Nitrogen mineralization in forest soil was studied in laboratory by incubating undisturbed soil cores enclosed within PVC columns at different temperatures to compare the effect of fluctuating temperature with that of...Nitrogen mineralization in forest soil was studied in laboratory by incubating undisturbed soil cores enclosed within PVC columns at different temperatures to compare the effect of fluctuating temperature with that of constant temperature, and to find out whether soil nitrification shows linearity over time. The results showed that there was no significant difference between soil nitrification at fluctuating temperature and that at constant temperature, and suggested that it must be careful to make the conclusion that soil nitrification has linearity over time.展开更多
Water is usally thought of a limiting factor for the restoration of semi-arid ecosystem. In the growing season of 2006, a study was conducted to determine the effects of modeling precipitation on seasonal patterns in ...Water is usally thought of a limiting factor for the restoration of semi-arid ecosystem. In the growing season of 2006, a study was conducted to determine the effects of modeling precipitation on seasonal patterns in concentrations of soil-available nitrogen and to describe the seasonal patterns in soil nitrogen availability and seasonal variation in the rates of net nitrogen mineralization of topsoil at Daqinggou ecological station in Keerqin sand lands, Inner Mongolia Autonomous Region, China. Manipulation of water （80 mm） was designed to be added to experiment plots of sandy grasslands in dry season. Water addition （W） treatment and control （CK） treatment were separately taken in six replications and randomly assigned in 12 plots （4 m×4 m for each） with 2-m buffers betweens. Results showed that the content of soil inorganic nitrogen and net nitrogen mineralization rate were not affected by adding water in sandy grassland of Keerqin sand lands. Net ni- trogen mineralization rates ranged from 0.5μg·g^-1,month^-1 to 4 μg.g^-1.month^-1. The highest values of soil inorganic nitrogen and net nitrogen mineralization occurred on October 15 in control plots. The seasonal changes of soil inorganic nitrogen contents exhibited ＂V＂ shape pattern that was related to seasonal patterns of soil ammonium-N （ascending trend） and nitrate-N transformation （descending trend）.展开更多
As clean energy,the microwave is commonly used to pretreat various ores.In this work,the microwave dielectric properties of limonitic laterite ore were measured by resonant cavity perturbation technique and the effect...As clean energy,the microwave is commonly used to pretreat various ores.In this work,the microwave dielectric properties of limonitic laterite ore were measured by resonant cavity perturbation technique and the effects from microwave were systematically investigated.Results indicated that limonitic laterite had high microwave absorbance.After microwave pretreatment,the microstructure of the laterite became less aggregated and more porous and the main phase transformed from goethite to hematite that improved leaching in nitric acid(1.2 kg HNO3/kg ore);Ni,Co,Fe,and Mg extraction ratios were 95.2%,98.1%,1.8%and 15%,respectively,after leaching for 60 min at 200°C and 500 r/min.Furthermore,in the process of goethite to hematite by microwave pretreatment,the nickel-containing mineral is activated,which makes nickel be leached easily.The leaching process has high Ni extraction ratio compared to that without microwave(82%)and conventional pretreatment(90.4%).Therefore,microwave pretreatment of limonitic laterite before nitric acid pressure leaching is an effective way to improve the selectivity and extraction of the leach.展开更多
Although to date individual gross N transformations could be quantified by 15N tracing method and models, studies are still limited in paddy soil. An incubation experiment was conducted using topsoil （0-20 cm） and s...Although to date individual gross N transformations could be quantified by 15N tracing method and models, studies are still limited in paddy soil. An incubation experiment was conducted using topsoil （0-20 cm） and subsoil （20-60 cm） of two paddy soils, alkaline and clay （AC） soil and neutral and silt loam （NSL） soil, to investigate gross N transformation rates. Soil samples were labeled with either 15NHaNO3 or NH4SN03, and then incubated at 25 ℃for 168 h at 60% water-holding capacity. The gross N mineralization （recalcitrant and labile organic N mineralization） rates in AC soil were 1.6 to 3.3 times higher than that in NSL soil, and the gross N nitrification （autotrophic and heterotrophic nitrification） rates in AC soil were 2.4 to 4.4 times higher than those in NSL soil. Although gross NO3 consumption （i.e., NO3 immobilization and dissimilatory NO3 reduction to NH＋） rates increased with increasing gross nitrification rates, the measured net nitrification rate in AC soil was approximately 2.0 to 5.1 times higher than that in NSL soil. These showed that high NO3 production capacity of alkaline paddy soil should be a cause for concern because an accumulation of NO3 can increase the risk of NO3 loss through leaching and denitrification.展开更多
The recently discovered nitrate ore field in the Turpan-Hami Basin of western China represents an estimated resource of 2.5 billion tons, and is comparable in scale to the Atacama Desert super-scale nitrate deposit in...The recently discovered nitrate ore field in the Turpan-Hami Basin of western China represents an estimated resource of 2.5 billion tons, and is comparable in scale to the Atacama Desert super-scale nitrate deposit in Chile. The research on this area is rarely carried out, and the origin of the deposits remains uncertain. In this study, new methods were used to systematically analyze N and O isotopes in nitrate minerals collected from the Kumutage, Xiaocaohu, Wuzongbulak, Dawadi, Tuyugou, and Shaer ore deposits in the Turpan-Hami Basin. The data showed that the δ15NAir value ranges from 0.7‰ to 27.6‰, but mostly between 2‰ and 6‰, which was similar to atmospheric NO3-. The 18O was highly enriched with δ18OV-SMOW varying from 30.2‰ to 46.7‰. This differs from levels in deposits derived from microbial nitrogen fixation, but is similar to those in atmospheric nitrates. N and O isotopes data indicated that nitrate deposits in Turpan-Hami Basin must be the result of deposition of atmospheric nitrate particles. Although atmospheric nitrate particles are common, the nitrate deposits could form only under the condition of long-term extreme drought climate and very limited biological activity. This paper summarized the ore-forming mechanism of different types nitrate deposits based on their geological setting.展开更多
文摘Nitrogen mineralization in forest soil was studied in laboratory by incubating undisturbed soil cores enclosed within PVC columns at different temperatures to compare the effect of fluctuating temperature with that of constant temperature, and to find out whether soil nitrification shows linearity over time. The results showed that there was no significant difference between soil nitrification at fluctuating temperature and that at constant temperature, and suggested that it must be careful to make the conclusion that soil nitrification has linearity over time.
基金This paper is supported by the Key Laboratory of Ter-restrial Ecological Process and Regional Ecological Safety in Liaoning Province (06ZDS212SS)the Knowledge Innovation Program of the Chinese Academy of Sciences (07SBS115S3).
文摘Water is usally thought of a limiting factor for the restoration of semi-arid ecosystem. In the growing season of 2006, a study was conducted to determine the effects of modeling precipitation on seasonal patterns in concentrations of soil-available nitrogen and to describe the seasonal patterns in soil nitrogen availability and seasonal variation in the rates of net nitrogen mineralization of topsoil at Daqinggou ecological station in Keerqin sand lands, Inner Mongolia Autonomous Region, China. Manipulation of water （80 mm） was designed to be added to experiment plots of sandy grasslands in dry season. Water addition （W） treatment and control （CK） treatment were separately taken in six replications and randomly assigned in 12 plots （4 m×4 m for each） with 2-m buffers betweens. Results showed that the content of soil inorganic nitrogen and net nitrogen mineralization rate were not affected by adding water in sandy grassland of Keerqin sand lands. Net ni- trogen mineralization rates ranged from 0.5μg·g^-1,month^-1 to 4 μg.g^-1.month^-1. The highest values of soil inorganic nitrogen and net nitrogen mineralization occurred on October 15 in control plots. The seasonal changes of soil inorganic nitrogen contents exhibited ＂V＂ shape pattern that was related to seasonal patterns of soil ammonium-N （ascending trend） and nitrate-N transformation （descending trend）.
基金Project(51974025)supported by the National Natural Science Foundation of ChinaProject(2018IA055)supported by the International Cooperation Project of Key Research and Development Plan of Yunan Province,ChinaProject(JKY2019-09)supported by State Key Laboratory of Nickel and Cobalt Resources Comprehensive Utilization,China。
文摘As clean energy,the microwave is commonly used to pretreat various ores.In this work,the microwave dielectric properties of limonitic laterite ore were measured by resonant cavity perturbation technique and the effects from microwave were systematically investigated.Results indicated that limonitic laterite had high microwave absorbance.After microwave pretreatment,the microstructure of the laterite became less aggregated and more porous and the main phase transformed from goethite to hematite that improved leaching in nitric acid(1.2 kg HNO3/kg ore);Ni,Co,Fe,and Mg extraction ratios were 95.2%,98.1%,1.8%and 15%,respectively,after leaching for 60 min at 200°C and 500 r/min.Furthermore,in the process of goethite to hematite by microwave pretreatment,the nickel-containing mineral is activated,which makes nickel be leached easily.The leaching process has high Ni extraction ratio compared to that without microwave(82%)and conventional pretreatment(90.4%).Therefore,microwave pretreatment of limonitic laterite before nitric acid pressure leaching is an effective way to improve the selectivity and extraction of the leach.
基金supported by the Ministry of Science and Technology of China(No.2007DFA30850)the German Ministry of Education and Research(No.0330800C)a German DAAD-PPP Project(No.50751522)joint with the China Scholarship Council(No.2011016097)
文摘Although to date individual gross N transformations could be quantified by 15N tracing method and models, studies are still limited in paddy soil. An incubation experiment was conducted using topsoil （0-20 cm） and subsoil （20-60 cm） of two paddy soils, alkaline and clay （AC） soil and neutral and silt loam （NSL） soil, to investigate gross N transformation rates. Soil samples were labeled with either 15NHaNO3 or NH4SN03, and then incubated at 25 ℃for 168 h at 60% water-holding capacity. The gross N mineralization （recalcitrant and labile organic N mineralization） rates in AC soil were 1.6 to 3.3 times higher than that in NSL soil, and the gross N nitrification （autotrophic and heterotrophic nitrification） rates in AC soil were 2.4 to 4.4 times higher than those in NSL soil. Although gross NO3 consumption （i.e., NO3 immobilization and dissimilatory NO3 reduction to NH＋） rates increased with increasing gross nitrification rates, the measured net nitrification rate in AC soil was approximately 2.0 to 5.1 times higher than that in NSL soil. These showed that high NO3 production capacity of alkaline paddy soil should be a cause for concern because an accumulation of NO3 can increase the risk of NO3 loss through leaching and denitrification.
基金supported by Basic Scientific Research Operation Cost of State-Leveled Public Welfare Scientific Research Courtyard (Grant No. K0926)National Natural Science Foundation of China (Grant Nos. 40543013, 40873003)Key Laboratory of Isotope Geology, Ministry of Land and Resources
文摘The recently discovered nitrate ore field in the Turpan-Hami Basin of western China represents an estimated resource of 2.5 billion tons, and is comparable in scale to the Atacama Desert super-scale nitrate deposit in Chile. The research on this area is rarely carried out, and the origin of the deposits remains uncertain. In this study, new methods were used to systematically analyze N and O isotopes in nitrate minerals collected from the Kumutage, Xiaocaohu, Wuzongbulak, Dawadi, Tuyugou, and Shaer ore deposits in the Turpan-Hami Basin. The data showed that the δ15NAir value ranges from 0.7‰ to 27.6‰, but mostly between 2‰ and 6‰, which was similar to atmospheric NO3-. The 18O was highly enriched with δ18OV-SMOW varying from 30.2‰ to 46.7‰. This differs from levels in deposits derived from microbial nitrogen fixation, but is similar to those in atmospheric nitrates. N and O isotopes data indicated that nitrate deposits in Turpan-Hami Basin must be the result of deposition of atmospheric nitrate particles. Although atmospheric nitrate particles are common, the nitrate deposits could form only under the condition of long-term extreme drought climate and very limited biological activity. This paper summarized the ore-forming mechanism of different types nitrate deposits based on their geological setting.
