Kien Giang, bordering Cambodia in the Mekong River Delta, is one of the two most vulnerable provinces in the region to coastal erosion and flooding. Coastal protection can conflict with current land use and economic development activities. The conditions of the mangrove forest and mainland coastline of the Kien Giang province were assessed using the Shoreline Video Assessment Method (SVAM) backed up with information from satellite images. Half of the 206 km Kien Giang coastline has been eroded or is being eroded. Protective mangrove forests naturally occurred in 74% of the coastline but have been under threat from illegal cutting, erosion and coastal retreat. Accurate information on the state of the coastline and mangrove forest health provided invaluable data for developing a new coastal rehabilitation plan to guard against future sea level rise. In contrast to the current boundary management of land and natural resources, this plan divided the provincial coastline into 19 sections based on the landscape condition and exposure to erosion. Priority strategic actions for erosion management, mangrove restoration and sustainable livelihood development for local communities for each section of coast were developed based on an integrated cross sectoral approach and practical experience in the Conservation and Development of the Kien Giang Biosphere Reserve Project.
To investigate climate variability in Asia during the last millennium, the spatial and temporal evolution of summer (June–July–August; JJA) temperature in eastern and south-central Asia is reconstructed using multi-proxy records and the regularized expectation maximization (RegEM) algorithm with truncated total least squares (TTLS), under a point-by-point regression (PPR) framework. The temperature index reconstructions show that the late 20th century was the warmest period in Asia over the past millennium. The temperature field reconstructions illustrate that temperatures in central, eastern, and southern China during the 11th and 13th centuries, and in western Asia during the 12th century, were significantly higher than those in other regions, and comparable to levels in the 20th century. Except for the most recent warming, all identified warm events showed distinct regional expressions and none were uniform over the entire reconstruction area. The main finding of the study is that spatial temperature patterns have, on centennial time-scales, varied greatly over the last millennium. Moreover, seven climate model simulations, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), over the same region of Asia, are all consistent with the temperature index reconstruction at the 99 % confidence level. Only spatial temperature patterns extracted as the first empirical orthogonal function (EOF) from the GISS-E2-R and MPI-ESM-P model simulations are significant and consistent with the temperature field reconstruction over the past millennium in Asia at the 90 % confidence level. This indicates that both the reconstruction and the simulations depict the temporal climate variability well over the past millennium. However, the spatial simulation or reconstruction capability of climate variability over the past millennium could be still limited. For reconstruction, some grid points do not pass validation tests and reveal the need for more proxies with high temporal resolution, accurate dating, and sensitive temperature signals, especially in central Asia and before AD 1400. 相似文献
Bioclogging and biocementation can be used to improve the geotechnical properties of sand. These processes can be performed by adsorption of urease-producing bacterial cells on the sand grain surfaces, which is followed by crystallization of calcite produced from the calcium salt and urea solution due to bacterial hydrolysis of urea. In this paper, the effect of intact cell suspension of Bacillus sp. strain VS1, suspension of the washed bacterial cells, and culture liquid without bacterial cells on microbially induced calcite precipitation in sand was studied. The test results showed that adsorption/retention of urease activity on sand treated with washed cells of Bacillus sp. strain VS1 was 5–8 times higher than that treated with culture liquid. The unconfined compressive strength of sand treated with the suspension of washed cells was 1.7 times higher than that treated with culture liquid. This difference could be due to fast inactivation of urease by protease which was present in the culture liquid. The adsorption of bacterial cells on sand pretreated with calcium, aluminum, or ferric salts was 29–37 % higher as compared with that without pretreatment. The permeability of sand varied with the content of precipitated calcium. For bioclogging of sand, the content of precipitated calcium had to be 1.3 % (w/w) or higher. The shear strength of biotreated sand was also dependent on the content of precipitated calcium. To achieve an unconfined compressive strength of 1.5 MPa or higher, the content of precipitated calcium in the treated sand had to be 4.2 % (w/w) or higher. These data can be used as the reference values for geotechnical applications such as bioclogging for reducing the permeability of sand and biocementation for increasing the shear strength of soil. 相似文献