Background:Rivers and streams are one of the primary sources of nitrous oxide(N_(2)O)which is an important greenhouse gas with great global warming potential.Yet,over the past century,human activities have dramaticall...Background:Rivers and streams are one of the primary sources of nitrous oxide(N_(2)O)which is an important greenhouse gas with great global warming potential.Yet,over the past century,human activities have dramatically increased reactive nitrogen loadings into and consequently led to increased N_(2)O emission from the river ecosystems.Here,we carried out a study in two subtropical rivers,i.e.,Jinshui River and Qi River with slight and intense human disturbance in their respective catchments in China.The study intended to explore spatial variability and seasonality in N_(2)O emissions,and the relative importance of physicochemical variables,nitrification and denitrification potentials,and functional genes abundance influencing N_(2)O emissions.Results:N_(2)O concentration,N_(2)O saturation,and N_(2)O flux of Jinshui River peaked in high flow season.N_(2)O concentration,N_(2)O saturations,and N_(2)O flux in Qi River and downstream of Jinshui River were significantly higher than that in other areas in normal and low flow seasons.N_(2)O concentration was positively correlated with water temperature,water NO_(3)^(−),and DOC,negatively correlated with water NH4+and DOC/NO_(3)^(−)(the ratio of dissolved organic carbon to NO_(3)^(−)in water),and positively correlated with potential nitrification rate in high flow season,but not correlated with functional genes abundance.Both rivers had lower N_(2)O saturation and flux than many freshwater systems,and their EFr-5(N_(2)O emission factor for river)was lower than the recommended values of IPCC.Conclusions:While the two rivers were moderate sources of N_(2)O and N_(2)O emissions in river systems were normally elevated in the summer,areas with intense human disturbance had higher N_(2)O concentration,N_(2)O saturations,and N_(2)O flux than those with slight human disturbance.Physicochemical variables were good indicators of N_(2)O emissions in the river ecosystems.展开更多
Air samples in China were collected and determined for the concentration of N_2O. The production rates of N_2O from agricultural soils were measured with the chamber method.The results in- dicate that the background c...Air samples in China were collected and determined for the concentration of N_2O. The production rates of N_2O from agricultural soils were measured with the chamber method.The results in- dicate that the background concentration of N_2O averages(308±5)×10^(-9)in 1989,which is close to that ob- tained at the other background stations abroad.However,at both urban and rural areas,atmospheric N_2O concentrations are higher.N_2O emission fluxes from several farmlands are different and dependent on the fac- tors of agricultural practice and climate.But their magnitudes are at the same order.Preliminary calculation shows that the released N_2O-N from agricultural sources(cultivated soil and N-fertilizers)amounts to 122 Gg/a in China in 1990.展开更多
At present,continuous observation data for atmospheric nitrous oxide（N_2O） concentrations are still lacking,especially in east Antarctica.In this paper,nitrous oxide background concentrations were measured at Zhongs...At present,continuous observation data for atmospheric nitrous oxide（N_2O） concentrations are still lacking,especially in east Antarctica.In this paper,nitrous oxide background concentrations were measured at Zhongshan Station（69°22′25″S,76°22′14″E）,east Antarctica during the period of 2008–2012,and their interannual and seasonal characteristics were analyzed and discussed.The mean N_2O concentration was 321.9 n L/L with the range of 320.5–324.8 n L/L during the five years,and it has been increasing at a rate of 0.29% year-1.Atmospheric N_2O concentrations showed a strong seasonal fluctuation during these five years.The concentrations appeared to follow a downtrend from spring to autumn,and then increased in winter.Generally the highest concentrations occurred in spring.This trend was very similar to that observed at other global observation sites.The overall N_2O concentration at the selected global sites showed an increasing annual trend,and the mean N_2O concentration in the Northern Hemisphere was slightly higher than that in the Southern Hemisphere.Our result could be representative of atmospheric N_2O background levels at the global scale.This study provided valuable data for atmospheric N_2O concentrations in east Antarctica,which is important to study on the relationships between N2 O emissions and climate change.展开更多
基金National Natural Science Foundation of China(Nos.32030069,31720103905).
文摘Background:Rivers and streams are one of the primary sources of nitrous oxide(N_(2)O)which is an important greenhouse gas with great global warming potential.Yet,over the past century,human activities have dramatically increased reactive nitrogen loadings into and consequently led to increased N_(2)O emission from the river ecosystems.Here,we carried out a study in two subtropical rivers,i.e.,Jinshui River and Qi River with slight and intense human disturbance in their respective catchments in China.The study intended to explore spatial variability and seasonality in N_(2)O emissions,and the relative importance of physicochemical variables,nitrification and denitrification potentials,and functional genes abundance influencing N_(2)O emissions.Results:N_(2)O concentration,N_(2)O saturation,and N_(2)O flux of Jinshui River peaked in high flow season.N_(2)O concentration,N_(2)O saturations,and N_(2)O flux in Qi River and downstream of Jinshui River were significantly higher than that in other areas in normal and low flow seasons.N_(2)O concentration was positively correlated with water temperature,water NO_(3)^(−),and DOC,negatively correlated with water NH4+and DOC/NO_(3)^(−)(the ratio of dissolved organic carbon to NO_(3)^(−)in water),and positively correlated with potential nitrification rate in high flow season,but not correlated with functional genes abundance.Both rivers had lower N_(2)O saturation and flux than many freshwater systems,and their EFr-5(N_(2)O emission factor for river)was lower than the recommended values of IPCC.Conclusions:While the two rivers were moderate sources of N_(2)O and N_(2)O emissions in river systems were normally elevated in the summer,areas with intense human disturbance had higher N_(2)O concentration,N_(2)O saturations,and N_(2)O flux than those with slight human disturbance.Physicochemical variables were good indicators of N_(2)O emissions in the river ecosystems.
文摘Air samples in China were collected and determined for the concentration of N_2O. The production rates of N_2O from agricultural soils were measured with the chamber method.The results in- dicate that the background concentration of N_2O averages(308±5)×10^(-9)in 1989,which is close to that ob- tained at the other background stations abroad.However,at both urban and rural areas,atmospheric N_2O concentrations are higher.N_2O emission fluxes from several farmlands are different and dependent on the fac- tors of agricultural practice and climate.But their magnitudes are at the same order.Preliminary calculation shows that the released N_2O-N from agricultural sources(cultivated soil and N-fertilizers)amounts to 122 Gg/a in China in 1990.
基金supported by the Program of China Polar Environment Investigation and Assessment (No.CHINARE 2011–2015)the National Natural Science Foundation of China (Nos.41176171,41576181)
文摘At present,continuous observation data for atmospheric nitrous oxide（N_2O） concentrations are still lacking,especially in east Antarctica.In this paper,nitrous oxide background concentrations were measured at Zhongshan Station（69°22′25″S,76°22′14″E）,east Antarctica during the period of 2008–2012,and their interannual and seasonal characteristics were analyzed and discussed.The mean N_2O concentration was 321.9 n L/L with the range of 320.5–324.8 n L/L during the five years,and it has been increasing at a rate of 0.29% year-1.Atmospheric N_2O concentrations showed a strong seasonal fluctuation during these five years.The concentrations appeared to follow a downtrend from spring to autumn,and then increased in winter.Generally the highest concentrations occurred in spring.This trend was very similar to that observed at other global observation sites.The overall N_2O concentration at the selected global sites showed an increasing annual trend,and the mean N_2O concentration in the Northern Hemisphere was slightly higher than that in the Southern Hemisphere.Our result could be representative of atmospheric N_2O background levels at the global scale.This study provided valuable data for atmospheric N_2O concentrations in east Antarctica,which is important to study on the relationships between N2 O emissions and climate change.
