Two series of soil subsamples, by spiking copper (Cu), lead (Pb), zinc (Zn) and cadmium (Cd) in an orthogonal design, were prepared using red soil and brown soil, respectively. The results indicated that heavy metal f...Two series of soil subsamples, by spiking copper (Cu), lead (Pb), zinc (Zn) and cadmium (Cd) in an orthogonal design, were prepared using red soil and brown soil, respectively. The results indicated that heavy metal fractions in these soil subsamples depended not only on soil types, but also on metal loading quantity as well as on interactions among metals in soil. Lead and Cu in red soil appeared mostly in weakly specifically adsorbed (WSA), Fe and Mn oxides bound (OX), and residual (RES) fractions. Zinc existed in all fractions except organic bound one, and Cd was major in water soluble plus exchangeable (SE) one. Different from the results of red soil, Pb and Cu was present in brown soil in all fractions except organic one, but over 75% of Zn and 90% of Cd existed only in SE fraction. Meanwhile, SE fraction for any metal in red soil was lower than that in brown soil and WSA and OX fractions were higher. It is in agreement with low cation exchange capacity and large amounts of metal oxides included in red soil. Metal fractions in soil, especially for water soluble plus exchangeable one, were obviously influenced by other coexisting metals. The SE fraction of heavy metals increased with increasing loading amounts of metals in red soil but not obviously in brown soil, which suggest that metal availability be easily affected by their total amounts spiked in red soil. In addition, more metals in red soil were extracted with 0.20 mol L-1 NH4Cl (pH 5.40) than that with 1.0 mol L-1 Mg(NO3)2 (pH 7.0), but the reverse happened in brown soil, implicating significantly different mechanisms of metal desorption from red soil and brown soil.展开更多
Phosphate-solubilizing bacterial strains(6 Nos.) were isolated from the rhizosphere soils of two seagrasses(Halophila ovalis(R.Br.) Hook and Halodule pinifolia(Miki) Hartog) in the Vellar estuary.Experimental studies ...Phosphate-solubilizing bacterial strains(6 Nos.) were isolated from the rhizosphere soils of two seagrasses(Halophila ovalis(R.Br.) Hook and Halodule pinifolia(Miki) Hartog) in the Vellar estuary.Experimental studies found that the strain PSSG6 was effective in phosphate solubilization with Phosphate Solubilization efficiency index E = 375 ± 8.54,followed by the strain PSSG5 with Phosphate Solubilization efficiency index E = 275 ± 27.3.Of the 6 strains isolated,the strains PSSG4 and PSSG5 be-longed to the genus Bacillus,and PSSG1,PSSG2 and PSSG3 were identified as Citrobacter sp.,Shigella sp.,and Klebsiella sp.,respectively,by conventional method,and PSSG6 was identified as Bacillus circulans using conventional and molecular methods.展开更多
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
The barometric process separation(BaPS)technique is a well-established incubation method to simultaneously measure gross nitrification and respiration rates in soil.Its application,however,is still critical in soils w...The barometric process separation(BaPS)technique is a well-established incubation method to simultaneously measure gross nitrification and respiration rates in soil.Its application,however,is still critical in soils with pH above 6.5.Here,a substantial part of microbial CO_2 production is retained in soil solution(CO_2,aq)due to shifts in the carbonate equilibrium.This may lead to substantial errors in gas balance calculation.Yet,utilization of the BaPS technique is only reliable if the critical term is adequately quantified.We present an easy,inexpensive,and direct method,the sterilization-CO_2-injection(SCI)method,to measure CO_2 retention during soil incubation.Sterilized soil was incubated in the BaPS system,and defined volumes of CO_2 were injected to stepwise increase CO_2partial pressure(p CO_2)inside the chamber and to analyse the physicochemical equilibration process.Five exemplary agricultural soils from Northeast China and Southwest Germany were used for method establishment,presenting pH values between 4.4 and 7.6 and carbonate contents between 0% and 3.9%.We observed that in soils with pH>6.5,70%–90% of the injected CO_2 was taken up by the soil until the equilibrium inside the chamber was re-established.As expected,in soils with low pH(<6.5),measured CO_2 retention was low.CO_2 retention patterns were sensitive to incubation temperature with tri-fold dissolution capacity at 5~?C compared to 25?C,but insensitive to variations in soil water content.The resulting soil-specific relationship between p CO_2 and CO_2,aq concentration allowed the quantification of CO_2,aq concentration as a function of headspace p CO_2.展开更多
基金Project supported by the President Foundation of the Chinese Academy of Sciences the Laboratory of Material Cycling in Pedosphere, the Chinese Academy of Sciences.
文摘Two series of soil subsamples, by spiking copper (Cu), lead (Pb), zinc (Zn) and cadmium (Cd) in an orthogonal design, were prepared using red soil and brown soil, respectively. The results indicated that heavy metal fractions in these soil subsamples depended not only on soil types, but also on metal loading quantity as well as on interactions among metals in soil. Lead and Cu in red soil appeared mostly in weakly specifically adsorbed (WSA), Fe and Mn oxides bound (OX), and residual (RES) fractions. Zinc existed in all fractions except organic bound one, and Cd was major in water soluble plus exchangeable (SE) one. Different from the results of red soil, Pb and Cu was present in brown soil in all fractions except organic one, but over 75% of Zn and 90% of Cd existed only in SE fraction. Meanwhile, SE fraction for any metal in red soil was lower than that in brown soil and WSA and OX fractions were higher. It is in agreement with low cation exchange capacity and large amounts of metal oxides included in red soil. Metal fractions in soil, especially for water soluble plus exchangeable one, were obviously influenced by other coexisting metals. The SE fraction of heavy metals increased with increasing loading amounts of metals in red soil but not obviously in brown soil, which suggest that metal availability be easily affected by their total amounts spiked in red soil. In addition, more metals in red soil were extracted with 0.20 mol L-1 NH4Cl (pH 5.40) than that with 1.0 mol L-1 Mg(NO3)2 (pH 7.0), but the reverse happened in brown soil, implicating significantly different mechanisms of metal desorption from red soil and brown soil.
文摘Phosphate-solubilizing bacterial strains(6 Nos.) were isolated from the rhizosphere soils of two seagrasses(Halophila ovalis(R.Br.) Hook and Halodule pinifolia(Miki) Hartog) in the Vellar estuary.Experimental studies found that the strain PSSG6 was effective in phosphate solubilization with Phosphate Solubilization efficiency index E = 375 ± 8.54,followed by the strain PSSG5 with Phosphate Solubilization efficiency index E = 275 ± 27.3.Of the 6 strains isolated,the strains PSSG4 and PSSG5 be-longed to the genus Bacillus,and PSSG1,PSSG2 and PSSG3 were identified as Citrobacter sp.,Shigella sp.,and Klebsiella sp.,respectively,by conventional method,and PSSG6 was identified as Bacillus circulans using conventional and molecular methods.
基金National Science Foundation of China(No.30370256&30670313)Chinese National Public-Benefit Program(No.200804006/rhh and 200704005/wb02)to Nanjing Forestry University
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funded by the German Research Foundation (DFG) in the framework of the SinoGerman Research Training Group "Sustainable Resource Use in North China"
文摘The barometric process separation(BaPS)technique is a well-established incubation method to simultaneously measure gross nitrification and respiration rates in soil.Its application,however,is still critical in soils with pH above 6.5.Here,a substantial part of microbial CO_2 production is retained in soil solution(CO_2,aq)due to shifts in the carbonate equilibrium.This may lead to substantial errors in gas balance calculation.Yet,utilization of the BaPS technique is only reliable if the critical term is adequately quantified.We present an easy,inexpensive,and direct method,the sterilization-CO_2-injection(SCI)method,to measure CO_2 retention during soil incubation.Sterilized soil was incubated in the BaPS system,and defined volumes of CO_2 were injected to stepwise increase CO_2partial pressure(p CO_2)inside the chamber and to analyse the physicochemical equilibration process.Five exemplary agricultural soils from Northeast China and Southwest Germany were used for method establishment,presenting pH values between 4.4 and 7.6 and carbonate contents between 0% and 3.9%.We observed that in soils with pH>6.5,70%–90% of the injected CO_2 was taken up by the soil until the equilibrium inside the chamber was re-established.As expected,in soils with low pH(<6.5),measured CO_2 retention was low.CO_2 retention patterns were sensitive to incubation temperature with tri-fold dissolution capacity at 5~?C compared to 25?C,but insensitive to variations in soil water content.The resulting soil-specific relationship between p CO_2 and CO_2,aq concentration allowed the quantification of CO_2,aq concentration as a function of headspace p CO_2.
