MULTI-ELEMENT ANALYSIS OF COASTAL MARINE SEDIMENT, AN IAEA PROPOSED REFERENCE MATERIAL (IAEA-356)     

A. MANNAN  S. WAHEED  A. RAHMAN  S. AHMAD  I.H. QURESHI 《Geostandards and Geoanalytical Research》1993,17(2):223-226

Proposed standard reference material, coastal marine sediment (IAEA-356) recently released under the IAEA Analytical Quality Control Services programme, has been analysed by instrumental neutron activation analysis technique. Up to 32 elements have been measured using the multi-element analysis approach. The precision of measurements varied from 1.3 to 12.5% with median value of 4.9%. The quality control of the data has been validated by analysing IAEA reference material of similar matrix which shows excellent agreement with IAEA values.  相似文献   

Resource degradation and livelihood in the coastal region of Bangladesh     

Giashuddin MIAH  Nasimul BARI  Abiar RAHMAN 《Frontiers of Earth Science》2010,4(4):427-437

A study was conducted in four selected upazilas under four coastal districts through participatory rural appraisal (PRA), household survey and monitoring, sampling, focal group discussions, personal interview, onfarm field visits, institutional consultations, and secondary information. The investigation revealed that the valuable natural resources of the whole region are at the verge of serious degradation. Various causes have been identified, which are responsible for degradation of both resources and production environments. These causes include human population growth, coastal embankment, upstream withdrawal of Ganges water, brackish water shrimp farming, salt production, use of agro-chemicals, industrial activities, commercial activities, over-exploitation, etc. The study also showed that the degradation of natural resources is the reason behind the squeezing of historically dominant livelihood opportunities of the coastal communities. The current scenarios of the coastal ecosystem urge necessary steps to be taken for sustainable management of valuable resources and to create alternative livelihood opportunities for the coastal communities.  相似文献   

Thermal and shock history of Almahata Sitta meteorite inferred from structure refinement of pyroxene and Mössbauer spectroscopy of Fe-Ni metal     

Yassir A. Abdu  Abbasher M. Gismelseed  Atta G. Attaelmanan  Muawia H. Shaddad  Frank C. Hawthorne 《Meteoritics & planetary science》2023,58(5):737-746

The crystal structures of orthopyroxene (En_86.3Fs_8.6Wo_5.1, space group Pbca) and pigeonite (En_81.7Fs_8.8Wo_9.5, space group P2₁/c) from the Almahata Sitta ureilite (fragment#051) have been refined to R1 indices of 3.10% and 2.53%, respectively, using single-crystal X-ray diffraction data. The unit formulas were calculated from electron microprobe analysis, and the occupancies at the M1 and M2 sites were refined for both pyroxenes from the single-crystal diffraction data. The results indicate a rather disordered intracrystalline Fe²⁺-Mg cation distribution over the M1 and M2 sites, with a closure temperature of 726(±55)°C for orthopyroxene and 704(±110)°C for pigeonite, suggesting fast cooling of these pyroxenes. The Mössbauer spectrum of the Fe-Ni metal particles of Almahata Sitta ureilite (fragment#051) is dominated by two overlapping magnetic sextets that are assigned to Fe atoms in Si-bearing kamacite, and arise from two different nearest-neighbor configurations of Fe* (=Fe+Ni) and Si atoms in the bcc structure of kamacite; (8F*, 0Si) and (7Fe*, 1Si). In addition, the spectrum shows weak absorption peaks that are attributed to the presence of small amounts of cohenite [(Fe,Ni)₃C], schreibersite [(Fe,Ni)₃P], and an Fe-oxide/hydroxide phase. The fast cooling of pyroxene to the closure temperature (after equilibration at ~1200°C) and the incorporation of Si in kamacite can be interpreted as due to a shock event that took place on the meteorite parent body, consistent with the proposed formation history of ureilites parent body where a fast cooling has occurred at a later stage of its formation.  相似文献   

中国超级杂交稻在孟印缅地区的生产潜力模拟     

王小博  王绍强  陈敬华  崔惠娟  吴宜进  N H RAVINDRANATH  A RAHMAN 《地理学报》2018,73(11):2184-2197

水稻是孟加拉国、印度和缅甸最重要的粮食作物,研究中国超级杂交稻对孟印缅地区的水稻增产潜力,对于保障孟中印缅经济走廊的粮食安全与区域可持续发展具有重要的现实意义。在全面收集孟印缅地区气候、土壤、田间管理信息和农业统计数据的基础上,结合中国籼型杂交稻F优498和丰两优4号的品种信息和区试数据,通过EPIC模型模拟了1996-2005年雨季孟印缅3国在不同情景下的超级稻生产潜力,并分析了孟印缅地区主要胁迫因子对超级稻单产潜力的影响。研究表明：① 中国超级杂交稻在孟印缅地区2000年的灌溉和施肥水平下单产潜力为10.22 t/ha,在充分灌溉且合理施肥的水平下单产潜力为11.33 t/ha。② 孟印缅地区雨季稻的增产空间达22771万t,水稻增产潜力最大的地区是印度的恒河平原东部、印度半岛东南沿海与缅甸的伊洛瓦底三角洲。③ 印度德干高原东北部、西南部和印度大平原西北部需要进一步完善灌溉设备以满足高产水稻用水,缅甸的中南部平原地区和印度的东北地区则需要增施氮肥以满足高产水稻用肥。  相似文献   

Insights From a Multi-Method Recharge Estimation Comparison Study     

David Walker  Geoff Parkin  Petra Schmitter  John Gowing  Seifu A. Tilahun  Alemseged T. Haile  Abdu Y. Yimam 《Ground water》2019,57(2):245-258

Although most recharge estimation studies apply multiple methods to identify the possible range in recharge values, many do not distinguish clearly enough between inherent uncertainty of the methods and other factors affecting the results. We investigated the additional value that can be gained from multi-method recharge studies through insights into hydrogeological understanding, in addition to characterizing uncertainty. Nine separate groundwater recharge estimation methods, with a total of 17 variations, were applied at a shallow aquifer in northwest Ethiopia in the context of the potential for shallow groundwater resource development. These gave a wide range of recharge values from 45 to 814 mm/a. Critical assessment indicated that the results depended on what the recharge represents (actual, potential, minimum recharge or change in aquifer storage), and spatial and temporal scales, as well as uncertainties from application of each method. Important insights into the hydrogeological system were gained from this detailed analysis, which also confirmed that the range of values for actual recharge was reduced to around 280-430 mm/a. This study demonstrates that even when assumptions behind methods are violated, as they often are to some degree especially when data are limited, valuable insights into the hydrogeological system can be gained from application of multiple methods.  相似文献   

新疆喀拉库姆沙漠新月形沙丘不同部位粒度特征     

俞胜清  阿布都米基提  周向玲  黄晓俊 《中国沙漠》2013,33(6):1629-1635

对新疆叶尔羌河流域绿洲边缘喀拉库姆沙漠高度在3～12 m的新月形沙丘进行了粒度分析。结果表明:表层和下层沉积物均以细砂和极细砂为主,二者含量达82%以上。表层沉积物较下层稍粗,平均粒径分别为2.09 Φ和2.16 Φ。下层沉积物较表层分选性好,σ均值分别为0.48和0.62。表层和下层沉积物偏度均为正偏,SK均值分别为0.21和0.24。峰态均为尖窄,Kg均值分别为1.18和1.11。表层和下层沉积物平均粒径均表现为丘顶最粗,背风坡坡脚最细,由两侧坡脚至丘顶平均粒径变粗,平均粒径与其他粒度特征参数之间均存在良好的相关性。分析表明,喀拉库姆沙漠沙丘沉积物粒度特征除受物源这一背景制约外,还与区域构造、沙漠地貌、植被、气候和较为复杂的风沙动力学过程等众多因素有关。  相似文献   

Abnormally large magnetospheric electric field on 9?November?2004 and its effect on equatorial ionosphere around the world     

R G Rastogi  H Chandra  Louis Condori  M A Abdu  B Reinisch  R T Tsunoda  D S V V D Prasad  T K Pant  T Maruyama 《Journal of Earth System Science》2012,121(5):1145-1161

  相似文献   

Midnight reversal of ionospheric plasma bubble eastward velocity to westward velocity during geomagnetically quiettime: Climatology and its model validation     

José H.A. Sobral  Vivian M. de Castilho  M.A. Abdu  Hisao Takahashi  I. Paulino  Ulisses A.C. Gasparelo  Daniela C.S. Arruda  Matheus Mascarenhas  C.J. Zamlutti  C.M. Denardini  Daiki Koga  A.F. de Medeiros  R.A. Buriti 《Journal of Atmospheric and Solar》2011,73(11-12):1520-1528

In an effort to better understand the dynamics of westward velocities of the nocturnal F-region plasma, the climatology of the westward traveling plasma bubbles – WTB – occurring during quiettime is studied here. The climatology of the WTB is analyzed here based on airglow images obtained during 14 quiet days between 2001 and 2006 at the Brazilian station São João do Cariri (Geographic 7.45°S, 36.5°W, dip ～20°S). The frequency of occurrence of the WTB maximizes in the descending phase of the solar cycle. The WTB velocities ranged between ～20 and 40 ms^?1. The frequency of occurrence had a peak value of only 3.65% at 2345 LT. The maximum occurrence of the WTB was in July–September. No WTB have been observed from November until April in all years 2001–2006. We show for the first time theoretically that the WTB dominant forcing mechanisms during geomagnetically quiet days are westward thermospheric winds.  相似文献   

Growth,Proximate Composition and Pigment Production of Tetraselmis chuii Cultured with Aquaculture Wastewater     

KHATOON Helena  HARIS Haris  RAHMAN Norazira Abdu  ZAKARIA Mimi Nadzirah  BEGUM Hasina  MIAN Sohel 《中国海洋大学学报(英文版)》2018,(3)

Microalgae are cultured commercially as healthy food, cosmetic products, food preservatives, and a source of valuable compounds. However, the high cost of commercial culture medium is one of the challenges to microalgal production. Therefore, it is essential to find an alternative cost-effective culture medium. Aquaculture wastewater is considered as a highly potential candidate due to its high nutrient content and large quantity generated from the rapid growth of aquaculture sector. In this study, Tetraselmis chuii cultured in different media with or without wastewater was evaluated for its growth, proximate composition and carotenoid production. The results showed that significantly(P 0.05) higher growth(4.3 × 105 cells mL~(-1)) and protein(56.4% dry weight), lipid(44% dry weight) and carbohydrate(20% of dry weight) contents were found in T. chuii when they were cultured in the combination of both wastewater and Conway(wastewater + Conway) medium. However, carotenoid production of T. chuii was significantly increased(P 0.05) when it was cultured in wastewater only, followed by Conway + wastewater and Conway medium only. Therefore, the incorporation of wastewater with commercial medium Convey is recommended for a cost-effective microalgae culture, as well as for the enhancement of growth and nutritional content of microalgae.  相似文献   

Volcanically Driven Terrestrial Environmental Perturbations during the Carnian Pluvial Episode in the Eastern Tethys     

Naveed Ur RAHMAN  XIAN Benzhong  FANG Linhao  CHEN Sirui  CHEN Peng  Zaheen ULLAH  WANG Pengyu 《《地质学报》英文版》2024,98(3):753-770

The Carnian Pluvial Episode (CPE) fingerprints global environmental perturbations and biological extinction on land and oceans and is potentially linked to the Wrangellia Large Igneous Province (LIP). However, the correlation between terrestrial environmental changes and Wrangellia volcanism in the Ordos Basin during the CPE remains poorly understood. Records of negative carbon isotopic excursions (NCIEs), mercury (Hg), Hg/TOC, and Hg enrichment factor (HgEF) from oil shales in a large-scale terrestrial Ordos Basin in the Eastern Tethys were correlated with marine and other terrestrial successions. The three significant NCIEs in the study section were consistently correlated with those in the CPE successions of Europe, the UK, and South and North China. The U-Pb geochronology indicates a Ladinian–Carnian age for the Chang 7 Member. A comprehensive overview of the geochronology, NCIE correlation, and previous bio- and chronostratigraphic frameworks shows that the Ladinian–Carnian boundary is located in the lower part of Chang 7 in the Yishicun section. HgEF may be a more reliable proxy for tracing volcanic eruptions than the Hg/TOC ratio because the accumulation rates of TOC content largely vary in terrestrial and marine successions. The records of Hg, Hg/TOC, HgEF, and NCIEs in the Ordos Basin aligned with Carnian successions worldwide and were marked by similar anomalies, indicating a global response to the Wrangellia LIP during the CPE. Anoxia, a warm-humid climate, enhancement of detrital input, and NCIEs are synchronous with the CPE interval in the Ordos Basin, which suggests that the CPE combined with the regional Qinling Orogeny should dominate the enhanced rate of terrigenous input and paleoenvironmental evolution in the Ordos Basin.  相似文献