The Paleocene coals of the Salt Range in the Punjab Province of Pakistan have great economic potential;however,their trace element and stable isotopic characteristics have not been studied in detail except for a few s...The Paleocene coals of the Salt Range in the Punjab Province of Pakistan have great economic potential;however,their trace element and stable isotopic characteristics have not been studied in detail except for a few sporadic samples.In this study,a total of 59 coal samples of which 14 are obtained from open cast mines have been investigated for elemental composition andδ^(13)C-δ^(15)N isotopic signatures.Average contents of trace elements such as Co,Cr,Cu,Pb,Sr,Th,U,V,and Zn are 7.4,41.7,11.2,12.5,90.2,4.0,1.9,128,and 31.1 mg/kg,respectively.These values,when compared with the World Coal Clarke values,were relatively higher in low-rank coals in comparison with Clarke values for brown coals.Likewise,As(20.4 mg/kg),Co(6.6 mg/kg),Cr(22.4 mg/kg),Cu(^(13).3 mg/kg),Pb(19.2 mg/kg),Sr(^(15)4.7 mg/kg),Th(2.5 mg/kg),V(47.8 mg/kg),and Zn(75.1 mg/kg)were significantly higher in the sub-bituminous to bituminous coals of the Salt Range.Mineralogical analysis,based on X-ray diffraction and energy dispersive X-ray spectroscopy,revealed that the studied samples contain illite,kaolinite calcite,gypsum,pyrite,and quartz.Elemental affinity with organic and inorganic phases of coals calculated by an indirect statistical approach indicated a positive association of ash content with Ag,Al,Co,Cr,Cs,Cu,Mn,P,Rb,Pb,Th,U,and V,suggesting the presence of inorganic components in studied coals.However,As,Fe,Sr,and Zn exhibit negative correlations that imply their association with the organic fraction.Theδ^(13)C andδ^(15)N isotopic range and average−24.94‰to−25.86‰(−25.41‰)and−2.77‰to 3.22‰(0.96‰),respectively,reflecting 3C type modern terrestrial vegetation were common in the palaeomires of studied coal seams.In addition,the trivial variations of 0.92‰and 0.45‰among^(13)C and^(15)N values can be attributed to water level fluctuations and plant assemblies.展开更多
A variable-charge （VC） and a permanent-charge paddy soil （PC） were selected to study nitrate-N （NO3^--N） and ammonium-N （NH4^＋-N） leaching with N isotopes for one consecutive year. An irrigation and intermitt...A variable-charge （VC） and a permanent-charge paddy soil （PC） were selected to study nitrate-N （NO3^--N） and ammonium-N （NH4^＋-N） leaching with N isotopes for one consecutive year. An irrigation and intermittent drainage pattern was adopted to mimic natural occurrence of rainfall during the upland crop season and drainage management during the flooded rice season. Treatments to each soil type were no-N controls （CK）, ^15N-labeled （NH4）2SO4 （NS）, and milk vetch （NV） applied at a rate equivalent to 238 kg N ha^-1 to unplanted lysimeters, totaling six treatments in triplicates. Results indicated that the soil type dominated N leaching characteristics. In the case of PC, NO3^--N accounted for 78% of the total leached inorganic N; NS was prone to leach three times more than the NV, being 8.2% and 2.4% of added ^15N respectively; and 〉 85% of leached NO3-N came from of the total inorganic N in leachate. Moreover, NH4^＋-N native N in the soil. In the case of VC, NH4^＋-N made up to 92% leaching was detected throughout the whole incubation, and was particularly high during the flooded season. NO3^--N leaching in VC occurred later at a lower rate compared to that in PC. The findings of this study indicate that NO3^--N leaching during the drained season in permanent-charge paddy soils and NH4^＋-N leaching in variable-charge soils deserve more attention for regional environmental control.展开更多
Elevated atmospheric nitrogen(N) deposition has been detected in many regions of China, but its effects on soil N transformation in temperate forest ecosystems are not well known. We therefore simulated N deposition w...Elevated atmospheric nitrogen(N) deposition has been detected in many regions of China, but its effects on soil N transformation in temperate forest ecosystems are not well known. We therefore simulated N deposition with four levels of N addition rate(N0, N30, N60, and N120) for6 years in an old-growth temperate forest in Xiaoxing’an Mountains in Northeastern China. We measured gross N transformation rates in the laboratory usingN tracing technology to explore the effects of N deposition on soil gross N transformations taking advantage of N deposition soils. No significant differences in gross soil N transformation rates were observed after 6 years of N deposition with various levels of N addition rate. For all N deposition soils, the gross NH~+ immobilization rates were consistently lower than the gross N mineralization rates,leading to net N mineralization. Nitrate(NO~-) was primarily produced via oxidation of NH~+(i.e., autotrophic nitrification), whereas oxidation of organic N(i.e., heterotrophic nitrification) was negligible. Differences between the quantity of ammonia-oxidizing bacteria and ammonia-oxidizing archaea were not significant for any treatment, which likely explains the lack of a significant effect on gross nitrification rates. Gross nitrification rates were much higher than the total NO~- consumption rates,resulting in a build-up of NO~-, which highlights the high risk of N losses via NO~- leaching or gaseous N emissions from soils. This response is opposite that of typical N-limited temperate forests suffering from N deposition,suggesting that the investigated old-growth temperate forest ecosystem is likely to approach N saturation.展开更多
We conducted a greenhouse experiment to investigate the role of seed source in growth and symbiotic nitrogen fixation of black locust （Robinia pseudoacacia L）. Seeds from different sources were planted in the same e...We conducted a greenhouse experiment to investigate the role of seed source in growth and symbiotic nitrogen fixation of black locust （Robinia pseudoacacia L）. Seeds from different sources were planted in the same environmental conditions and inoculated with a suspension of mixed Rhizobium. We used the modified ^15N isotope dilution method to estimate biological nitrogen fixation of Robinia trees. Different Robinia seed sources differed significantly in terms of tissue dry weight （50.6-80.1 g）, total N （1.31-2.16 g） and proportion of nitrogen derived from the atmosphere （ 0-51%）. A higher nitrogen fixation rate of Robinia trees was associated with higher dry weight. Moreover, the leaves of Robinia proved to adequately represent the nitrogen fixation capacity of entire plants. Our results confirmed that assessment of seed sources is a useful way to improve the nitrogen fixation capacity and therefore the growth rate of Robinia.展开更多
The denitrifier method is widely used as a novel pretreatment method for the determination of nitrogen and oxygen isotope ratios as it can provide quantitative and high-sensitivity measurements. Nevertheless, the meth...The denitrifier method is widely used as a novel pretreatment method for the determination of nitrogen and oxygen isotope ratios as it can provide quantitative and high-sensitivity measurements. Nevertheless, the method is limited by relatively low measurement accuracy for δ18 O. In this study, we analyzed the factors influencing the accuracy of δ18 O determination, and then systematically investigated the effects of dissolved oxygen concentrations and nitrate sample sizes on estimates of the δ15 N and δ18 O of nitrate reference materials. The δ18 O contraction ratio was used to represent the relationship between the measured difference and true difference between two reference materials. We obtained the following main results:(1) a gas-liquid ratio of 3:10(v/v) in ordinary triangular flasks and a shaking speed of 120 r/min produced an optimal range(1.9 to 2.6 mg/L) in the concentration of dissolved oxygen for accurately determining δ18 O, and(2) the δ18 O contraction ratio decreased as nitrate sample size decreased within a certain range(1.0 to 0.1 μmol). Our results suggested that δ18 O contraction is influenced mainly by dissolved oxygen concentrations in pure culture, and provided a model for improving the accuracy of oxygen isotope analysis.展开更多
The problem of nitrate accumulation in aerobic tank and total nitrogen excessive discharge in effluent was very common in traditional livestock and poultry farming wastewater treatment systems owing to the lengthy pro...The problem of nitrate accumulation in aerobic tank and total nitrogen excessive discharge in effluent was very common in traditional livestock and poultry farming wastewater treatment systems owing to the lengthy process flow and low process control level.A strain LYX of aerobic bacterium was isolated from the activated sludge of a wastewater treatment system in a pig farm,which could remove nitrate effectively in aerobic tank and was identified Pseudomonas mendocina by 16S rRNA sequencing.Under the condition of nitrate as the sole nitrogen source,this strain removed over 90%of NO_(3)^(−)-N with an initial concentration of 110 mg/L under aerobic conditions within 48 hours.Among them,37.9%of NO_(3)^(−)-N was assimilated into Bio-N,about 51.9%was reduced to gaseous nitrogen and less than 0.5%of nitrogen was replaced by NO_(3)^(−)-N and NH_(4)^(+)-N,9.7%NO_(3)^(−)-N remained in the effluent at the end.At the same time,four key genes(napA,nirK,norB and nosZ)related to nitrate nitrogen removal were expressed during the denitrification process of P.mendocina LYX,in which the transcription level of the indicator genes of this aerobic denitrifying bacterium(napA)was the highest.In addition,it was found with the 15N tracer technique that inoculation of this strain on sludge increased the amount of nitrogen loss from 9.26 nmol N/(g·h)to 23.835 nmol N/(g·h).Therefore,P.medocina LYX is a potential bioagent for advanced nitrogen removal by assimilating and reducing nitrate simultaneously in aerobic tanks.展开更多
Rice-paddies are regarded as one of the main agricultural sources of N 2O and NO emissions. To date, however, specific N2O and NO production pathways are poorly understood in paddy soils. ^15N-tracing experiments were...Rice-paddies are regarded as one of the main agricultural sources of N 2O and NO emissions. To date, however, specific N2O and NO production pathways are poorly understood in paddy soils. ^15N-tracing experiments were carded out to investigate the processes responsible for N2O and NO production in two paddy soils with substantially different soil properties. Laboratory incubation experiments were carried out under aerobic conditions at moisture contents corresponding to 60% of water holding capacity. The relative importance of nitrification and denitrification to the flux of NaO was quantified by periodically measuring and comparing the enrichments of the N2O, NH^-N and NO3-N pools. The results showed that both N2O and NO emission rates in an alkaline paddy soil with clayey texture were substantially higher than those in a neutral paddy soil with silty loamy texture. In accordance with most published results, the ammonium N pool was the main source of N2O emission across the soil profiles of the two paddy soils, being responsible for 59.7% to 97.7% of total N2O emissions. The NO3-N pool of N2O emission was relatively less important under the given aerobic conditions. The rates of N2O emission from nitrification （N2On） among different soil layers were significantly different, which could be attributed to both the differences in gross N nitrification rates and to the ratios of nitrified N emitted as NzO among soil layers. Furthermore, NO fluxes were positively correlated with the changes in gross nitrification rates and the ratios of NO/N2O in the two paddy soils were always greater than one （from 1.26 to 6.47）. We therefore deduce that, similar to N2O, nitrification was also the dominant source of NO in the tested paddy soils at water contents below 60% water holding capacity.展开更多
基金the Higher Education Commission Pakistan for funding the lab research under its International Research Support Initiative Program (IRSIP) programthe Department of Environmental Science, Quaid-i-Azam University, Islamabad (especially Environmental Hydro geochemistry Lab)the Environment & Sustainability Institute and Camborne School of Mines, University of Exeter, for technical support in conducting lab analysis
文摘The Paleocene coals of the Salt Range in the Punjab Province of Pakistan have great economic potential;however,their trace element and stable isotopic characteristics have not been studied in detail except for a few sporadic samples.In this study,a total of 59 coal samples of which 14 are obtained from open cast mines have been investigated for elemental composition andδ^(13)C-δ^(15)N isotopic signatures.Average contents of trace elements such as Co,Cr,Cu,Pb,Sr,Th,U,V,and Zn are 7.4,41.7,11.2,12.5,90.2,4.0,1.9,128,and 31.1 mg/kg,respectively.These values,when compared with the World Coal Clarke values,were relatively higher in low-rank coals in comparison with Clarke values for brown coals.Likewise,As(20.4 mg/kg),Co(6.6 mg/kg),Cr(22.4 mg/kg),Cu(^(13).3 mg/kg),Pb(19.2 mg/kg),Sr(^(15)4.7 mg/kg),Th(2.5 mg/kg),V(47.8 mg/kg),and Zn(75.1 mg/kg)were significantly higher in the sub-bituminous to bituminous coals of the Salt Range.Mineralogical analysis,based on X-ray diffraction and energy dispersive X-ray spectroscopy,revealed that the studied samples contain illite,kaolinite calcite,gypsum,pyrite,and quartz.Elemental affinity with organic and inorganic phases of coals calculated by an indirect statistical approach indicated a positive association of ash content with Ag,Al,Co,Cr,Cs,Cu,Mn,P,Rb,Pb,Th,U,and V,suggesting the presence of inorganic components in studied coals.However,As,Fe,Sr,and Zn exhibit negative correlations that imply their association with the organic fraction.Theδ^(13)C andδ^(15)N isotopic range and average−24.94‰to−25.86‰(−25.41‰)and−2.77‰to 3.22‰(0.96‰),respectively,reflecting 3C type modern terrestrial vegetation were common in the palaeomires of studied coal seams.In addition,the trivial variations of 0.92‰and 0.45‰among^(13)C and^(15)N values can be attributed to water level fluctuations and plant assemblies.
基金Project supported by the National Natural Science Foundation of China (No. 30390080)the Nanjing Science and Technology Bureau,China (No. 200901063)
文摘A variable-charge （VC） and a permanent-charge paddy soil （PC） were selected to study nitrate-N （NO3^--N） and ammonium-N （NH4^＋-N） leaching with N isotopes for one consecutive year. An irrigation and intermittent drainage pattern was adopted to mimic natural occurrence of rainfall during the upland crop season and drainage management during the flooded rice season. Treatments to each soil type were no-N controls （CK）, ^15N-labeled （NH4）2SO4 （NS）, and milk vetch （NV） applied at a rate equivalent to 238 kg N ha^-1 to unplanted lysimeters, totaling six treatments in triplicates. Results indicated that the soil type dominated N leaching characteristics. In the case of PC, NO3^--N accounted for 78% of the total leached inorganic N; NS was prone to leach three times more than the NV, being 8.2% and 2.4% of added ^15N respectively; and 〉 85% of leached NO3-N came from of the total inorganic N in leachate. Moreover, NH4^＋-N native N in the soil. In the case of VC, NH4^＋-N made up to 92% leaching was detected throughout the whole incubation, and was particularly high during the flooded season. NO3^--N leaching in VC occurred later at a lower rate compared to that in PC. The findings of this study indicate that NO3^--N leaching during the drained season in permanent-charge paddy soils and NH4^＋-N leaching in variable-charge soils deserve more attention for regional environmental control.
基金supported by Grants from the ‘‘973’’ Project(2014CB953803)the Fundamental Research Funds for the Central Universities(2572017EA02)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD,164320H116)
文摘Elevated atmospheric nitrogen(N) deposition has been detected in many regions of China, but its effects on soil N transformation in temperate forest ecosystems are not well known. We therefore simulated N deposition with four levels of N addition rate(N0, N30, N60, and N120) for6 years in an old-growth temperate forest in Xiaoxing’an Mountains in Northeastern China. We measured gross N transformation rates in the laboratory usingN tracing technology to explore the effects of N deposition on soil gross N transformations taking advantage of N deposition soils. No significant differences in gross soil N transformation rates were observed after 6 years of N deposition with various levels of N addition rate. For all N deposition soils, the gross NH~+ immobilization rates were consistently lower than the gross N mineralization rates,leading to net N mineralization. Nitrate(NO~-) was primarily produced via oxidation of NH~+(i.e., autotrophic nitrification), whereas oxidation of organic N(i.e., heterotrophic nitrification) was negligible. Differences between the quantity of ammonia-oxidizing bacteria and ammonia-oxidizing archaea were not significant for any treatment, which likely explains the lack of a significant effect on gross nitrification rates. Gross nitrification rates were much higher than the total NO~- consumption rates,resulting in a build-up of NO~-, which highlights the high risk of N losses via NO~- leaching or gaseous N emissions from soils. This response is opposite that of typical N-limited temperate forests suffering from N deposition,suggesting that the investigated old-growth temperate forest ecosystem is likely to approach N saturation.
文摘We conducted a greenhouse experiment to investigate the role of seed source in growth and symbiotic nitrogen fixation of black locust （Robinia pseudoacacia L）. Seeds from different sources were planted in the same environmental conditions and inoculated with a suspension of mixed Rhizobium. We used the modified ^15N isotope dilution method to estimate biological nitrogen fixation of Robinia trees. Different Robinia seed sources differed significantly in terms of tissue dry weight （50.6-80.1 g）, total N （1.31-2.16 g） and proportion of nitrogen derived from the atmosphere （ 0-51%）. A higher nitrogen fixation rate of Robinia trees was associated with higher dry weight. Moreover, the leaves of Robinia proved to adequately represent the nitrogen fixation capacity of entire plants. Our results confirmed that assessment of seed sources is a useful way to improve the nitrogen fixation capacity and therefore the growth rate of Robinia.
基金Project supported by the National Key R&D Program of China(No.2016YFD0200106)the National Natural Science Foundation of China(No.41571450)
文摘The denitrifier method is widely used as a novel pretreatment method for the determination of nitrogen and oxygen isotope ratios as it can provide quantitative and high-sensitivity measurements. Nevertheless, the method is limited by relatively low measurement accuracy for δ18 O. In this study, we analyzed the factors influencing the accuracy of δ18 O determination, and then systematically investigated the effects of dissolved oxygen concentrations and nitrate sample sizes on estimates of the δ15 N and δ18 O of nitrate reference materials. The δ18 O contraction ratio was used to represent the relationship between the measured difference and true difference between two reference materials. We obtained the following main results:(1) a gas-liquid ratio of 3:10(v/v) in ordinary triangular flasks and a shaking speed of 120 r/min produced an optimal range(1.9 to 2.6 mg/L) in the concentration of dissolved oxygen for accurately determining δ18 O, and(2) the δ18 O contraction ratio decreased as nitrate sample size decreased within a certain range(1.0 to 0.1 μmol). Our results suggested that δ18 O contraction is influenced mainly by dissolved oxygen concentrations in pure culture, and provided a model for improving the accuracy of oxygen isotope analysis.
基金This work was financially supported by the National Key R&D Program of China(Grant No.2016YFC0400706)the National Natural Science Foundation of China(Grant Nos.41671481 and 41977340)+1 种基金the Science&Technology Plan Project of Guangdong(No.2016B020240003)Key-Area Research and Development Program of Guangdong Province(No.2019B110205004).We would like to thank Professor Hong YG and Dr.Wu JP(Guangzhou University)for their warmful help on 15N labeling test and analysis.
文摘The problem of nitrate accumulation in aerobic tank and total nitrogen excessive discharge in effluent was very common in traditional livestock and poultry farming wastewater treatment systems owing to the lengthy process flow and low process control level.A strain LYX of aerobic bacterium was isolated from the activated sludge of a wastewater treatment system in a pig farm,which could remove nitrate effectively in aerobic tank and was identified Pseudomonas mendocina by 16S rRNA sequencing.Under the condition of nitrate as the sole nitrogen source,this strain removed over 90%of NO_(3)^(−)-N with an initial concentration of 110 mg/L under aerobic conditions within 48 hours.Among them,37.9%of NO_(3)^(−)-N was assimilated into Bio-N,about 51.9%was reduced to gaseous nitrogen and less than 0.5%of nitrogen was replaced by NO_(3)^(−)-N and NH_(4)^(+)-N,9.7%NO_(3)^(−)-N remained in the effluent at the end.At the same time,four key genes(napA,nirK,norB and nosZ)related to nitrate nitrogen removal were expressed during the denitrification process of P.mendocina LYX,in which the transcription level of the indicator genes of this aerobic denitrifying bacterium(napA)was the highest.In addition,it was found with the 15N tracer technique that inoculation of this strain on sludge increased the amount of nitrogen loss from 9.26 nmol N/(g·h)to 23.835 nmol N/(g·h).Therefore,P.medocina LYX is a potential bioagent for advanced nitrogen removal by assimilating and reducing nitrate simultaneously in aerobic tanks.
基金supported by the Sino-German collaborative project:"Innovative nitrogen management technologies to improve agricultural production and environmental protection in intensive Chinese agriculture"co-funded by the Chinese Ministry of Science and Technology(MOST grant no.2007DFA30850)the German Ministry of Education and Research(BMBF FKZ:0330800C)
文摘Rice-paddies are regarded as one of the main agricultural sources of N 2O and NO emissions. To date, however, specific N2O and NO production pathways are poorly understood in paddy soils. ^15N-tracing experiments were carded out to investigate the processes responsible for N2O and NO production in two paddy soils with substantially different soil properties. Laboratory incubation experiments were carried out under aerobic conditions at moisture contents corresponding to 60% of water holding capacity. The relative importance of nitrification and denitrification to the flux of NaO was quantified by periodically measuring and comparing the enrichments of the N2O, NH^-N and NO3-N pools. The results showed that both N2O and NO emission rates in an alkaline paddy soil with clayey texture were substantially higher than those in a neutral paddy soil with silty loamy texture. In accordance with most published results, the ammonium N pool was the main source of N2O emission across the soil profiles of the two paddy soils, being responsible for 59.7% to 97.7% of total N2O emissions. The NO3-N pool of N2O emission was relatively less important under the given aerobic conditions. The rates of N2O emission from nitrification （N2On） among different soil layers were significantly different, which could be attributed to both the differences in gross N nitrification rates and to the ratios of nitrified N emitted as NzO among soil layers. Furthermore, NO fluxes were positively correlated with the changes in gross nitrification rates and the ratios of NO/N2O in the two paddy soils were always greater than one （from 1.26 to 6.47）. We therefore deduce that, similar to N2O, nitrification was also the dominant source of NO in the tested paddy soils at water contents below 60% water holding capacity.
