By searching literature databases, we obtained more than 200 articles published since 1993 that related to the measurements of topsoil organic carbon (SOC) in different regions. To objectively evaluate the changes in ...By searching literature databases, we obtained more than 200 articles published since 1993 that related to the measurements of topsoil organic carbon (SOC) in different regions. To objectively evaluate the changes in the SOC over the last two decades, we selected 132 representative articles from these documented articles. More than sixty thousand soil samples and/or sampling sites were included in the selected articles. Results from ana- lyzing these data sets indicated that the concentra- tion of SOC increased in 53%-59%, decreased in 30%-31% and stabilized in 4%-6% of the national croplands, respectively. A further investigation showed that the total increment of SOC in Chinese croplands ranged from 311.3 Tg to 401.4 Tg. In terms of administrative region, significant increase occurred in eastern and northern China and decrease in northeastern China, respectively. When evaluated by soil great groups, the SOC increased considerably in paddy soils and fluvo-aquic soils and reduced con- spicuously in black soils. The increase of SOC is attributed to the amendments of crop residues and organic manure, the augment of synthetic fertilizer application and the optimal combination of nutrients, and the development of no-tillage and reduced-tillage practice. Water loss and soil erosion and low input induced a great decrease of the SOC in black soils. In order to effectively enhance soil C sequestrations and to greatly control the SOC reduction in north- eastern China, future efforts should be made in de- veloping new techniques, training farmers and con- summating the policy of governmental compensation,by which the application of crop straw, the improve- ment of fertilization, the practice of no-tillage and reduced-tillage, and the control of water loss and soil erosion could be further realized. To respond to the increasing pressure from the Kyoto Protocol thence- forward, four aspects were further addressed for fu- ture research needs, including the quantification of SOC storage in the Second State Soil Survey and at p展开更多
Environmental magnetic measurements were carried out on the samples of street dust and topsoil,which were collected along the roadway in the urban and suburb of Beijing,including magnetic sus-ceptibility(χ),anhystere...Environmental magnetic measurements were carried out on the samples of street dust and topsoil,which were collected along the roadway in the urban and suburb of Beijing,including magnetic sus-ceptibility(χ),anhysteretic remanent magnetization(ARM),isothermal remanent magnetization(IRM)of all samples and temperature-dependence of magnetic susceptibilities and magnetic hysteresis pa-rameters of representative samples.Obvious differences exist between the samples of street dust and those of topsoil.Compared with topsoil samples,the concentration of magnetic particles and high-coercivity components in street dust samples are higher,and the magnetic grains are coarser.Both dust and topsoil samples are dominated by ferrimagnetic minerals,and iron particles are only detected in some dust samples.These results suggest that street dust samples reflect the characteris-tic of particles produced by industrial and traffic activities,and the magnetic property of topsoil sam-ples represents the characteristic of particles from both anthropogenic and natural sources.The dis-tribution of magnetic parameters is influenced by the environment where the samples are collected,like industry,traffic density and other road conditions.Hard isothermal remanent magnetization(HIRM)may be used as an indicator of particles produced by traffic activity.Dust storm samples collected on 17 and 18 April,2006 have different magnetic properties from street dust and natural particles,like loess and paleosol,which indicate that the dust storm might be mixed with anthropogenic particulates during transport and falling.展开更多
Forty-five acid sulfate topsoil samples (depth < 0.5 m) from 15 soil cores at 11 locations along the New South Wales coast, Australia, were selected to investigate the chemical behavior of Zn, Mn, Cr, Co and Pb in ...Forty-five acid sulfate topsoil samples (depth < 0.5 m) from 15 soil cores at 11 locations along the New South Wales coast, Australia, were selected to investigate the chemical behavior of Zn, Mn, Cr, Co and Pb in these soils. The amount of HCI-extractable Mn was much smaller than the mean value of the total Mn documented for other soils. This may be attributed to enhanced mobilization of Mn from the soils under the extremely acidic and seasonally flooded conditions encountered in the investigated soils. The pH-dependency of soluble Zn and Mn was strongly affected by the availability of acid reactive Zn and Mn compounds. There were fairly good relationships between soluble Zn and acid reactive Zn compounds, and between soluble Mn and acid reactive Mn compounds. Soluble Zn and soluble Mn concentrations were important controls on exchangeable Zn and Mn concentrations, respectively. In contrast to the suggestion by other authors that adsorption of Co was closely associated with Mn oxides present in soils, the exchangeable Co in the investigated acid sulfate soils was not clearly related to the abundance of Mn minerals. In addition to the fact that there are few Mn minerals present in the soils, this might also be because the availability of canon exchange sites on the crystal surfaces of Mn oxides was reduced under extremely acidic conditions.展开更多
文摘By searching literature databases, we obtained more than 200 articles published since 1993 that related to the measurements of topsoil organic carbon (SOC) in different regions. To objectively evaluate the changes in the SOC over the last two decades, we selected 132 representative articles from these documented articles. More than sixty thousand soil samples and/or sampling sites were included in the selected articles. Results from ana- lyzing these data sets indicated that the concentra- tion of SOC increased in 53%-59%, decreased in 30%-31% and stabilized in 4%-6% of the national croplands, respectively. A further investigation showed that the total increment of SOC in Chinese croplands ranged from 311.3 Tg to 401.4 Tg. In terms of administrative region, significant increase occurred in eastern and northern China and decrease in northeastern China, respectively. When evaluated by soil great groups, the SOC increased considerably in paddy soils and fluvo-aquic soils and reduced con- spicuously in black soils. The increase of SOC is attributed to the amendments of crop residues and organic manure, the augment of synthetic fertilizer application and the optimal combination of nutrients, and the development of no-tillage and reduced-tillage practice. Water loss and soil erosion and low input induced a great decrease of the SOC in black soils. In order to effectively enhance soil C sequestrations and to greatly control the SOC reduction in north- eastern China, future efforts should be made in de- veloping new techniques, training farmers and con- summating the policy of governmental compensation,by which the application of crop straw, the improve- ment of fertilization, the practice of no-tillage and reduced-tillage, and the control of water loss and soil erosion could be further realized. To respond to the increasing pressure from the Kyoto Protocol thence- forward, four aspects were further addressed for fu- ture research needs, including the quantification of SOC storage in the Second State Soil Survey and at p
基金国家自然科学基金(批准号:2983719030230310+5 种基金20077004和20477004)北京市自然科学基金(批准号:89910028041003)资助项目教育部高等学校博士学科点专项科研基金(20010027017)中国科学院百人计划 大气边界层物理和大气化学国家重点实验室(LAPC)以及Swedish International Development Cooperation Agency(SIDA)部分资助项目
基金Ministry of Education of China(Grant No.NCET-04-0727)the National Natural Science Foundation of China(Grant No.40032010B)111 Project(Grant No.B07011)
文摘Environmental magnetic measurements were carried out on the samples of street dust and topsoil,which were collected along the roadway in the urban and suburb of Beijing,including magnetic sus-ceptibility(χ),anhysteretic remanent magnetization(ARM),isothermal remanent magnetization(IRM)of all samples and temperature-dependence of magnetic susceptibilities and magnetic hysteresis pa-rameters of representative samples.Obvious differences exist between the samples of street dust and those of topsoil.Compared with topsoil samples,the concentration of magnetic particles and high-coercivity components in street dust samples are higher,and the magnetic grains are coarser.Both dust and topsoil samples are dominated by ferrimagnetic minerals,and iron particles are only detected in some dust samples.These results suggest that street dust samples reflect the characteris-tic of particles produced by industrial and traffic activities,and the magnetic property of topsoil sam-ples represents the characteristic of particles from both anthropogenic and natural sources.The dis-tribution of magnetic parameters is influenced by the environment where the samples are collected,like industry,traffic density and other road conditions.Hard isothermal remanent magnetization(HIRM)may be used as an indicator of particles produced by traffic activity.Dust storm samples collected on 17 and 18 April,2006 have different magnetic properties from street dust and natural particles,like loess and paleosol,which indicate that the dust storm might be mixed with anthropogenic particulates during transport and falling.
基金supported by a grant from Australian Research Council.
文摘Forty-five acid sulfate topsoil samples (depth < 0.5 m) from 15 soil cores at 11 locations along the New South Wales coast, Australia, were selected to investigate the chemical behavior of Zn, Mn, Cr, Co and Pb in these soils. The amount of HCI-extractable Mn was much smaller than the mean value of the total Mn documented for other soils. This may be attributed to enhanced mobilization of Mn from the soils under the extremely acidic and seasonally flooded conditions encountered in the investigated soils. The pH-dependency of soluble Zn and Mn was strongly affected by the availability of acid reactive Zn and Mn compounds. There were fairly good relationships between soluble Zn and acid reactive Zn compounds, and between soluble Mn and acid reactive Mn compounds. Soluble Zn and soluble Mn concentrations were important controls on exchangeable Zn and Mn concentrations, respectively. In contrast to the suggestion by other authors that adsorption of Co was closely associated with Mn oxides present in soils, the exchangeable Co in the investigated acid sulfate soils was not clearly related to the abundance of Mn minerals. In addition to the fact that there are few Mn minerals present in the soils, this might also be because the availability of canon exchange sites on the crystal surfaces of Mn oxides was reduced under extremely acidic conditions.
