Direct nitrous oxide(N2O) emissions(DNEs) from croplands are required in national inventories of greenhouse gases. The Intergovernmental Panel on Climate Change(IPCC) guidelines provide an approach using direct emissi...Direct nitrous oxide(N2O) emissions(DNEs) from croplands are required in national inventories of greenhouse gases. The Intergovernmental Panel on Climate Change(IPCC) guidelines provide an approach using direct emission factors(EFds) to estimate DNEs, which are constants for large regions. The goal of this paper is to establish empirical models to account for the temporal and spatial variations of EFds, which, apart from the nitrogen addition rate, also vary with a range of environmental factors, so as to enhance the accuracy of regional/national DNE estimates. Therefore, the seasonal/annual DNEs(n = 71) from upland croplands, which are the differences in N2 O emissions between fields with and without fertilizer-nitrogen addition, were used to statistically relate DNEs to regulating factors including the fertilizer-nitrogen addition rate(FN), and environmental(climate and soil) factors. The multivariate stepwise linear regression results showed positive combined effects of FN and clay fraction on DNEs(R2 = 0.61, p < 0.001). Furthermore, the nonlinear regression of FN, precipitation, and clay fraction was also adopted for prediction(R2 = 0.50, p < 0.001). Validation with an independent dataset(n = 31) suggested that both models were better predictors of DNEs than the IPCC model, which only depends on FN. These empirical models may provide simple but reliable approaches for compiling regional/national, and even global inventories of DNEs from croplands. However, both models were restricted to a limited sample size. Understandably, more field observations are still required to further validate the global applicability of these simple approaches.展开更多
Denitrification-induced nitrogen(N) losses from croplands may be greatly increased by intensive fertilization.However,the accurate quantification of these losses is still challenging due to insufficient available in s...Denitrification-induced nitrogen(N) losses from croplands may be greatly increased by intensive fertilization.However,the accurate quantification of these losses is still challenging due to insufficient available in situ measurements of soil dinitrogen(N) emissions.We carried out two one-week experiments in a maize-wheat cropping system with calcareous soil using theN gas-flux(NGF) method to measure in situ Nfluxes following urea application.Applications ofN-labeled urea(99 atom%,130-150 kg N ha) were followed by irrigation on the 1 st,3 rd,and 5 th days after fertilization(DAF 1,3,and 5,respectively).The detection limits of the soil Nfluxes were 163-1 565,81-485,and 54-281 μg N mhfor the two-,four-,and six-hour static chamber enclosures,respectively.The Nfluxes measured in 120 cases varied between 159 and 2 943(811 on average) μg N mh.which were higher than the detection limits,with the exception of only two cases.The Nfluxes at DAF 3 were significantly higher(by nearly 80%(P<0.01)) than those at DAF 1 and 5 in the maize experiment,while there were no significant differences among the irrigation times in the wheat experiment.The Nfluxes and the ratios of nitrous oxide(NO) to the NO plus Nfluxes following urea application to maize were approximately 65% and 11 times larger,respectively(P<0.01),than those following urea application to wheat.Such differences could be mainly attributed to the higher soil water contents,temperatures,and availability of soil N substrates in the maize experiment than in the wheat experiment.This study suggests that theNGF method is sensitive enough to measure in situ Nfluxes from intensively fertilized croplands with calcareous soils.展开更多
To the editor： Acute pyelonephritis is a common kidney disease in female adult, but an unusual cause of acute renal failure（ARF）. We reported one woman suffered from acute pyelonephritis due to Klehsiella pneumonia...To the editor： Acute pyelonephritis is a common kidney disease in female adult, but an unusual cause of acute renal failure（ARF）. We reported one woman suffered from acute pyelonephritis due to Klehsiella pneumoniae infection presented with ARF and unremarkable abdominal signs, however with a favorable prognosis after appropriate antibiotic treatment.A 23-year-old woman was admitted to the First Affiliated Hospital of Sun Yat-sen University with a 10-day history of abdominal bloating, lower flank pain; 3-day history of fatigue, without fever, urinary urgency, frequency, dysuria or oliguria. She had a history of taking the herbs medicine lbr removing urinary calculi （Wu Lin Hua Shi Dan and other unknown herbs） by herself for one week.展开更多
基金supported by the Ministry of Science and Technology(Grant No. 2012CB417106)the National Natural Science Foundation of China(Grant No. 41321064)
文摘Direct nitrous oxide(N2O) emissions(DNEs) from croplands are required in national inventories of greenhouse gases. The Intergovernmental Panel on Climate Change(IPCC) guidelines provide an approach using direct emission factors(EFds) to estimate DNEs, which are constants for large regions. The goal of this paper is to establish empirical models to account for the temporal and spatial variations of EFds, which, apart from the nitrogen addition rate, also vary with a range of environmental factors, so as to enhance the accuracy of regional/national DNE estimates. Therefore, the seasonal/annual DNEs(n = 71) from upland croplands, which are the differences in N2 O emissions between fields with and without fertilizer-nitrogen addition, were used to statistically relate DNEs to regulating factors including the fertilizer-nitrogen addition rate(FN), and environmental(climate and soil) factors. The multivariate stepwise linear regression results showed positive combined effects of FN and clay fraction on DNEs(R2 = 0.61, p < 0.001). Furthermore, the nonlinear regression of FN, precipitation, and clay fraction was also adopted for prediction(R2 = 0.50, p < 0.001). Validation with an independent dataset(n = 31) suggested that both models were better predictors of DNEs than the IPCC model, which only depends on FN. These empirical models may provide simple but reliable approaches for compiling regional/national, and even global inventories of DNEs from croplands. However, both models were restricted to a limited sample size. Understandably, more field observations are still required to further validate the global applicability of these simple approaches.
基金jointly supported by the National Natural Science Foundation of China(41877333,41830751 and 41761144054)the Basic Research Program of Frontier Sciences of Chinese Academy of Sciences(ZDBSLY-DQCOO7)the National Key Research and Development Program of China(2017YFD0200100)。
文摘Denitrification-induced nitrogen(N) losses from croplands may be greatly increased by intensive fertilization.However,the accurate quantification of these losses is still challenging due to insufficient available in situ measurements of soil dinitrogen(N) emissions.We carried out two one-week experiments in a maize-wheat cropping system with calcareous soil using theN gas-flux(NGF) method to measure in situ Nfluxes following urea application.Applications ofN-labeled urea(99 atom%,130-150 kg N ha) were followed by irrigation on the 1 st,3 rd,and 5 th days after fertilization(DAF 1,3,and 5,respectively).The detection limits of the soil Nfluxes were 163-1 565,81-485,and 54-281 μg N mhfor the two-,four-,and six-hour static chamber enclosures,respectively.The Nfluxes measured in 120 cases varied between 159 and 2 943(811 on average) μg N mh.which were higher than the detection limits,with the exception of only two cases.The Nfluxes at DAF 3 were significantly higher(by nearly 80%(P<0.01)) than those at DAF 1 and 5 in the maize experiment,while there were no significant differences among the irrigation times in the wheat experiment.The Nfluxes and the ratios of nitrous oxide(NO) to the NO plus Nfluxes following urea application to maize were approximately 65% and 11 times larger,respectively(P<0.01),than those following urea application to wheat.Such differences could be mainly attributed to the higher soil water contents,temperatures,and availability of soil N substrates in the maize experiment than in the wheat experiment.This study suggests that theNGF method is sensitive enough to measure in situ Nfluxes from intensively fertilized croplands with calcareous soils.
文摘To the editor： Acute pyelonephritis is a common kidney disease in female adult, but an unusual cause of acute renal failure（ARF）. We reported one woman suffered from acute pyelonephritis due to Klehsiella pneumoniae infection presented with ARF and unremarkable abdominal signs, however with a favorable prognosis after appropriate antibiotic treatment.A 23-year-old woman was admitted to the First Affiliated Hospital of Sun Yat-sen University with a 10-day history of abdominal bloating, lower flank pain; 3-day history of fatigue, without fever, urinary urgency, frequency, dysuria or oliguria. She had a history of taking the herbs medicine lbr removing urinary calculi （Wu Lin Hua Shi Dan and other unknown herbs） by herself for one week.
