Dong Zhibao

VERTICAL DISTRIBUTION OF GRAIN-SIZE PARAMETERS OF DRIFTING PARTICLES DURING SAND STORMS IN THE TAKLAMAKAN DESERT, CENTRAL ASIA

The vertical distributions of grain-size parameters of drifting sand flux during sand storms in the Taklamakan Desert, Central Asia, were investigated through field observation and laboratory wind-tunnel tests. The results show that grain-size parameters of the drifting sands near the ground surface are similar to those of the source deposits. Fine and very fine sands in the flux layer near the ground surface (from zero to 20 cm high) comprise more than 85% of the samples weight, with a mean diameter of 0.09 mm. The distributions of transported particles are mainly negatively skewed, with good sorting. The creep population consists of poorly sorted coarser particles. In the saltation layer, particle size becomes finer as a power function of height from 4 to 14 cm. Sorting in the saltation layer is good and improves as a logarithmic function of height. The higher the transport layer, the more negatively skewed the particle distribution becomes as a logarithmic function of height. It becomes more leptokurt...

Abiotic Soil Crust Formation on Dunesin an Extremely Arid Environment: A 43-year Sequential Study

The spatial and temporal patterns of soil crust formation on stabilized dunes at Shapotou, northwestern China, were studied on a time sequence of 0, 18, 35, and 43 years. The spatial pattern of soil formation was estimated by measuring the thickness of accumulated sand fractions on the stabilized dune surface and by analyzing the particle size distribution of soil crust. The results showed that the materials forming the embryonic crusts did not come entirely from atmospheric dustfall, but more likely originated from the deflation process of shifting sand and were related to the characteristics of shifting sand particles. Irrespective of the age, all crusts contained a relatively large proportion of 0.01-0.05 mm particles, suggesting that the 0.01-0.05 mm particles provide a material basis and are a prerequisite to the formation of soil crusts. The formation of crust was a sorting and accumulation process of 0.01-0.05 mm particles. Simultaneously, the formation of stable soil crust apparently tended to be subjected to aggregation processes that include aggregation of inorganic particles themselves and aggregation of organic and inorganic particles. The soil crust was in a constantly alternating process of formation and disruption. The alternation period was about one year. Through this alternation, the fine soil layer beneath the crust can be continuously widened and thickened with increasing stabilization time.

Sand harm in Taklimakan Desert highway and sand control

Reputed as a wonderful achievement of the world’s highway construction history, the Taklimakan Desert highway is now facing serious sand drift encroachment problems due to its 447-km-long passage of sand sea consisting of crescent dunes, barchan chains, compound transverse dune ridges and complex megadunes. To solve some technical problems in the protection of the highway from sand drift encroachment, desert experts have been conducting the theoretical and applied studies on sand movement laws; causes, severities and time-space differentiation of sand drift damages; and control ways including mechanical, chemical and biological measures. In this paper the authors give an overall summary on the research contents and recent progress in the control of sand drift damages in China and hold that the theoretical research results and practices in the prevention of sand drift encroachment on the cross-desert highway represent a breakthrough and has an epoch-making significance. Since the construction of protective forest along the cross-desert highway requires large amount of ground water, what will be its environmental consequence and whether it can effectively halt sand drift encroachment on the highway forever are the questions to be studied urgently.Reputed as a wonderful achievement of the world’s highway construction history, the Taklimakan Desert highway is now facing serious sand drift encroachment problems due to its 447-km-long passage of sand sea consisting of crescent dunes, barchan chains, compound transverse dune ridges and complex megadunes. To solve some technical problems in the protection of the highway from sand drift encroachment, desert experts have been conducting the theoretical and applied studies on sand movement laws; causes, severities and time-space differentiation of sand drift damages; and control ways including mechanical, chemical and biological measures. In this paper the authors give an overall summary on the research contents and recent progress in the control of sand drift damages in China and hold that the theoretical research results and practices in the prevention of sand drift encroachment on the cross-desert highway represent a breakthrough and has an epoch-making significance. Since the construction of protective forest along the cross-desert highway requires large amount of ground water, what will be its environmental consequence and whether it can effectively halt sand drift encroachment on the highway forever are the questions to be studied urgently.

Land use and land cover change and its driving forces in the source region of the Yangtze River during 1990–2005

Land use and cover change (LUCC) is an important field in studying the global change or global warming. The source region of the Yangtze River locates in the northeast of Qinghai-Tibetan Plateau. The ecosystem there is extremely vulnerable and sensitive to global climate change and human activities, which have brought in significant change of eco-environment in this region in recent years. Therefore it is essential to investigate the land use and land cover change, and to explore its driving forces in the source of the Yangtze River. In this study, we used Landsat images obtained in 1990 and 2005 to establish databases of land use and cover. Then we derived LUCC information by overlaying these layers using GIS software. To examine the processes responsible for LUCC, we discussed its driving forces including climatic change, human activities, animal and insect damage. During the past 15 years, the forest, grassland experienced the most significant decrease. The forest and grassland decreased by 2509 hm2, 41847.1 hm2, respectively. However, unused land and water area showed the opposite trend, increased by 33903.8 hm2, 10480.1 hm2 respectively. The farmland and build-up land changed no obvious in past 15 years. These results suggested that the degradation of the eco-environment is obvious, showing a decrease in the forest, grassland, and an increase in the area of unused land. The major factors responsible for LUCC include increasing temperature, decreasing precipitation in summer and autumn, variation in the frozen soil environment, human activity (seasonal overgrazing) and rodent damage.

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

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

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

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 moderate-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 factors that influence the LUCC include increasing temperature, variation in the seasonal frozen soil environment, seasonal overgrazing, and pest and rodent damage.