A comparative study of the main factors controlling geohazards induced by 10 strong earthquakes in Western China since the Wenchuan earthquake in 2008

Determining the main controlling factors of earthquake-triggered geohazards is a prerequisite for studying earthquake geohazards and post-disaster emergency response.By studying these factors,the geomorphic and geological factors controlling the nature,condition,and distribution of earthquake-induced geohazards can be analyzed.Such insights facilitate earthquake disaster prediction and emergency response planning.The authors combined field investigations and spatial data analysis to examine geohazards induced by seismic events,examining ten earthquakes including the Wenchuan,Yushu,Lushan events,to elucidate the main control factors of seismic geohazard.The authors observed that seismic geohazard occurrence is usually affected by many factors,among which active nature of the seismogenic fault,seismic peak ground acceleration(PGA),topographic slope and geomorphic height differences,and distance from the fault zone and river system are the most important.Compared with strike-slip earthquakes,thrust earthquakes induce more high-altitude and high-speed remote landslides,which can cause great harm.Slopes of 0°–40°are prone to secondary seismic geohazards,which are mainly concentrated 0–6 km from the river system.Secondary geohazards are not only related to seismogenic fault but also influenced by the associated faults in the earthquake area.The maximum seismic PGA and secondary seismic geohazard number are positively correlated,and the horizontal and vertical ground motions play leading and promoting roles in secondary geohazard formation,respectively.Through the research,the spatial distribution of seismic geohazards is predicted,providing a basis for the formulation of emergency response plans following disasters.

Cross-border Urban Networks Based on Manufacturing Global Value Chain:A Study of Listed Companies in Western China

Cross-border investment is essential for western China’s globalization.Global value chain(GVC)forms cross-border investment networks between industries in western China and overseas cities.Focusing on GVC,this study uses the social network analysis method,entropy method,multi-index comprehensive evaluation method,and quadratic assignment procedure analysis method to examine the characteristics and influencing factors of the urban networks of research and development(R&D),production,and sales formed as a result of the overseas investments of listed manufacturing companies in western China.Results showed that the three types of investment networks involved multiple industry types and multiple central cities with differentiated diversity and multicentrality.The R&D urban network’s leading sub-industries were the mechanical equipment and instruments,medicine and biological products,and metal and nonmetal industries.The destination cities were mostly those home to educational and scientific research centers.The production urban network’s leading sub-industries were the mechanical equipment,instrument,and food and beverage industries.The destination cities were mostly regional central cities in developing countries.The sales urban network’s leading sub-industries were the mechanical equipment and instrument,metal and nonmetal,and petrochemical and plastics industries.The destination cities were numerous and scattered.In addition,the R&D urban network easily formed specialized clusters,core nodes easily controlled the production urban network,and individual nodes did not easily control the sales urban network.Technological and economic system advantages greatly impacted the three network types.Considering the different influencing factors,this study suggests optimizing the institutional investment environment to narrow the institutional gap,adjusting and optimizing the investment layout to expand overseas markets,and increasing R&D funds to stimulate technological progress and overseas investments in western China.

Research on the Industrial Transfer and Restructuring Path of the Energy-Intensive Manufacturing Industry in Western China

The orderly transfer of the manufacturing industry is a major action in China’s industrial restructuring.From the perspective of industrial transfer,we used the concentration ratio to depict the trend of the industrial transfer of energy-intensive manufacturing in the eastern,central,and western regions since the policy of large-scale development of western China was implemented.We measured the total factor productivity(TFP)of western China using the DEAMalmquist index method.We conducted a regression analysis to measure the effect of western China’s undertaking of the transfer of the energy-intensive manufacturing industry.The findings of this study show that during 2000–2019,eleven provinces(as well as autonomous regions and municipalities)in western China undertook the transfer of the energy-intensive manufacturing industry from the eastern and central regions to varying degrees,exhibiting significant phase features regarding the rate and scale of transfers.Further investigation also demonstrated that the transfer of energy-intensive manufacturing industries has a U-shaped enabling effect on TFP in western China with the scale effect greater than the technology effect.Therefore,it is necessary to transition from“extensive industrial transfer”at the cost of the labor force,land,and resources to“modern industrial transfer”featured by technology and efficiency improvements to contribute to industrial restructuring in western China effectively.

Eco-environment Evolution and Its Sustainable Development Strategies in Western China

Natural condition in Western China is relatively poor and regional economy level is low. The ecological environment has been seriously damaged by population growth and over-exploitation of natural resources. It is very important for coordinating the regional development and safeguarding ecological security to discuss the eco-environment evolution trend and its sustainable development strategies in Western China. Based on analyzing documents and relative research,the changes of main ecological and environmental problems in the western region,such as degradation of forest and grassland ecosystems,shrinkage of wetland,desertification,water and soil erosion,etc. were synthetically discussed. Then,according to the development trend,some countermeasures for eco-environment protection and rehabilitation and sustainable development were proposed.

Canonical Correlation Analysis of Agronomic Characters of Brassica juncea in Western China

[Objective] The study aimed at exploring the relationship among the agronomic characters of B. juncea in western China, in order to provide scientific basis for the breeding of B. juncea in western China. [Method] 39 B. juncea materials from western China were used for the canonical correlation analysis, and canonical correlations between each pair of the four ecological character （containing 18 variables） were verified, including yield characters （5 variables）, caulis characters （6 variables）, branch characters （3 variables） and pod characters （3 variables）. [Result] Yield per plant of B. juncea in western China suffered a tremendous influence from effective pod number per plant while was not significantly affected by the total pod number per plant, seed number per pod and 1 000-seed weight; the most important character related with the yield character of B. juncea in western China was caulis character, followed by the branch character and pod character; yield characters, caulis characters, branch characters and pod characters of B. juncea in western China were closely correlated. [Conclusion] In order to improve the yield characters of B. juncea in western China, caulis characters should be focused on, followed by branch characters and pod characters; rapeseed varieties with high performance in total pod number per plant and effective pod number per plant should be chosen through the perspectives of effective branch number, plant height, pod number of main inflorescence, fruit stalk number of main inflorescence and other traits, while rapeseed varieties with high performance in seed number per pod and 1 000-seed weight should be chosen through the perspectives of beak length and other traits.

Earthquake relocation and 3-dimensional crustal structure of P-wave velocity in cen-tral-western China

采用中国中西部地区(2l°～36°N，98°～112°E)193个地震台在1992～1999年间记录到的9988次地震的Pg和Sg震相走时的读数资料，用Roecker的SPHYPIT90程序，反演了该地区三维地壳P波速度结构，并用SPHREL3D90程序进行了地震的重新定位．反演结果揭示了中国中西部地区地震P波速度结构明显的横向不均匀性，这些不同深度上波速的横向变化多以该地区的活动断裂为分界线．可以看出活动断裂两侧存在明显的速度反差．通过重新定位，得到了6459次地震的震源参数，这些精确定位的地震震中明显沿该区活动断裂呈现条带状分布，其范围和尺度清晰地表示了这一地区地震活动与活动断裂的紧密关系．其中，82％重新精确定位的事件的震源深度在20km以内．这一结果与笔者用双差地震定位法得到的重新定位的震源深度分布相一致．

Spatial-temporal Dynamics and Driving Forces of Land Development Intensity in the Western China from 2000 to 2015

The change in land development intensity is an important perspective to reflect the variation in regional social and economic development and spatial differentiation.In this paper,spatial statistical analysis,Ordinary Least Squares(OLS),and Geographically weighted regression(GWR)methods are used to systematically analyse the spatial-temporal characteristics and driving forces of land development intensity for 131 spatial units in the western China from 2000 to 2015.The findings of the study are as follows:1)The land development intensity in the western China has been increasing rapidly.From 2000 to 2015,land development intensity increased by 3.4 times on average.2)The hotspot areas have shifted from central Inner Mongolia,northern Shaanxi and the Beibu Gulf of Guangxi to the Guanzhong Plain and the Chengdu-Chongqing urban agglomeration.The areas of cold spots were mainly concentrated in the Qinghai-Tibet Plateau,Yunnan,and Xinjiang.3)Investment intensity and the natural environment have always been the main drivers of land development intensity in the western China.Investment played a powerful role in promoting land development intensity,while the natural and ecological environment distinctly constrained such development.The effect of the economic factors on land development intensity in the western China has changed,which is reflected in the driving factor of construction land development shifting from economic growth in 2000 to economic structure,especially industrial structure,in 2015.

Assessing ecological vulnerability in western China based on Time-Integrated NDVI data

Arid and semi-arid areas are the most vulnerable regions to climate change. Clear understanding of the effects of climate change on ecosystems in arid and semi-arid regions and the ecosystem vulnerability is important for ecosystem management under the background of climate change. In this study, we conducted a vulnerability assessment on various ecosystems from 1982 to 2013 in western China with large areas of arid and semi-arid lands based on the Time-Integrated Normalized Difference Vegetation Index （TINDVI） data and climate data. The results indicated that grasslands were the most vulnerable ecosystem to climate change in western China, especially for those in Tibetan Plateau. Croplands in oases were not vulnerable to climate change compared to rain-fed croplands in semi-arid regions （e.g. Gansu and Inner Mongolia）, which was attributed to the well-developed drip irrigation technology in oases. Desert and Gobi ecosystems were slightly vulnerable to climate change during the past several decades. The assessment results, as revealed in this study, can provide a reference for taking appropriate actions to protect the ecosystems in western China.

Classification of Complex Reservoirs in Superimposed Basins of Western China

Many of the sedimentary basins in western China were formed through the superposition and compounding of at least two previously developed sedimentary basins and in general they can be termed as complex superimposed basins. The distinct differences between these basins and monotype basins are their discontinuous stratigraphic sedimentation, stratigraphic structure and stratigraphic stress-strain action over geological history. Based on the correlation of chronological age on structural sections, superimposed basins can be divided into five types in this study： （1） continuous sedimentation type superimposed basins, （2） middle and late stratigraphic superimposed basins, （3） early and late stratigraphic superimposed basins, （4） early and middle stratigraphic superimposed basins, and （5） long-term exposed superimposed basins. Multiple source-reservoir-caprock assemblages have developed in such basins. In addition, multi-stage hydrocarbon generation and expulsion, multiple sources, polycyclic hydrocarbon accumulation and multiple-type hydrocarbon reservoirs adjustment, reformation and destruction have occurred in these basins. The complex reservoirs that have been discovered widely in the superimposed basins to date have remarkably different geologic features from primary reservoirs, and the root causes of this are folding, denudation and the fracture effect caused by multiphase tectonic events in the superimposed basins as well as associated seepage, diffusion, spilling, oxidation, degradation and cracking. Based on their genesis characteristics, complex reservoirs are divided into five categories： （1） primary reservoirs, （2） trap adjustment type reservoirs, （3） component variant reservoirs, （4） phase conversion type reservoirs and （5） scale-reformed reservoirs.

STUDY ON INDEX SYSTEM OF ASSESSMENT OF PUBLIC DISASTER PERCEPTION IN THE WESTERN CHINA

The study on humanity response to global environment change is a new direction in the research of global change science, of which an important aspect is to study the adaptation strategies of human being to environmental changes in different regions. One reasonable and scientific adaptation strategy is based on not only scientific assessment of the impact of environmental change on society, but also correct estimation of the public perception of environmental change, whereas the research on the latter is terribly weak. This paper intends to understand the personality difference in public perception of environment in the western China primarily by establishing the assessment index system of nation environmental perception and analyzing the results of questionnaire survey in some regions of Shaanxi Province. The conclusions are as follows: 1) The state of public perception of disaster is one of the foundations of constituting and enforcing reasonable adaptation strategy to environmental change. 2) The personality differences of public perception of disaster appear as follows: female disaster perception is stronger than male;the order of disaster perception from strong to weak from the point of age characteristics is 20-30, 0-20, 40-50, 30-40, 50-60, 60 year old or over in turns; the order of disaster perception from strong to weak from the point of educational characteristics is senior high school, college, illiterate, junior high school, primary school, in turns; the order of disaster perception from strong to weak from the point of occupation characteristics is student, farmer, teacher, worker and functionary, in turns; the order of disaster perception from strong to weak from the point of habitat characteristics is city, countryside, towns, and metropolis in turns.

Epidemiological Features of Allergic Rhinitis in Four Major Cities in Western China

Allergic rhinitis（AR）,with an increasing uptrend of the prevalence in many developed and developing countries,is a global health problem that affects people of all ages and ethnic groups.However,data on the prevalence of self-reported AR in western China are rare.This study investigated the epidemiological features of self-reported AR in western China.In the cross-sectional,population-based study,a validated questionnaire survey on self-reported AR was carried out in 4 major cities in western China by multistage,stratified and cluster sampling,from January to December 2008.The total prevalence rate was 34.3%,with 32.3%（Chongqing）,34.3%（Chengdu）,37.9%（Urumqi）,30.3%（Nanning）,respectively.The prevalence presented to increase with age before 30 years old while decrease with age after 30 years old,and the highest prevalence was in 19-30 years group in Chongqing,Chengdu and Nanning which significantly showed ＂persistent and moderate-severe＂ type（P0.0001）;In Urumqi,there wasn＇t a significant increasing or decreasing trend of prevalence rate with age but with an ＂intermittent and mild＂predominance（P0.0001）.There were no distinct sexual differences in prevalence rates in the 4 cities.The morbidity was positively related to monthly average temperature and sunshine（r=0.76645,P=0.0036;r=0.67303,P=0.0165）,but negatively associated with relative humidity（r=-0.64391,P=0.0238） in Urumqi.Interestingly,the monthly morbidity was negatively associate with average temperature,sunshine and precipitation in Nanning（r=-0.81997,P=0.0011;r=-0.60787,P=0.0360;r=-0.59443,P=0.0415）.Self-reported AR is becoming common in western China with a rapid development in recent years,affecting about three persons out of ten.The climatic factors may have an indirect impact on the prevalence rate through the effects on the local allergens.

The Crustal Structure and Assembly of Terranes in the Qaidam-Qilian-Beishan Area, Western China

Abstract: Through a study of the geotransect from Golmud to Ejin Qi published recently, the tectonics of the crust beneath the area from the northern Qinghai-Tibet plateau (Qaidam and the Qilian Mountains) to the border between China and Mongolia and its structure, composition and tectonic evolution have been revealed, and abundant information about the deep structures has been provided. Based on the research into the geotransect, it is suggested that the crust in this area was formed by the assembly of the terranes in different geological stages. Following the formation of the Palaeo-Asian continent, the north part of the corridor of the transect became a part of the huge unifying continent by the end of the Early Permian. In the Mesozoic and Cenozoic, as a result of the compression mainly by the push of the Qinghai-Tibet plateau on the south, the unique crustal structure and geomorphologic features on the northern Qinghai-Tibet plateau were formed. This geotransect together with the Yadong-Golmud geotransect constitutes a long geotransect which runs across the western Chinese continent.

Characteristics of Changes in Karst Rocky Desertification in Southtern and Western China and Driving Mechanisms

The karst landform is a typical ecologically vulnerable region,and the problem of karst rocky desertification in southtern and western China has led to impoverishment and a degraded local ecological environment,which severely limits local socioeconomic development.An effective and appropriate control of karst rocky desertification in southtern and western China requires knowledge about its characteristics of variation and driving mechanisms.In this study,we chose eight regions in the southtern and western China as research areas and analysed the characteristics of the changes in karst ecosystem patterns and rocky desertification from 2000 to 2015.Based on these characteristics,we present the mechanisms that drive karst rocky desertification in the southtern and western China by utilizing the redundancy analysis(RDA)ordination method.The results show that the total area of rocky desertification in southtern and western China had been continuously decreasing from 2000 to 2015,revealing a positive development trend in rocky desertification.Rocky desertification variations were mainly affected by human activities.The reduction in farmland area improved farmland management and increased regional gross industrial product,which together with continuously rising gross domestic product of the tertiary industry caused a positive rocky desertification development.However,the local karst tourism has a certain effect on inducing slight rocky desertification.

Assessment on the Effects of Hepatitis B Prevention and Control Measures in Western China:A Comparison of Three Population-based Serosurveys

Objective Despite the remarkable progress in efforts to control disease spread,the nationwide elimination of hepatitis B in China is still hindered by the persistently high rate of hepatitis B virus(HBV)infection in Western China.This study aimed to evaluate the strategy of hepatitis B prevention and control in Western China and identify potential areas and strategies for improvement.Methods Susceptible population vaccination,health education,professional training of doctors,and other prevention and control measures have been implemented in Wuwei city since 2010.Data were obtained from three representative cross-sectional serosurveys conducted in 2010,2013,and 2015.The serum samples were subjected to enzyme-linked immunosorbent assays to detect the following seromarkers:HBV surface antigen(HBsAg),antibody against hepatitis B surface antigen(anti-HBs),and antibody against hepatitis B core antigen(anti-HBc).Estimates of variance were determined using Taylor series linearization methods.Results The three serosurveys revealed decreases in the prevalence of HBsAg(7.19% in 2010 vs.6.51% in 2013 vs.5.87% in 2015)and anti-HBc positivity(43.89%vs.32.87%vs.28.46%)and an increase in the prevalence of anti-HBs positivity(49.07%vs.53.66%vs.53.72%)over time.From 2010 to 2015,the legally reported incidence of hepatitis B in Wuwei city decreased from 686.53/100,000 to 53.72/100,000.Notably,persistently high HBsAg-positive rates(above 5.40%)were observed among subjects aged 20–69 years old in the three serosurveys;the prevalence of HBsAg was above 1% among children younger than 10 years old.Furthermore,rural subjects had higher rates of HBsAg and anti-HBc positivity than their urban counterparts(6.04%vs.4.83% and 30.26%vs.20.35%,respectively)in 2015 but had a lower rate of anti-HBs positivity(49.68 vs.55.18%).Multivariate regression analysis showed that age,urban and rural areas,and education level were the main factors affecting HBV infection.Conclusion Although vaccine-based prevention and control measures reduced the rate of HBV infection in Wuwei City over time,the hepatitis B infection rate in children younger than 10 years was still higher than the national average level.Therefore,the prevention and control of mother-to-child transmission and the management of the infected should be the focus of future prevention and control work.

Discovery of the Dagele Eclogite in East Kunlun,Western China and Its Zircon SHRIMP U-Pb Ages:New Constrains on the Central Kunlun Suture Zone

Objective Eclogites are important indicators of ancient plate boundaries or paleosuture zones. Despite their great geological significance, very few investigations have been carried out in the Kunlun region. The Central East Kunlun fault zone was believed to be an Early Paleozoic suture zone, but there has been no reliable evidence for this, though studies on ophiolite, granite, and basic granulite indicate that the Early Paleozoic orogeny occurred in the East Kunlun. This work focused on the Dagele eclogites in Central East Kunlun to provide new constraints for the Central East Kunlun suture zone.

Granitic Magmatism in Eastern Tethys Domain(Western China) and their Geodynamic Implications

Western China locates in the eastern section of the Tethys domain, granitic rocks in this region with variable formation ages and geochemistry record key information about the crust-mantle structure and thermal evolution during the convergent process of Tethys. In this study, we focus on some crucial granitic magmatism in the western Yangtze, Qinling orogen, and western Sanjiang tectonic belt, where magma sequence in the convergent orogenic belt can provide important information about the crust-mantle structure, thermal condition and melting regime that related to the evolution processes from Pre-to Neo-Tethys. At first, we show some features of Pre-Tethyan magmatism, such as Neoproterozoic magmatism(ca. 870–740 Ma) in the western margin of the Yangtze Block were induced by the assembly and breakup of the Rodinia supercontinent. The complication of voluminous Neoproterozoic igneous rocks indicated that the western Yangtze Block underwent the thermodynamic evolution from hot mantle-cold crust stage(ca. 870–850 Ma) to hot mantle and crust stage(ca. 850–740 Ma). The Neoproterozoic mantle sources beneath the western Yangtze Block were progressively metasomatized by subduction-related compositions from slab fluids(initial at ca. 870 Ma), sediment melts(initial at ca. 850 Ma), to oceanic slab melts(initial at ca. 825–820 Ma) during the persistent subduction process. Secondly, the early Paleozoic magmatism can be well related to three distinctive stages(variable interaction of mantle-crust to crustal melting to variable sources) from an Andeans-type continental margin to collision to extension in response to the evolution of ProtoTethys and final assembly of Gondwana continent. Thirdly, the Paleo-Tethys magmatism, Triassic granites in the Qinling orogenic display identical formation ages and Lu-Hf isotopic compositions with the related mafic enclaves, indicate a coeval melting event of lower continental crust and mantle lithosphere in the Triassic convergent process and a continued hot mantle and crust thermal condition through the interaction of subducted continental crust and upwelling asthenosphere. Finally, the Meso-and Neo-Tethyan magmatism: Early Cretaceous magmatism in the Tengchong Block are well responding to the subduction and closure of Bangong-Nujiang Meso-Tethys, recycled sediments metasomatized mantle by subduction since 130 Ma and subsequently upwelling asthenosphere since ca. 122 Ma that causes melting of heterogeneous continental crust until the final convergence, this process well recorded the changing thermal condition from hot mantlecold crust to hot mantle and crust;The Late Cretaceous to Early Cenozoic magmatism well recorded the processes from Neo-Tethyan ocean slab flat subduction, steep subduction, to initial collision of India-Asia, it resulted in a series of continental arc magmatism with enriched mantle to crustal materials at Late Cretaceous, increasing depleted and/or juvenile materials at the beginning of early Cenozoic, and increasing evolved crustal materials in the final stage, implying a continued hot mantle and crust condition during that time. Then we can better understand the magmatic processes and variable melting from the mantle to crust during the evolution of Tethys, from Pre-, Paleo-, Meso-, to Neo-, both they show notably intensive interaction of crust-mantle and extensive melting of the heterogeneous continent during the final closure of Tethys and convergence of blocks, and thermal perturbation by a dynamic process in the depth could be the first mechanism to control the thermal condition of mantle and crust and associated composition of magmatism.

Evaluation of boron isotopes in halite as an indicator of the salinity of Qarhan paleolake water in the eastern Qaidam Basin, western China

In this study, nineteen brine samples from the Qarhan Salt Lake(QSL) in western China were collected and analyzed for boron(B) and chlorine(Cl) concentrations, total dissolved solids(TDS), pH values and stable B isotopic compositions. The B concentrations and δ^(11) B values of brines in the QSL range from 51.6 mg/L to138.4 mg/L, and from +9.32& to +13.08&, respectively. By comparison of B concentrations and TDS of brines in QSL with evaporation paths of brackish water, we found that B enrichment of brines primarily results from strong evaporation and concentration of Qarhan lake water. Combining with comparisons of B concentrations, TDS, p H values and δ^(11) B values of brines, previously elemental ratios(K/Cl, Mg/Cl, Ca/Cl, B/Cl) and δ^(11) B values of halite from a sediment core(ISL1 A), we observe good correlations between B concentrations and TDS, TDS and pH values, pH and δ^(11) B values of brines, which demonstrate that higher B concentrations and more positive δ^(11) B values of halite indicate higher salinity of the Qarhan paleolake water as well as drier paleoclimatic conditions. Based on this interpretation of the δ^(11) B values of halite in core ISL1 A, higher salinity of the Qarhan paleolake occurred during two intervals, around 46-34 ka and26-9 ka, which are almost coincident with the upper and lower halite-dominated salt layers in core ISL1 A,drier climate phases documented from the δ^(18) O record of carbonate in core ISL1 A and the paleomoisture record in monsoonal central Asia, and a higher solar insolation at 30°N. These results demonstrate that the δ^(11) B values of halite in the arid Qaidam Basin could be regarded as a new proxy for reconstructing the salinity record of paleolake water as well as paleoclimate conditions.

Impacts of formal credit on rural household income:Evidence from deprived areas in western China

Financial support is a crucial part of China's poverty alleviation effort.Thus,it is vital to understand how formal credit impacts income growth in rural households.In 2012,2015,and 2018,a survey was conducted to obtain a panel dataset of 592 rural households from 6 poverty-stricken counties in western China,including counties in Guizhou,Yunnan,and Shaanxi provinces.We use the data to examine the effect of formal credit on rural household income and the mechanism that underlies this effect.We find that formal credit can significantly increase rural households'income in deprived areas in western China.Furthermore,formal credit promotes the reallocation of household labor from the agricultural sector to the non-agricultural sector and changes rural households'decisions about investment-consumption behavior.These are the drivers of changes in the amount and structure of household income.Further analyses show that formal credit may widen income inequality among rural households in western China's deprived areas.The individual characteristics of rural households,such as different levels of material capital,human capital,and social capital,bring about differences in the effects of formal credit on income growth.This study emphasizes that the implementation of formal credit is an essential strategy for poverty alleviation in underdeveloped areas,but policymakers should not excessively interfere with the financial market.

Effects of groundwater level on vegetation in the arid area of western China

At present,investigation about the relationship between the change of groundwater level and vegetation mostly focuses on specific watersheds,i.e.limited in river catchment scale.Understanding the change of groundwater level on vegetation in the basin or large scale,be urgently needed.To fill this gap,two typical arid areas in the west of China(Tarim Basin and Qaidam Basin)were chosen the a typical research area.The vegetation status was evaluated via normalization difference vegetation index(NDVI)from 2000 to 2016,sourced from MODN1F dataset.The data used to reflect climate change were download from CMDSC(http://data.cma.cn).Groundwater level data was collected from monitor wells.Then,the relationship of vegetation and climate change was established with univariate linear regression and correlation analysis approach.Results show that:Generally,NDVI value in the study area decreased before 2004 then increased in the research period.Severe degradation was observed in the center of the basin.The area with an NDVI value>0.5 decreased from 12%to 6%between 2000 and 2004.From 2004 to 2014,the vegetation in the study area was gradually restored.The whole coverage of Qaidam Basin was low.And the NDVI around East Taigener salt-lake degraded significantly,from 0.596 to 0.005,2014 and 2016,respectively.The fluctuation of groundwater level is the main reason for the change of surface vegetation coverage during the vegetation degradation in the basin.However,the average annual precipitation in the study area is low,which is not enough to have a significant impact on vegetation growth.The annual average precipitation showed an increase trend during the vegetation restoration in the basin,which alleviates the water shortage of vegetation growth in the region.Meanwhile,the dependence of surface vegetation on groundwater is obviously weakened with the correlation index is−0.248.The research results are of some significance to eco-environment protection in the arid area of western China.

Variations in rare earth elements with environmental factors in lake surface sediments from 17 lakes in western China

Numerous lakes in western China are excellent sites for understanding environmental change.However,what dominates rare earth element(REE) variations are still under debate in the lake environmental research.In this study,we selected 28 surface sediment samples from 17 lakes(i.e.largescale lakes,small water bodies,etc.) in the QinghaiTibet Plateau and Xinjiang area.These samples were analyzed to reveal the behavior of the REEs and major elements.These REE patterns are characterized by light rare earth element(LREE) enrichment,weak Ce anomaly(0.84-0.98,0.94 on average) and negative Eu anomaly(0.53-1.00,0.67 on average).The homogeneous REE patterns may reflect similar REE of the source lithologys.However,the REE abundances showed some significant differences.In this study,water chemistry data analyses inferred that the highly REE values appear possibly in the saltwater lake,and also related to carbonate mineral,whereas p H played a minor role in REE concentrations.In large-scale lakes(e.g.Lake Bosten and Lake Ulungur),the results showed that the relatively larger REE values are in the margins of lakes.Moreover,lower REE contents are towards the central region.Comprehensive study suggested that five major factors control the REE contents:(1) The REE tends to increase with the increase of the weathering intensity.(2) Likewise,heavy mineral(i.e.rutile,anatase,zircon,etc.) are probably primary in these sediments because they are highly enriched in the REE.(3) The contribution of Fe-Mn oxides is significant in sediments because their concentrations highly correlate with the REE.(4) The carbonate mineral(mainly calcite) played a significant role on the REE values in the lakes because the REEs are incorporated into the carbonate minerals generating the low REE concentrations.(5) Major element analysis,mineral analysis,and grain-size data analysis showed that the REE distribution is chiefly influenced by finer grain-size component of lake sediments due to the decreasing proportion of quartz and feldspar than coarser one.Moreover,the clay minerals in finer grain-size sediments can highly absorb the REE.