Land use and land cover change in Greater Dhaka, Bangladesh: Using remote sensing to promote sustainable urbanization

This study evaluates land use/cover changes and urban expansion in Greater Dhaka, Bangladesh, between 1975 and 2003 using satellite images and socio-economic data. Spatial and temporal dynamics of land use/cover changes were quantified using three Landsat images, a supervised classification algorithm and the post-classification change detection technique in GIS. Accuracy of the Landsat-derived land use/cover maps ranged from 85 to 90%. The analysis revealed that substantial growth of built-up areas in Greater Dhaka over the study period resulted significant decrease in the area of water bodies, cultivated land, vegetation and wetlands. Urban land expansion has been largely driven by elevation, population growth and economic development. Rapid urban expansion through infilling of low-lying areas and clearing of vegetation resulted in a wide range of environmental impacts, including habitat quality. As reliable and current data are lacking for Bangladesh, the land use maps produced in this study will contribute to both the development of sustainable urban land use planning decisions and also for forecasting possible future changes in growth patterns.     

Wakefieldite‐(Nd), a New Neodymium Vanadate Mineral in the Arase Stratiform Ferromanganese Deposit,Kochi Prefecture,Japan

Wakefieldite‐(Nd), NdVO₄, is a new mineral found from the Arase stratiform ferromanganese deposit in Kochi Prefecture, Shikoku Island, Japan. It is the Nd‐dominant analogue of wakefieldite‐(Y) and wakefieldite‐(Ce). The ferromanganese ore specimen mainly consists of hematite and caryopilite, and wakefieldite‐(Nd) is typically enclosed in caryopilite. Wakefieldite‐(Nd) is tetragonal, I4₁/amd, a = 7.338(16) Å, c = 6.509(19) Å, V = 350.5(18) ų, Z = 4. The four strongest lines in the X‐ray diffraction pattern [d(Å), I/I₀, hkl] using a Gandolfi camera are (3.67, 100, 200); (2.74, 51, 112); (4.84, 27, 101) and (1.89, 25, 312). Chemical composition of wakefieldite‐(Nd) are V₂O₃ 35.25, As₂O₃ 0.93, SiO₂ 0.14, MnO 1.45, Fe₂O₃ 0.41, Y₂O₃ 2.87, La₂O₃ 7.61, Ce₂O₃ 7.37, Pr₂O₃ 6.04, Nd₂O₃ 26.79, Sm₂O₃ 4.41, Eu₂O₃ 1.36, Gd₂O₃ 3.41, Tb₂O₃ 0.22, Dy₂O₃ 1.41, Er₂O₃ 0.10, total 99.77 wt.%. The empirical formula is (Nd_0.403La_0.118Ce_0.114Pr_0.093Y_0.064Sm_0.064Mn_0.052Gd_0.048Eu_0.020Dy_0.019Fe_0.013Tb_0.003Er_0.001)_1.012(V_0.981As_0.020Si_0.006)_1.007O₄ on the basis of O = 4. The calculated density is 4.782 g/cm³. Microtexture and co‐existing relationship between wakefieldite‐(Nd) and caryopilite suggest that recrystallization and dehydration of Fe‐ and Mn‐oxyhydroxide led to the generation of hematite, caryopilite, rhodochrosite and wakefieldite‐(Nd) by the metamorphism during the accretion of the host unit of the Arase deposit. Chondrite‐normalized REE pattern of the host ferromanganese ore, which is regarded as oceanic metalliferous sediment in origin, shows negative Ce anomaly. Chemical composition of wakefieldite‐(Nd) reflects Ce‐depleted bulk composition of REE‐enriched ferromanganese ore.     

Gold Content in Siliceous Deposits Formed from Acidic and Iron-rich Geothermal Waters at Hatchobaru, Central Kyushu, Japan

Abstract: The gold content in siliceous deposits formed from geothermal waters at the Hatchobaru geothermal power station in central Kyushu, Japan, was determined by inductively coupled plasma quadrupole mass spectrometry (ICP–MS). It ranges from 1.3 to 4.6 mg/kg. The highest gold content was obtained from the siliceous deposit formed from acidic waters. In this siliceous deposit, hydrous iron(III) oxide of amorphous state is a major constituent, suggesting that hydrous iron(III) oxide might play an important role when gold is concentrated into siliceous deposits formed from acidic and iron-rich geothermal waters.     

Lunar mare volcanism in the eastern nearside region derived from Clementine UV/VIS data

Abstract— Clementine UV/VIS multi‐spectral data were used to map mare deposits in the eastern lunar nearside region (Mare Tranquillitatis, Mare Fecunditatis, Mare Serenitatis, Mare Crisium, Mare Nectaris) to understand the volcanic history of this region. An array of Clementine and Clementine‐derived data were used to classify mare basalts; these include: 750 nm albedo, UV/VIS ratio, 1 μm absorption signatures, and Clementine derived FeO and TiO₂ contents. We have successfully identified several new geological units and have determined their spectral characteristics. For example, the relatively younger low‐Ti basalts were recognized in the eastern part of Mare Tranquillitatis. The central low‐Ti basalts in Mare Serenitatis, which had been classed as mISP, were divided into 2 groups. In Mare Nectaris, 2 types of mare basalts were identified, while only 1 group was recognized in the previous study. The stratigraphy constructed from the spectral analysis indicates that the mare deposits tend to become younger in the northern maria, including Serenitatis and Crisium, and older in the southern maria, including Tranquillitatis, Fecunditatis, and Nectaris. According to the relationship between the titanium contents of the mare units and their stratigraphy, the titanium content decreases with time in the early stage but increases toward the end of volcanism in the Serenitatis and Crisium region, while it increases with time but finally decreases in the Tranquillitatis and Fecunditatis region. In connection with the distribution of mare basalts, a large amount of high‐Ti mare basalts are found in Mare Tranquillitatis, especially in the western part, while other maria are covered by low‐Ti basalts. The iron contents show a similar distribution to that of titanium.     

Oxidative stress responses of submerged macrophyte Vallisneria asiatica to different concentrations of cyanobacteria

In a 10-day aquarium experiment,this investigation examines macrophyte restoration in eutrophic Lake Taihu,the physiological effects of different plant biomass levels and of increasing natural cyanobacterial concentrations on a submerged macrophyte,Vallisneria asiatica. Cyanobacterial stress suppressed the superoxide dismutase(SOD) activity of the plant's leaves and induced the catalase(CAT) and peroxidase(POD) activities of its roots. The soluble protein content in V. asiatica decreased with an increase in natural cyanobacterial concentrations,whereas the malonaldehyde(MDA) increased significantly at chlorophylla(Chl a) concentrations of 222 and 262 μg/L in water. V. asiatica adapted to the stress caused by cyanobacterial concentrations by adjusting its antioxidant defense system to remove the excessive reactive oxygen species when the algal Chl a concentration was 109 μg/L. Additionally,high biomass of V. asiatica(2 222 g FW/m 2) can inhibit the reproduction of cyanobacteria more significantly than low biomass(1 111 g FW/m2). High biomass of V. asiatica increased the oxidative stress in an individual plant when the initial Chl a concentration in the water reached 222 and 262 μg/L,as expressed by the increased MDA in leaves,compared with low biomass of V. asiatica. This provides a basis for controlling cyanobacterial concentrations and V. asiatica biomass for the recovery of V. asiatica in eutrophic Lake Taihu.     

Volume transport in the Soya Strait during 2006–2008

Time-series data of the vertical structure of the Soya Warm Current (SWC) were obtained by a bottom-mounted acoustic Doppler current profiler (ADCP) in the middle of the Soya Strait from September 2006 to July 2008. The site of the ADCP measurement was within the coverage of the ocean-radar measurement around the strait. The volume transport of the SWC through the strait is estimated on the basis of both the vertical structure observed by the ADCP and the horizontal structure observed by the radars for the first time. The annual transport estimates are 0.62–0.67 Sv (1 Sv = 10⁶ m³s⁻¹). They are somewhat smaller than the difference between the previous estimates of the inflow and outflow through other straits in the Sea of Japan, and smaller than those obtained in the region downstream of the strait during 2004–05 (0.94–1.04 Sv). The difference in the two periods may be attributed to interannual variability of the SWC and/or the different measurement locations.     

VCS柱状采样及其在中国太湖富营养化评价中的应用

The lake sediments, especially in recent years, genuinely record human being''s activities upon the lake environment. The top 30cm sections are of significance in the process of advanced cultural eutrophication and water quality deterioration. Based on the data of 4 core sam-ples obtained in June 19-22, 1997, with VCS in northern, western and southern Taihu Lake, some preliminary results are reported. Further analyses on the physico-chemical items as well as element content may reveal more information of the accelerating cultural eutrophication.     

日本岛根县石见银矿区英安质火山岩中的黑云母矿物学特征及其K-Ar和40Ar-39Ar年代学研究

以显微镜、X射线衍射仪和电子探针等方法,对日本岛根县石见银矿区所产英安质火山岩中的黑云母进行了详细的研究．观察到部分黑云母经受了不同程度的热液蚀变作用。根据对未蚀变、或仅受到轻微蚀变作用的黑云母所进行的^40Ar-^39Ar同位素年龄测定,它们主要为第四纪产物。但是,从经受强热液蚀变作用的黑云母所获得的^40Ar-^39Ar同位素结果表明,后期的高温热液活动可以破坏晶体中的原始K—Ar同位素平衡,使得其。^40Ar-^39Ar同位素年龄与高于从未蚀变矿物所获得的结果,从而产生严重的年代失真。所以,对来自热液蚀变带的样品需要进行详细的矿物学研究。估计对黑云母的原始KAr同位素体系产生破坏的热扰动临界温度可能在200℃左右。