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201.
This study provided a picture of the spatial and temporal distributions of Cr, Co, Ni Cu, Zn, As, Cd and Pb in bottom sediments
of Tolo Harbour. The concentrations of the eight heavy metals differed significantly between sites due to the poor tidal flushing
in Tolo Harbour. The levels of Cu, Zn, Cd and Pb were generally enriched in sediments from inner Tolo Harbour, while sediments
from outer Tolo Harbour (Tolo Channel) had higher levels of Cr, Co and Ni. The redox sensitive element arsenic showed no distinct
spatial pattern in Tolo Harbour. The decreasing levels of Cu, Zn, Pb and Cd in sediments with increasing distance from land
demonstrated a typical diffusion pattern from land to the direction of sea. Two hot spots of Cu, Zn, Pb and Cd in sediments
were located near Tai Po and Sha Tin new town, indicating that Cu, Zn, Pb and Zn were from land-derived sources. The sites
with relatively high levels of Cr, Co and Ni in sediments were located in areas close to waste spoil in sea floor. The natural
and anthropogenic inputs from Sha Tin and Tai Po to Tolo Harbour were mostly responsible for Cu, Zn, Cd and Pb enrichment
in sediments from inner Tolo Harbour. The waste spoil in sea floor was believed to contribute to the Cr, Co and Ni in outer
Tolo Harbour. The results of correlation coefficient between the eight heavy metals showed that Cu, Zn, Cd and Pb were strongly
positively correlated, and Cr, Co and Ni were also significantly correlated with each other. The best explanation of strong
correlation was their similar source. As, however, is not well correlated with the other seven heavy metals. The average concentrations
of Cu and Zn displayed general increasing trends from 1978 to 2006 in Tolo Harbour, while the mean levels of Cr and Pb displayed
a substantial decrease from 1978 to 1987, then a slight increase after 1987. No distinct temporal trends of the concentrations
of Ni and As were observed from 1978 due to the inconsecutive data. On the other hand, the increasing trends of Cr, Cu, Zn,
Cd and Pb were observed since 1996. 相似文献
202.
A palygorskite unit was discovered in a road cut of undifferentiated Tertiary limestone between the villages of El Pariso
and San Roman (18°49.309N, 88°37.861W) in the southeastern Yucatán Peninsula, Mexico. This is the southern most locality of
a clay-rich sedimentary unit reported in the literature for the Tertiary carbonates of the Yucatán Peninsula. This occurrence
indicates a much wider range of palygorskite-rich clay deposition than previously recognized. The lithology is 99% clay and
1% sand to silt size diagenetic quartz grains. The clay consists of approximately 85% palygorskite, 15% montmorillonite and
trace amounts of titanium oxides. EDS analyses on palygorskite are largely consistent with sedimentary palygorskites from
other coastal marine settings, however palygorskite has a low total Fe content (average = 0.40 wt% expressed as Fe2O3) compared to many other sedimentary palygorskites. Montmorillonite chemical compositions are typical and compared to the
palygorskite have substantially higher Fe2O3 concentrations (average = 3.90 wt%). The low percentage of coarse grains in the lithology combined with a high proportion
of palygorskite and lack of detrimental trace minerals suggest the deposit is of industrial grade; however, it has limited
reserves (6,000 m3). The unit could be potentially used in a wide array of environmental applications which are needed in the region including
liners for landfills and constructed wetlands. The unit is in a geographic location which would serve the expanding economy
of the region. This resource has the potential to have great impact on the quality of the local environment and the economy
of a region under great environmental threat. 相似文献
203.
Satoru Haraguchi Teruaki Ishii Jun-Ichi Kimura Yasuhiro Kato 《Contributions to Mineralogy and Petrology》2012,163(3):483-504
The northern Kyushu-Palau Ridge (KPR), remnant conjugate arc of the Izu-Ogasawara (Bonin)-Mariana (IBM) active arc, is dominated
by basalt-andesite except for the Komahashi-Daini Seamount where acidic plutonic rocks of 38 Ma were recovered. These mafic
to intermediate volcanics are produced by the rifting volcanism in the proto-IBM arc associated with spreading of the Shikoku
Basin. The HFSE and HREE contents and ratios of these volcanics indicate enriched source mantle composition compared to recent
volcanic front. The LILE ratios exhibit similar characteristics to reararc volcanism of the recent Izu arc, and some enriched
volcanics exhibit high abundance of sediment melt inputs. Based on these observations and compilations of the published data
set, the replacement event of the wedge mantle under the IBM arc occurred two times. The first event occurred between 45 and
38 Ma, with Pacific type mantle being replaced by depleted Indian type mantle. The second event occurred between 36 and 25 Ma,
enriched mantle flowed from reararc side. The slab component during the proto-IBM arc rifting was a similar characteristic
to recent reararc volcanism of the Izu arc, and sediment melt added in a local area. 相似文献
204.
Citizens as sensors: the world of volunteered geography 总被引:62,自引:0,他引:62
Michael F. Goodchild 《GeoJournal》2007,69(4):211-221
In recent months there has been an explosion of interest in using the Web to create, assemble, and disseminate geographic information provided voluntarily by individuals. Sites such as Wikimapia and OpenStreetMap are empowering citizens to create a global patchwork of geographic information, while Google Earth and other virtual globes are encouraging volunteers to develop interesting applications using their own data. I review this phenomenon, and examine associated issues: what drives people to do this, how accurate are the results, will they threaten individual privacy, and how can they augment more conventional sources? I compare this new phenomenon to more traditional citizen science and the role of the amateur in geographic observation. 相似文献
205.
M. Julleh Jalalur Rahman Rumana Yeasmin Tom McCann 《Journal of the Geological Society of India》2016,88(6):705-710
Mineralogical and chemical investigations (<2μm clay separates) of shale samples from the Neogene-age Surma Group obtained from four wells (Habiganj-11, Shahbazpur-1, Titas-11, Titas-15) in the Bengal basin, Bangladesh, were carried out in order to reveal the clay mineral composition as reservoir exploration and exploitation requires a good understanding of the clay minerals. The samples were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-Ray fluorescence spectrometry (XRF). Mineralogically, the sub-surface Surma Group shales comprise predominantly quartz, plagioclase, illite, chlorite, kaolinite, with lesser amounts of K-feldspar, dolomite and smectite, and minor to trace amounts of calcite, siderite and pyrite. The chemical composition of the <2 μm clay separates also suggests an illite and chlorite-rich composition. With increasing burial depth, the Surma Group shales are enriched in illite. The gradual decreasing of the smectite clays with depth and ultimate disappearance at greater depths (≥ 3000 m) may have been responsible for the presence of the diagenetic illite. Based on the mineralogical composition it is most likely that the illite-chlorite associations together with quartz and feldspar were predominantly detrital in origin and thus reflect the presence of a rapidly-rising source terrain not subjected to intense weathering. 相似文献
206.
207.
Gour Chandra Paul Ahmad Izani Md. Ismail Azizur Rahman Md. Fazlul Karim Ashabul Hoque 《Estuaries and Coasts》2016,39(6):1582-1599
In this paper, a two-dimensional, vertically integrated hydrodynamic model is developed taking into account entrained air bubbles during storm surges as well as incorporating inverted barometer, and river and land dynamics. The model is specifically designed for the coastal region of Bangladesh. A nested scheme method with a fine mesh scheme (FMS), capable of incorporating the complex coastline and all major offshore islands accurately, nested into a coarse mesh scheme (CMS) covering up to 15° N latitude in the Bay of Bengal is used. To incorporate the small and big offshore islands in the Meghna estuarine region with its complex coastline accurately, a very fine mesh scheme (VFMS) is again nested into the FMS. Along the northeast corner of the VFMS, the Meghna river discharge is taken into account. The coastal and island boundaries are approximated through proper stair steps. The model equations are solved by a semi-implicit finite difference technique using a staggered C-grid. A stable appropriate tidal condition over the model domain is generated by applying tidal forcing with the four major tidal constituents M 2, S 2, K 1, and O 1 along the southern open boundary of the CMS. This tidal regime is introduced as the initial state of the sea for nonlinear interaction of tide and surge. The model is applied to simulate water levels due to the interaction of tide and surge associated with the cyclones April 1991 and Aila at different coastal and island locations along the coast of Bangladesh. The results are found to be quite satisfactory with root mean square error of ~0.50 m as calculated for both the storm events. Tests of sensitivities on water levels are carried out for air bubbles, offshore islands, river discharge, inverse barometer, and grid resolution. The presence of air bubbles increases simulated water levels a little bit in our model, and the contribution of air bubbles in increasing water level is found around 2 %. Further, water levels are found to be influenced by offshore islands, river discharge, inverse barometer as well as grid resolution. 相似文献
208.
María Teresa Rodríguez-Salazar Ofelia Morton-Bermea Elizabeth Hernández-Álvarez Rufino Lozano Victor Tapia-Cruz 《Environmental Earth Sciences》2011,62(5):899-905
This research presents and discusses information concerning the spatial distribution of heavy metals (Pb, Cu, Zn, Ba, Co,
Cr, Ni and V) in the urban environments of Mexico City using geographical information system and statistical analysis. Superficial
soil samples (n = 146) were analyzed. The highest contamination indices were found in the north and center zone of the metropolitan area.
In contrast, the surrounding rural fields show a lower impact grade. The higher concentrations of Pb, Cu, Zn and Ba were observed
as being related to high vehicular traffic, nevertheless other elements such as Co, Cr, Ni and V do not show anthropogenic
influence and their content can be attributed to the parental rock. The results are compared with previous surveys carried
out in 2003 in order to evaluate temporal deposition trends. No changes were found on reported concentrations except for Cu
and Zn, whose concentration has increased in later years. The results suggest that spatial distribution analysis and results
in comparison with previous studies could be useful for the management and sustainable development of the metropolitan area
of Mexico City. 相似文献
209.
Weidong Sun Jin-tuan Wang Li-peng Zhang Chan-chan Zhang He Li Ming-xing Ling Xing Ding Cong-ying Li Hua-ying Liang 《中国地球化学学报》2017,36(1):9-15
Copper is a moderately incompatible chalcophile element. Its behavior is strongly controlled by sulfides. The speciation of sulfur is controlled by oxygen fugacity. Therefore, porphyry Cu deposits are usually oxidized (with oxygen fugacities > ΔFMQ +2) (Mungall 2002; Sun et al. 2015). The problem is that while most of the magmas at convergent margins are highly oxidized, porphyry Cu deposits are very rare, suggesting that high oxygen fugacity alone is not sufficient. Partial melting of mantle peridotite even at very high oxygen fugacities forms arc magmas with initial Cu contents too low to form porphyry Cu deposits directly (Lee et al. 2012; Wilkinson 2013). Here we show that partial melting of subducted young oceanic slabs at high oxygen fugacity (>ΔFMQ +2) may form magmas with initial Cu contents up to >500 ppm, favorable for porphyry mineralization. Pre-enrichment of Cu through sulfide saturation and accumulation is not necessarily beneficial to porphyry Cu mineralization. In contrast, re-melting of porphyritic hydrothermal sulfide associated with iron oxides may have major contributions to porphyry deposits. Thick overriding continental crust reduces the “leakage” of hydrothermal fluids, thereby promoting porphyry mineralization. Nevertheless, it is also more difficult for ore forming fluids to penetrate the thick continental crust to reach the depths of 2–4 km where porphyry deposits form. 相似文献
210.
Contamination and distribution of heavy metals in urban and suburban soils in Zhangzhou City,Fujian, China 总被引:2,自引:0,他引:2
Zhen-ang Cui Sheng-ying Qiao Zheng-yu Bao Neng-you Wu 《Environmental Earth Sciences》2011,64(6):1607-1615
The urban environment is of growing concern as its continued population increase in China. Due to the urbanization and industrialization,
heavy metals have been continuously discharged into the soil recently, and creating the anthropogenic contamination. This
study investigated heavy metals contamination in urban and suburban soils in Zhangzhou City, Fujian, China. Multivariate analysis
and geographical information system technology were employed in source identification and contamination assessment of heavy
metals in the city soils. The survey results indicated that the urban soils were contaminated by heavy metals, especially
by Hg, Cd and Pb. The multivariate analysis demonstrated that the distribution of Cu, Zn, Cr and Ni was controlled by pedogenesis,
Cd and Pb had been disturbed by industrialization in some urban locations, and Hg was mainly influenced by the hot-spring
in some urban park sites. The distribution of heavy metals and soil pollution index suggested the soils of Zhangzhou City
have been affected by human activities. 相似文献