Methane (CH4) and nitrous oxide (N2O) saturation concentration and gas-water interface emission flux in surface water of the Yangtze Delta plain river net were investigated in summer at representative sites including ...Methane (CH4) and nitrous oxide (N2O) saturation concentration and gas-water interface emission flux in surface water of the Yangtze Delta plain river net were investigated in summer at representative sites including the upper reaches of the Huangpu River and the rivers in the Chongming Island. The results show that the CH4 concentration in river water ranged from 0.30±0.03 to 6.66±0.14 μmol.L-1, and N2O concentration ranged from 13.8±2.33 to 435±116 nmol.L-1. River surface water had a very high satura- tion level of CH4 (from 468±49.0% to 11560±235%) and that of N2O (from 175±29.5% to 4914±1304%). Dissolved oxygen (DO) was the primary factor controlling the CH4 concentration in water. N2O concentration had significant negative correlation with salinity and a significant positive correlation with nitrate (NO3-), nitrite (NO2-), chemical oxygen demand (CODcr) concentration and pH of river water. CH4 and N2O of river water were brought about mainly by methanogenesis and denitrification in river bottom sediment that diffused through sediment-water interface into the water body and then into atmosphere through the gas-water interface. The emission flux of CH4 and N2O at river gas-water interface reached 778±59.8 and 236±63.6 μmol.m-2.h-1, respectively in summer. The river net was a potential source of atmospheric CH4 and N2O because of eutrophication of the water body.展开更多
利用NOAA Earth System Research Laboratory提供的1991─2004年Tae-ahn(韩国),Ulaan Uul(蒙古)以及瓦里关(中国)的大气温室气体CO2和CH4的数据,对东亚地区大气温室气体的浓度特征及变化趋势进行研究.结果表明:14年来东亚地区大气中φ(C...利用NOAA Earth System Research Laboratory提供的1991─2004年Tae-ahn(韩国),Ulaan Uul(蒙古)以及瓦里关(中国)的大气温室气体CO2和CH4的数据,对东亚地区大气温室气体的浓度特征及变化趋势进行研究.结果表明:14年来东亚地区大气中φ(CO2)和φ(CH4)月和年平均值总体呈明显上升趋势;3个监测站的φ(CO2)年线性递增率比较接近,平均值为1.91×10-6a-1,季节变化较一致;从沿海到内陆这2种温室气体的浓度均随海拔升高而逐渐降低.展开更多
The concentrations of CH4 in the atmosphere over the past 2000 years have been deduced by extracting and analyzing the air in bubbles embedded in the Dasuopu ice core, Qing-hai-Tibetan Plateau. Upon analyzing 57 ice c...The concentrations of CH4 in the atmosphere over the past 2000 years have been deduced by extracting and analyzing the air in bubbles embedded in the Dasuopu ice core, Qing-hai-Tibetan Plateau. Upon analyzing 57 ice core samples we found that the concentration of CH4 200 years ago and earlier was 0.85 μ mol· mol-1 or about 40% of present atmospheric CH4 levels over Qinghai-Tibetan Plateau. A rapid and significant increase of atmospheric CH4 started about 200–250 a ago. For a given age before 19th century, the Dasuopu CH4 concentrations were about 15%-20% higher than those in Antarctic and Greenland references. It was also found that the Dasuopu CH4 concentrations changed more frequently, and its fluctuations could reflect the temperature change sensitively.展开更多
The CO2reforming of CH4is studied over MgO‐promoted Ni catalysts,which were supported on alumina prepared from hydrotalcite.This presents an improved stability compared with non‐promoted catalysts.The introduction o...The CO2reforming of CH4is studied over MgO‐promoted Ni catalysts,which were supported on alumina prepared from hydrotalcite.This presents an improved stability compared with non‐promoted catalysts.The introduction of the MgO promoter was achieved through the‘‘memory effect’’of the Ni‐Al hydrotalcite structure,and ICP‐MS confirmed that only0.42wt.%of Mg2+ions were added into the Ni‐Mg/Al catalyst.Although no differences in the Ni particle size and basicity strength were observed,the Ni‐Mg/Al catalyst showed a higher catalytic stability than the Ni/Al catalyst.A series of surface reaction experiments were used and showed that the addition of a MgO promoter with low concentration can promote CO2dissociation to form active surface oxygen arising from the formation of the Ni‐MgO interface sites.Therefore,the carbon‐resistance promotion by nature was suggested to contribute to an oxidative environment around Ni particles,which would increase the conversion of carbon residues from CH4cracking to yield CO on the Ni metal surface.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No. 40730526)the Science & Technology Department of Shanghai (Grant No. 07DZ12037)+1 种基金the National Great Water Issue Project of China (Grant No. 2008ZX07317-006)China Postdoctoral Science Foundation (Grant No. 20060400635)
文摘Methane (CH4) and nitrous oxide (N2O) saturation concentration and gas-water interface emission flux in surface water of the Yangtze Delta plain river net were investigated in summer at representative sites including the upper reaches of the Huangpu River and the rivers in the Chongming Island. The results show that the CH4 concentration in river water ranged from 0.30±0.03 to 6.66±0.14 μmol.L-1, and N2O concentration ranged from 13.8±2.33 to 435±116 nmol.L-1. River surface water had a very high satura- tion level of CH4 (from 468±49.0% to 11560±235%) and that of N2O (from 175±29.5% to 4914±1304%). Dissolved oxygen (DO) was the primary factor controlling the CH4 concentration in water. N2O concentration had significant negative correlation with salinity and a significant positive correlation with nitrate (NO3-), nitrite (NO2-), chemical oxygen demand (CODcr) concentration and pH of river water. CH4 and N2O of river water were brought about mainly by methanogenesis and denitrification in river bottom sediment that diffused through sediment-water interface into the water body and then into atmosphere through the gas-water interface. The emission flux of CH4 and N2O at river gas-water interface reached 778±59.8 and 236±63.6 μmol.m-2.h-1, respectively in summer. The river net was a potential source of atmospheric CH4 and N2O because of eutrophication of the water body.
文摘利用NOAA Earth System Research Laboratory提供的1991─2004年Tae-ahn(韩国),Ulaan Uul(蒙古)以及瓦里关(中国)的大气温室气体CO2和CH4的数据,对东亚地区大气温室气体的浓度特征及变化趋势进行研究.结果表明:14年来东亚地区大气中φ(CO2)和φ(CH4)月和年平均值总体呈明显上升趋势;3个监测站的φ(CO2)年线性递增率比较接近,平均值为1.91×10-6a-1,季节变化较一致;从沿海到内陆这2种温室气体的浓度均随海拔升高而逐渐降低.
基金the National Natural Science Foundation of China (Grant No.49671021), the National Key Project for Basic Research (Grant No. KZ951-A1-204), CAS Project for Tibetan Research Project (Grant No. KZ95-T-06) and Innovation Project of Cold and Arid Regions E
文摘The concentrations of CH4 in the atmosphere over the past 2000 years have been deduced by extracting and analyzing the air in bubbles embedded in the Dasuopu ice core, Qing-hai-Tibetan Plateau. Upon analyzing 57 ice core samples we found that the concentration of CH4 200 years ago and earlier was 0.85 μ mol· mol-1 or about 40% of present atmospheric CH4 levels over Qinghai-Tibetan Plateau. A rapid and significant increase of atmospheric CH4 started about 200–250 a ago. For a given age before 19th century, the Dasuopu CH4 concentrations were about 15%-20% higher than those in Antarctic and Greenland references. It was also found that the Dasuopu CH4 concentrations changed more frequently, and its fluctuations could reflect the temperature change sensitively.
基金supported by the National Natural Science Fundation of China(U1361202,51276120)~~
文摘The CO2reforming of CH4is studied over MgO‐promoted Ni catalysts,which were supported on alumina prepared from hydrotalcite.This presents an improved stability compared with non‐promoted catalysts.The introduction of the MgO promoter was achieved through the‘‘memory effect’’of the Ni‐Al hydrotalcite structure,and ICP‐MS confirmed that only0.42wt.%of Mg2+ions were added into the Ni‐Mg/Al catalyst.Although no differences in the Ni particle size and basicity strength were observed,the Ni‐Mg/Al catalyst showed a higher catalytic stability than the Ni/Al catalyst.A series of surface reaction experiments were used and showed that the addition of a MgO promoter with low concentration can promote CO2dissociation to form active surface oxygen arising from the formation of the Ni‐MgO interface sites.Therefore,the carbon‐resistance promotion by nature was suggested to contribute to an oxidative environment around Ni particles,which would increase the conversion of carbon residues from CH4cracking to yield CO on the Ni metal surface.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.
