Salinity impacts on agro-biodiversity in three coastal, rural villages of Bangladesh

Salinity increase has been one of the major problems for traditional agricultural practices in coastal Bangladesh for several decades, but very few studies have been conducted on effects of salinity on agro-biodiversity in this area. This study investigated the salinity effects on agro-biodiversity in rice (Oryza sativa L.), vegetables, and fruit trees in three coastal, rural villages; Putia (Satkhira district), Srifaltala (Bagerhat district) and Hogolbunia (Khulna district). Information was collected by participatory rural appraisal methods including transect walks, group discussions, key informant interviews, and 121 personal interviews from July to December 2006. The study revealed that increased salinity had significant negative impacts on the overall agro-biodiversity. From 1975 to 2006 the number of indigenous rice varieties declined from seventeen to zero in Putia, from twelve to nine in Hogolbunia and from fifteen to two in Srifaltala. The encroachment of shrimp ponds near the homestead, and cultivation of high yielding, salt-tolerant rice varieties contributed to the decline of indigenous rice varieties. The occurrence of vegetable and fruit tree species declined from 1975 to 1990. The farmers appeared generally unaware of the importance of conservation of seeds and local landraces. This paper highlights factors directly and indirectly influencing farmers’ agricultural practices, and contributes to the discussion as to how environmental changes influence agro-biodiversity conservation and food production. The large reduction in agro-biodiversity, largely induced by increasing salinity, is alarming and threatens the Bangladeshi farmers’ ability to continue crop cultivation and thus their livelihood.     

Improvement of very soft ground by a high-efficiency vacuum preloading method: A case study

This paper describes a full-scale test on a very soft clay ground around 70,000?m², which is conducted in Huizhou of Guangdong Province, China, to present a new method of vacuum preloading method. A novel moisture separator was developed, which can automatically regulate the vacuum pressure variation by changing the volume of the gas inside it. A large quantity of water drained by the proposed moisture separators can be directly used as a surcharge loading, which would shorten the ground improvement time and save costs as well. Three levels of silt-prevention prefabricated vertical drains were used in the treating process to accelerate the consolidation. In addition, the vacuum preloading method also included an effective radial drainage device which would strengthen the dredged soft clay fill in a deep layer. In the in situ test, tens of piezometers and settlement plates were installed to measure the variations of excess pore water pressures and settlement of two stages of observation points at different positions in the ground. The results show that the largest average consolidation settlement was 314.1?cm and made a saving of more than 66% in power consumption compared with traditional method. It demonstrates that this adopted method is an efficient, cost-effective, and environmentally friendly method for improving sites with low bearing capacity and high compressibility soils.     

Sea Level Changes Along Bangladesh Coast in Relation to the Southern Oscillation Phenomenon

Interannual variations of sea level along the Bangladesh coast are quite pronounced and often dominate the long-term sea level trends that are taking place. The El Niño/Southern Oscillation (ENSO) induced variation is an important component of interannual mode of variations. The present article deals with the relationship between the sea level variations along the Bangladesh coast and the Southern Oscillation phenomenon. The mean tide level data of monsoon season (June to September) pertaining to Hiron Point (in Sundarbans) and Char Changa (on the mouth of Meghna River) have been analyzed and correlated to the Southern Oscillation Index (SOI). The annual variation of mean tide level in the coastal areas of Bangladesh reveals that the tide level reaches its peak during the monsoon season. The maximum tide level during the calendar year is recorded in August. Thus, it is not surprising that the inundation of the coastal belt of Bangladesh due to the floods is most common during the summer monsoon season, especially from July to September. Therefore, the sea level variations during the monsoon are of paramount importance to Bangladesh. The results of the present study show that both at Hiron Point and Char Changa there is a substantial difference between the mean tide level during the El Niño and La Niña monsoons. The mean tide level at Hiron Point is higher by about 5 cm during August of La Niña years as compared to that during the El Niño years. The difference at Char Changa, which is located at the mouth of Meghna River, is much higher. This is probably due to the increased fresh water discharge into the Meghna River during La Niña years. Thus at the time of crossing of a monsoon depression, the chances of widespread inundation are higher during a La Nin~a year as compared to that during an El Niño year. The Correlation Coefficients (CCs) between Mean Tide Levels (MTLs) at Hiron Point and Char Changa and the SOI during September (at the end of monsoon) are +0.33 and +0.39 respectively. These CCs are statistically significant at 90% and 95% levels, respectively. These results may find applications in the preparedness programs for combating sea level associated disasters in Bangladesh.     

Geochemical investigation of selected elements in coastal and riverine sediments from Ube, Kasado, and Suo-Oshima Bays in the western Seto Inland Sea, Southwest Japan

This paper presents the geochemical study of sediments along Ube, Suo-Oshima, and Kasado Bays in the Seto Inland Sea of Japan. We examined the distribution and abundances of 13 elements (As, Pb, Zn, Cu, Ni, Cr, Sr, Ca, Fe, Ti, P, Mn, and total S) in 40 coastal and river sediment samples, to evaluate the factors controlling their abundances, possible sources, and environmental implications. Average concentrations of As, Pb, Zn, Cu, Ni, and Cr at Ube were 12, 26, 86, 16, 43, and 92?mg/kg, 6, 25, 31, 8, 9, and 29?mg/kg at Kasado, and 5, 20, 28, 3, 5, and 18?mg/kg at Suo-Oshima, respectively. Average As, Pb, Zn, and Cr concentrations at Ube were comparable or enriched relative to those of the upper continental crust and Japan upper crust, whereas most major elements, Cu, and Ni were depleted at Kasado and Suo-Oshima. Enrichment factor values show low to moderate enrichment of Zn, Ni, and Cr, whereas As and Pb show significant contamination at some sites, suggesting contributions from anthropogenic sources. Anthropogenic contributions of most metals mainly originate from natural processes; however, As and Pb ranges of 73–79 and 66–81?%, respectively, confirm their anthropogenic contribution. Factor analysis and correlation matrices suggest that elevated metal concentrations at Ube, especially in samples located in the river basin, may be controlled by Fe–Mn oxy-hydroxides. Deposition of metals at Kasado and Suo-Oshima might be controlled by non-ferrous metal (i.e., aluminosilicates), sediment grain size, or source rock composition (granite and gneiss).     

Inversion of Gravity Data for Imaging of a Sediment-basement Interface: A Case Study in the Northwestern Part of Bangladesh

Gravity data collected by the Geological Survey of Bangladesh are processed and interpreted for imaging of a sediment-basement interface over the northwestern part of Bangladesh. The observed gravity data are processed for discriminating gravitational fields contributed subtly from the shallow basement topographic feature with the twelve nodal piecewise cubic polynomial–based finite–element approach. In spectral analysis, the presence of a widely spread shallow basement feature has been detected and interpretation of gravity data using a two-dimensional gravity inversion technique indicates that its depth ranges from 0.041 km to 0.570 km relative to ground surface. In the northern part of the study area, the inferred basement configuration shows a general depression of the basement in the Takurgaon-Panchagar and Lalmonirhat districts and reaches a maximum depth of about 0.570 km. In the Nilphamari district and its southwestern part, the basement occurs at the most shallow depth due to its upliftment. However, the estimated sediment-basement interface depths are compared with the borehole and other geophysical interpretative information and are found to be consistent.     

The Distribution of Riparian Corridor Plants and the Relations to River Water Salinity along Perai River, Penang, Malaysia

Ecological surveys were carried out to investigate the distribution and characterization of riparian corridor plants along the Perai River,Penang,Malaysia from July 2007 to March 2008.Surveys were design to represent horizon-tal sections of the river starting from the river mouth towards the upper reaches for 20 km.A total of 84 species of plants from 30 families were recorded.They consisted of 28 species of standing plants(plants with height of more than 1 m)and 56 species of weedy plants(plants with heigh...     

Some electrically charged relativistic stellar models in general relativity

Some new families of electrically charged stellar models of ultra-compact star have been studied. With the help of particular form of one of the metric potentials the Einstein–Maxwell field equations in general relativity have been transformed to a system of ordinary differential equations. The interior matter pressure, energy–density, and the adiabatic sound speed are expressed in terms of simple algebraic functions. The constant parameters involved in the solution have been set so that certain physical criteria satisfied. Based on the analytic model developed in the present work, the values of the relevant physical quantities have been calculated by assuming the estimated masses and radii of some well known potential strange star candidates like X-ray pulsar Her X-1, millisecond X-ray pulsar SAX J 1808.4-3658, and 4U 1820-30. The analytical equations of state of the charged matter distribution may play a significant role in the study of the internal structure of highly compact charged stellar objects in general relativity.     

基于AHP_熵权法的孟印缅地区洪水灾害风险评估

孟印缅三国地处亚热带与热带季风气候区,因自然条件制约,洪涝灾害频繁发生,对“孟中印缅经济走廊”建设将会带来重大影响。开展孟印缅地区的洪水风险评估可为“孟中印缅经济走廊”的建设安全提供必要的信息和科技支撑。利用1980—2016年的降水数据,结合河网、数字高程和土地利用等数据,选取雨季降雨量、暴雨天数、高程、坡度、河网密度、植被覆盖度、土壤可蚀性、人口密度、地均GDP和土地利用10个指标,采用层次分析法和AHP_熵权法对孟印缅地区的洪水灾害风险分布进行了比较研究。研究表明：孟印缅地区高风险区和较高风险区分别占总面积的1.05%和28.76%,高风险区主要分布在印度北部的恒河平原、印度东北部的阿萨姆邦、孟加拉国大部分地区和缅甸南部。受自然、人口和经济条件的制约,孟加拉国是孟印缅三国中洪水风险最高的国家,高风险区和较高风险区分别占总面积的10.61%和65.87%。层次分析法和AHP_熵权法结果间的比较表明,后者比前者识别出更大范围的洪水高风险区。本研究为中国开展周边国家自然灾害的风险评估提供了有效的方法,有助于推进国家孟中印缅经济走廊的建设。