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2021, 13 (3) Online: 30 June 2021 Previous issue
  • A concise overview on historical black carbon in ice cores and remote lake sediments in the northern hemisphere
  • Poonam Thapa,JianZhong Xu,Bigyan Neupane
  • DOI: 10.3724/SP.J.1226.2021.20055.
  • 2021, Vol.13 (3): 179–194 Abstract ( 352) HTML ( 82) PDF (5910 KB) ( 133 )
  • Black Carbon (BC), as a driver of environmental change, could significantly impact the snow by accelerating melting and decreasing albedo. Systematic documentation of BC studies is crucial for a better understanding of its spatial and temporal trends. This study reviewed the BC studies in the ice core and remote lake sediments and their sources in the northern hemisphere. The literature surveyed points to around 2.9 to 3.7 times increase of BC in the European Alps and up to a three-fold increase of BC in the Himalayan-Tibetan Plateau (HTP) after the onset of industrialization in Europe and Asia, respectively. BC concentration from Greenland ice core showed seven times increase with an interrupted trend after 1950's. South Asian emissions were dominant in the HTP along with a contribution from the Middle East, whereas Western European and local emissions were responsible for the change in BC concentration in the European Alps. In the Arctic, contributions from North America, Europe and Asia persisted. Similarly, a historical reconstruction of lake sediments records demonstrates the effects of emissions from long-range transport, sediment focusing, local anthropogenic activities, precipitation and total input of flux on the BC concentration.

  • Summary of research on frost heave for subgrade in seasonal frozen ground
  • Shuang Jia,BoWen Tai,ShouChen Qi,Lei Li,Tao Chen
  • DOI: 10.3724/SP.J.1226.2021.20092.
  • 2021, Vol.13 (3): 195–205 Abstract ( 87) HTML ( 78) PDF (1441 KB) ( 138 )
  • The building of railways on seasonally frozen ground is inevitable as China pursues economic development and the improvement of its citizens' living standards. However, railway construction in seasonally frozen soil areas is often faced with frost heave, leading to uneven subgrades which seriously threaten traffic safety. This article summarizes extant research results on frost heave mechanism, frost heave factors, and anti-frost measures of railway subgrades in seasonally frozen soil areas.

  • Overview of an early warning system for Glacial Lake outburst flood risk mitigation in Dudh-Koshi Basin, Nepal
  • Sanjaya Gurung,Saroj Dhoj Joshi,Binod Parajuli
  • DOI: 10.3724/SP.J.1226.2021.20076.
  • 2021, Vol.13 (3): 206–219 Abstract ( 148) HTML ( 97) PDF (9420 KB) ( 133 )
  • Natural disasters inflict severe damage on almost the entire spectrum of social and natural habitats. This ranges from housing and shelter, water, food, health, sanitation to information and communication networks, supply of power and energy, transportation infrastructure, and others. Nepal is a risk prone country for Glacial Lake Outburst Flood (GLOF). GLOFs exist as major challenges as they repeatedly cause a heavy toll of life and property. During such a disaster, major challenges are indeed the protection of life, property and vital life-supporting infrastructure. Any delay or laxity in disaster relief can escalate the magnitude of distress for the victims. Thus, rather than trying to take curative measures, it is better to minimize the impacts of GLOF. These measures subsequently help in reducing the magnitude of death and casualties due to a GLOF event. This reduction of impact is often achieved by optimizing preventive measures. For applying necessary deterrent measures, it is essential to disseminate information about the danger beforehand. Early Warning System (EWS) is an important step for such information dissemination for GLOF disaster management and helps to anticipate the risk of disaster and disseminate information to lives at risk. It is impossible and impractical to reduce all GLOF risks, but it is possible to reduce several impacts of a GLOF through the implementation of the EWS. This paper presents the design and implementation of an EWS for monitoring potential outbursts of a glacier lake in the Dudh-Koshi Basin, Nepal.

  • Temporal changes in seasonal precipitation over the Sahara Desert from 1979 to 2016
  • Sindikubwabo Celestin,Qi Feng,RuoLin Li,WenJu Cheng,Jian Ma,Habiyakare Telesphore,Nzabarinda Vincent
  • DOI: 10.3724/SP.J.1226.2021.19059.
  • 2021, Vol.13 (3): 220–233 Abstract ( 150) HTML ( 11) PDF (12422 KB) ( 93 )
  • Rainfall variability dominates livelihoods in all countries of Saharan Africa. To better understand the processes involved in Sahara precipitation changes, we used the Global Precipitation Climatology Center (GPCC) dataset to examine dry and wet seasonal trends in the Sahara region from 1979 to 2016. We also used the European Centre for Medium-Range Weather Forecasts (ECMWF) to evaluate the general atmospheric circulation associated with seasonal change of Sahara precipitation. The Mann-Kendall test and Theil sens' slope estimator methods were adopted to test and estimate the significance and weight of precipitation trend, respectively. The results revealed that Sahara precipitation has increased significantly. The seasonal evaluation shows a positive trend of 0.42 mm/decade and 1.43 mm/decade in JAS (June, August, and September) seasons for the northern and southern Saharan Desert, respectively. Moreover, the JFMA (January, February, March, and April) period shows a negative trend but not statistically significant. An examination of the general circulation and moisture transport changes suggested an increase of rainfall in southern Sahara. The wet period is also driven by northward penetration of moisture originating from the Sahel region, African Easterly Jet (AEJ), and weakening in the upper tropospheric zonal wind. Summer rainfall has also been likely associated with positive anomalies of sea surface temperature (SST) in the North Tropical Atlantic (NTA) and the Mediterranean Sea.

  • Centrifuge model test on performance of thermosyphon cooled sandbags stabilizing warm oil pipeline buried in permafrost
  • GuoYu Li,HongYuan Jing,Nikolay Volkov,Wei Ma,PengChao Chen
  • DOI: 10.3724/SP.J.1226.2021.20075.
  • 2021, Vol.13 (3): 234–255 Abstract ( 69) HTML ( 8) PDF (14609 KB) ( 82 )
  • The thaw settlement of pipeline foundation soils in response to the operation of the first China-Russia Crude Oil Pipeline along the eastern flank of the northern Da Xing'anling Mountains in Northeast China was simulated in a physical model test (with a similitude ratio of 1/73) in a geotechnical centrifuge. Two pipes of a supported and an unsupported section were evaluated over a testing period for simulating 20 years of actual pipeline operation with seasonal cyclically changing oil and ambient temperatures. The results show that pipe settlement of the supported pipe was 45% of settlement of the unsupported pipe. Settlement for the unsupported section was approximately 35% of the thaw bulb depth below the initial pipe elevation, only 30% of that for the supported pipe due to the influence of the supports. The final thaw bulbs extended approximately 3.6 and 1.6 times of the pipe diameter below the unsupported and supported pipe bottom elevations, respectively. The sandbag supports kept frozen during the test period because of cooling effect of the thermosyphons. The maximum bending stress induced over the 20 m span length from bearing of the full cover over the pipe would be equivalent to 40% specified minimum yield strength (SMYS). Potential buckling of the pipe should be considered as the ground thaws. This study also offers important data for calibration and validation of numerical simulation models.

  • Changes in morphology and soil nutrient patterns of nebkhas in arid regions along a precipitation gradient
  • WeiCheng Luo,WenZhi Zhao,Bing Liu,Heng Ren
  • DOI: 10.3724/SP.J.1226.2021.20058.
  • 2021, Vol.13 (3): 256–267 Abstract ( 79) HTML ( 12) PDF (4703 KB) ( 99 )
  • Nebkhas, discrete mounds of sand and vegetation, are a common landscape feature critical to the stability of desert ecosystems and supported by limited precipitation. Nebkha morphology and spatial pattern vary in landscapes, but it is unclear how they change along precipitation gradients in arid and semi-arid regions. In this study we determined morphology and soil nutrient patterns of nebkha from different regions of northwestern China. The objective of this study was to understand zonal differences among nebkhas and how morphological characteristics and soil nutrient patterns of nebkha change along a precipitation gradient in northwestern China. Our results shows that mean annual precipitation (MAP) had significant effects on morphological characteristics of nebkhas such as height, area, and volume which significantly decreased with an increase in MAP. MAP had significant positive effects on shrub cover and species richness of nebkha. Soil nutrients such as soil organic matter (SOM), total carbon (TC), total nitrogen (TN), and total phosphorus (TP) in the 0-10 cm layer increased with an increase of MAP, and soil nutrient content within nebkhas was higher than in inter-nebkha areas. We concluded that nebkhas are "fertile islands" with an important role in ecosystem dynamics in study regions. Further, MAP is a key factor which determined zonal differences, morphological, and soil nutrients patterns of nebkhas. However, disturbance, such as animal grazing, and planted sand-stabilizing vegetation accelerated the degeneration of nebkha landscapes. We recommend implementation of protective measures for nebkhas in arid and semi-arid areas of China.