increased Pb movement to the tops. e) Effects of other elements- Jing and Logan (1992) Alloway (1995) Kabata-Pendias and Pendias(1992) Antagonistic effect-
  16. 16. f) CaCO3 content-  At high pH and high pCO2 (partial pressure of CO2) values, calcite (CaCO3) sorbs Cd as CdCO3 and diminishes its availability. Evans (1989) Other metals likely to precipitate as carbonates at high pCO2 and pH values include: Fe2+, Zn2+ and Pb2+ Evans(1989)
  17. 17. Movement of metals within the profiles of sludged soil  Cd, Cr, Cu, Mo, Ni, Pb and Zn all moved from the surface to within the top 10 cm of the profile, but an average of 87% of metals (range 60-100%)remained in the upper 5 cm after application of sewage- sludge in grassland. Applications of composted sewage sludge 150 and300 dry t ha-1 on a silt loam soil Zn and Cu concentrations increased down upto 75cm depth with most of the movement occurring in the first year.  In California, found that even after applications of sludges amounting to a maximum of 1800 dry t ha- 1 on a loam soil, Cd, Zn, Ni, and Co tended to remain in the zone of incorporation over a 9 year period. Williams et al. (1987) Evans, L.J (1989) Darmody et al. (1993)
  18. 18. Table 5. Average heavy metal concentration at different depths in a sewage irrigated soil(mg kg-1) Depth (cm) Cd Cr Ni Cu Zn Pb As Hg 0-20 0.85 91.21 64.19 41.17 276.41 41.56 17.72 1.72 20-40 0.32 28.18 26.39 8.96 17.25 15.33 15.24 0.83 40-60 0.20 25.29 24.91 7.74 10.26 14.29 6.84 0.21 60-80 0.49 26.08 24.43 7.22 39.60 13.31 2.88 0.09 Wang et al, (2012)
  19. 19. g) Other factors- Soil moisture Soil temperature Soil aeration
  20. 20. Table 5. Total heavy metals content (mg kg−1) in waste water irrigated soils of peri-urban Kolkata(0-20cm) Parameters Zn Cu Pb Cd Ni Mean 66.56 27.81 102.9 15.95 36.81 Median 67.42 26.39 106.02 16.72 37.33 Minimum 52.60 13.20 80.08 8.80 19.50 Maximum 84.35 47.40 121.78 18.08 55.40 SD 10.36 10.33 10.22 2.27 9.60 (Saha et al, 2015)
  21. 21. Parameters Unamended soil 6 kg m-2 SSA 9 kg m-2 SSA 12 kg m-2 SSA pH (1:5) 8.18 8.06 8.09 7.85 EC (mScm-1) 0.24 0.29 0.32 0.39 Organic C (%) 0.77 1.41 1.52 1.74 Total N (%) 0.18 0.20 0.20 0.21 P (mg kg-1) 54.43 111.81 124.2 132.8 Cu (mg kg-1) 3.51 8.50 10.81 11.13 Mn (mg kg-1) 13.27 34.36 41.17 42.05 Zn (mg kg-1) 2.11 11.95 22.95 30.91 Cr (mg kg-1) 0.34 0.77 1.50 1.66 Cd (mg kg-1) 1.51 6.39 6.44 7.36 Ni (mg kg-1) 4.95 9.69 10.29 10.75 Pb (mg kg-1) 2.83 8.49 10.04 11.06 Singh & Agrawal (2010) Table 6. Effect of sewage sludge on nutrient and heavy metal content in soil
  22. 22. Heavy metal accumulation in soils and plants
  23. 23. Plant factors a) Plant species Metal High accumulations Low accumulations Cd Spinach, Lettuce, Celery, Cabbage Potato, Maize, French bean, Peas Pb Rye grass, Celery, Kale Some barley cultivars, Potato, Maize Cu Sugar beet, Certain barley cultivars, Cabbage, Onion,Leek Ni Sugar beet, Rye grass, Turnip Maize, Leek, Barley, onion Zn Spinach, Sugar beet, Beetroot Potato, Leek, Tomato, Onion McCutcheon & Schnoor (2003)
  24. 24. Table 8. Accumulation of heavy metals (mg kg−1) in crops grown in sewage-irrigated soils Crops Zn Cu Pb Cd Ni Sesame (n=10) 24.4 7.9 66.3 13.5 23.8 Chilli (n=6) 32.4 11.2 65.5 11.8 15.4 Okra (n=9) 34.2 9.0 73.3 13.0 19.3 Jute (n=10) 30.7 4.8 68.4 12.7 16.9 Brinjal (n=6) 35.5 6.9 76.4 12.6 23.5 Poi (n=10) 37.5 6.8 79.9 13.1 19.1 Amaranthus (n=4) 33.9 4.8 84.8 13.3 26.6 Colocasia (n=4) 39.3 21.3 91.9 16.8 21.1 Cowpea (n=6) 37.1 4.9 84.1 12.9 21.4 Cauliflower (n=6) 37.3 3.8 70.7 11.6 13.4 All values are mean values Saha et al. (2015)
  25. 25. Other plant factors: b) Cultivars 15 cultivars of potato varied widely in Cd concentrations on the same soil with ranges of 9-39 μgkg-1 on one site and 29-56 μgkg-1 at others. McLaughlin et al. (1994) c) Genotype The differences between plant genotypes in term of Cd uptake have also been reported. Hocking & McLaughlin (2000)
  26. 26. Soil-Plant Transfer Coefficient Transfer Coefficient (TC)= ---------------- [M]plant [M]soil [M]plant- concentration of an metal in the test plant tissues [M]soil- total concentration of the same metal in the soil where this plant is grown
  27. 27. Table 9. Transfer coefficient (TC) of metals from soil to plants in waste water-irrigated soils of peri-urban Kolkata Metal Sesame Chilli Okra Brinjal Cauliflower Zn 0.26–0.70 0.38–0.56 0.28–0.77 0.48–0.65 0.46–0.83 Cu 0.19–0.93 0.15–0.66 0.16–0.69 0.16–0.30 0.07–0.24 Pb 0.44–0.87 0.50–0.77 0.57–1.05 0.59–0.97 0.56–0.71 Cd 0.72–0.94 0.46–0.97 0.52–1.03 0.68–0.83 0.51–0.82 Ni 0.50–1.25 0.22–0.63 0.19–0.93 0.40–0.73 0.22–0.67 Saha et al. (2015)
  28. 28. Effect of sewage sludge amendment on microorganisms activity  A 50% reduction in nitrogen fixation is obesrved in a soil following sewage sludge application. McGrath et al. (1988)  Application of sludge containing low concentration of heavy metals improved soil microbial activities.  Elevated metal concentration have been shown to reduce soil microbial biomass levels, inhibit nitrogen fixation and reduce enzyme activities. High levels of sludge application (200 t ha–1) significantly reduced the functional diversity of soil community. Powlson (2002) Akmal (2005) Banerjee et al. (1997)
  29. 29. Changes in the availability of heavy metals to crops during the residual period Any changes which are observed in the bioavailability of metals through time could be due to combinations of several factors-  soil physical properties  changes in soil pH  Presence of amount of organic matter  the reactivity of soil minerals (hydrous oxides of Fe and Mn) Two types of reversion occurred-  Reduction in the formation of soluble ligands due to microbial action.  Slow reaction of metals with minerals in solid-solution reactions. Chang et al. (1987)
  30. 30. Changes in the availability of heavy metals to crops during the residual period (contd.)  The metals remained available for uptake, giving anomalously high concentrations of metals in plant organs for many years after application. Chaney et al. (1988)  Availability remained roughly the same. Chang et al. (1982)  Heavy metal concentration decreases after the last sludge application. Hinesly et al. (1979)  McGrath (1987) points out that 9 out of 11 papers showed availability to remain more or less constant over several years. Changes in the availability of heavy metals to crops during the residual period(contd.)
  31. 31. Table 10. Concentration of heavy metals (mg kg-1) in leaves of Chinese cabbage grown in soil amended with various content of sewage sludge Heavy metal Control 5% a 10% a 15% a 20% a 25% a Limits b As 2.1 5.8 5.9 7.4 10 7.9 0.05 Cd 0.14 0.15 0.25 0.25 0.41 0.24 0.2 Cr 0.7 2.4 3.1 3.2 5.5 5.8 0.5 Pb 0.08 0.17 0.24 0.27 0.19 0.22 9 Ni 1.2 0.6± 1.6 1.6 2.1 3.1 10 Cu 2.6 4.7 5.6±1.1 4.2±0.8 3.6 4.2 20 Zn 43.4 63.3 65.9 78.9 72.5 69.5 100 a Percentages of sewage sludge in soil b Maximum permissible limits of metal contaminants (CEPA) wang et al. (2008)
  32. 32. Table 11. Concentrations of heavy metals in vegetable edible parts (mg kg-1) Vegetable Type Vegetable Species Pb (mg kg- 1) Cd (mg kg- 1) Cu (mg kg- 1) Zn (mg kg- 1) Root (n=3) Carrot 0.23 0.02 0.22 1.59 Sweet potato 0.61 0.13 0.01 4.67 Solanaceou s (n=3) Brinjal 0.42 0.28 0.93 2.78 Tomato 0.07 0.02 0.46 1.41 Leafy (n=8) Cabbage 0.67 0.03 0.31 9.92 Spinach 0.97 0.51 0.96 20.81 Lettuce 1.16 0.46 0.77 11.79 Legume (n=2) Asparagrass bean 0.70 0.01 1.99 6.68 Kidney bean 0.03 0.01 1.31 5.66 Zhou et al., 2016
  33. 33. Cumulative accumulation of heavy metals (Cd, Cr, Ni) in edible parts of vegetables (mg kg−1 dry weight) grown in treated sewage water irrigated soils Ghosh et al., (2011)
  34. 34. Table 12. Yield parameters of mung bean plants grown at different Sewage Sludge amended rates(SSA) Treatment No. of pods/plant Yield (g m-2) Harvest index (g g-1) Unamended soil 24.0 102.88 0.34 6kg m-2 SSA 28.67 143.34 0.40 9kg m-2 SSA 36.67 180.78 0.41 12kg m-2 SSA 33.3 164.50 0.42 Table13 . Heavy metal concentrations in seed of mung bean at different sewage-sludge amendment rates(SSA) Treatment Cu Mn Zn Cr Cd Ni Pb Unamended soil 0.48 1.43 11.58 0.32 0.23 0.43 0.42 6kg m-2 SSA 0.77 1.92 20.58 0.83 0.80 1.47 1.88 9kg m-2 SSA 1.65 2.18 20.62 1.18 1.35 2.85 2.62 12kg m-2 SSA 2.22 2.82 22.07 1.47 1.62 5.67 3.47 Singh and Agrawal (2008) Singh and Agrawal (2008)
  35. 35. Way outs A) Prevention of heavy metal contamination B) Management of contaminated soil
  36. 36. Prevention of heavy metal contamination i) Reducing heavy metal content of sewage sludge- Acid thermal hydrolysis Alkaline thermal hydrolysis
  37. 37. Table14. Concentration (mg kg-1 dry solid) of heavy metals in the sludge cake after subjected to hydrolysis Heavy metals Untreated Acid thermal hydrolysis Alkaline thermal hydrolysis Cd 2.05 0.83 2.17 Cr 25.5 15.4 14.7 Cu 183 189 45 Pb 158 148 57 Ni 12.7 2.1 13.2 Zn 2144 370 1712 Dewil et al. (2006) Order of metal removal from sewage sludge -  Acid thermal hydrolysis : Zn = Ni > Cd > Cr >Pb> Cu > Hg  Alkali thermal hydrolysis : Cu >Pb> Cr > Zn > Cd = Hg =Ni
  38. 38. Management of contaminated soil Increasing the soil pH to 6.5 or higher Draining wet soils Applying phosphate Careful selection of plants Application of organic matter
  39. 39. Conclusions Heavy metal content of both sewage sludge and soil should be considered during making decisions regarding sewage sludge use in agriculture. Risks of heavy metal contamination of crops grown in sewage sludge amended soils can be minimized to some extent by altering various physico-chemical properties of the soil. Use of sewage sludge should be avoided in crops that accumulate heavy metals in levels toxic to humans without themselves showing any toxicity symptoms. For safe agricultural use of sewage sludge, regular monitoring of soil and crop edible parts for heavy metal accumulation is necessary.

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