A long-term field experiment was carried out in the experiment farm of the Sao Paulo State University,Brazil,to evaluate the phytoavailability of Zn,Cd and Pb in a Typic Eutrorthox soil treated with sewage sludge for ...A long-term field experiment was carried out in the experiment farm of the Sao Paulo State University,Brazil,to evaluate the phytoavailability of Zn,Cd and Pb in a Typic Eutrorthox soil treated with sewage sludge for nine consecutive years,using the sequential extraction and organic matter fractionation methods.During 2005-2006,maize(Zea mays L.) was used as test plants and the experimental design was in randomized complete blocks with four treatments and five replicates.The treatments consisted of four sewage sludge rates(in a dry basis):0.0(control,with mineral fertilization),45.0,90.0 and 127.5 t ha-1,annually for nine years.Before maize sowing,the sewage sludge was manually applied to the soil and incorporated at 10 cm depth.Soil samples(0-20 cm layer) for Zn,Cd and Pb analysis were collected 60 days after sowing.The successive applications of sewage sludge to the soil did not affect heavy metal(Cd and Pb) fractions in the soil,with exception of Zn fractions.The Zn,Cd and Pb distributions in the soil were strongly associated with humin and residual fractions,which are characterized by stable chemical bonds.Zinc,Cd and Pb in the soil showed low phytoavailability after nine-year successive applications of sewage sludge to the soil.展开更多
Brazilian industry produces huge amounts of tannery sludge as residues,which is often disposed by landfilling or land application.However,consecutive amendment of such composted industrial wastes may cause shifts in s...Brazilian industry produces huge amounts of tannery sludge as residues,which is often disposed by landfilling or land application.However,consecutive amendment of such composted industrial wastes may cause shifts in soil microbial biomass(SMB) and enzyme activity.This study aimed to evaluate SMB and enzyme activity after 3-year consecutive composted tannery sludge(CTS) amendment in tropical sandy soils.Different amounts of CTS(0.0,2.5,5.0,10.0,and 20.0 t ha^(-1)) were applied to a sandy soil.The C and N contents of SMB,basal and substrate-induced respiration,respiratory quotient(qCO_2),and enzyme activities were determined in the soil samples collected after CTS amendment for 60 d at the third year.After 3 years,significant changes were found in soil microbial properties in response to different CTS amounts applied.The organic matter and Cr contents significantly increased with increasing CTS amounts.SMB and soil respiration peaked following amendment with 10.0 and 20.0 t ha-1 of CTS,respectively,while qCO_2was not significantly affected by CTS amendment.However,soil enzyme activity decreased significantly with increasing CTS amounts.Consecutive CTS amendment for 3 years showed inconsistent and contrasting effects on SMB and enzyme activities.The decrease in soil enzyme activities was proportional to a substantial increase in soil Cr concentration,with the latter exceeding the permitted concentrations by more than twofold.Thus,our results suggest that a maximum CTS quantity of 5.0 t ha^(-1) can be applied annually to tropical sandy soil,without causing potential risks to SMB and enzyme activity.展开更多
基金Supported by the Sao Paulo State Research Foundation(FAPESP),Brazil,and the master scholarship granted to the first author(No.06/54620-6)
文摘A long-term field experiment was carried out in the experiment farm of the Sao Paulo State University,Brazil,to evaluate the phytoavailability of Zn,Cd and Pb in a Typic Eutrorthox soil treated with sewage sludge for nine consecutive years,using the sequential extraction and organic matter fractionation methods.During 2005-2006,maize(Zea mays L.) was used as test plants and the experimental design was in randomized complete blocks with four treatments and five replicates.The treatments consisted of four sewage sludge rates(in a dry basis):0.0(control,with mineral fertilization),45.0,90.0 and 127.5 t ha-1,annually for nine years.Before maize sowing,the sewage sludge was manually applied to the soil and incorporated at 10 cm depth.Soil samples(0-20 cm layer) for Zn,Cd and Pb analysis were collected 60 days after sowing.The successive applications of sewage sludge to the soil did not affect heavy metal(Cd and Pb) fractions in the soil,with exception of Zn fractions.The Zn,Cd and Pb distributions in the soil were strongly associated with humin and residual fractions,which are characterized by stable chemical bonds.Zinc,Cd and Pb in the soil showed low phytoavailability after nine-year successive applications of sewage sludge to the soil.
基金Supported by the Conselho Nacional de Desenvolvimento Cientifico e Tecnológico,Brazil(No.302999/2011-6)the Fundacao de Amparo a Pesquisa do Estado do Piaui,Brazil(No.032/2011)
文摘Brazilian industry produces huge amounts of tannery sludge as residues,which is often disposed by landfilling or land application.However,consecutive amendment of such composted industrial wastes may cause shifts in soil microbial biomass(SMB) and enzyme activity.This study aimed to evaluate SMB and enzyme activity after 3-year consecutive composted tannery sludge(CTS) amendment in tropical sandy soils.Different amounts of CTS(0.0,2.5,5.0,10.0,and 20.0 t ha^(-1)) were applied to a sandy soil.The C and N contents of SMB,basal and substrate-induced respiration,respiratory quotient(qCO_2),and enzyme activities were determined in the soil samples collected after CTS amendment for 60 d at the third year.After 3 years,significant changes were found in soil microbial properties in response to different CTS amounts applied.The organic matter and Cr contents significantly increased with increasing CTS amounts.SMB and soil respiration peaked following amendment with 10.0 and 20.0 t ha-1 of CTS,respectively,while qCO_2was not significantly affected by CTS amendment.However,soil enzyme activity decreased significantly with increasing CTS amounts.Consecutive CTS amendment for 3 years showed inconsistent and contrasting effects on SMB and enzyme activities.The decrease in soil enzyme activities was proportional to a substantial increase in soil Cr concentration,with the latter exceeding the permitted concentrations by more than twofold.Thus,our results suggest that a maximum CTS quantity of 5.0 t ha^(-1) can be applied annually to tropical sandy soil,without causing potential risks to SMB and enzyme activity.
