Knowledge of soil carbon（C） distribution and its relationship with the environment can improve our understanding of its biogeochemical cycling and help to establish sound regional models of C cycling. However, such ...Knowledge of soil carbon（C） distribution and its relationship with the environment can improve our understanding of its biogeochemical cycling and help to establish sound regional models of C cycling. However, such knowledge is limited in environments with complex landscape configurations. In this study, we investigated the vertical distribution and storage of soil organic carbon（SOC） and soil inorganic carbon（SIC） in the 10 representative landscapes（alpine meadow, subalpine shrub and meadow, mountain grassland, mountain forest, typical steppe, desert steppe, Hexi Corridor oases cropland, Ruoshui River delta desert, Alxa Gobi desert, and sandy desert） with contrasting bioclimatic regimes in the Heihe River Basin, Northwest China. We also measured the 87 Sr/86 Sr ratio in soil carbonate to understand the sources of SIC because the ratio can be used as a proxy in calculating the contribution of pedogenic inorganic carbon（PIC） to total SIC. Our results showed that SOC contents generally decreased with increasing soil depth in all landscapes, while SIC contents exhibited more complicated variations along soil profiles in relation to pedogenic processes and parent materials at the various landscapes. There were significant differences of C stocks in the top meter among different landscapes, with SOC storage ranging from 0.82 kg C/m^2 in sandy desert to 50.48 kg C/m^2 in mountain forest and SIC storage ranging from 0.19 kg C/m^2 in alpine meadow to 21.91 kg C/m^2 in desert steppe. SIC contributed more than 75% of total C pool when SOC storage was lower than 10 kg C/m^2, and the proportion of PIC to SIC was greater than 70% as calculated from Sr isotopic ratio, suggesting the critical role of PIC in the C budget of this region. The considerable variations of SOC and SIC in different landscapes were attributed to different pedogenic environments resulted from contrasting climatic regimes, parent materials and vegetation types. This study provides an evidence for a general trade-off pattern between SOC and SIC, showing the compensatory effects of environmental conditions（especially climate） on SOC and SIC formation in these landscapes. This is largely attributed to the fact that the overall decrease in temperature and increase in precipitation from arid deserts to alpine mountains simultaneously facilitate the accumulation of SOC and depletion of SIC.展开更多
Polymer dispersants are widely used as grinding aids to reduce the viscosity of mineral particle suspensions and to improve energy efficiency during fine grinding. The authors studied here the effects of polymer dispe...Polymer dispersants are widely used as grinding aids to reduce the viscosity of mineral particle suspensions and to improve energy efficiency during fine grinding. The authors studied here the effects of polymer dispersants of different molecular structure on limestone suspension properties in wet stirred media milling. The polymers differed in their molecular weight and PDI （polydispersity index）. Two traditionally fractionated polymer dispersants having a high PDI （over 2） and one made by controlled radical polymerization having a low PDI （1.2） were tested. It was noticed that these dispersants worked as electrosteric stabilizers and prevented the agglomeration of ground limestone particles. Their addition allowed increased solids concentrations to be used in the grinding experiments and at the same time lowered the particle size and specific energy consumption. The particle sizes obtained were about 1 μm regardless of the dispersant or its dose. The dispersant with a low PDI reduced the viscosity more than did the high PDI dispersants. The results indicate that higher solids concentrations can be used at the same dispersant dose when a low PDI dispersant is used, leading to energy savings via increased throughput. Alternatively, a lower dose of low PDI polymer dispersant than of a high PDI polymer dispersant can be used at the same solids concentration.展开更多
基金supported by the National Natural Science Foundation of China(91325301,41130530,41371224,41601221)
文摘Knowledge of soil carbon（C） distribution and its relationship with the environment can improve our understanding of its biogeochemical cycling and help to establish sound regional models of C cycling. However, such knowledge is limited in environments with complex landscape configurations. In this study, we investigated the vertical distribution and storage of soil organic carbon（SOC） and soil inorganic carbon（SIC） in the 10 representative landscapes（alpine meadow, subalpine shrub and meadow, mountain grassland, mountain forest, typical steppe, desert steppe, Hexi Corridor oases cropland, Ruoshui River delta desert, Alxa Gobi desert, and sandy desert） with contrasting bioclimatic regimes in the Heihe River Basin, Northwest China. We also measured the 87 Sr/86 Sr ratio in soil carbonate to understand the sources of SIC because the ratio can be used as a proxy in calculating the contribution of pedogenic inorganic carbon（PIC） to total SIC. Our results showed that SOC contents generally decreased with increasing soil depth in all landscapes, while SIC contents exhibited more complicated variations along soil profiles in relation to pedogenic processes and parent materials at the various landscapes. There were significant differences of C stocks in the top meter among different landscapes, with SOC storage ranging from 0.82 kg C/m^2 in sandy desert to 50.48 kg C/m^2 in mountain forest and SIC storage ranging from 0.19 kg C/m^2 in alpine meadow to 21.91 kg C/m^2 in desert steppe. SIC contributed more than 75% of total C pool when SOC storage was lower than 10 kg C/m^2, and the proportion of PIC to SIC was greater than 70% as calculated from Sr isotopic ratio, suggesting the critical role of PIC in the C budget of this region. The considerable variations of SOC and SIC in different landscapes were attributed to different pedogenic environments resulted from contrasting climatic regimes, parent materials and vegetation types. This study provides an evidence for a general trade-off pattern between SOC and SIC, showing the compensatory effects of environmental conditions（especially climate） on SOC and SIC formation in these landscapes. This is largely attributed to the fact that the overall decrease in temperature and increase in precipitation from arid deserts to alpine mountains simultaneously facilitate the accumulation of SOC and depletion of SIC.
文摘Polymer dispersants are widely used as grinding aids to reduce the viscosity of mineral particle suspensions and to improve energy efficiency during fine grinding. The authors studied here the effects of polymer dispersants of different molecular structure on limestone suspension properties in wet stirred media milling. The polymers differed in their molecular weight and PDI （polydispersity index）. Two traditionally fractionated polymer dispersants having a high PDI （over 2） and one made by controlled radical polymerization having a low PDI （1.2） were tested. It was noticed that these dispersants worked as electrosteric stabilizers and prevented the agglomeration of ground limestone particles. Their addition allowed increased solids concentrations to be used in the grinding experiments and at the same time lowered the particle size and specific energy consumption. The particle sizes obtained were about 1 μm regardless of the dispersant or its dose. The dispersant with a low PDI reduced the viscosity more than did the high PDI dispersants. The results indicate that higher solids concentrations can be used at the same dispersant dose when a low PDI dispersant is used, leading to energy savings via increased throughput. Alternatively, a lower dose of low PDI polymer dispersant than of a high PDI polymer dispersant can be used at the same solids concentration.
