Skip to main content
SpringerLink
Log in

Role of Biochar in Remediating Heavy Metals in Soil

  • Chapter
  • First Online:
Phytoremediation

Abstract

Heavy metals are persistent pollutants in the environment which contaminate the food chain, pose risk to human health, and intimidate soil quality. Biochar has been proved efficient to reduce the heavy metal toxicity in contaminated soils. In this paper the properties of biochar and its ability to remediate heavy metals, i.e., Pb, Cd, Cr, As, Ni, Zn, and Cu, in soils are elaborated. Biochar application enhances soil fertility, crop yield, plant growth, carbon content, and nutrients availability. The different types of biochar, i.e., chicken manure, green waste, hardwood, oakwood, sewage sludge, rice straw, dairy manure, and cotton, can be applied by various methods for removal of heavy metals. pH is one of the main parameters among many which influence the function of biochar. Although heavy metal-contaminated soils can be reclaimed effectively by application of biochar, further research is needed to explore its long-term environmental and economic aspect to gain maximum benefits from this novel material.

This is a preview of subscription content, log in via an institution to check access.

Access this chapter

Log in via an institution
Chapter
USD 29.95
Price excludes VAT (USA)
  • Available as PDF
  • Read on any device
  • Instant download
  • Own it forever
eBook
USD 169.00
Price excludes VAT (USA)
  • Available as EPUB and PDF
  • Read on any device
  • Instant download
  • Own it forever
Softcover Book
USD 219.99
Price excludes VAT (USA)
  • Compact, lightweight edition
  • Dispatched in 3 to 5 business days
  • Free shipping worldwide - see info
Hardcover Book
USD 219.99
Price excludes VAT (USA)
  • Durable hardcover edition
  • Dispatched in 3 to 5 business days
  • Free shipping worldwide - see info

Tax calculation will be finalised at checkout

Purchases are for personal use only

Institutional subscriptions

References

  1. Mendez A, Ferreiro JP, Gasco G (2014) Biochar from pyrolysis of drinking paper sludge and its use in the treatment of a nickel polluted soil. J Anal Appl Pyrolysis 107:46–52

    Article  CAS  Google Scholar 

  2. Lu H, Li Z, Fu S, Mendez A, Gasco G, Ferreiro JP (2014) Can biochar and phytoextractors be jointly used for cadmium remediation? PLoS One 9:1–7

    Article  Google Scholar 

  3. Abdelhafez AA, Li J, Abbas MHH (2014) Feasibility of biochar manufactured from organic wastes on the stabilization of heavy metals in a metal smelter contaminated soil. Chemosphere 117:66–71

    Article  CAS  PubMed  Google Scholar 

  4. Nabulo G (2009) Assessing risks to human health from peri-urban agriculture in Uganda. Ph.D. thesis, University of Nottingham

    Google Scholar 

  5. Mahmood A, Malik RN (2014) Human health risk assessment of heavy metals via consumption of contaminated vegetables collected from different irrigation sources in Lahore, Pakistan. Arab J Chem 7:91–99

    Article  CAS  Google Scholar 

  6. Singh KP, Mohon D, Sinha S, Dalwani R (2004) Impact assessment of treated/untreated wastewater toxicants discharge by sewage treatment plants on health, agricultural and environmental quality in wastewater disposal area. Chemosphere 55:227–255

    Article  CAS  PubMed  Google Scholar 

  7. Mapanda F, Mangwayana EN, Nyamangara J, Giller KE (2005) The effect of long-term irrigation using wastewater on heavy metal contents of soils under vegetables in Harare, Zimbabwe. Agr Ecosyst Environ 107:151–165

    Article  CAS  Google Scholar 

  8. Anwar J, Shafique U, Zaman WU, Salman M, Dar A, Anwar S (2010) Removal of Pb(II) and Cd(II) from water by adsorption on peels of banana. Bioresour Technol 101:1752–1755

    Article  CAS  PubMed  Google Scholar 

  9. Xu D, Zhao Y, Sun K, Gao B, Wang Z, Jin J, Zhang Z, Wang S, YanY LX, Wu F (2014) Cadmium adsorption on plant- and manure-derived biochar and biochar-amended sandy soils: Impact of bulk and surface properties. Chemosphere 11:320–326

    Article  Google Scholar 

  10. Javied S, Mehmood T, Choodhry MM, Tufail M, Irfan N (2009) Heavy metal pollution from phosphate rock used for the production of fertilizer in Pakistan. Microchem J 91:94–99

    Article  Google Scholar 

  11. Khan S, Rehman S, Khan AZ, Khan MA, Shah MT (2010) Soil and vegetables enrichment with heavy metals from geological sources in Gilgit, northern Pakistan. Ecotoxicol Environ Saf 73:1820–1827

    Article  CAS  PubMed  Google Scholar 

  12. Kloss S, Zehetner F, Obergur E, Buecker J, Kitzler B, Wenzel WW, Wimmer B, Soja G (2014) Trace element concentrations in leachates and mustard plant tissue (Sinapis alba L.) after biochar application to temperate soils. Sci Total Environ 481:498–508

    Article  CAS  PubMed  Google Scholar 

  13. Al-Wabel MI, Usman ARA, El-Naggar AH, Aly AA, Ibrahim HM, Elmaghraby S, Al-Omran A (2014) Conocarpus biochar as a soil amendment for reducing heavy metal availability and uptake by maize plants. Saudi J Biol Sci 22:503–511

    Article  PubMed  PubMed Central  Google Scholar 

  14. Houben D, Evrard L, Sonnet P (2013) Mobility, bioavailability and pH-dependent leaching of cadmium, zinc and lead in a contaminated soil amended with biochar. Chemosphere 92:1450–1457

    Article  CAS  PubMed  Google Scholar 

  15. Carter S, Shackley S, Sohi S, Suy TB, Haefele S (2013) The impact of biochar application on soil properties and plant growth of pot grown lettuce (Lactuca sativa) and cabbage (Brassica chinensis). Agronomy 3:404–418

    Article  CAS  Google Scholar 

  16. Mackie KA, Marhan S, Ditterich F, Schmidt HP, Kandeler E (2015) The effects of biochar and compost amendments on copper immobilization and soil microorganisms in a temperate vineyard. Agric Ecosyst Environ 201:58–69

    Article  CAS  Google Scholar 

  17. Rutigliano FA, Romano M, Marzaioli R, Baglivo I, Baronti S, Miglietta F, Castaldi S (2014) Effect of biochar addition on soil microbial community in a wheat crop. Eur J Soil Biol 60:9–15

    Article  CAS  Google Scholar 

  18. Fang Y, Singh B, Singh BP (2015) Effect of temperature on biochar priming effects and its stability in soils. Soil Biol Biochem 80:136–145

    Article  CAS  Google Scholar 

  19. Lehmann J, Joseph S (2009) Biochar for environmental management: an introduction. In: Lehmann J, Joseph S (eds) Biochar for environmental management-science and technology. Earthscan, London, pp 1–9

    Google Scholar 

  20. Park JH, Choppala GK, Bolan NS, Chung JW, Chuasavathi T (2011) Biochar reduces the bioavailability and phytotoxicity of heavy metals. Plant Soil 348:439–451

    Article  CAS  Google Scholar 

  21. Hass A, Gonzalez JM, Lima IM, Godwin HW, Halvorson JJ, Boyer DG (2011) Chicken manure biochar as liming and nutrient source for acid Appalachian soil. J Environ Qual 41:1096–1106

    Article  Google Scholar 

  22. Lucchini P, Quilliam RS, DeLuca TH, Vamerali T, Jones DL (2014) Does biochar application alter heavy metal dynamics in agricultural soil? Agric Ecosyt Environ 184:149–157

    Article  CAS  Google Scholar 

  23. Marris E (2006) Putting the carbon back: black is the new green. Nature 442:624–626

    Article  CAS  PubMed  Google Scholar 

  24. Lehmann J (2007) A handful of carbon. Nature 447:143–144

    Article  CAS  PubMed  Google Scholar 

  25. Khan S, Reid BJ, Li G, Zhu YG (2014) Application of biochar to soil reduces cancer risk via rice consumption: A case study in Miaoqian village, Longyan, China. Environ Int 68:154–161

    Article  CAS  PubMed  Google Scholar 

  26. Uchimiya M, Lima IM, Klasson KT, Wartelle LH (2010) Contaminant immobilization and nutrient release by biochar soil amendment: Roles of natural organic matter. Chemosphere 80:935–940

    Article  CAS  PubMed  Google Scholar 

  27. Fellet G, Marmiroli M, Marchiol L (2014) Elements uptake by metal accumulator species grown on mine tailings amended with three types of biochar. Sci Total Environ 468–469:598–608

    Article  PubMed  Google Scholar 

  28. Borchard N, Wolf A, Laabs V, Aeckersberg R, Scherer HW, Moeller A, Amelung W (2012) Physical activation of biochar and its meaning for soil fertility and nutrient leaching-a greenhouse experiment. Soil Use Manage 28:177–184

    Article  Google Scholar 

  29. Ahmad M, Lee SS, Yang JE, Ro HM, Lee YH, Ok YS (2012) Effects of soil dilution and amendments (mussel shell, cow bone, and biochar) on Pb availability and phytotoxicity in military shooting range soil. Ecotoxicol Environ Saf 79:225–231

    Article  CAS  PubMed  Google Scholar 

  30. Uchimiya M, Klasson KT, Wartelle LH, Lima IM (2011) Influence of soil properties on heavy metal sequestration by biochar amendment: 2. Copper desorption isotherms. Chemosphere 82:1438–1447

    Article  CAS  PubMed  Google Scholar 

  31. Turkdogan MK, Fevzi K, Kazim K, Ilyas T, Ismail U (2003) Heavy metals in soil, vegetables and fruits in the endemic upper gastrointestinal cancer region of Turkey. Environ Toxicol Pharm 13:175–179

    Article  CAS  Google Scholar 

  32. Lu H, Li Z, Fu S, Mendez A, Gasco G, Ferriero JP (2015) Combining phytoextraction and biochar addition improves soil biochemical properties in a soil contaminated with Cd. Chemosphere 119:209–216

    Article  CAS  PubMed  Google Scholar 

  33. Baccio D, Kopriva S, Sebastiani L, Rennenberg H (2005) Does glutathione metabolism have a role in the defence of poplar against zinc excess. New Phytol 167:73–80

    Article  PubMed  Google Scholar 

  34. Cameron RE (1992) Guide to site and soil description for hazardous waste site characterization, EPA/600/4-91/029, vol 1, Metals. US Environmental Protection Agency, Washington, DC

    Google Scholar 

  35. Manivasagaperumal R, Balamurugan S, Thiyagarajan G, Sekar J (2011) Effect of zinc on germination, seedling growth and biochemical content of cluster bean (Cyamopsis tetragonoloba (L.) Taub). Curr Bot 2:11–15

    CAS  Google Scholar 

  36. Gregory SJ, Anderson CWN, Arbestain MC, McManus MT (2014) Response of plant and soil microbes to biochar amendment of an arsenic-contaminated soil. Agric Ecosyst Environ 191:133–141

    Article  CAS  Google Scholar 

  37. Wyszkowska J (2002) Soil contamination by chromium and its enzymatic activity and yielding. Pollut Environ Stud 11:79–84

    CAS  Google Scholar 

  38. Namgay T, Singh B, Singh BP (2010) Influence of biochar application to soil on the availability of As, Cd, Cu, Pb, and Zn to maize (Zea mays L.). Soil Res 48:638–647

    Article  CAS  Google Scholar 

  39. Novak JM, Busscher WJ, Laird DL, Ahmedna M, Watts DW, Niandou MAS (2009) Impact of biochar amendment on fertility of a south eastern coastal plain soil. Soil Sci 174:105–112

    Article  CAS  Google Scholar 

  40. Zhang X, Wang H, He L, Lu K, Sarmah A, Li J, Bolan NS, Pei J, Huang H (2013) Using biochar for remediation of soils contaminated with heavy metals and organic pollutants. Environ Sci Pollut Res 20:8472–8483

    Article  CAS  Google Scholar 

  41. Cao X, Ma L, Liang Y, Gao B, Harris W (2011) Simultaneous immobilization of lead and atrazine in contaminated soils using dairy-manure biochar. Environ Sci Technol 45:4884–4889

    Article  CAS  PubMed  Google Scholar 

  42. Jianga J, Xua R, Jianga T, Li Z (2012) Immobilization of Cu(II), Pb(II) and Cd(II) by the addition of rice straw derived biochar to a simulated polluted Ultisol. J Hazard Mater 229–230:145–150

    Article  Google Scholar 

  43. Cao X, Harris W (2010) Properties of dairy-manure-derived biochar pertinent to its potential use in remediation. Bioresour Technol 101:5222–5228

    Article  CAS  PubMed  Google Scholar 

  44. Jiang T, Jiang J, Xu R, Li Z (2012) Adsorption of Pb (II) on variable charge soils amended with rice-straw derived biochar. Chemosphere 89:249–256

    Article  CAS  PubMed  Google Scholar 

  45. Ahmad M, Lee SS, Lim JE, Lee S, Cho JS, Moon DH, Hashimoto Y, Ok YS (2014) Speciation and phytoavailability of lead and antimony in a small arms range soil amended with mussel shell, cow bone and biochar: EXAFS spectroscopy and chemical extractions. Chemosphere 95:433–441

    Article  CAS  PubMed  Google Scholar 

  46. Uzoma KC, Inoue M, Andry H, Fujimaki H, Nishihara E, Zahoor A (2011) Effect of cow manure biochar on maize productivity under sandy soil condition. Soil Use Manage 27:205–212

    Article  Google Scholar 

  47. Lu H, Zhang W, YangY HX, Wang S, Qiu R (2012) Relative distribution of Pb 2D sorption mechanisms by sludge-derived biochar. Water Res 46:854–862

    Article  CAS  PubMed  Google Scholar 

  48. Uchimiya M, Bannon DI, Wartell LH, Lima IM, Klasson KT (2012) Lead retention by broiler litter biochars in small arms range soil: impact of pyrolysis temperature. Agric Food Chem 60:5035–5044

    Article  CAS  Google Scholar 

  49. Younis U, Shah MHR, Danish S, Malik SA, Ameer A (2014) Biochar role in improving biometric and growth attributes of S. oleracea and T. corniculata under cadmium stress. Int J Biosci 5:84–90

    CAS  Google Scholar 

  50. Tong X, Li J, Yuan J, Xu R (2011) Adsorption of Cu (II)by biochars generated from three crop straws. Chem Eng J 172:828–834

    Article  CAS  Google Scholar 

  51. Agrafioti E, Bouras G, Kalderis D, Diamadopoulos E (2013) Biochar production by sewage sludge pyrolysis. J Anal Appl Pyrolysis 101:72–78

    Article  CAS  Google Scholar 

  52. Sun J, Lian F, Liu Z, Zhu L, Song Z (2014) Biochars derived from various crop straws: characterization and Cd(II) removal potential. Ecotoxicol Environ Saf 106:226–231

    Article  CAS  PubMed  Google Scholar 

  53. Uchimiya M, Lima IM, Klasson KT, Chang SC, Wartelle LH, Rodgers JE (2010) Immobilization of heavy metals ions (CuII, CdII, NiII, and PbII) by broiler litter-derived biochar in water and soil. J Agric Food Chem 58:5538–5544

    Article  CAS  PubMed  Google Scholar 

  54. Fisher D, Glaser B (2012) Synergism between compost & biochar for sustainable soil amelioration. Intech Open Sci/Open Mind 32:167–198

    Google Scholar 

  55. Novak JM, Busscher WJ (2012) Selection and use of designer biochars to improve characteristics of southeastern USA Coastal Plain degraded soils. In: Lee JE (ed) Advanced biofuels and bioproducts. Springer, New York

    Google Scholar 

  56. Yao Y, Gao B, Zhang M, Inyang M, Zimmerman AR (2012) Effect of biochar amendment on sorption & leaching of nitrate, ammonium& phosphate in a sandy soil. Chemosphere 89:1467–1471

    Article  CAS  PubMed  Google Scholar 

  57. Jones DL, Murphy DV, Khalid M, Ahmed W, Jones GE, Deluca TH (2011) Short term biochar-induced increase in soil CO2 release in both biotically & abiotically mediated. Soil Biol Biochem 43:1723–1731

    Article  CAS  Google Scholar 

  58. Ahmad M, Rajapaksha AU, Lim JE, Zhang M, Bolan N, Mohan D, Vithanage M, Lee SS, Ok YS (2014) Biochar as a sorbent for contaminant management in soil and water: a review. Chemosphere 99:19–33

    Article  CAS  PubMed  Google Scholar 

  59. Younis U, Qayyum MF, Shahi MHR, Malik SA (2014) Nutrient shift modeling in Fenugreek (Trigonella corniculata L.) under biochar and cadmium treatment. Int J Biosci 5:64–74

    CAS  Google Scholar 

  60. Bolan NS, Kunhikrishnan A, Choppala GK, Thangarajan R, Chung JW (2012) Stabilization of carbon in composts and biochars in relation to carbon sequestration and soil fertility. Sci Total Environ 424:264–270

    Article  CAS  PubMed  Google Scholar 

  61. Jiang J, Xu RK (2013) Evaluating role of alkali and organic functional group in Cu(II) immobilization. Bioresour Technol 133:537–545

    Article  CAS  PubMed  Google Scholar 

  62. Kolodyriska D, Wnetrzak R, Leahy JJ, Hayes MHB, Kwapiriski W, Hubicki Z (2012) Kinetic and adsorption characterization of biochar in metal ions removal. Chem Eng J 197:295–305

    Article  Google Scholar 

  63. Xu X, Cao X, Zhao L, Wang H, Yu H, Gao B (2013) Removal of Cu, Zn and Cd from aqueous solutions by the dairy manure-derived biochar. Environ Sci Pollut Res 20:358–368

    Article  CAS  Google Scholar 

  64. Ahmad M, Lee SS, RajapakshaAU VM, Zhang M, Cho JS, Lee SE, Ok YS (2013) Trichloroethylene adsorption by pine needle biochars produces at various pyrolysis temperature. Bioresour Technol 143:615–622

    Article  CAS  PubMed  Google Scholar 

  65. Ska DK, Trzak RW, Leahy JJ, Hayes MHB, Ski WK, Hubicki Z (2012) Kinetic and adsorption characterization of biochar in metal ions removal. Chem Eng J 197:295–305

    Article  Google Scholar 

  66. Harvey OR, Kuo LJ, Zimmerman AR, Louchouarn P, Amonette JE, Herbert BE (2012) An index based approach to assessing recalcitrance and soil carbon sequestration potential of engineered black carbons (biochar). Environ Sci Technol 46:1415–1421

    Article  CAS  PubMed  Google Scholar 

  67. Beesley L, Jiménez EM, Eyles JLG (2010) Effects of biochar and green waste compost amendments on mobility, bioavailability and toxicity of inorganic and organic contaminants in a multi-element polluted soil. Environ Pollut 158:2282–2287

    Article  CAS  PubMed  Google Scholar 

  68. Khan S, Chao C, Waqas M, Arp HPH, Zhu YG (2013) Sewage sludge biochar influence upon rice (Oryza sativa L.) yield, metal bioaccumulation and greenhouse gas emissions from acidic paddy soil. Environ Sci Technol 47:8624–8632

    Article  CAS  PubMed  Google Scholar 

  69. Uchimiya M, Wartelle LH, Klasson T, Fortier CA, Lima IM (2011) Influence of pyrolysis temperature on biochar property and function as a heavy metal sorbent in soil. J Agric Food Chem 59:2501–2510

    Article  CAS  PubMed  Google Scholar 

  70. Karami N, Clemente R, Moreno-Jiménez E, Lepp NW, Beesley L (2011) Efficiency of green waste compost and biochar soil amendments for reducing lead and copper mobility and uptake to ryegrass. J Hazard Mater 191:41–48

    Article  CAS  PubMed  Google Scholar 

  71. Uchimiya M, Klasson KT, Wartelle LH, Lima IM (2011) Influence of soil properties on heavy metal sequestration by biochar amendment: 1. Copper sorption isotherms and the release of cations. Chemosphere 82:1431–1437

    Article  CAS  PubMed  Google Scholar 

  72. Ma JW, Wang H, Luo QS (2007) Movement-adsorption and its mechanism of Cd in soil under combining effect of electrokinetics and a new type of bamboo charcoal. Environ Sci 28:1829–1834

    CAS  Google Scholar 

  73. Beesley L, Marmiroli M (2011) Theimmobilisation and retention of soluble arsenic, cadmium and zinc by biochar. Environ Pollut 159:474–480

    Article  CAS  PubMed  Google Scholar 

  74. Beesley L, Dickinson N (2011) Carbon and trace element fluxes in the pore water of an urban soil following greenwaste compost, woody and biochar amendments, inoculated with the earthworm Lumbricus terrestris. Soil Biol Biochem 43:188–196

    Article  CAS  Google Scholar 

  75. Debela F, Thring RW, Arocena JM (2012) Immobilization of heavy metals by Co-pyrolysis of contaminated soil with woody biomass. Water Air Soil Pollut 223:1161–1170

    Article  CAS  Google Scholar 

  76. Zhou JB, Deng CJ, Chen JL, Zhang QS (2008) Remediation effects of cotton stalk carbon on cadmium (Cd) contaminated soil. Ecol Environ 17:1857–1860

    Google Scholar 

  77. Hartley W, Dickinson NM, Riby P, Lepp NW (2009) Arsenic mobility in brownfield soils amended with green waste compost or biochar and planted with Miscanthus. Environ Pollut 157:2654–2662

    Article  CAS  PubMed  Google Scholar 

  78. Fellet G, MarchiolL DVG, Peressotti A (2011) Application of biochar on mine tailings: effects and perspectives for land reclamation. Chemosphere 83:1262–1297

    Article  CAS  PubMed  Google Scholar 

  79. Choppala GK, Bolan NS, Mallavarapu M, Chen Z, Naidu R (2012) The influence of biochar and black carbon on reduction and bioavailability of chromate in soils. J Environ Qual 41:1–10

    Article  Google Scholar 

  80. Mendez A, Gomez A, Ferreiro JP, Gasco G (2012) Effects of sewage sludge biochar on plant metal availability after application to a Mediterranean soil. Chemosphere 89:1354–1359

    Article  CAS  PubMed  Google Scholar 

  81. Suppadit T, Kitikoon V, Phubphol A, Neumnoi P (2012) Effect of quail litter biochar on productivity of four new physic nut varieties planted in Cadmium-contaminated soil. Chilean J Agric Res 72:125–132

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Department of Environmental Sciences and Engineering, Government College University, Allama Iqbal Road, 38000, Faisalabad, Pakistan

    Amina Hayyat, Maryam Javed, Iqra Rasheed, Shafaqat Ali, Munazzam Jawad Shahid & Muhammad Rizwan

  2. Department of Botany, Government College University, Allama Iqbal Road, 38000, Faisalabad, Pakistan

    Muhammad Tariq Javed & Qasim Ali

Authors
  1. Amina Hayyat
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Maryam Javed
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Iqra Rasheed
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Shafaqat Ali
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Munazzam Jawad Shahid
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Muhammad Rizwan
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Muhammad Tariq Javed
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Qasim Ali
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Shafaqat Ali .

Editor information

Editors and Affiliations

  1. Department of Biology Faculty of Science, University of Tabuk, Tabuk, Saudi Arabia

    Abid Ali Ansari

  2. Centre for Biotechnology, MD University, Rohtak, Haryana, India

    Sarvajeet Singh Gill

  3. Centre for Biotechnology, MD University, Rohtak, Haryana, India

    Ritu Gill

  4. College of Environmental Science, State University of New York, Syracuse, New York, USA

    Guy R. Lanza

  5. College of Environmental Science, State University of New York, Syracuse, New York, USA

    Lee Newman

Rights and permissions

Reprints and permissions

Copyright information

© 2016 Springer International Publishing Switzerland

About this chapter

Cite this chapter

Hayyat, A. et al. (2016). Role of Biochar in Remediating Heavy Metals in Soil. In: Ansari, A., Gill, S., Gill, R., Lanza, G., Newman, L. (eds) Phytoremediation. Springer, Cham. https://doi.org/10.1007/978-3-319-40148-5_14

Download citation

Publish with us

Policies and ethics

Search

Navigation