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Pattern analysis of a linear dune field on the northern margin of Qarhan Salt Lake,northwestern China

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Journal of Arid Land 2016年第5期8卷 670-680页

作者： LI Jiyan DONG Zhibao QIAN Guangqiang ZHANG Zhengcai luo wanyin LU Junfeng WANG Meng Taiyuan Normal University Jinzhong 030619 China Key Laboratory of Desert and Desertification Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China

In terms of formation mechanisms of linear dunes,there are open arguments for their widespread distribution and multi-morphological *** order to clarify the formation mechanism of linear dunes of Qarhan Salt Lake,we used pattern analysis method to analyze the statistical characteristics and spatial variation of their pattern *** at the west-northwest margin,the pattern parameters showed regular spatial variation from the up-middle part towards the downwind end of the dune *** on the cumulative probability plots for inter-crest spacing and crest length,we divided the linear dunes into three groups,which corresponding to the three evolution stages of these *** first group comprises erosional relics,with shorter crests,smaller inter-crest spacing and more random dune *** second group comprises dunes whose sand supply is just sufficient to maintain stability and these dunes are approaching the net erosion *** crest length and inter-crest spacing of these dunes are much larger than those of the first group,and dune orientation is closer to the resultant drift direction （RDD） .The last group comprises linear dunes that are still undergoing vertical accretion and longitudinal elongation,which follows the RDD of the modern wind *** presence of regular spatial variation of pattern parameters and a similar geometry with the vegetated linear dunes suggest that deposition and erosion coexist in the development and evolution of linear dunes of Qarhan Salt Lake,*** predominates at the downwind end of linear dunes in the vertical accretion and longitudinal elongation stage,whereas erosion mainly occurs at the upwind end of linear dunes in the degradation ***,the formation mechanism of linear dunes in Qarhan Salt Lake can be reasonably explained by the combination of depositional and erosional theories.

关键词： pattern analysis self-organization linear dunes dune field Qarhan Salt Lake Qaidam Basin

Land use and land cover change and its driving forces in Maqu County, China in the past 25 years

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Research in Cold and Arid Regions 2016年第5期8卷 432-440页

作者： JunFeng Lu ZhiBao Dong GuangYin Hu WenJin Li wanyin luo MingLiang Tan Key Laboratory of Desert and Desertification Northwest Institute of Eco-Environment and Resources Chinese Academy of Sciences State Key Laboratory of Grassland Agroecosystems School of Life Sciences Lanzhou University

Maqu County is located in the northeast Qinghai-Tibetan Plateau, and it is the main watershed for the Yellow River. The ecosystem there is extremely vulnerable and sensitive to climate change and human activities, which have caused significant deterioration of the eco-environment in this region. In order to restore the ecological environment, a government project to restore the grazing areas to grassland was implemented in Maqu County in early 2004. This study evaluates the effects of that restoration project on land use and land cover change （LUCC）, and explores the driving forces of LUCC in Maqu County. In the study we used Landsat images obtained in 1989, 2004, 2009, and 2014 to establish databases of land use and land cover. Then we derived LUCC information by overlaying these layers using GIS software. Finally, we analyzed the main forces responsible for LUCC. The results showed that forests, high-coverage grasslands, and marshes experienced the most significant decreases during 1989–2004, by 882.8 ha, 35,250.4 ha, and 2,753.4 ha, respectively. However, moderate- and low-coverage grasslands and sand lands showed the opposite trend, increasing by 12,529.7 ha, 25,491.0 ha, and 577.5 ha, respectively. LUCC in 2004–2009 showed that ecological degradation slowed compared with 1989？2004. During 2009–2014, high- and moderate-coverage grasslands increased obviously, but low-coverage grasslands, marshes, unused lands, sand lands, and water areas showed the opposite trend. These results suggested that the degradation of the eco-environment was obvious before 2009, showing a decrease in the forests, grasslands, and water areas, and an increase in unused lands. The ecological degradation was reversed after 2009, as was mainly evidenced by increases in high- and mod-erate-coverage grasslands, and the shrinkage rate of marshes decreased obviously. These results showed that the project of restoring grazing lands to grassland had a positive effect on the LUCC. Other major fac

关键词： LUCC driving forces Maqu County source region of the Yellow River

An investigation of the effects of dust storms on rat lung using HRCT and blood gas analysis

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Research in Cold and Arid Regions 2016年第4期8卷 319-324页

作者： FengFeng Lei wanyin luo ZhiBao Dong YingZhu Sang LiZhu luo Gang Huang Hua Liu QiZhang Chen Department of Respiration the People's Hospital of Gansu Province Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Department of Radiation Imaging the People's Hospital of Gansu Province

The increasing intensity and frequency of sand-dust storms in China has led to greater prominence of associated environmentaland health issues. Many studies have focused on the health effects of air particulate contaminants, but fewformal investigations have studied the effects of sand-dust storms on human and animal health. The aim of this study wasto investigate the effects of dust storms on rat lung by using high resolution computed tomography （HRCT） and blood gasanalysis through a wind tunnel simulating. We found that the rat lung damage effects can be detected by the HRCT imagingafter exposure to sand-dust storm environments, but had no obvious result through blood gas analysis. Exposure durationspositively correlated with the damage degree to lung tissue. These will provide some evidence for clinical diagnosis ofnon-occupational pneumoconiosis.

关键词： dust storm lung blood gas analysis HRCT wind tunnel simulation

Measuring the velocity of sand particles in an air/particle two-phase flow:A comparison of several commonly used methods

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Research in Cold and Arid Regions 2010年第3期2卷 185-197页

作者： Zhibao Dong GuangQiang Qian wanyin luo HongTaoWang Key Laboratory of Desert and Desertification CoM and Arid Regions Environmental and Engineering Research Institute Chinese Aeademy of Sciences Lanzhou Gansu 730000 China

The velocity of blown sand particles is an important parameter in aeolian movement （a special case of gas particle two-phase flow） and has ever been a topic of interest. At present, several techniques have been applied in measuring velocity of the blown sand particles. This paper reviews the measurement results of several commonly used methods： photoelectric cell method, high-speed photographic method, Particle Dynamics Analyzer （PDA） method and Particle Image Velocimetry （PIV） method. Photoelectric cell method, high-speed photograph method and PDA method are useful in studying the velocity distribution of particles. PIV is a whole-flow-field technique and a useful tool to study the average velocity field in a target area. These methods got some similar results but considerable differences also exist. They have come to similar conclusions on the velocity distributions at a single height but direct measurement results with respect to the velocity distribution very close to the surface are still scarce except some PDA results. The magnitude of measured mean particle velocity differs greatly. The relationship obtained by different methods between mean particle velocity and wind velocity, particle size and possibly other influencing factors also differs considerably. Although several authors have proposed similar power functions to describe the variation with height of the mean particle velocity, the predicted results have wide differences. Each technique is based on some unique principles, and has its advantages and disad- vantages. To make full use of different techniques, a lot of work needs be done to validate them. Developing a reliable technique to measure the velocity of blown particles is still a necessary task in aeolian research.

关键词： aeolian transport velocity of particles measurement techniques

Spatial trends of dustfall over northern China in the spring and their influencing factors

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Research in Cold and Arid Regions 2010年第6期2卷 529-537页

作者： JinChang Li ZhiBao Dong GuangQiang Qian wanyin luo Institute of Loess Plateau Shanxi UniversityTaiyuanShanxi 030006China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of ScienceLanzhouGansu 730000China

The spatial trends of dustfall of different sizes over northern China during April and May 2001,and March 2002,and their influencing factors,were *** divided the dustfall into seven grades based on particle *** dustfall and dustfall for each grade were highest in desert regions then in regions undergoing desertification,and the total dustfall,dustfall 250 μm were higher in western agricultural regions closer to desert areas than in eastern agricultural *** spatial trends in dustfall <300 μm in diameter were most strongly correlated with dust events,and the content of coarse particles increased with increasing severity of dust *** the spatial trend for dust events appears to be controlled by geomorphic conditions,vegetation coverage,soil moisture,and the distance from dust source,dustfall <300 μm in diameter appears to have the same controlling factors as dust events,but the control decreases with increasing particle ***,the driving force for dust emissions,also influenced the spatial trends in dustfall <200 μm in diameter,and especially for dustfall 50 to 100 μm in *** dustfall <300 μm in diameter and precipitation were not strongly spatially correlated,there is some evidence that high precipitation decreased deposition by restraining blowing *** coarser the dustfall,the weaker the correlation with wind speed;however,transport of larger particles still occurs,and further research will be required to test the possibility that this dust is entrained mainly by the small-scale dust devils that are commonly observed in the study area.

关键词： dustfall desertification spatial trends dust events geomorphic conditions Northern China

Effects of geomorphic conditions, wind speed, and precipitation on dustfall over northern China

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Research in Cold and Arid Regions 2010年第4期2卷 354-363页

We investigated how dustfall flux (DF) and dust particle size (DPS) were affected by geomorphic conditions, wind speed, and precipitation using data from 27 sites in northern China. The sites with the greatest DF and greatest median diameter of dustfall (MDD) were primarily in desert regions and had extensive mobile sands. DF and MDD were lowest in agricultural regions, which had low levels of coarse particles because of human land use and high vegetation coverage that restrained blowing sand. DF values were higher and MDD values were lower in the western agricultural region than in the eastern agricultural region because the former is closer to desert regions and contains more fine dust that has traveled far. In regions with extensive desertified lands, DF values were lower than those in desert regions, and MDD values were greater than in agricultural regions, possibly due to coarsening of soil texture by desertification processes combined with higher vegetation coverage and soil moisture than in desert regions, thereby restraining blowing sand. Although high DF and MDD always coincided spatially with strong winds and low precipitation, the strong winds and low precipitation did not always mean high DF and MDD. High DF also coincided temporally with periods of low precipitation, but low precipitation did not always mean high DF. Thus, although the spatial trends in DF and DPS were controlled mostly by geomorphic conditions, and monthly trends in DF were controlled mainly by wind speed, weak wind and high precipitation can restrain the blowing sand at certain times and locations. Seasonal changes in DPS may be controlled simultaneously by geomorphic conditions, meteorological factors, and distance from source areas, not solely by the winter monsoon.

关键词： dustfall flux grain size geomorphic conditions wind speed northern China

Threshold wind velocity in the lee of two-dimensional transverse dunes

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Research in Cold and Arid Regions 2010年第1期2卷 1-6页

作者： ZhiBao Dong HongTao Wang GuangQiang Qian wanyin luo Key Laboratory of Desert and Desertification Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou Gansu 730000 China

Secondary flow plays an important role in the development of dunes. To investigate this phenomenon, we simulated models of transverse dunes with different stoss slopes in a wind tunnel. We measured the threshold wind velocity at different locations in the lee of the dunes, and observed the corresponding particle movement characteristics under threshold conditions to assess the sedi-mentological significance of secondary airflow. Threshold wind velocity changed with both horizontal distance and stoss slope. Its variation with horizontal distance is characterized by a region in which a rapid reduction occurs, a region with a minimum value, and a region with high value. We confirmed the presence of reversal cells, irrespective of the stoss slope. Neither the variation in threshold wind velocity nor the variation in reattachment distance as a function of stoss slope followed a monotonic function. The 15° stoss slope had the greatest threshold wind velocity and reattachment distance.

关键词： Aeolian geomoephology dune dynamics transverse dunes

Evaluating the optimal porosity of fences for reducing wind erosion

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Research in Cold and Arid Regions 2011年第1期3卷 1-12页

作者： ZhiBao Dong wanyin luo GuangQiang Qian HongTao Wang Key Laboratory of Desert and Desertification Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou Gansu 730000 China

Porosity is the most important parameter determining the shelter efficiency of fences. Wind measurements were made around fence models with different porosities in a wind tunnel. The optimal fence porosity is evaluated by means of Gandemer＇s method that combines the effects of wind reduction and turbulence fields on the shelter efficiency for abating wind erosion. Defining the optimal porosity must take into account of its own purposes, required shelter degree and area to be sheltered. Turbulence has profound impacts on the shelter efficiency of high degree. Two concepts： absolute optimal porosity and practical optimal porosity concerning optimal porosity are proposed. Choosing the practical optimal porosity means reducing cost without significant expense of shelter efficiency. According to the evaluation in present study, the absolute optimal porosity for providing high degree of shelter to abate wind erosion is 0.20 while the practical optimal porosity is around 0.40. Ifa less shelter degree but over wider area is required, the absolute optimal porosity ranges from 0.05 to 0.10 and the practical optimal porosity is 0.10. For any degree of shelter for abating wind erosion effectively, the fence porosity must be less than or equal 0.40.

关键词： windbreak shelter efficiency optimal design

Aeolian dust transportation and deposition by near-surface winds in arid and semiarid China

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Research in Cold and Arid Regions 2010年第2期2卷 137-142页

Dustfall collections were carried out in April and May 2001 and in March 2002 at six sites in northern *** results showed that the total deposition of dust fractions <250 μm in diameter and the deposition of Fe both decreased exponentially with increasing distances from the source areas,and that the half-attenuation distance (HAD) for dust deposition was about 229 km in this *** HAD was closely related to the grain-size distribution of the dust,and the 15 to 20 μm fractions had the longest ***,the fractions <15 μm in diameter can be easily adsorbed to coarse particles and deposited after only short distances,and the HAD for the fractions 15 to 100 μm in diameter showed a power relationship with the grain-size *** HAD for Fe deposition was 233 km,which was a little longer than that of total dust deposition,which suggests that the Fe content is higher in fine particles than in coarse particles,as previous studies have *** addition,our analysis showed that under the control of current climatic conditions,the coarse fractions in dust derived from northwestern China cannot be transported over long distances,instead,it is transported primarily by near-surface winds (<3 km above the ground).The Fe in aeolian dust generated from arid and semiarid regions of China and deposited in the North Pacific region is usually transported by the upper westerlies.

关键词： dust deposition half-attenuation distance near-surface wind arid and semiarid regions of China