Pollution Induced Community Tolerance(PICT) of Microorganisms in Soil Incubated with Different Levels of PB
Soil microbial activity is adversely affected by pollutants such as heavy metals, antibiotics and pesticides. Organic amendments including sewage sludge, municipal compost and vermicompost are recently used to improve soil structure and fertility. But, these materials contain heavy metals including Pb, Cd, Zn, Ni and Cu that are toxic to soil microorganisms and may lead to occurrence of more tolerant microbes. Among these, Pb is the most abundant and has more negative effect on soil microbial ecology. In this study, Pb levels of 0, 100, 200, 300, 400 and 500 mg Pb [as Pb(NO3)2] per kg soil were added to the pots containing 2 kg of a loamy soil and incubated for 6 months at 25°C with soil moisture of - 0.3 MPa. Dehydrogenase activity of soil as a measure of microbial activity was determined on 15, 30, 90 and 180 days after incubation. Triphenyl tetrazolium chloride (TTC) was used as an electron acceptor in this assay. PICTs (IC50 values) were calculated for each Pb level and incubation time. Soil microbial activity was decreased by increasing Pb level during 30 days of incubation but the induced tolerance appeared on day 90 and thereafter. During 90 to 180 days of incubation, the PICT was gradually developed by increasing Pb level up to 200 mg kg-1, but the rate of enhancement was steeper at higher concentrations.
[1] S.R. Smith, "Agricultural Recycling of Sewage Sludge in the
Environment" CABI Biosciences, Wallingford, UK, 1996.
[2] K.E. Giller, E. Witter, and S.P. McGrath, "Toxicity of heavy metals to
microorganisms and microbial process in agricultural soils: a review"
Soil Biol. Biochem. vol. 300, pp.1389-1414, 1998.
[3] P.C. Brookes, "The potential of microbiological properties as indicators
in soil-pollution monitoring" in Soil Monitoring. Early Detection and
Surveying of Soil Contamination and Degradation, R. Schulin, A.
Desaules, R. Webster, and B. von Steiger, Eds. Birkha¨user Verlag,
Basel, Switzerland, 1993, pp 229-254.
[4] S.P. MacGrath, "Effects of heavy metals from sewage sludge on soil
microbes in agricultural ecosystems" in Toxic metals in soil-plant
systems, S.M. Ross, Ed., John Wiley, Chichester, 1994, pp. 242-274
[5] S.P. MacGrath, A.M. Chaudri, and K.E. Giller, "Longterm effects of
metals in sewage sludge on soils, microorganisms and plants" J. Ind.
Microbiol. Vol.14, pp.94-104, 1995.
[6] K. Chander, and P.C. Brookes, "Effects of heavy metals from past
applications on microbial biomass and organic matter accumulation in a
sandy loam U.K. soil" Soil Biol. Biochem. Vol.23, pp. 927-932, 1991.
[7] K. Chander, and P.C. Brookes, "Residual effects of zinc, copper and
nickel in sewage sludge on microbial biomass in a sandy loam" Soil
Biol. Biochem,vol. 25, pp.1231-1239, 1993.
[8] B. Olson, and I. Thornton, "The resistance patterns to metals of bacterial
populations in contaminated land" J Soil Sci. vol.33, pp.271-277, 1982.
[9] M. Diaz-Ravina, and E. Bååth, "Development of metal tolerance in soil
bacterial communities exposed to experimentally increased metal levels"
Appl Environ Microbiol. Vol.62, pp.2970-2977, 1996.
[10] M. Diaz-Ravina, and E. Bååth, "Response of soil bacterial communities
pre-exposed to different metals and reinoculated in an unpolluted soil"
Soil Biol Biochem. Vol.33, pp.241-248, 2001.
[11] H. Blanck, S.A. Wangberg, and S. Molander, "Pollution-induced
community tolerance. A new ecotoxicological tool" in Functional
Testing of Aquatic Biota for Estimating Hazards of Chemicals STP 988.
J.J. Cairns, and J.R. Pratt, Eds. American Society for Testing,
Philadelphia, PA, 1988, pp. 219-230.
[12] P. Van Beelen, A.K. Fleuren-Kemila, and T. Aldenberg, "The relation
between extrapolated risk, expressed as potentially affected fraction, and
community effects, expressed as pollution-induced community
tolerance" Environ Toxicol Chem. Vol.20, pp.1133-1140, 2001.
[13] M.E.Y. Boivin, A.M. Breure, L. Posthuma, and M. Rutgers,
"Determination of field effects of contaminants-significance of
pollution- induced community tolerance" Human and Ecological Risk
Assessment, vol. 8, pp.1035-1055,2002.
[14] K. Lock, and C.R. Janssen, "Influence of soil zinc concentrations on
zinc sensitivity and functional diversity of microbial communities"
Environ. Pollut. Vol.136, pp.275-281, 2005.
[15] H. Bayer, M. Mitterer, and F. Schinner, "Der Ein.uss von Insektiziden
auf mikrobiogene Prozesse in Ah-Materialien eines landwirtschaftlich
genutzten Bodens" Pedobiologia, vol. 23, pp.311-319, 1982.
[16] R.P. Dick, "Soil enzyme activities as integrative indicators of soil
health" in Biological indicators of soil health,C.E. Pankhurst, B.M.
Doube, and V.V.S.R. Gupta, Eds. Wallingford, USA, CAB
International, 1997, pp. 121-156.
[17] E.M. Top, M.P. Maila, M. Clerinx, J. Goris, P. De Vos, and W.
Verstraete, "Methane oxidation as method to evaluate the removal of
2,4-D from soil by plasmid-mediated bioaugumentation" FEMS
Microbiol. Ecol. Vol.28, pp.203-213,1999.
[18] L. Gianfreda, M.A. Rao, A. Piotrowska, G. Palumbo, and C. Colombo,
"Soil enzyme activities as affected by anthropogenic alterations:
intensive agricultural practices and organic pollution" Sci. Total
Environ. Vol.341, pp. 265-279, 2005.
[19] P. Doelman, and L. Haanstra, "Short and long term effects of heavy
metals on urease activity in soils" Biol. Fertil. Soils. Vol.2, pp. 213-218,
1894.
[20] C. Marzadori, C. Ciavatta, D. Montecchio, and C. Gessa, "Effetcs of
lead pollution on different soil enzyme activities" Biol. Fertil. Soils.
Vol.22, pp.53-58, 1996.
[21] S.P. Mathur, J.I. MacDougall, and M. McGrath, "Levels of activities of
some carbohydrates, protease, lipase and phosphates in organic soils of
differing copper content" Soil Science. Vol.129, pp.376-385, 1980.
[22] G. Tyler, "Heavy metal pollution and soil enzyme activity" Plant and
Soil. Vol.41, pp.303-311, 1974.
[23] M.A. Tabatabai, "Effects of trace elements on urease activity" Soil
Biol. Biochem. vol.9, pp.9-13, 1977.
[24] M.B. Hinojosa, J.A. Carreira, R. García-Ruíz, and R.P. Dick, "Soil
moisture pre-treatment effects on enzyme activities as indicators of
heavy metal-contaminated and reclaim soils" Soil Biol. Biochem.
vol.30, pp.1559-1568, 2004.
[25] P. Nannipieri, "The potential use of soil enzymes as indicators of
productivity, sustainability and pollution" in Soil Biota, Management
in Sustainable Farming Systems, C.E. Pankhurst, B.M. Doube,
,V.V.S.R. Gupta, and P.R.Grace, Eds. Australia, CSIRO Publication,
1994, pp.238-244.
[26] C. Trasar-Cepeda, M.C. Leir├│s, S. Seoane, and F. Gil-Sotres,
"Limitations of soil enzymes as indicators of soil pollution" Soil Biol.
Biochem. vol.32, pp.1867-1875, 2000.
[27] J.H. Bolton, Elliot, L.F. R.I. Papendick, and D.F. Berdicek, "Soil
microbial biomass and selected soil enzyme activities: effects of
fertilization and cropping practices" Soil Biol. Biochem. Vol.14, pp.
423-427, 1985.
[28] G. Shen, Y. Lu, Q. Zhou, and J. Hong, "Interaction of polycyclic
aromatic hydrocarbons and heavy metals on soil enzyme"
Chemosphere. Vol.61, pp.1175-1182, 2005.
[29] A.L. Page, "Methods of Soil Analysis" Part 2, Chemical and
Microbiological Properties. Second edition. Agronomy number 9.
U.S.A, 1982.
[30] M. Rutgers, and A.M. Breure, "Risk assessment, microbial communities
and pollution-induced community tolerance" Human and Ecol Risk
Assessment. Vol.5, pp.661-670, 1998.
[31] C.O. Nweke, C. Ntinugwa, I.F. Obach, S.C. Ike, G.E. Eme, E.C.
Opara, J.C. Okolo, and C.E. Nwanyanwu, "In vitro effects of metals
and pesticides on dehydrogenase activity in microbial community of
cowpea (Vigna unguiculata) rhizoplane" African J. Biotech. Vol.6,
pp.290-295, 2007.
[32] L. Alden Demoling, and E. Bååth, "Use of pollution-induced
community tolerance of the bacterial community to detect phenol
toxicity in soil" Environ. Toxicol. Chem. Vol.27, pp. 344-350, 2008.
[33] L.S. Zeng, M. Liao, C.L. Chen, and C.Y. Huang, "Effects of lead
contamination on soil enzymatic activities, microbial biomass and rice
physiological indices in soil-lead-rice (Oryza sativa L.) system.
Ecotoxicol" Environ. Safety. Vol.67, pp.67-74, 2007.
[34] K. Saeki, T. Kunito, H. Oyaizu, and S. Matsumoto, "Relationships
between bacterial tolerance levels and forms of copper and zinc in soils"
J. Environ. Qual. Vol.31, pp.1570-1575, 2002.
[35] A.R. Almas, L.R. Bakken, and J. Mulder, " Changes in tolerance of soil
microbial communities in Zn and Cd contaminated soils" Soil Biol.
Biochem. Vol.36, pp.805-813, 2004.
[36] M. Diaz-Ravina, R. Calvo de Anta, and E. Bååth, "Tolerance (PICT) of
the bacterial communities to copper in Vineyards soils from Spain" J.
Environ. Qual. Vol.36, pp.1760-1764, 2007.
[37] M. Niklinska, M.Chodak, and R. Laskowski, "Pollution-induced
community tolerance of microorganisms from forest soil organic layers
polluted with Zn or Cu" Appl Soil Ecol. Vol. 32, pp.265-272, 2006.
[38] K. Kaiser, and G. Guggenberger, "The role of DOM sorption to mineral
surfaces in the preservation of organic matter in soils" Org. Geochem.
Vol.31, pp.711-725, 2000.
[39] Y. Wang, J. Shi, Q. Lin, X. Chen, and Y. Chen, "Heavy metal
availability and impact on activity of soil microorganisms along a
Cu/Zn contamination gradient" J. Environ Sci. vol.19, pp.848-853,
2007.
[40] J.J. Kelly, M. Häggblom, and R.L. Tate ΙΙΙ, "Changes in soil microbial
communities over time resulting from one time application of zinc: a
laboratory microcosm study" Soil Biol. Biochem. vol.31, pp.1455-1465,
1999.
[41] M. Liao, L. Yun-kuo, Z. Xiao-min, and H. Chang-yong, "Toxicity of
cadmium to soil microbial biomass and its activity: Effect of incubation
time on Cd ecological dose in paddy soil" J. Zhejiang University
Science. Vol.5, pp.324-330, 2005.
[42] E. Kandeler, D. Tscherko, K.D. Bruce, M. Stemmer, P.J. Hobbs, R.D.
Bardgett, and W. Amelung, "Structure and function of the soil
microbial community in microhabitats of a heavy metal polluted soil"
Biol. Fertil Soil. Vol.32, pp.390-400, 2000.
[43] T.W. Speir, H.A. Kettles, A. Parshotam, P.L. Searle, and L.N.C. Vlaar,
"A simple kinetic approach to derive the ecological dose value, ED50,
for the assessment of Cr (VI) toxicity to soil biological properties" Soil
Biol. Biochem. vol.27, pp.801-810,1995.
[44] L. Alden Demoling, and E. Bååth, "No long-term persistence of
bacterial pollution-induced community tolerance in tylosin-polluted
soil" Environ. Sci. Tecchnol. Vol.42, pp. 6917-6921, 2008.
[45] M. Diaz-Ravina, and E. Bååth, "Influence of different temperatures on
metal tolerance measurements and growth response of bacterial
communities from unpolluted and polluted soils" Biol. Fertil. Soils.
Vol.21, pp. 233-238, 1996.
[46] T. Duxbury, "Ecological aspects of heavy metal responses in
microorganisms" in Advances in Microbial Ecology, K.C. Marshall,
Ed. vol. 8. Plenum, New York, 1985, pp. 185-236.
[47] L.Posthuma, "Effects of toxicants on population and community
parameters in field conditions, and their potential use in the validation
of risk assessment methods" in Ecological risk assessment of
contaminats in soil, N.M. Van Straalen., and H. Lokke, Eds. Chapman
and Hall, London, 1997, pp. 85-117.
[1] S.R. Smith, "Agricultural Recycling of Sewage Sludge in the
Environment" CABI Biosciences, Wallingford, UK, 1996.
[2] K.E. Giller, E. Witter, and S.P. McGrath, "Toxicity of heavy metals to
microorganisms and microbial process in agricultural soils: a review"
Soil Biol. Biochem. vol. 300, pp.1389-1414, 1998.
[3] P.C. Brookes, "The potential of microbiological properties as indicators
in soil-pollution monitoring" in Soil Monitoring. Early Detection and
Surveying of Soil Contamination and Degradation, R. Schulin, A.
Desaules, R. Webster, and B. von Steiger, Eds. Birkha¨user Verlag,
Basel, Switzerland, 1993, pp 229-254.
[4] S.P. MacGrath, "Effects of heavy metals from sewage sludge on soil
microbes in agricultural ecosystems" in Toxic metals in soil-plant
systems, S.M. Ross, Ed., John Wiley, Chichester, 1994, pp. 242-274
[5] S.P. MacGrath, A.M. Chaudri, and K.E. Giller, "Longterm effects of
metals in sewage sludge on soils, microorganisms and plants" J. Ind.
Microbiol. Vol.14, pp.94-104, 1995.
[6] K. Chander, and P.C. Brookes, "Effects of heavy metals from past
applications on microbial biomass and organic matter accumulation in a
sandy loam U.K. soil" Soil Biol. Biochem. Vol.23, pp. 927-932, 1991.
[7] K. Chander, and P.C. Brookes, "Residual effects of zinc, copper and
nickel in sewage sludge on microbial biomass in a sandy loam" Soil
Biol. Biochem,vol. 25, pp.1231-1239, 1993.
[8] B. Olson, and I. Thornton, "The resistance patterns to metals of bacterial
populations in contaminated land" J Soil Sci. vol.33, pp.271-277, 1982.
[9] M. Diaz-Ravina, and E. Bååth, "Development of metal tolerance in soil
bacterial communities exposed to experimentally increased metal levels"
Appl Environ Microbiol. Vol.62, pp.2970-2977, 1996.
[10] M. Diaz-Ravina, and E. Bååth, "Response of soil bacterial communities
pre-exposed to different metals and reinoculated in an unpolluted soil"
Soil Biol Biochem. Vol.33, pp.241-248, 2001.
[11] H. Blanck, S.A. Wangberg, and S. Molander, "Pollution-induced
community tolerance. A new ecotoxicological tool" in Functional
Testing of Aquatic Biota for Estimating Hazards of Chemicals STP 988.
J.J. Cairns, and J.R. Pratt, Eds. American Society for Testing,
Philadelphia, PA, 1988, pp. 219-230.
[12] P. Van Beelen, A.K. Fleuren-Kemila, and T. Aldenberg, "The relation
between extrapolated risk, expressed as potentially affected fraction, and
community effects, expressed as pollution-induced community
tolerance" Environ Toxicol Chem. Vol.20, pp.1133-1140, 2001.
[13] M.E.Y. Boivin, A.M. Breure, L. Posthuma, and M. Rutgers,
"Determination of field effects of contaminants-significance of
pollution- induced community tolerance" Human and Ecological Risk
Assessment, vol. 8, pp.1035-1055,2002.
[14] K. Lock, and C.R. Janssen, "Influence of soil zinc concentrations on
zinc sensitivity and functional diversity of microbial communities"
Environ. Pollut. Vol.136, pp.275-281, 2005.
[15] H. Bayer, M. Mitterer, and F. Schinner, "Der Ein.uss von Insektiziden
auf mikrobiogene Prozesse in Ah-Materialien eines landwirtschaftlich
genutzten Bodens" Pedobiologia, vol. 23, pp.311-319, 1982.
[16] R.P. Dick, "Soil enzyme activities as integrative indicators of soil
health" in Biological indicators of soil health,C.E. Pankhurst, B.M.
Doube, and V.V.S.R. Gupta, Eds. Wallingford, USA, CAB
International, 1997, pp. 121-156.
[17] E.M. Top, M.P. Maila, M. Clerinx, J. Goris, P. De Vos, and W.
Verstraete, "Methane oxidation as method to evaluate the removal of
2,4-D from soil by plasmid-mediated bioaugumentation" FEMS
Microbiol. Ecol. Vol.28, pp.203-213,1999.
[18] L. Gianfreda, M.A. Rao, A. Piotrowska, G. Palumbo, and C. Colombo,
"Soil enzyme activities as affected by anthropogenic alterations:
intensive agricultural practices and organic pollution" Sci. Total
Environ. Vol.341, pp. 265-279, 2005.
[19] P. Doelman, and L. Haanstra, "Short and long term effects of heavy
metals on urease activity in soils" Biol. Fertil. Soils. Vol.2, pp. 213-218,
1894.
[20] C. Marzadori, C. Ciavatta, D. Montecchio, and C. Gessa, "Effetcs of
lead pollution on different soil enzyme activities" Biol. Fertil. Soils.
Vol.22, pp.53-58, 1996.
[21] S.P. Mathur, J.I. MacDougall, and M. McGrath, "Levels of activities of
some carbohydrates, protease, lipase and phosphates in organic soils of
differing copper content" Soil Science. Vol.129, pp.376-385, 1980.
[22] G. Tyler, "Heavy metal pollution and soil enzyme activity" Plant and
Soil. Vol.41, pp.303-311, 1974.
[23] M.A. Tabatabai, "Effects of trace elements on urease activity" Soil
Biol. Biochem. vol.9, pp.9-13, 1977.
[24] M.B. Hinojosa, J.A. Carreira, R. García-Ruíz, and R.P. Dick, "Soil
moisture pre-treatment effects on enzyme activities as indicators of
heavy metal-contaminated and reclaim soils" Soil Biol. Biochem.
vol.30, pp.1559-1568, 2004.
[25] P. Nannipieri, "The potential use of soil enzymes as indicators of
productivity, sustainability and pollution" in Soil Biota, Management
in Sustainable Farming Systems, C.E. Pankhurst, B.M. Doube,
,V.V.S.R. Gupta, and P.R.Grace, Eds. Australia, CSIRO Publication,
1994, pp.238-244.
[26] C. Trasar-Cepeda, M.C. Leir├│s, S. Seoane, and F. Gil-Sotres,
"Limitations of soil enzymes as indicators of soil pollution" Soil Biol.
Biochem. vol.32, pp.1867-1875, 2000.
[27] J.H. Bolton, Elliot, L.F. R.I. Papendick, and D.F. Berdicek, "Soil
microbial biomass and selected soil enzyme activities: effects of
fertilization and cropping practices" Soil Biol. Biochem. Vol.14, pp.
423-427, 1985.
[28] G. Shen, Y. Lu, Q. Zhou, and J. Hong, "Interaction of polycyclic
aromatic hydrocarbons and heavy metals on soil enzyme"
Chemosphere. Vol.61, pp.1175-1182, 2005.
[29] A.L. Page, "Methods of Soil Analysis" Part 2, Chemical and
Microbiological Properties. Second edition. Agronomy number 9.
U.S.A, 1982.
[30] M. Rutgers, and A.M. Breure, "Risk assessment, microbial communities
and pollution-induced community tolerance" Human and Ecol Risk
Assessment. Vol.5, pp.661-670, 1998.
[31] C.O. Nweke, C. Ntinugwa, I.F. Obach, S.C. Ike, G.E. Eme, E.C.
Opara, J.C. Okolo, and C.E. Nwanyanwu, "In vitro effects of metals
and pesticides on dehydrogenase activity in microbial community of
cowpea (Vigna unguiculata) rhizoplane" African J. Biotech. Vol.6,
pp.290-295, 2007.
[32] L. Alden Demoling, and E. Bååth, "Use of pollution-induced
community tolerance of the bacterial community to detect phenol
toxicity in soil" Environ. Toxicol. Chem. Vol.27, pp. 344-350, 2008.
[33] L.S. Zeng, M. Liao, C.L. Chen, and C.Y. Huang, "Effects of lead
contamination on soil enzymatic activities, microbial biomass and rice
physiological indices in soil-lead-rice (Oryza sativa L.) system.
Ecotoxicol" Environ. Safety. Vol.67, pp.67-74, 2007.
[34] K. Saeki, T. Kunito, H. Oyaizu, and S. Matsumoto, "Relationships
between bacterial tolerance levels and forms of copper and zinc in soils"
J. Environ. Qual. Vol.31, pp.1570-1575, 2002.
[35] A.R. Almas, L.R. Bakken, and J. Mulder, " Changes in tolerance of soil
microbial communities in Zn and Cd contaminated soils" Soil Biol.
Biochem. Vol.36, pp.805-813, 2004.
[36] M. Diaz-Ravina, R. Calvo de Anta, and E. Bååth, "Tolerance (PICT) of
the bacterial communities to copper in Vineyards soils from Spain" J.
Environ. Qual. Vol.36, pp.1760-1764, 2007.
[37] M. Niklinska, M.Chodak, and R. Laskowski, "Pollution-induced
community tolerance of microorganisms from forest soil organic layers
polluted with Zn or Cu" Appl Soil Ecol. Vol. 32, pp.265-272, 2006.
[38] K. Kaiser, and G. Guggenberger, "The role of DOM sorption to mineral
surfaces in the preservation of organic matter in soils" Org. Geochem.
Vol.31, pp.711-725, 2000.
[39] Y. Wang, J. Shi, Q. Lin, X. Chen, and Y. Chen, "Heavy metal
availability and impact on activity of soil microorganisms along a
Cu/Zn contamination gradient" J. Environ Sci. vol.19, pp.848-853,
2007.
[40] J.J. Kelly, M. Häggblom, and R.L. Tate ΙΙΙ, "Changes in soil microbial
communities over time resulting from one time application of zinc: a
laboratory microcosm study" Soil Biol. Biochem. vol.31, pp.1455-1465,
1999.
[41] M. Liao, L. Yun-kuo, Z. Xiao-min, and H. Chang-yong, "Toxicity of
cadmium to soil microbial biomass and its activity: Effect of incubation
time on Cd ecological dose in paddy soil" J. Zhejiang University
Science. Vol.5, pp.324-330, 2005.
[42] E. Kandeler, D. Tscherko, K.D. Bruce, M. Stemmer, P.J. Hobbs, R.D.
Bardgett, and W. Amelung, "Structure and function of the soil
microbial community in microhabitats of a heavy metal polluted soil"
Biol. Fertil Soil. Vol.32, pp.390-400, 2000.
[43] T.W. Speir, H.A. Kettles, A. Parshotam, P.L. Searle, and L.N.C. Vlaar,
"A simple kinetic approach to derive the ecological dose value, ED50,
for the assessment of Cr (VI) toxicity to soil biological properties" Soil
Biol. Biochem. vol.27, pp.801-810,1995.
[44] L. Alden Demoling, and E. Bååth, "No long-term persistence of
bacterial pollution-induced community tolerance in tylosin-polluted
soil" Environ. Sci. Tecchnol. Vol.42, pp. 6917-6921, 2008.
[45] M. Diaz-Ravina, and E. Bååth, "Influence of different temperatures on
metal tolerance measurements and growth response of bacterial
communities from unpolluted and polluted soils" Biol. Fertil. Soils.
Vol.21, pp. 233-238, 1996.
[46] T. Duxbury, "Ecological aspects of heavy metal responses in
microorganisms" in Advances in Microbial Ecology, K.C. Marshall,
Ed. vol. 8. Plenum, New York, 1985, pp. 185-236.
[47] L.Posthuma, "Effects of toxicants on population and community
parameters in field conditions, and their potential use in the validation
of risk assessment methods" in Ecological risk assessment of
contaminats in soil, N.M. Van Straalen., and H. Lokke, Eds. Chapman
and Hall, London, 1997, pp. 85-117.
@article{"International Journal of Earth, Energy and Environmental Sciences:53543", author = "N. Aliasgharzad and A. Molaei and S. Oustan", title = "Pollution Induced Community Tolerance(PICT) of Microorganisms in Soil Incubated with Different Levels of PB", abstract = "Soil microbial activity is adversely affected by pollutants such as heavy metals, antibiotics and pesticides. Organic amendments including sewage sludge, municipal compost and vermicompost are recently used to improve soil structure and fertility. But, these materials contain heavy metals including Pb, Cd, Zn, Ni and Cu that are toxic to soil microorganisms and may lead to occurrence of more tolerant microbes. Among these, Pb is the most abundant and has more negative effect on soil microbial ecology. In this study, Pb levels of 0, 100, 200, 300, 400 and 500 mg Pb [as Pb(NO3)2] per kg soil were added to the pots containing 2 kg of a loamy soil and incubated for 6 months at 25°C with soil moisture of - 0.3 MPa. Dehydrogenase activity of soil as a measure of microbial activity was determined on 15, 30, 90 and 180 days after incubation. Triphenyl tetrazolium chloride (TTC) was used as an electron acceptor in this assay. PICTs (IC50 values) were calculated for each Pb level and incubation time. Soil microbial activity was decreased by increasing Pb level during 30 days of incubation but the induced tolerance appeared on day 90 and thereafter. During 90 to 180 days of incubation, the PICT was gradually developed by increasing Pb level up to 200 mg kg-1, but the rate of enhancement was steeper at higher concentrations.
", keywords = "Induced tolerance, soil microorganisms, Pb, PICT, pollutants.", volume = "5", number = "12", pages = "799-5", }
