Permafrost and taliks and their changes on the south and north banks of the Tuotuo River in the Qinghai-Tibet Plateau under the climate warming北大核心CSCD

The distribution of permafrost and taliks is very complex in the Tuotuo River Basin(TRB), which is located in interior of the Qinghai-Tibet Plateau. Characterizing the spatial distribution and the thermal stability of permafrost and taliks is of great significance to community activities and engineering construction in TRB. Based on the zonation of permafrost and talik distribution around TRB conducted in the 1980s, the soil temperature and its variation process of permafrost and taliks in the south and north banks of the Tuotuo River were analyzed by using the observation data of five boreholes(N1~N5)along the Qinghai-Tibet Railway in the north bank and five boreholes(S1~S5)on the first terrace in the south bank. The results showed that, under the climate warming, permafrost and taliks in the north banks experienced significant degradation and warming process. From 2005 to 2020, the permafrost at the N1 borehole has undergone a significant down-draw degradation process, from extremely unstable and high-temperature permafrost to thawed zone. From 2005 to 2013, the annual average ground temperature of the talik at N2 increased at a rate of 0. 3~0. 4 °C·(10a)-1. At Maqutang on the south bank, permafrost prevails from the first-class terrace to the gentle slope of the Kaixinling Mountain, with both through and non-through taliks on the first-class terrace. The spatial distribution and the thermal stability of permafrost and talik in the TRB are further promoted by analyzing the changes in temperatures at boreholes in the basin. However, to meet the requirements of mapping and engineering construction of permafrost and taliks in the TRB, it is still necessary to carry out geological investigation with multiple methods and in-depth research on development mechanism of taliks in the future. © 2022 Nanjing Forestry University. All rights reserved.     

Simulation and assessment of soil temperature and moisture in seasonally frozen soil regions of the Tibetan Plateau based on SHAW model北大核心CSCD

In recent years,more and more attention has been paid to the problem of the cryosphere changes on the Tibetan Plateau,and it has gradually become a hot issue for scholars. Known as the“water tower of Asia”,the Tibetan Plateau is the source of many major rivers in Asia. Under the combined influence of climate change and human activities,water resources on the Tibetan Plateau have undergone profound changes,especially soil water,as an important component of water resources,which plays an important role in regulating vegetation and crop growth,rainfall and runoff. However,global warming leads to the degradation of permafrost and seasonal⁃ ly frozen soil,which affects the original water cycle process and the spatial and temporal pattern of water re⁃ sources by changing the properties of soil water storage and water transport. In the Tibetan Plateau,where there are few data,it is difficult to directly study the soil water cycle process under freezing-thawing by using original data. Therefore,it is an important means to simulate the variation characteristics of soil water and temperature under freezing-thawing in seasonally frozen soil regions of the Tibetan Plateau by using coupling model of soil water and heat. Aiming at the key problem of the difference of soil temperature and moisture characteristics in typical seasonally frozen soil regions under different meteorological conditions,this paper simulated the charac⁃ teristics of soil moisture and temperature change in Maqu,Naqu（Nagqu）and Shiquanhe from 2017 to 2018 by using SHAW（Simultaneous Heat and Water）model and three soil moisture characteristic curve models. The simulation effect and variation characteristics of soil moisture and temperature under different meteorological conditions were analyzed,and the influence of soil moisture characteristic curve model on the simulation effect was studied. The results show that SHAW model can well simulate the temporal variation and vertical distribu⁃ tion of soil temperature and moisture under different meteorological conditions. The simulation effect of soil tem⁃ perature is better than that of soil moisture. The average NSE,R2 and RMSE of soil temperature are 0. 88,0. 96 and 2. 20 ℃,respectively. The mean NSE,R2 and RMSE of soil moisture are 0. 60,0. 72 and 0. 03 m3·m-3,respec⁃ tively. In terms of different meteorological conditions,the simulation effect of soil temperature in relatively dry region was significantly better than that in humid region,while the simulation effect of soil water in relatively hu⁃ mid region was significantly better than that in arid region. From different depths in soil,the simulation effect of soil temperature decreases gradually with the increase of depth,while the simulation effect of soil moisture in the middle and lower layers is better than that in the surface layer. From the view of different soil moisture character⁃ istic curve models,different soil water characteristic curve models have no significant effect on soil temperature simulation effect,but there are significant differences in soil moisture simulation effect. In addition,there are great differences and uncertainties in simulating soil temperature and moisture in different freezing-thawing stag⁃ es. With the increasing trend of climate warming,permafrost and seasonally frozen soil on the Tibetan Plateau may continue to degrade,may change the current water resources pattern,resulting in frequent extreme weather events. Therefore,from the perspective of numerical simulation,this paper verified the applicability of soil moisture and heat coupling model in soil temperature and moisture simulation under different meteorological con⁃ ditions,revealed the influence of precipitation and temperature on soil temperature and moisture simulation at different depths in seasonally frozen soil regions,and analyzed the differences in simulation effects of different soil moisture characteristic curve models. The results provide reference for the study of soil water resources vari⁃ ation under freezing-thawing conditions. © 2023 Chinese Journal of General Practitioners. All rights reserved.     

http://www.sciencedirect.com/science/article/pii/S1674987111000156

Employing the Unit Soil Carbon Amount (USCA) approach, soil carbon storage was calculated across the Northeast Plain of China based on the Multi-purpose Regional Geochemical Survey conducted in 2004 – 2006 (MRGS). The results indicated that the soil organic carbon (SOC) storage in topsoil (0 – 0.2 m), subsoil (0 – 1 m) and deep soil (0 – 1.8 m) was 768.1 Mt, 2978.4 Mt and 3729.2 Mt with densities of 3327.8 t/km2, 12,904.7 t/km2 and 16,157.5 t/km2, respectively. These values were consistent with national averages, whereas the soil carbon densities showed a clear increasing trend from the southern area of the Northeast Plain (Liaoning), to the middle (Jilin) and the northern Plain (Heilongjiang) — particularly in terms of topsoil carbon density, which increased from 2284.2, to 3436.7 and 3861.5 t/km2, respectively. In comparison to carbon data obtained from the Second National Soil Survey in 1984 – 1986 (SNSS), the topsoil SOC storage values from the MRGS were found to have decreased by 320.59 Mt (29.4%), with an average annual decline of 16.0 Mt (l.73%) over the 20 years. In the southern, middle and northern areas of the plain, soil carbon densities decreased by 1060.6 t/km2, 1646.4 t/km2 and 1300.2 t/km2, respectively, with an average value of 1389.0 t/km2 for the whole plain. These findings indicate that the decrease in soil carbon density varied according to the different ecosystems and land use types. Therefore, ratios of soil carbon density were calculated in order to study the carbon dynamic balance between ecosystems, and to further explore distribution characteristics, as well as the sequestration potential of SOC.     

Stable carbon isotopic composition of soil organic matter in the karst areas of Southwest China

This study dealt with the distribution characteristics of soil organic carbon （SOC） and the variation of stable carbon isotopic composition （δ^13C values） with depth in six soil profiles, including two soil types and three vegetation forms in the karst areas of Southwest China. The δ^13C values of plant-dominant species, leaf litter and soils were measured using the sealed-tube high-temperature combustion method. Soil organic carbon contents of the limestone soil profiles are all above 11.4 g/kg, with the highest value of 71.1 g/kg in the surface soil. However, the contents vary between 2.9 g/kg and 46.0 g/kg in three yellow soil profiles. The difference between the maximum and minimum δ^13C values of soil organic matter （SOM） changes from 2.2‰ to 2.9‰ for the three yellow soil profiles. But it changes from 0.8‰ to 1.6‰ for the limestone soil profiles. The contrast research indicated that there existed significant difference in vertical pattems of organic carbon and δ^13C values of SOM between yellow soil and limestone soil. This difference may reflect site-specific factors, such as soil type, vegetation form, soil pH value, and clay content, etc., which control the contents of different organic components comprising SOM and soil carbon turnover rates in the profiles. The vertical variation patterns of stable carbon isotope in SOM have a distinct regional character in the karst areas.     

http://www.sciencedirect.com/science/article/pii/S1674987110000113

<正>Against the current background of global climate change,the study of variations in the soil carbon pool and its controlling factors may aid in the evaluation of soil's role in the mitigation or enhancement of greenhouse gas.This paper studies spatial and temporal variation in the soil carbon pool and their controlling factors in the southern Song-nen Plain in Heilongjiang Province,using soil data collected over two distinct periods by the Multi-purpose Regional Geochemical Survey in 2005—2007, and another soil survey conducted in 1982—1990.The study area is a carbon source of 1479 t/km~2 and in the past 20 years,from the 1980s until 2005.the practical carbon emission from the soil was 0.12 Gt.Temperature,which has been found to be linearly correlated to soil organic carbon,is the dominant climatologic factor controlling soil organic carbon contents.Our study shows that in the relevant area and time period the potential loss of soil organic carbon caused by rising temperatures was 0.10 Gt,the potential soil carbon emission resulting from land-use change was 0.09 Gt,and the combined potential loss of soil carbon(0.19 Gt) caused by warming and land-use change is comparable to that of fossil fuel combustion(0.21 Gt).Due to the time delay in soil carbon pool variation,there is still 0.07 Gt in the potential emission caused by warming and land-use change that will be gradually released in the future.     

Research status and prospect of tensile strength of frozen soil北大核心CSCD

A comprehensive grasp of the research status of tensile strength of frozen soil is the basis for further research. Firstly,the typical methods that can be used to test the tensile strength of frozen soil are introduced,and the test conditions,sample forms and stress mechanism of different test methods are described in detail. The advantages and disadvantages of typical tensile strength test methods are compared and listed. Secondly,the research work and shortcomings based on different test methods are summarized. Then,the latest research progress of the influence of temperature,water content,loading（deformation）rate,soil quality and sample size on the change law of frozen soil tensile strength is comprehensively analyzed. Finally,it is proposed to develop and improve the research method and system of frozen soil tensile strength,and increase the testing research of warm frozen soil tensile strength,so as to obtain the prospect of more accurately simulating the tensile failure behavior of frozen soil. It is pointed out that the internal cause of the formation of the tensile strength and the tensile failure mechanism of frozen soil should be thoroughly revealed by combining the research methods of microstructure and digital image technology of frozen soil. Based on the multi-factor test,a more perfect prediction method of frozen soil tensile strength is explored. Meanwhile,expand the in-situ test research on the tensile strength of frozen soil,and strengthen the parallel research ideas of indoor and outdoor double tracks. Through the analysis of the research status and development trend at home and abroad,it provides reference and guidance for the experimental study of frozen soil tensile strength,the improvement of theoretical model of frost heave,geotechnical engineering design in cold regions and artificial freezing reinforcement engineering. © 2022 Science Press (China).     

The solution of the double-sphere model and experimental research of the longterm shear strength of frozen sand based on spherical template indenter test北大核心CSCD

The distribution of frozen soil in our country is very broad, and the area of permafrost alone accounts for 22. 4% of the total land area. As a special kind of soil, frozen soil has many properties that thawing soil does not have due to the influence of ice cement in the soil. Among the many properties of frozen soil, the deformation and strength of frozen soil are the basic problems affecting engineering construction in frozen soil areas. The spherical template indenter test is widely used in the test of the mechanical properties of frozen soil because of its simple test process and relatively accurate test results. Compared with the conventional triaxial test or direct shear test, the test process of the spherical template indenter test is simple and easy to implement, the test period is short, and the sample preparation requirements are low. The advantage of effective cohesion is more significant. Therefore, based on the spherical template indenter test of the frozen soil, this paper estimates the strength and mechanical index of the soil through the indentation depth of the spherical template indenter test, and establishes the relationship between the force of the sample and the indentation depth of the indenter test. The specific test method is as follows:take the water-saturated frozen sandy soil made of different particle size groups(the moisture content of the sample is affected by the particle size in the saturated state)as the research object, study the variation law of the depth of the frozen soil sample pressed into the soil by the spherical indenter with time under the conditions of different fixed loads. By comparing and referring to the frozen sands of each particle size group, the long-term equivalent cohesion of the frozen sands of different particle size groups is summarized. The change law of force(long-term shear strength)with time, and the research method of elastic mechanics to solve space problems, summed up the mutual conversion between the depth St of spherical template indenters pressed into frozen sand samples under different fixed load test conditions relation. The research results show that the long-term shear strength of frozen sand based on the spherical mold test is positively correlated with its particle size. At the same time, since the ice content of frozen soil samples is proportional to its particle size, the long-term shear strength of frozen sand is also proportional to the test. The ice content of the sample increases year-on-year;the long-term shear strength of the frozen sand is related to the maximum contact pressure on the contact surface between the frozen soil and the indenter during the test, which can be expressed as Ct = γq0. The size of the relationship coefficient γ is inversely proportional to the diameter of the spherical indenter. In this paper, the spherical indenter is selected as 22 mm, and γ=3. 82×10-3. By establishing the relationship between the maximum contact pressure q0 and the long-term shear strength Ct When the maximum contact pressure q0 is the same under different fixed loads, the long-term shear strength Ct is also the same. According to this, the depth curve and the freezing depth of the frozen sand pressed into the soil by the spherical indenter over time under different fixed loads can be converted. Long-term shear strength curve of frozen sandy soil with time. It has been verified by experiments that the conversion curve of the depth of the indenter pressed into the soil with time under a fixed load of 7. 0 kg is highly consistent with the measured curve of the depth of the indenter pressed into the soil with time under a fixed load of 5. 1 kg and 7. 0 kg. © 2022 Nanjing Forestry University. All rights reserved.     

Transformation of organic carbon and its potential impact on lead weathering in firing range soils

Lead （Pb） is normally considered as a trace element in soils and sediments for geochemical study. However, the concentration of Pb in firing range soils is generally so high that it should be considered as a major element during the evaluation of the soil geochemical properties. Soil organic matter （SOM） has been reported as one of the major factors to expedite the corrosion of metallic lead （Pb） in acidic and organic-rich soils. The main impacts of SOM on the fate and transport of Pb in firing range soils lie in the following two aspects; （1） the complexation of organic matter with Pb, which has received lots of attention, and; （2） changes in soil redox potential due to the transformation of SOM and its subsequent impact on Pb speciation, which has rarely been investigated. Soils from 6 different firing ranges are selected for this study. These samples have been stored under a closed condition for more than 3 years. The soil moisture contents were well-retained, as all the samples were kept in closed plastic buckets. The analytical data showed that the summation of the soil total organic carbon content （TOC） and inorganic carbon contents （TIC） were consistent with soil total carbon contents （TC） measured in previous years, although the TOC and TIC contents have changed respectively after years of storage. In general, it is observed that the soil TOC decreased against an increase of TIC. The mass balance on such a transformation suggested a major conversion of organic carbon （Corg） to inorganic carbon （CO3^2-） in the stored soils.     

Estimating contributions of sources of soil CO2 at the shallower layer in a Japanese larch forest area

Soils contain about twice the amount of carbon presented in the atmosphere, so a small change in the soil carbon will influence atmospheric chemistry and heat balance. The soil carbon ultimately exchanged with the atmospheric CO2 as soil CO2, which mainly exists at the depth of 0-20 cm. The transport of soil CO2 is affected by the sources of soil CO2. Thus, separation of the contributions of sources of soil CO2 is a fundamental need to understand and predict implications of environmental change on soil carbon cycling and sequestration. It is a complicated task, so that a number of different methodological approaches such as component integration, root removal, and gap analyses have been developed. However, these methods could not avoid changing soil characteristics such as air-filled porosity, soil temperature and soil water contents. Consequently, fractional contributions of respiration of living root and decomposition of soil organic matter to the total soil CO2 cannot be estimated correctly. In this study, based on mass balance theory of both concentrations and δ^13C of soil CO2, a trenching method with a stable-isotope technique was used to determine both soil CO2 sources at the depth of 3-13 cm in a Japanese larch forest area during 30 May to 7 October 2005 and fractional contributions of these sources. Experimental results showed that the amount of atmospheric CO2 invaded the soil air was not significantly variable while its percent rate in the total soil CO2 had significantly temporal variations with the lower values between 5 August and 1 September. The litter-layer decomposition was very small. The soil CO2 derived from the respiration of living root and the decomposition of soil organic matter showed significantly temporal variations with increase from 30 May to 5 Aug. and decrease from 1 September to 7 October, 2005; and it accounted for 82%-98% of the total soil CO2 in which the respiration of living root was in the range from 32% to 62%.     

青藏铁路多年冻土工程地质勘察

The effective and assured measures in criteria of formulation, procedures, techniques and methods for geological prospecting of Qinghai-Xizang Railway have been made. The permafrost engineering geological investigation indicate the talik and those sections with annual average ground temperature higher than 1 ℃ takes up 68.8% of total amount; the high ice content permafrost also account for 50% of real permafrost section. The distribution of permafrost characteristics is obviously influenced by altitude and latitude. The prospecting also shows the distribution of permafrost characteristics is rather complicated. Based on two predications of air temperature-rising tendency, by calculating climate model of permafrost thermal status, and comparing and analyzing geological distribution of Qinghai-Xizang Railway, the tendency of permafrost recession range has been predicated.     

内蒙古中北部土壤碳库构成及其影响因素

采用网格采样法荻取内蒙古中北部半干旱区土壤样品共527件,分析其碳库构成特征及其影响因素,并初步评估了未来气候变化背景下的碳库变化趋势。结果表明,研究区土壤碳库仍以有机碳为主,不同土壤类型中有机碳占总碳61％～97％,其中沼泽土有机碳密度最高,风沙土最低,盐土无机碳密度最高,暗棕壤最低;在空间分布上,土壤碳受气温和降水...     

东北平原土壤有机碳分布与变化趋势研究

在多目标区域地球化学调查基础上,采用"单位土壤碳量"方法计算土壤碳储量,显示东北平原(约23万km2)土壤有机碳总体分布:表层(0～0.2m)土壤有机碳为768.07Mt,碳密度为3327.8t/km2;中层(0～1.0m)为2978.41Mt,碳密度为12904.7t/km2;深层(0～1.8m)为3729.16Mt,碳密度为16157.5t/km2。东北平原土壤碳密度处于全国平均水平。土壤碳密度由东北平原南部(辽宁)、中部(吉林)到北部(黑龙江)从暖温带、温带向寒温带过渡呈现增高趋势,其中表层土壤碳密度由2284.2、3436.7增加到3861.5t/km2。与第二次土壤普查比较,20年期间东北平原表层土壤有机碳总体减少320.59Mt,占29.4%,年均减少16.03Mt,年均递减率1.73%。表层土壤碳密度由南向北依次减少1060.6、1646.4、1300.2t/km2,平均减少1389.0t/km2。不同生态系统和土地利用类型土壤有机碳减少程度不同。采用土壤碳密度比方法研究生态系统之间土壤碳密度动态平衡关系,研究土壤有机碳储量及其变化趋势,为进一步探讨土壤有机碳分布分配特征及土壤固碳潜力等提供科学依据。     

气候变暖对多年冻土区土壤有机碳库的影响

多年冻土区存储了大量土壤有机碳。气候变暖、 多年冻土退化导致其长期封存的有机碳逐渐或快速释放, 进入大气圈或水系统, 改变原有多年冻土区碳循环, 并可能显著加速气候变暖。通过综述气候变暖对多年冻土区碳库的影响研究进展, 主要包括多年冻土碳库储量、 降解机理及变化预测, 研究表明： 北半球多年冻土区的碳储量巨大, 但不确定性很高, 尤其是海底多年冻土和水合物碳库储量的评估; 多年冻土碳库对气候变暖的响应速度受土壤水热特性、 土壤有机质C/N比、 有机碳含量和微生物群落特征等多种环境因素的控制或影响; 目前, 关于北半球多年冻土碳库对气候变暖响应模拟结果说明, 多年冻土退化短期内不会导致经济和生产方面的灾难性后果。但是, 无论是针对多年冻土碳库评估, 还是多年冻土有机碳库对气候变暖的响应模拟研究结果, 都有较大的不确定性。未来多年冻土碳库变化的模拟和预测研究应更多考虑多年冻土快速退化和多年冻土区水合物分解, 如中小尺度热喀斯特的生态环境和碳的源汇效应。准确的多年冻土区有机碳排放模拟可为未来多年冻土碳与气候反馈的预估提供重要支持。     

青藏高原多年冻土和季节性冻土区土壤水分变化及其与降水的关系

使用地面观测数据对欧洲空间局(ESA)发布的气候变化倡议(CCI)土壤水分产品进行精度校准,结合青藏高原及其周边降水气象站数据,分析土壤水分动态变化及其与降水的关系.结果表明:(1)校正后的CCI主被动组合产品所反演的青藏高原土壤水分获得了更高的精度,且显示1986～2016年暖季土壤水分在多年冻土区的逐年变化更为稳定...     

大兴安岭秋季冻结期土壤水热变化对多年冻土泥炭地可溶性有机碳的影响北大核心CSCD

土壤温度和含水量是影响可溶性有机碳(DOC)变化的重要因素。然而,多年冻土泥炭地土壤DOC变化对秋季冻结期土壤水热变化的响应尚不明确。本研究选取大兴安岭3种多年冻土泥炭地[小叶章泥炭地(CP)、兴安落叶松-泥炭藓泥炭地(LP)、白毛羊胡子苔草泥炭地(EP)]作为研究对象,开展野外原位试验探究秋季冻结期土壤水热变化对多年冻土泥炭地土壤DOC变化的影响。结果表明:秋季冻结期土壤DOC含量表现为EP>CP>LP,平均含量分别为83.99、45.75和43.13mg·L^(-1)。在秋季冻结前期3种类型多年冻土泥炭地土壤DOC含量均呈波动下降趋势,中、后期CP,LP土壤DOC变化较平缓。在秋季冻结前期,CP整体土壤DOC含量随浅层土壤温度的降低而减少;在后期CP浅层和整体土壤DOC含量随浅层土壤含水量的增加而增加。在秋季冻结中期,LP浅层土壤温度升高和含水量的减少,降低了土壤DOC含量;LP整体土壤DOC的变化随着浅层温度的升高逐渐降低。在秋季冻结后期,EP深层和整体土壤DOC含量随深层含水量增加而增加。在整个秋季冻结期,LP浅层土壤DOC主要受地表温度驱动,深层土壤DOC则主要受深层含水量的影响;整体土壤DOC则受地表温度影响较大。研究表明秋季冻结期多年冻土泥炭地土壤水热变化驱动土壤DOC含量的变化。研究结果为多年冻土区碳循环和“双碳”背景下的碳排放研究提供基础科学数据。     

东北多年冻土地区地基承载力对气候变化敏感性分析

近年来,中国东北多年冻土地区正处于显著的增温过程中。由此导致多年冻土逐渐退化,并严重影响到构筑物的稳定性。以0.05 ℃的年平均气温上升率为背景,采用带有相变的传热学有限元方法,对中国东北多年冻土地区不同初始气温条件和不同含冰量类型冻土的地基温度状况以及季节活动层厚度变化进行了模拟;利用温度场有限元数值试验结果和已有承载力试验数据分析了不同类型冻土地基的力学性质对气温变化敏感性,评估了气温变化对各类冻土地基承载力的影响。气候变化对多年冻土地区构筑物稳定性影响程度取决于两个环节：其一,冻土地基温度状况对气候变化的响应;其二,冻土地基力学性质对地基温度变化的敏感性。研究结果表明,冻土地基含冰量和温度状态对其承载力随气温变化的敏感性具有显著的影响。含土冰层地基承载力对气温变化最为敏感,气温变化对高温冻土地区浅层地基承载力以及桩-土冻结强度影响较大;而深基础桩端冻土地基承载力受气候变化影响相对较小。     

基于地理加权回归的青藏高原季节冻土区土壤有机碳空间分布研究

青藏高原土壤有机碳储量（soil organic carbon stocks, SOCS）对于区域生态环境演替具有重要作用, 但是其空间分布数据还比较缺乏, 特别是季节冻土区的数据较少。基于378个土壤剖面数据, 结合与土壤有机碳（soil organic carbon, SOC）相关的地形、 气候以及植被等环境因子, 使用地理加权回归（geographically weighted regression, GWR）模型模拟了青藏高原季节冻土区0 ~ 30 cm、 0 ~ 50 cm、 0 ~ 100 cm和0 ~ 200 cm深度的SOC总量和空间分布。结果表明： 青藏高原季节冻土区SOCS自东南向西北递减, 表层0 ~ 200 cm的SOC总量约15.37 Pg; 季节冻土区不同植被类型SOC从大到小依次为森林、 灌丛、 高寒草甸、 高寒草原和高寒荒漠; 各土壤类型中棕壤、 黑钙土和泥炭土的SOC最大, 而棕钙土、 棕漠土、 灰棕漠土、 风沙土、 石质土、 盐土、 冷钙土、 寒漠土以及冷漠土的SOC最小。研究结果给出了青藏高原季节冻土区SOC的总量、 空间分布及规律, 可为相关地球模式的发展提供基础数据。     

冻土机械切削破碎机理的研究进展

冻土开挖困难、破碎效率低是高寒地区工程建设、地基施工等面临的技术难题。冻土机械切削破碎是冻土开挖的主要方法,其机理研究是提高冻土破碎效率的前提和基础。首先总结了温度、含水率、围压等对冻土复杂力学特性的影响,进而调研分析了冻土机械切削破碎的典型切削力学模型,发现冻土切削机械破碎模式不仅与冻土力学特性密切相关,也与切削参数和刀具结构直接相关,冻土切削过程中存在着最优的切削前角（30°~60°）,且深切削和浅切削时冻土内部受力方式存在差异也会导致破坏形式的不同;温度、含水率、围压所造成的冻土力学性能变化会直接导致冻土破坏过程和切削破碎机理的改变,冻土强度随着温度降低表现出先升高然后保持稳定的特性,随着含水率升高呈现出先升高后降低的趋势,冻土破碎存在脆性、塑脆过渡及塑性等不同破坏形式。通过系统总结冻土切削破碎机理研究进展,进一步明确了冻土力学性质主要影响因素、变化特点及其切削破坏损伤特征,为冻土机械切削破碎的切削参数和切削具结构优化提供了设计依据。     

长江流域典型区域土壤碳库变化及其影响因素

土壤碳库是全球碳库的重要组成部分,其微小幅度的碳源汇变化就可以较显著的影响大气碳库。本文选择长江流域多目标区域地球化学调查覆盖区,利用多目标区域地球化学调查数据和第二次全国土壤普查数据计算了土壤碳密度及储量,对比了20年来土壤碳库变化趋势,并分析土壤碳源汇的影响因素。结果表明：从20世纪80年代到2000年,研究区大部分区域土壤有机碳密度明显增加,尤其成都平原西部的龙门山地区、雅安南侧地区和贵阳周边地区,其增加量约为312.38 TgC。导致研究区土壤碳库增加的主要因素是,林地草地等植被恢复性生长、农业耕作水平提高,土地利用变化对研究区土壤碳库变化的影响较小,土壤侵蚀因素对研究区的水田基本没有影响,但对旱地影响比较明显,而气候变化对该区域土壤碳库没有明显影响。     

Influence of fluctuations of frozen soil in North Asia on groundwater and assessment on resources

The distribution and fluctuations of frozen soil in North Asia are closely related to the groundwater recharge-runoff-discharge in this area, and play a role in controlling the hydrogeological conditions of North Asia. By using NOAA satellite remote sensing interpretation data of frozen soil distribution in 2009 in conjunction with local hydrogeological conditions, the frozen soil area of North Asia according to the different characteristics of its impact on the groundwater was divided into three great hydrogeologic units, i.e. continuous permafrost, island permafrost, and high-altitude permafrost. By water balance method, the amount of natural renewable resources in North Asia was calculated as 1 007.45×109 m3/a, with mineable resource of 705.21×109 m3/a, which indicates that the reduction of frozen soil range due to climate change in recent years gives rise to the richer groundwater resources and greater potential of mineable resources in North Asia, and frozen soil melting poses a relatively significant influence on the groundwater environment and ecological environment in North Asia