The formation of manganese oxides in nature is commonly mediated by microorganisms. In this study, the mineralization of biogenic manganese oxidation mediated by Pseudomanas putida has been experimentally investigated...The formation of manganese oxides in nature is commonly mediated by microorganisms. In this study, the mineralization of biogenic manganese oxidation mediated by Pseudomanas putida has been experimentally investigated by employing various characterization techniques, including SEM, FESEM, TEM, XRD, and STXM-NEXAFS. The results indicate that Mn^2＋ ions can be oxidized into Mn （IV） minerals （birnessite and pyrolusite） and Mn（III） minerals （hausmannite and feitknechtite）, successively. The primary products （birnessite and pyrolusite） further transformed into hausmannite and feitknechtite under Mn^2＋ ion-enriched conditions. However, birnessite and pyrolusite are the end- products of the continuous microbial oxidation processes. These biogenic Mn oxides are poorly crystallized, which provides them with a high potential for usage in environmental restoration of contaminated soils and waters contaminated with heavy metals. The approaches employed in this study will also enrich genesis research of biological oxidation of Mn（II） species in nature.展开更多
Nitrate(NO3^(-))is known to be actively involved in the processes of mineralization and heavy metal transformation;however,it is unclear whether and how it affects the bioavailability of antimony(Sb)in paddy soils and...Nitrate(NO3^(-))is known to be actively involved in the processes of mineralization and heavy metal transformation;however,it is unclear whether and how it affects the bioavailability of antimony(Sb)in paddy soils and subsequent Sb accumulation in rice.Here,the effects of NO3^(-)on Sb transformation in soil-rice system were investigated with pot experiments over the entire growth period.Results demonstrated that NO3^(-)reduced Sb accumulation in brown rice by 15.6%compared to that in the control.After amendment with NO3^(-),the Sb content in rice plants increased initially and then gradually decreased(in roots by 46.1%).During the first 15 days,the soil p H increased,the oxidation of Sb(Ⅲ)and sulfides was promoted,but the reduction of iron oxide minerals was inhibited,resulting in the release of adsorbed and organic-bound Sb from soil.The microbial arsenite-oxidizing marker gene aox B played an important role in Sb(Ⅲ)oxidation.From days 15 to 45,after NO3^(-)was partially consumed,the soil p H decreased,and the reductive dissolution of Fe(Ⅲ)-bearing minerals was enhanced;consequently,iron oxide-bound Sb was transformed into adsorbed and dissolved Sb species.After day 45,NO3^(-)was completely reduced,Sb(V)was evidently reduced to Sb(Ⅲ),and green rust was generated gradually.Thus,the available Sb decreased due to its enhanced affinity for iron oxides.Moreover,NO3^(-)inhibited the reductive dissolution of iron minerals,which ultimately caused low Sb availability.Therefore,NO3^(-)can chemically and biologically reduce the Sb availability in paddy soils and alleviate Sb accumulation inrice.This study provides a potential strategy for decreasing Sb accumulation in rice in the Sb-contaminated sites.展开更多
Land-use and soil management affects soil organic carbon （SOC） pools, nitrogen, salinity and the depth distribution. The objective of this study was to estimate land-use effects on the distribution of SOC, labile fr...Land-use and soil management affects soil organic carbon （SOC） pools, nitrogen, salinity and the depth distribution. The objective of this study was to estimate land-use effects on the distribution of SOC, labile fractions C, nitrogen （N） and salinity in saline-alkaline wetlands in the middle reaches of the Heihe River Basin. Three land-use types were selected： intact saline-alkaline meadow wetland, artificial shrubbery （planting Tamarix） and farmland （cultivated for 18 years） of soils previously under meadow wetland. SOC, easily oxidized carbon, microbial biomass carbon, total N, NO3--N and salinity concentrations were measured. The results show that SOC and labile fraction carbon contents decreased significantly with increasing soil depth in the three land-use wetlands. The labile fraction carbon contents in the topsoil （0-20cm） in cultivated soils were significantly higher than that in intact meadow wetland and artificial shrubbery soil. The aboveground biomass and soil permeability were the primary influencing factors on the contents of SOC and the labile carbon in the intact meadow wetland and artificial shrubbery soil, however, the farming practice was a factor in cultivated soil. Agricultural measures can effectively reduce the salinity contents; however, it caused a significant increase of NO 3--N concentrations which posed a threat to groundwater quality in the study area.展开更多
As a case study, refined iron（Fe） speciation and quantitative characterization of the reductive reactivity of Fe（Ⅲ）oxides are combined to investigate Fe diagenetic processes in a core sediment from the eutrophic ...As a case study, refined iron（Fe） speciation and quantitative characterization of the reductive reactivity of Fe（Ⅲ）oxides are combined to investigate Fe diagenetic processes in a core sediment from the eutrophic Jiaozhou Bay.The results show that a combination of the two methods can trace Fe transformation in more detail and offer nuanced information on Fe diagenesis from multiple perspectives. This methodology may be used to enhance our understanding of the complex biogeochemical cycling of Fe and sulfur in other studies. Microbial iron reduction（MIR） plays an important role in Fe（Ⅲ） reduction over the upper sediments, while a chemical reduction by reaction with dissolved sulfide is the main process at a deeper（〉 12 cm） layer. The most bioavailable amorphous Fe（Ⅲ） oxides [Fe（Ⅲ）am] are the main source of the MIR, followed by poorly crystalline Fe（Ⅲ） oxides [Fe（Ⅲ）pc）]and magnetite. Well crystalline Fe（Ⅲ） oxides [Fe（Ⅲ）wc] have barely participated in Fe diagenesis. The importance of the MIR over the upper layer may be a combined result of the high availability of highly reactive Fe oxides and low availability of labile organic matter, and the latter is also the ultimate factor limiting sulfate reduction and sulfide accumulation in the sediments. Microbially reducible Fe（Ⅲ） [MR-Fe（Ⅲ）], which is quantified by kinetics of Fe（II）-oxide reduction, mainly consists of the most reactive Fe（Ⅲ）am and less reactive Fe（Ⅲ）pc. The bulk reactivity of the MR-Fe（Ⅲ） pool is equivalent to aged ferrihydrite, and shows down-core decrease due to preferential reduction of highly reactive phases of Fe oxides.展开更多
An intramolecular isotopic study was conducted on natural gases collected from coal-derived gas reser-voirs in sedimentary basins of China to determine their position-specific isotope distributions.The propane from th...An intramolecular isotopic study was conducted on natural gases collected from coal-derived gas reser-voirs in sedimentary basins of China to determine their position-specific isotope distributions.The propane from the Turpan-Hami Basin exhibited negativeΔc-T(δ13Ccentral-δ13Cterminal)values ranging from-3.9‰to-0.3‰,with an average of-2.1‰.Propane from the Ordos Basin,Sichuan Basin,and Tarim Basin showed positiveΔC-T values,with averages of 1.3‰,5.4‰and 7.6‰,respectively.Positionspecific carbon isotope compositions reveal the precursors and the propane generation pathways in the petroliferous basins.Propane formed from the thermal cracking of TypeⅢkerogen has largerδ13Ccentral andδ13Cterminal values than propane from TypeⅠ/Ⅱkerogen.The precursor for natural gases collected in this study is identified to be TypeⅢkerogen.Comparing our data to calculated results for thermal cracking of TypeⅢkerogen,we found that propane from the low-maturity gas reservoir in the Turpan Basin was generated via the i-propyl radical pathway,whereas propane from the Sulige tight gas reservoir in the Ordos Basin was formed via the n-propyl radical pathway.δ13Cterminal values covered a narrow range across basins,in contrast toδ13Ccentral.The terminal carbon position in propane is less impacted by microbial oxidation and more relevant to maturity levels and precursors.Thus,δ13Cterminal has a good potential to infer the origin and maturity level of natural gas.In examining post-generation processes,we proposed an improved identification strategy for microbial oxidation of natural gases,based on the position-specific carbon isotope distributions of propane.Samples from the Liaohe Depression of the Bohai Bay Basin and the Sichuan Basin were detected of post-generation microbial oxidation.Overall,position-specific carbon isotope composition of propane provides new insights into the generation mechanism and post-generation processes of natural gas in the geological period at the atomic level.展开更多
基金financial supported by the National Basic Research Program of China(No.2014CB846004)National Natural Science Foundation of China(Grant Nos.41425009 and 41272056)
文摘The formation of manganese oxides in nature is commonly mediated by microorganisms. In this study, the mineralization of biogenic manganese oxidation mediated by Pseudomanas putida has been experimentally investigated by employing various characterization techniques, including SEM, FESEM, TEM, XRD, and STXM-NEXAFS. The results indicate that Mn^2＋ ions can be oxidized into Mn （IV） minerals （birnessite and pyrolusite） and Mn（III） minerals （hausmannite and feitknechtite）, successively. The primary products （birnessite and pyrolusite） further transformed into hausmannite and feitknechtite under Mn^2＋ ion-enriched conditions. However, birnessite and pyrolusite are the end- products of the continuous microbial oxidation processes. These biogenic Mn oxides are poorly crystallized, which provides them with a high potential for usage in environmental restoration of contaminated soils and waters contaminated with heavy metals. The approaches employed in this study will also enrich genesis research of biological oxidation of Mn（II） species in nature.
基金the National Key Research and Development Program of China(Nos.2017YFD0801002,2018YFF0213403)GDAS’Project of Science and Technology Development(No.2020GDASYL-20200103076)China Postdoctoral Science Foundation(No.2019M652834)。
文摘Nitrate(NO3^(-))is known to be actively involved in the processes of mineralization and heavy metal transformation;however,it is unclear whether and how it affects the bioavailability of antimony(Sb)in paddy soils and subsequent Sb accumulation in rice.Here,the effects of NO3^(-)on Sb transformation in soil-rice system were investigated with pot experiments over the entire growth period.Results demonstrated that NO3^(-)reduced Sb accumulation in brown rice by 15.6%compared to that in the control.After amendment with NO3^(-),the Sb content in rice plants increased initially and then gradually decreased(in roots by 46.1%).During the first 15 days,the soil p H increased,the oxidation of Sb(Ⅲ)and sulfides was promoted,but the reduction of iron oxide minerals was inhibited,resulting in the release of adsorbed and organic-bound Sb from soil.The microbial arsenite-oxidizing marker gene aox B played an important role in Sb(Ⅲ)oxidation.From days 15 to 45,after NO3^(-)was partially consumed,the soil p H decreased,and the reductive dissolution of Fe(Ⅲ)-bearing minerals was enhanced;consequently,iron oxide-bound Sb was transformed into adsorbed and dissolved Sb species.After day 45,NO3^(-)was completely reduced,Sb(V)was evidently reduced to Sb(Ⅲ),and green rust was generated gradually.Thus,the available Sb decreased due to its enhanced affinity for iron oxides.Moreover,NO3^(-)inhibited the reductive dissolution of iron minerals,which ultimately caused low Sb availability.Therefore,NO3^(-)can chemically and biologically reduce the Sb availability in paddy soils and alleviate Sb accumulation inrice.This study provides a potential strategy for decreasing Sb accumulation in rice in the Sb-contaminated sites.
基金supported by one of Major State Basic Research Development Program (2009CB421302)the Gansu Provincial Natural Science Foundation of China (2008GS01759)
文摘Land-use and soil management affects soil organic carbon （SOC） pools, nitrogen, salinity and the depth distribution. The objective of this study was to estimate land-use effects on the distribution of SOC, labile fractions C, nitrogen （N） and salinity in saline-alkaline wetlands in the middle reaches of the Heihe River Basin. Three land-use types were selected： intact saline-alkaline meadow wetland, artificial shrubbery （planting Tamarix） and farmland （cultivated for 18 years） of soils previously under meadow wetland. SOC, easily oxidized carbon, microbial biomass carbon, total N, NO3--N and salinity concentrations were measured. The results show that SOC and labile fraction carbon contents decreased significantly with increasing soil depth in the three land-use wetlands. The labile fraction carbon contents in the topsoil （0-20cm） in cultivated soils were significantly higher than that in intact meadow wetland and artificial shrubbery soil. The aboveground biomass and soil permeability were the primary influencing factors on the contents of SOC and the labile carbon in the intact meadow wetland and artificial shrubbery soil, however, the farming practice was a factor in cultivated soil. Agricultural measures can effectively reduce the salinity contents; however, it caused a significant increase of NO 3--N concentrations which posed a threat to groundwater quality in the study area.
基金The National Natural Science Foundation of China under contract Nos 41576078 and 41276069the Shandong Province Natural Science Foundation of China under contract No.ZR2015DM006the National Key Research and Development Program of China under contract No.2016YFA0601301
文摘As a case study, refined iron（Fe） speciation and quantitative characterization of the reductive reactivity of Fe（Ⅲ）oxides are combined to investigate Fe diagenetic processes in a core sediment from the eutrophic Jiaozhou Bay.The results show that a combination of the two methods can trace Fe transformation in more detail and offer nuanced information on Fe diagenesis from multiple perspectives. This methodology may be used to enhance our understanding of the complex biogeochemical cycling of Fe and sulfur in other studies. Microbial iron reduction（MIR） plays an important role in Fe（Ⅲ） reduction over the upper sediments, while a chemical reduction by reaction with dissolved sulfide is the main process at a deeper（〉 12 cm） layer. The most bioavailable amorphous Fe（Ⅲ） oxides [Fe（Ⅲ）am] are the main source of the MIR, followed by poorly crystalline Fe（Ⅲ） oxides [Fe（Ⅲ）pc）]and magnetite. Well crystalline Fe（Ⅲ） oxides [Fe（Ⅲ）wc] have barely participated in Fe diagenesis. The importance of the MIR over the upper layer may be a combined result of the high availability of highly reactive Fe oxides and low availability of labile organic matter, and the latter is also the ultimate factor limiting sulfate reduction and sulfide accumulation in the sediments. Microbially reducible Fe（Ⅲ） [MR-Fe（Ⅲ）], which is quantified by kinetics of Fe（II）-oxide reduction, mainly consists of the most reactive Fe（Ⅲ）am and less reactive Fe（Ⅲ）pc. The bulk reactivity of the MR-Fe（Ⅲ） pool is equivalent to aged ferrihydrite, and shows down-core decrease due to preferential reduction of highly reactive phases of Fe oxides.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.42102202 and 41930426).
文摘An intramolecular isotopic study was conducted on natural gases collected from coal-derived gas reser-voirs in sedimentary basins of China to determine their position-specific isotope distributions.The propane from the Turpan-Hami Basin exhibited negativeΔc-T(δ13Ccentral-δ13Cterminal)values ranging from-3.9‰to-0.3‰,with an average of-2.1‰.Propane from the Ordos Basin,Sichuan Basin,and Tarim Basin showed positiveΔC-T values,with averages of 1.3‰,5.4‰and 7.6‰,respectively.Positionspecific carbon isotope compositions reveal the precursors and the propane generation pathways in the petroliferous basins.Propane formed from the thermal cracking of TypeⅢkerogen has largerδ13Ccentral andδ13Cterminal values than propane from TypeⅠ/Ⅱkerogen.The precursor for natural gases collected in this study is identified to be TypeⅢkerogen.Comparing our data to calculated results for thermal cracking of TypeⅢkerogen,we found that propane from the low-maturity gas reservoir in the Turpan Basin was generated via the i-propyl radical pathway,whereas propane from the Sulige tight gas reservoir in the Ordos Basin was formed via the n-propyl radical pathway.δ13Cterminal values covered a narrow range across basins,in contrast toδ13Ccentral.The terminal carbon position in propane is less impacted by microbial oxidation and more relevant to maturity levels and precursors.Thus,δ13Cterminal has a good potential to infer the origin and maturity level of natural gas.In examining post-generation processes,we proposed an improved identification strategy for microbial oxidation of natural gases,based on the position-specific carbon isotope distributions of propane.Samples from the Liaohe Depression of the Bohai Bay Basin and the Sichuan Basin were detected of post-generation microbial oxidation.Overall,position-specific carbon isotope composition of propane provides new insights into the generation mechanism and post-generation processes of natural gas in the geological period at the atomic level.
